Ladder testing 284 Win with 2213sc powder
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Barry Davies
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Each to his own. There is a hundred ways of doing load development and if you know how to look at the data then you can get just as much information out of a 10 shot string in 0.1 grain increments as you can from a 10 shot group. I say this with a touch of reservation however as not all ladders are done correctly and if your velocity spread is high then it is harder to get good info as it is lost in the deviations.
Personally I do 3 shot replicated ladders with about 1% load increase and 15 shot strings so this allows me to cover 2.0 grains or so in each with very good feedback with essentially 15 shot strings for velocity sd etc.
I will try and attach some examples later and some examples of how to obtain velocity sd, angular accuracy and a great deal of data from single shot (or three shot) ladders. - it is all about adjusting the data around a fitted line.
Tony - yes you can expect "Wide" nodes from the 284 (and indeed most rifles) if the rifles are built for the job and you have a good combination of powder, projectile, seating depth, primer. This is another topic in itself though.
Personally I do 3 shot replicated ladders with about 1% load increase and 15 shot strings so this allows me to cover 2.0 grains or so in each with very good feedback with essentially 15 shot strings for velocity sd etc.
I will try and attach some examples later and some examples of how to obtain velocity sd, angular accuracy and a great deal of data from single shot (or three shot) ladders. - it is all about adjusting the data around a fitted line.
Tony - yes you can expect "Wide" nodes from the 284 (and indeed most rifles) if the rifles are built for the job and you have a good combination of powder, projectile, seating depth, primer. This is another topic in itself though.
Last edited by DaveMc on Tue Dec 25, 2012 10:55 pm, edited 1 time in total.
If your an average joe shooter and have a chronograph (only one) what is to say that your chronograph is 100% reliable and repeatable in its outputs each shot? To me it only adds a variable into the equation. Yes it may be a tool that helps, but unless its perfect each and every time I see it to be a hinderance compared to shooting time.
I personally start at 100m and start low working up looking for pressure signs. When I hit my max that I feel safe shooting then it goes to a ladder test in 0.2gr increments then shooting groups with what looks to be promising around that node working on powder charge, primer choice and then seating depth at the end.
But hey if your using a chrony successfully dont stop, it just isnt my thing.
I personally start at 100m and start low working up looking for pressure signs. When I hit my max that I feel safe shooting then it goes to a ladder test in 0.2gr increments then shooting groups with what looks to be promising around that node working on powder charge, primer choice and then seating depth at the end.
But hey if your using a chrony successfully dont stop, it just isnt my thing.
https://docs.google.com/open?id=0B6Fwvt ... 1JONzgwLTA
Lets try this.
Now this is 2213 with a jam 180 VLD - I can get an estimate of velocity sd from fitting a line through the data and "adjusting" the resultant velocity from the expected velocity (from fitted line) - in this case sd 5. Personally if I see great differences in velocity spread or accuracy over a couple of grains I search on. When you are igniting the powder well and have a good balanced load all the crap seems to disappear. I run this "standard ladder" on the combinations I am testing until it looks good.
Once I see a ladder like this then I go on and verify with 15-20 shot groups and confirm velocity sd. If this was done in single shots with smaller increments the picture would look similar and give similar data. There is "power" in it by combining them together.
Barry - I think ladders are generally used to "rough out a load" not confirm it for reliability. At least most of the people I know using them do this.
Brad - for me it is all about 1000 yards - get it to work at 1000 and the rest will fall into place. To do that with a 300 yard ladder is difficult without a good chrono. A rifle with angular accuracy like this and sd around 5 will hold the x ring most of the time (on a good elevation range/day) but I take your point not all will have a chrono (or a good one). But look at the data. everything from 2800 - 2900 fps 9 shots fell within a quarter minute band at 300. However this same spread (100fps) will take you out to 2.5 minutes at 1000!
Lets try this.
Now this is 2213 with a jam 180 VLD - I can get an estimate of velocity sd from fitting a line through the data and "adjusting" the resultant velocity from the expected velocity (from fitted line) - in this case sd 5. Personally if I see great differences in velocity spread or accuracy over a couple of grains I search on. When you are igniting the powder well and have a good balanced load all the crap seems to disappear. I run this "standard ladder" on the combinations I am testing until it looks good.
Once I see a ladder like this then I go on and verify with 15-20 shot groups and confirm velocity sd. If this was done in single shots with smaller increments the picture would look similar and give similar data. There is "power" in it by combining them together.
Barry - I think ladders are generally used to "rough out a load" not confirm it for reliability. At least most of the people I know using them do this.
Brad - for me it is all about 1000 yards - get it to work at 1000 and the rest will fall into place. To do that with a 300 yard ladder is difficult without a good chrono. A rifle with angular accuracy like this and sd around 5 will hold the x ring most of the time (on a good elevation range/day) but I take your point not all will have a chrono (or a good one). But look at the data. everything from 2800 - 2900 fps 9 shots fell within a quarter minute band at 300. However this same spread (100fps) will take you out to 2.5 minutes at 1000!
Also Tony - looking at those velocities it really looks like something went wrong with chrony towards the end. The standard chronys will do that with a change in light conditions. At the loads you got up to I would suspect you are around the 2800+ fps area at the end - a very nice place to be for most 284's.
Dave
Dave
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bruce moulds
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two comments.
alan,
ladders are a case of less is more.
dave,
your ladder presents no node.
there could be one on the lowest load, but you would have to try lower loads to find out. 500 mt shooting would demonstrate this more clearly.
also, there is no point in talking std deviation of velocities with the no of shots.
the whole point of the ladder is to find a point where variations make the least difference to vert.
this is why it is rediculous to spend huge ammounts of money on expensive scales. a good node should allow thrown charges, and going one better than that with reasonable scales is all you have to do. that will allow for minor variations in case capacity.
the chronograph is only a means of trying to predict results on target. another approach here is to do away with the chronograph, and let the target do the job.
tony,
my suggestion to you is to verify that node with fireformed brass, get your head in the widreading place, and do as much shooting in as foul a conditions as you can.
your node is as good as it gets, believe me, and you will score a lot more points mastering the wind than you will chooking around with silver bullets.
keep safe,
bruce.
alan,
ladders are a case of less is more.
dave,
your ladder presents no node.
there could be one on the lowest load, but you would have to try lower loads to find out. 500 mt shooting would demonstrate this more clearly.
also, there is no point in talking std deviation of velocities with the no of shots.
the whole point of the ladder is to find a point where variations make the least difference to vert.
this is why it is rediculous to spend huge ammounts of money on expensive scales. a good node should allow thrown charges, and going one better than that with reasonable scales is all you have to do. that will allow for minor variations in case capacity.
the chronograph is only a means of trying to predict results on target. another approach here is to do away with the chronograph, and let the target do the job.
tony,
my suggestion to you is to verify that node with fireformed brass, get your head in the widreading place, and do as much shooting in as foul a conditions as you can.
your node is as good as it gets, believe me, and you will score a lot more points mastering the wind than you will chooking around with silver bullets.
keep safe,
bruce.
"SUCH IS LIFE" Edward Kelly 11 nov 1880
http://youtu.be/YRaRCCZjdTM
http://youtu.be/YRaRCCZjdTM
Bruce - could you clarify - what are you looking at? No node? Where? No scatter node or no accuracy node? or no velocity compensation node - they are quite different kettles of fish - I will address all in turn.
Compensation node. Between 2800 and 2900 there is no significant rise? AND INDEED SOME SIGNIFICANT 300 YARD COMPENSATION. I agree I need to go lower (and did)- below this there is a steeper rise from 2750 - 2800 similar to that from 2900 to 2950. All shots within this band fall within a quarter minute. When you look at the 2800-2850 it is 0.15minutes and very flat. On many confirmations later this is the sweet spot. At 500 the compensation is a little less and at 1000 compensation matters for SFA it is more a matter of velocity sd out there in these barrels. Maybe other rifle combinations will have faster vibrations and more compensation but that is not what I want. There is a point here. This rifle (and my latest RSAUM) were built to create as little "vibration impulses" as possible - in theory anyway - and seems to have worked with both. When combined with the right powder, primer, seating combo there is little high frequency scattering and more evident slower "wide nodes" In other words - forgiving for loads creeping up and down with temp, travel or barrel age and fouling. THAT IS WHAT I WANT (along with low v SD)
There also is effectively no significant "scatter" nodes in this rifle combo from 2700-2970 (the extent of my load development). Maybe minor ones but I can't tell at the range - all loads hold good waterline. In fact I have shot this rifle in competition everywhere from 2800-2930 fps and had great success.
On No of shots. - the sd of 5 was calculated on all 15 shots. I agree it is not enough. Indeed I would like 30 and 20 would be better but 15 starts to give you a good indication. If anything when shooting a single load (and 20 shot strings) this rifle has proved itself to be capable of that or better.
BUT enough on this rifle - I didn't post that ladder to talk about my gear but I was using it as a demonstration of how to calc v sd from ladders. By fitting a line and adjusting the expected v from the fitted line of load vs velocity. This is reasonably valid to estimate sd over a ladder and if anything it can improve as you narrow in on the best "load for burn" spot (as Barry indicated). BUT my feeling is when you get them tuned for best burn curve there is also a "wider forgiveness" in velocity spread too.
Compensation node. Between 2800 and 2900 there is no significant rise? AND INDEED SOME SIGNIFICANT 300 YARD COMPENSATION. I agree I need to go lower (and did)- below this there is a steeper rise from 2750 - 2800 similar to that from 2900 to 2950. All shots within this band fall within a quarter minute. When you look at the 2800-2850 it is 0.15minutes and very flat. On many confirmations later this is the sweet spot. At 500 the compensation is a little less and at 1000 compensation matters for SFA it is more a matter of velocity sd out there in these barrels. Maybe other rifle combinations will have faster vibrations and more compensation but that is not what I want. There is a point here. This rifle (and my latest RSAUM) were built to create as little "vibration impulses" as possible - in theory anyway - and seems to have worked with both. When combined with the right powder, primer, seating combo there is little high frequency scattering and more evident slower "wide nodes" In other words - forgiving for loads creeping up and down with temp, travel or barrel age and fouling. THAT IS WHAT I WANT (along with low v SD)
There also is effectively no significant "scatter" nodes in this rifle combo from 2700-2970 (the extent of my load development). Maybe minor ones but I can't tell at the range - all loads hold good waterline. In fact I have shot this rifle in competition everywhere from 2800-2930 fps and had great success.
On No of shots. - the sd of 5 was calculated on all 15 shots. I agree it is not enough. Indeed I would like 30 and 20 would be better but 15 starts to give you a good indication. If anything when shooting a single load (and 20 shot strings) this rifle has proved itself to be capable of that or better.
BUT enough on this rifle - I didn't post that ladder to talk about my gear but I was using it as a demonstration of how to calc v sd from ladders. By fitting a line and adjusting the expected v from the fitted line of load vs velocity. This is reasonably valid to estimate sd over a ladder and if anything it can improve as you narrow in on the best "load for burn" spot (as Barry indicated). BUT my feeling is when you get them tuned for best burn curve there is also a "wider forgiveness" in velocity spread too.
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ecomeat
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Dave,
i hope this does'nt seem like too silly a question.....
Is your "Velocity Fitted Line" the true mathematical average of the 3 shots fired of each load ? Could you possibly add the actual recorded velocities so i can grasp it better ?
And what is the criteria (or how do you arrive at a figure) for the expected Velocity that you then compare to your fitted line velocity ? Is it just your best "guesstimate" from experience, or are you using Quickload or something similar ?
I had never heard of your strain guage technology before you mentioned it here, but what i have seen (RSI pages) makes fascinating reading, and i can see that it "could" play a huge role in long range accuracy work in the near future. Hell, 18 months ago I had never seen the word harmonics used on the same page as "barrel" or "accuracy" so this is all an enormously steep learning curve for me.
I have to confess that I cant get my head right around the concept of "Compensation Node" and hope you might accept a PM on that.
i hope this does'nt seem like too silly a question.....
Is your "Velocity Fitted Line" the true mathematical average of the 3 shots fired of each load ? Could you possibly add the actual recorded velocities so i can grasp it better ?
And what is the criteria (or how do you arrive at a figure) for the expected Velocity that you then compare to your fitted line velocity ? Is it just your best "guesstimate" from experience, or are you using Quickload or something similar ?
I had never heard of your strain guage technology before you mentioned it here, but what i have seen (RSI pages) makes fascinating reading, and i can see that it "could" play a huge role in long range accuracy work in the near future. Hell, 18 months ago I had never seen the word harmonics used on the same page as "barrel" or "accuracy" so this is all an enormously steep learning curve for me.
I have to confess that I cant get my head right around the concept of "Compensation Node" and hope you might accept a PM on that.
Extreme accuracy and precision shooting at long range can be a very addictive pastime.
No problems Tony - happy to explain.
And the actual velocities are in the spreadsheet in the second post.
Compensatory nodes are the heart of an audette ladder and basically means the barrel is "dropping" as velocity is increasing. This will result as a "flat line" of point of impact with increasing load at some range. The faster the barrel drop (stiffer shorter barrels) the further out this will occur and indeed in close they can "overcompensate" and actually have the poi dropping with increasing velocity. Indeed as Bruce points out you can actually have a load that requires little in regard to accurate powder measuring BUT with a word of warning this generally only occurs over a few ranges (normally 3-700 - beyond that you normally need more than just compensation)
It really is different to the optimal charge theory where you are avoiding "scatter nodes" where the higher frequency vibrations hit the end of the barrel at same time as bullet.
In my rifles the compensation "flat line" is generally between 300-500 yards and means stuff all at 1000. Some rifles may well be able to compensate at 1000 but I have seen very little evidence of this in all my testing (doesn't mean it cant happen though - anyone???)
At 1000 velocity sd is king. A standard deviation of 5 generally means (as a rule of thumb) you will hold the x ring, 10 for the 6 ring providing you have good short range or angular accuracy. To me quoting es is not a good indicator but most shooters tend to do it so we fall into that mode to keep with the norm.
There is several semi valid ways of estimating sd from a ladder but I think the a good overall approach which encompasses single shot and replicate ladders is
1) simply plot load vs velocity (load on x axis, velocity on y) in a graph on excel (or similar spreadsheet). A good chrono is important here - but evaluating sd with a poor one is hardly worth it anyway. Use an xy scattergraph then fit a "trendline" and tick the box to display equation on chart.
2) Once you have the equation - copy into a cell adjacent to your other results - change the "x" to the cell corresponding to your load and copy down. This equation will give you the expected velocity at that load from the fitted line (average of all groups if you like).
3) In the next column just subtract the fitted line values from the recorded ones (you can plot this against load as well if you like) then calculate sd from there.
Note: This sd encompasses the full load spectrum and indeed (as Barry pointed out) you can see certain volumes of powder burning better for better spread at points within the spectrum. So this sd should be greater than that you see at an individual point of best combustion. But I argue if you get close to the right combination of components then the velocity variation is better over a wider curve.
And the actual velocities are in the spreadsheet in the second post.
Compensatory nodes are the heart of an audette ladder and basically means the barrel is "dropping" as velocity is increasing. This will result as a "flat line" of point of impact with increasing load at some range. The faster the barrel drop (stiffer shorter barrels) the further out this will occur and indeed in close they can "overcompensate" and actually have the poi dropping with increasing velocity. Indeed as Bruce points out you can actually have a load that requires little in regard to accurate powder measuring BUT with a word of warning this generally only occurs over a few ranges (normally 3-700 - beyond that you normally need more than just compensation)
It really is different to the optimal charge theory where you are avoiding "scatter nodes" where the higher frequency vibrations hit the end of the barrel at same time as bullet.
In my rifles the compensation "flat line" is generally between 300-500 yards and means stuff all at 1000. Some rifles may well be able to compensate at 1000 but I have seen very little evidence of this in all my testing (doesn't mean it cant happen though - anyone???)
At 1000 velocity sd is king. A standard deviation of 5 generally means (as a rule of thumb) you will hold the x ring, 10 for the 6 ring providing you have good short range or angular accuracy. To me quoting es is not a good indicator but most shooters tend to do it so we fall into that mode to keep with the norm.
There is several semi valid ways of estimating sd from a ladder but I think the a good overall approach which encompasses single shot and replicate ladders is
1) simply plot load vs velocity (load on x axis, velocity on y) in a graph on excel (or similar spreadsheet). A good chrono is important here - but evaluating sd with a poor one is hardly worth it anyway. Use an xy scattergraph then fit a "trendline" and tick the box to display equation on chart.
2) Once you have the equation - copy into a cell adjacent to your other results - change the "x" to the cell corresponding to your load and copy down. This equation will give you the expected velocity at that load from the fitted line (average of all groups if you like).
3) In the next column just subtract the fitted line values from the recorded ones (you can plot this against load as well if you like) then calculate sd from there.
Note: This sd encompasses the full load spectrum and indeed (as Barry pointed out) you can see certain volumes of powder burning better for better spread at points within the spectrum. So this sd should be greater than that you see at an individual point of best combustion. But I argue if you get close to the right combination of components then the velocity variation is better over a wider curve.
Dave- as usual your posts are very informative. Totally raised the bar as to what I thought people did. I always thought shooting to get the best groups at 300-500yds was about it, and all the work on ES and SD was a waste of effort when you could be shooting groups. Now I see there is much more to it and sadly that much more is alot of maths.
Couple of questions if I may and sorry Tony for hijacking your thread.
1) Obviously barrel wear is a bit of a thing to work around when tuning for different calibres. Have you done alot of this work over a number of barrels and worked out your load tuning procedure for each one or does this generally fit into any barrel you have used? Even one you may have considered a bit of a lemon and good for club shoots only? Im not really interested in using 1/4 of a barrels life for the sake of maths, but shooting groups is fine by me
2) Out of all the loads in the pic and spreadsheet, was the first one or the third one the load of choice? Me still looking at groups I see the waterline better in #1 and notice the numbers better in #3
3) When plotting your velocity, mean velocity and working your SD's for a load, then other loads in turn, I take it you are looking at the angles the plot line is making on the graph. Steeper rises would indicate between nodes yet a plateau would indicate something of interest yes?
Couple of questions if I may and sorry Tony for hijacking your thread.
1) Obviously barrel wear is a bit of a thing to work around when tuning for different calibres. Have you done alot of this work over a number of barrels and worked out your load tuning procedure for each one or does this generally fit into any barrel you have used? Even one you may have considered a bit of a lemon and good for club shoots only? Im not really interested in using 1/4 of a barrels life for the sake of maths, but shooting groups is fine by me
2) Out of all the loads in the pic and spreadsheet, was the first one or the third one the load of choice? Me still looking at groups I see the waterline better in #1 and notice the numbers better in #3
3) When plotting your velocity, mean velocity and working your SD's for a load, then other loads in turn, I take it you are looking at the angles the plot line is making on the graph. Steeper rises would indicate between nodes yet a plateau would indicate something of interest yes?
Hi Brad,
I have generally used up to 200 rounds to get a barrel going but only in my 7mm's. The smaller calibers are only used for short range so they are easier to tune. This is shortening as I get to know what to look for and how to tune for it but I am happy with that. 200 rounds in a 284 is less than 10% of its barrel life and they generally "break in" around there. (((NB These bloody hybrids have cost more barrel life than anything
but I am starting to get to know my way around them 
)
On the groups - I really don't look at any three shot group in load development (might explain a little more on this later) but rather the trends. My short range load for this rifle I dropped in the middle of the "plateau" between 2800-2850 (300-700 yards) and that performs brilliantly. It also shoots well at 1000 because it has low velocity variation (When loading for 300-700 yards I don't do any of the time consuming stuff I do for the long range loads). BUT - here is the kicker I have a long range load as well - 2920 fps with the hybrid. This also goes great (even though it is in the "steeper" part of the curve - and I can hear Bruce groaning from here) but has a very tight velocity spread and holds very good 1000 yard elevation. ...
As I said earlier - each to his own and whatever gets you to the load you need is OK. Of course running groups at the range you want to shoot will also work.
For a short range load - yes the plateau of height vs load is what I am looking for (as a standard audette ladder does). BUT for 1000 yd load I am interested more in the total ladders output and velocity sd. ie Tight vertical across the boards and low velocity deviation - you could do this without a chrono if you checked at 1000. But I have had a few loads that work very well at 300-500 (compensated) but only just hold the 6 ring at 1000.
I have generally used up to 200 rounds to get a barrel going but only in my 7mm's. The smaller calibers are only used for short range so they are easier to tune. This is shortening as I get to know what to look for and how to tune for it but I am happy with that. 200 rounds in a 284 is less than 10% of its barrel life and they generally "break in" around there. (((NB These bloody hybrids have cost more barrel life than anything
but I am starting to get to know my way around them )
On the groups - I really don't look at any three shot group in load development (might explain a little more on this later) but rather the trends. My short range load for this rifle I dropped in the middle of the "plateau" between 2800-2850 (300-700 yards) and that performs brilliantly. It also shoots well at 1000 because it has low velocity variation (When loading for 300-700 yards I don't do any of the time consuming stuff I do for the long range loads). BUT - here is the kicker I have a long range load as well - 2920 fps with the hybrid. This also goes great (even though it is in the "steeper" part of the curve - and I can hear Bruce groaning from here) but has a very tight velocity spread and holds very good 1000 yard elevation. ...
As I said earlier - each to his own and whatever gets you to the load you need is OK. Of course running groups at the range you want to shoot will also work.
For a short range load - yes the plateau of height vs load is what I am looking for (as a standard audette ladder does). BUT for 1000 yd load I am interested more in the total ladders output and velocity sd. ie Tight vertical across the boards and low velocity deviation - you could do this without a chrono if you checked at 1000. But I have had a few loads that work very well at 300-500 (compensated) but only just hold the 6 ring at 1000.
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ecomeat
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Dave,
This compensatory node at shorter ranges has got me fascinated.
It would mean that there would be tens of thousands of rifles on the mound at any given time that are red hot potential winners, at 300-500 or whatever.....and then be heartbreakers at 1000 yds.
Can (and have you done it) the strain guages or anything similar prove that this load that works brilliantly at say 500 yards, just cant ever "cut it" at 1000 yards ? ie is it possible to scientifically prove that a great node at say 500 yards is a "Compensatory node".......as opposed to being an "accuracy node" ??
And how does your 2920 fps 1000 yard load perform at 300-500 yds ? Is it maybe 0.250 moa or so, that it would (once have been !) normal to assume it had to be if its a match winner at 1000 yards ?
This compensatory node at shorter ranges has got me fascinated.
It would mean that there would be tens of thousands of rifles on the mound at any given time that are red hot potential winners, at 300-500 or whatever.....and then be heartbreakers at 1000 yds.
Can (and have you done it) the strain guages or anything similar prove that this load that works brilliantly at say 500 yards, just cant ever "cut it" at 1000 yards ? ie is it possible to scientifically prove that a great node at say 500 yards is a "Compensatory node".......as opposed to being an "accuracy node" ??
And how does your 2920 fps 1000 yard load perform at 300-500 yds ? Is it maybe 0.250 moa or so, that it would (once have been !) normal to assume it had to be if its a match winner at 1000 yards ?
Extreme accuracy and precision shooting at long range can be a very addictive pastime.
Tony,
There are essentially several components here.
1) Angular accuracy (short range) - there are a lot of accuracy issues here that can affect shooting even short range groups. e.g. bedding, crown, bullets, bullet entry into lands, other aspects of rifle design etc etc.
2) barrel harmonics. What does your rifle do?? for instance a glued in action with 32 inch 1.25 straight or heavy barrel tuner will "vibrate" very differently to a short barrel with front recoil lug on an aluminium stock and different again to a barrel block (essentially circular recoil lug) or tube gun. The "harmonics" of each are vastly different.
3) velocity spread. Tight velocity spread is required in addition to the top two to maintain good elevation out to 1000 (and beyond).
Now to answer your questions.
Yes we have done countless tests at my home range here (I have 300,500 and 1000 yard mounds) and yes - a brilliant 300-500 yard load with large velocity spread is crap at 1000 in all my (and couple of other) rifles (maybe not all rifles though?). This can also be proven mathematically and I may have a go at explaining that later. But as some rules of thumb - for a normal distribution (and most groups seem to follow normal distributions) if you have a 20 shot sd of 10 then 65% of your shots will fall +/- 1 sd from the line so on average 13 shots will be holding the x ring. then 95% will be within 2 sd's so on average (another 6) will stay in 6 ring. that poor loner will be outside this. To keep 95% of your shots in the x ring you need 1) Great angular accuracy, 2) 20 shot velocity sd of below 5 fps 3) Avoid nasty barrel vibrations. OH - and also other things such as bullet uniformity (BC consistency), etc.
The big question is - can compensation help??? - answer yes but not as much as people hope and almost insignificant (SFA really in my rifles) at 1000+. To compensate for a 40 fps spread (sd around 10) you would need to have your barrel drop angularly at 1 minute over 40 fps. This is a "large and fast drop" and if so can therefore only operate over a tight band (otherwise you will need muzzle moving many minutes) - get out of this band and the reverse will happen - you will have quickly rising barrel with rising velocity = DISASTER!!! To me this is something to avoid at all costs.
The strain gauges are a new addition - they are more from interest and trying to help tune for consistent burn curves. Underprimed or slow powders are of particular interest to me at the moment and trying to get these type of cases tuned for "most consistent ignition and burn".
Yes the 2920 load does work at short range as well (most good 1000 yard loads do) but I want a lighter load (for barrel and more importantly case life). The "compensatory node" is also really easy to load for - I wouldn't go as far as "throwing charges" but it could possibly be done.
There are essentially several components here.
1) Angular accuracy (short range) - there are a lot of accuracy issues here that can affect shooting even short range groups. e.g. bedding, crown, bullets, bullet entry into lands, other aspects of rifle design etc etc.
2) barrel harmonics. What does your rifle do?? for instance a glued in action with 32 inch 1.25 straight or heavy barrel tuner will "vibrate" very differently to a short barrel with front recoil lug on an aluminium stock and different again to a barrel block (essentially circular recoil lug) or tube gun. The "harmonics" of each are vastly different.
3) velocity spread. Tight velocity spread is required in addition to the top two to maintain good elevation out to 1000 (and beyond).
Now to answer your questions.
Yes we have done countless tests at my home range here (I have 300,500 and 1000 yard mounds) and yes - a brilliant 300-500 yard load with large velocity spread is crap at 1000 in all my (and couple of other) rifles (maybe not all rifles though?). This can also be proven mathematically and I may have a go at explaining that later. But as some rules of thumb - for a normal distribution (and most groups seem to follow normal distributions) if you have a 20 shot sd of 10 then 65% of your shots will fall +/- 1 sd from the line so on average 13 shots will be holding the x ring. then 95% will be within 2 sd's so on average (another 6) will stay in 6 ring. that poor loner will be outside this. To keep 95% of your shots in the x ring you need 1) Great angular accuracy, 2) 20 shot velocity sd of below 5 fps 3) Avoid nasty barrel vibrations. OH - and also other things such as bullet uniformity (BC consistency), etc.
The big question is - can compensation help??? - answer yes but not as much as people hope and almost insignificant (SFA really in my rifles) at 1000+. To compensate for a 40 fps spread (sd around 10) you would need to have your barrel drop angularly at 1 minute over 40 fps. This is a "large and fast drop" and if so can therefore only operate over a tight band (otherwise you will need muzzle moving many minutes) - get out of this band and the reverse will happen - you will have quickly rising barrel with rising velocity = DISASTER!!! To me this is something to avoid at all costs.
The strain gauges are a new addition - they are more from interest and trying to help tune for consistent burn curves. Underprimed or slow powders are of particular interest to me at the moment and trying to get these type of cases tuned for "most consistent ignition and burn".
Yes the 2920 load does work at short range as well (most good 1000 yard loads do) but I want a lighter load (for barrel and more importantly case life). The "compensatory node" is also really easy to load for - I wouldn't go as far as "throwing charges" but it could possibly be done.
Last edited by DaveMc on Thu Dec 27, 2012 7:26 am, edited 1 time in total.
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Barry Davies
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Compensation is a reality but is brought about by large variations in projectile speed -- as was the case with older military ammo.
If your ammo is of low extreme spread then compensation does not really come into the equation to any marked ( and noticeable degree ) and compensation usually only applies at one range--usually beyond 700 yards.
A good reason to chronograph your ammo to find that load with the least ES then tune the rifle to it.
As Dave pointed out an excellent source of information are graphs relating to Load, speed, ES and corresponding group size. From this much can be learned as to what happens with respect to barrel vibrations ( point of exit ) at various loads -- from graphs, the best operating points ( load/speed/ES ) can be clearly seen, as well as the repeating points ( nodes as some call them )The laws of physics are indisputable and apply equally as well in ballistics.
If your ammo is of low extreme spread then compensation does not really come into the equation to any marked ( and noticeable degree ) and compensation usually only applies at one range--usually beyond 700 yards.
A good reason to chronograph your ammo to find that load with the least ES then tune the rifle to it.
As Dave pointed out an excellent source of information are graphs relating to Load, speed, ES and corresponding group size. From this much can be learned as to what happens with respect to barrel vibrations ( point of exit ) at various loads -- from graphs, the best operating points ( load/speed/ES ) can be clearly seen, as well as the repeating points ( nodes as some call them )The laws of physics are indisputable and apply equally as well in ballistics.
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