Long Range Load Development

[AlanF]

Ned suggested a topic on load development for long range. A good read on this subject can be found in ATRs 84 and 85, in Spencer Dunstall's "Simply Shooting" series. There are also plenty of tips on the likes of Benchrest.com, if you search for them. However Australian F-Classers seem to keep their methods fairly close to the chest, a bit like an angler with a favourite fishing spot, or hunters who know the whereabouts of a big sambur. So if you do have some knowledge to impart, remember that many will be happy to read it, while not as many willing to give out their own.

I'll start the ball rolling by revealing that I rely mainly on ladder testing, then confirm (or otherwise ) the findings during shoots. For those who don't know how it works, you start at the minimum powder charge you would consider usable as a match load (velocity-wise) and load in small increments up to the maximum acceptable charge (usually determined by pressure signs). The increments might be as little as 0.1gn if you use small cases or if you want plenty of information, up to about 0.5gn for the other extremes. Normally I do the shooting at either 300 or 500yds in conditions with as little vertical as possible. You plot the shot position and/or velocity on a graph against the powder charge, and the graph curve can reveal "nodes" where velocity/elevation variation is minimal over several powder charges. I also do velocity only testing at home, through the chronograph and into a hole in a bank. For this I usually reload the same case, to eliminate things like variable case volume and neck tension, and concentrate on powder charge variation alone.

One of the main reasons I use ladder testing is that it's a more economical way of getting there (I've learnt not to trust 5 shot groups). However if using a tuner, then a group strategy is more economical if done this way : at each tuner setting shoot a group until it gets unacceptably bad, then move on to the next setting. So at some settings you may only need to 2 shots to eliminate it. When you do find a good setting, keep shooting until you are satisfied with the accuracy - this could be 8 - 10 shots to be sure about it. You can also use this strategy with seating depth if you have a quick method for altering it e.g. Wilson straight line.

Comments welcome.

Alan

[johnk]

Like most with a TR background, I didn't spend a lot of time hassling with loads until I put a scope on a rifle, ie when I started shootign match rifle in 2001.

In that discipline, velocity at 1200 yards is one of the major considerations, if not the most important, as long as other issues don't impinge on it. Of course, they can, particularly excessive velocity spreads which, on thir own, would result in vertical stringing, although that seems to be ameliorated by what's generally called barrel tune these days.

I found that what worked for me with match rifle was to:

shoot loads over a chronograph until acceptable spreads for 15 shot groups were achieved
use a barrel tuner to optomise those groups at 100 yards
refine that tune at the longest safe distance (depending on conditions on the day), although anything from 900 yards on seems toi suit

My FS gun is a different kettle of fish. I've only shot it with 2 barrels, the first being my final TR tube & one I installed for Bendigo 2009. Both those barrels shot acceptably with the "standard" load I'd been using for the last 10 years or so, running a BJD of either snout at around 2950-2980 fps. The same load & jump worked perfectly when I fiddled with the Lapua Palma brass recently, but it's OK, I've learned to live with the shame of not needing to experiment.

It's not all that simple though. My MR was shooting like stink with Rudolph projectiles from their old white boxes, but blew out to 1½-2MOA when I used the same pills from hologram boxes. I'm still beating myself for not proving those pills by my normal routine & cringe every time I look at my scores in the 2010 Aussie championship.

[RDavies]

I would say I am like a lot of shooters out there who cant get out to a SSAA range to do endless testing at 1-200 yds. So here is what I do with the limited opportunity I get to test.
Running in day.
After the initial running in, try to find a freindly property where you can just fire some shots into bank over a cronograph. Load each case with progressively hotter loads until you get to about3070, 2950 fps or 2820 fps with a 30" barrel and bullets about .010" in and again with bullets with about .010" jump.

Most nodes being about 120-130 fps apart.

The node for 6x47s, hot loaded 6.5-284s, 22BR etc being about 3070 fps

The node for 308s, 6 Dashers, medium 6.5s etc are usualy around 2950 fps.

The 6BRs, 284s and 30 cals shooting heavy bullets at around 2820

These are ball park common speeds, a good place to start if you dont have a tuner.

1st club shoot.
Once you get a load for these velocities, go to a club shoot and load 7 rounds (2 sighters) with this load jammed into the lands, and 5 off the lands. Off the lands will usualy need another .2gns more powder to get the same speed, as you probably found in your crony session.

On your first target, you will find out whether your rifle likes bullets jammed or jumping.
On your second target , with the bullets seated where the first load shot best, jumping or jammed,have 7 cases loaded with the load it took to get to the speeds above, and 5 loaded either .3gns up or down.
This will tell you which way is closer to the velocity node.

2nd club shoot
At the next club shoot, 1st target, say you rifle shot best jammed into the lands .010", load 7 shots at .005" jam and 5 with .015" jam, this will tell you how much the load wants to be jammed (or jumped). If it prefered jumping, make bigger changes, say .015" difference as some bullets such as HBCs shoot best at .050" jump
For your 2nd target seat bullets to the most accurate depth found just before, but once again go up or down .2-.3 in your powder loads.

By this stage after about 70 rounds through the barrel, you usualy have the rifle pretty well tuned and you will find a trend, whether it likes jamming or jumping and what speed the barrel is in its node.

After this, I dont usualy do any testing until I find the barrels personality. If I am shooting an improved cartridge, I will do personality testing while fire forming the last 80 shots after running in.

[AlanF]

I made a statement in an earlier post about learning not to trust 5 shot groups. In case anyone thought I was just whinging, I decided to do a little investigation, and came up with some results which may surprise some. I won’t bore you with the exact method except to say that it was done with a simulation using statistical functions in MS Excel. Anyone who is interested, please PM me and I’ll send you a copy of the spreadsheet.

Here is what I found. Suppose you have 4 loads, of which the accuracy is known exactly in terms of their SD (standard deviation) in MOA from the centre of the group. Let’s say they are 0.2, 0.25, 0.31 and 0.39 respectively. Note that after the first one, each subsequent one increases by a factor of about 1.25, and the worst one (0.39) is about double the best (0.2). This means in effect that if you were able to fire hundreds of shots with these four loads, average group sizes for the best load would be about half those of the worst, with the other two loads somewhere in between.

Now here’s the catch : if you fire a 5 shot group with each of these loads, there is less than a 50% chance that the best load will produce the smallest group . And from another perspective, there is about a 25% chance that the best group will come from one of the two worst loads !

One of my own testing methods has been to shoot 4 groups of 5 shots, each with something (e.g. powder charge) slightly different. Based on these simulation results, the assumption that the smallest group will indicate the most accurate load is at best very flakey.

Okay, then what should you do? I'm not sure actually - extending the simulation to 10 shots, there's still only about a 60% chance the best load will produce the smallest group. All I can say with any certainty is that the more shots you fire, the better idea you'll have of the accuracy.

Alternatively, you could just keep buying barrels until you get a hummer .

Alan

[Chopper]

10 plus shot groups are better, Chop.

[ned kelly]

G'day all,
aggregates of 4-5 x 5 shot groups are good indicators or several 10 shot groups also show the ability of the shooter/rifle combo.

FWIW, BRT suggest 10 shot groups shot at the longest distance you can and then ignore the widest 2 shots as flyer's as a good indication of load accuracy when testing at new ranges.

Personally at Victoria's SSAA Little River range at Lara, several 3 shot groups ('cause the conditions dont hang around long enuff for more shots!) are a good indicator and if they show promise and with a lot of patience try some 5 shot groups then test at longer ranges at Werribee if possible.

cheerio Ned

[AlanF]

...FWIW, BRT suggest 10 shot groups shot at the longest distance you can and then ignore the widest 2 shots as flyer's ...

Hmmm... I could simulate that and see how it stacks up. Need to reload for tomorrow, but will have a look at that tomorrow evening.

Alan

[Lynn Otto]

FWIW, BRT suggest 10 shot groups shot at the longest distance you can and then ignore the widest 2 shots as flyer's

Hmm do you think I can convince my scorer's to ignore the widest two shots...

[ned kelly]

G'Day All,
the BRT suggestion for 10 shots is for SR BR so that usually means 200yds for most BR matches.

No Lynn I dont think it would work

Cheerio Ned

[M12LRPV]

With my current rifle I did 5 shot groups of various powder charges all jambed at 100 then moved out to 200 and checked seating depth with the best one. Then shot some more groups with that seating depth and the best charge +/- 0.3

I repeated it for a number of projectile changes too.

I did that at the SSAA Silverdale because its the only range around that's open all day and has a reloading room meters from the line.

I will not be doing it again as I realised that it was a complete waste of ammunition and barrel life but as a first timer I did learn a few things.

I learnt that the jamb or jump will show what the rifle and projectile combination likes regardless of the charge. So I switched to doing that first with an intermediate load so that the main testing was at the final preferred seating depth.

I found that the group at 100 was usually the same size as the group tested at 200 so short range testing at 100 is an unreliable indicator of long range performance.

The biggest surprise for me though has come from Rod Davies post in this thread because the chronographed velocity of my final load is 2823fps, which is right on one of his nodes

With a rebarreling in the wind I will be doing my initial testing into dirt over a chronograph for velocity followed by a quick ladder test of the same. I don't have a chronograph that I can do both at once with plus one will be at 100m and the other will be at a much longer range.
Then a couple of groups with seating depth variations and the rest I'll leave to the tuner to look after and tune on the line.

That's my plan. It will change a dozen times between now and the end of February

[AlanF]

...FWIW, BRT suggest 10 shot groups shot at the longest distance you can and then ignore the widest 2 shots as flyer's ...

Hmmm... I could simulate that and see how it stacks up. Need to reload for tomorrow, but will have a look at that tomorrow evening.

Alan

Ned,

I've had a look at this, and according to my simulation, it comes in slightly better than 5 shot groups - I found that 54% of the time, the best group will be from the best load (c.f. 48% for 5 shot groups). BUT, doing 10 shot groups and INCLUDING the widest 2 shots, does better again at 59%! When you think about it, it makes sense, because ignoring the widest shots is actually denying the reality that you will get flyers, so you're not using all the available information.

Alan