Can someone help me analyse these groups?

[Winston]

Hi Folks,

Playing with a new 6x47 barrel today, doing the first lot of load development. I started with a quickload prediction of a node and worked 1.2gr either side of it in 0.3gr increments. Below are the best 4 groups (all 4 shot) from this afternoon. It was 100 yards, slightly gusty coming from my 5 o'clock.

I can't be sure that the high shot on 39.0 wasn't me, but I would like to think I'm a better shot than that. 38.4 is a larger group, but has less vertical than 38.7, both measuring around 0.25-0.3".

Can any of you gurus give me some pointers on what to try next? I understand group shape can tell you a thing or two, but I have no knowledge of that, so am hoping someone can give me a gentle nudge in the right direction. I'm guessing that there may be a node centered somewhere around 38.5?

Cheerio
Alex

[macguru]

there is a node in the mid to high 39s, between 39.5 and 40g 2209. i agree your 38.4 looks the best but i have never tried under 39g 2209. I generally load test at 300m and get groups around 1" or a bit better for 5 shots when its near a node. i have 5-10 thou jump and interestingly 105 hybrids and 108 boattails shoot to exactly the same point of impact.

[plumbs7]

38.7 turns me on . But between 38.4-38.7. But be careful as Dave Mac will tell you it's only an indication . But if it were me I would go for 38.7 if the sd was in single figures and go from there.
Regards Graham.

[macguru]

have you access to a chrono ?

[Winston]

G'day Andrew,

Yes - I have a full power labradar that was snuck out of the states. Didn't chrono yesterday since I was in a bit of a rush.

What COAL are you running to get the node in the mid-high 39s? I have a fairly short throat, (loading at 2.660"), so perhaps I'm on the same node still? My barrel is a short 25", I'm guessing that has some ramifications, too
Cheerio
Alex

[macguru]

I have a similar throat, best load I found was 40gr 2209 , gave 1/2" elev at 300m but i am pretty sure its right on or close to the max load and should give over 3200 from a 30" tube. but i have not checked the speed i am just going off the ballistics . There are no pressure signs but i would not go any higher. Another 6x47 user i know well got to 40.3 but was compensating for a shorter tube that has been rechambered a couple of times. A node around 38gr would be better for everyday use but then you probably just have a big dasher , not that there is anything wrong with dashers ! (or br-x's or brackleys etc)

[Winston]

Thank you to everyone that has offered advice so far, both here and via PM. I went out on the weekend and had a play to get a better sample size. Conditions were pretty bad to be doing load development with a lityle crosswind, but I don't get a lot of time to test, so I went ahead, hoping to see a trend. From what's below, I decided on touching the lands at 38.3gr. I shot a pair of 59s with that load at 800 yesterday, which got me off rifle, but I'm not convinced it's the best.

Any more advice now that there's a bigger sample size, folks?

[bartman007]

Winston, why have you discounted 20 thou jump at 38.5 grains?

If as you said there was wind at play, then this flat shoot would seem ideal to me.

[Winston]

Winston, why have you discounted 20 thou jump at 38.5 grains?

If as you said there was wind at play, then this flat shoot would seem ideal to me.

Only because there seemed to be no trend in 38.5s (and I still haven't mastered what I'm doing here with load development!) - couldn't be sure if it was a fluked group or not (though it ties nicely with my initial development, now that I look at it)

Youre right that it's easily the nicest for vertical. Be worth shooting a stage with, you reckon?

Alex

[bartman007]

Yep, I'd shoot 7 shot groups now to see how it performs.

Depending on the temperature of the day you shot these, I'd try the following:

20 thou jam for all.
38.4gn
38.6gn
38.8gn

Make sure you use a clean barrel, fire 2 foulers (dirties barrel, and warms it up) then do your 3 groups one after the other.

I picked 7 shots per string to get a total 23 shots fired for the test. I feel that should aid in taking excess fouling out of the group dynamics. Otherwise clean between groups and do 2 foulers each time.

My 2 cents worth.