A5BLASTER Wrote:Having worked with this bullet a good bit.

I would do a 10 shot set at 28.8, 28.9 and 29 grains and see what the sd and es numbers look like.

Also 30.6, 30.7 and 30.8 as well.

You had a pressure spike at 31 grains.

Whatever 10 shot group gives you the best sd and es numbers would be the one I go with then I would play with seating depth to shrink the group up if need be.

Klem Wrote:Ronin,

I would be cautious about using your velocity testing to infer anything more than what velocity you get for what amount of powder (for a particular bullet and cartridge length). I think there is a false belief that velocity variations across a range translate into accuracy on the target. It is a clumsy correlation at best and given shooting is a system of averages the fewer bullets you shoot the less meaningful and valid your findings are.

Here are your results graphed.
[ATTACH=CONFIG]16028[/ATTACH]

I have drawn a straight line through the wobbly results because again, it's a game of averages and at this stage you have fired only one round at each of those powder increments. If you were to repeat this test and the second wobbly line matched exactly the first; including sharp rises and plateaus in exactly the same spots then I would say you are on to something. Otherwise, you can infer the wobbles could also be indicators of vagaries in neck tension, brass volume, the unique way each powder column ignited, differences in primer function, and the inbuilt error in your Magnetospeed.Sometimes we also make errors when transcribing data...just saying.

Towards the end the velocity starts to climb above the straight line. This could be due to the powder starting to be compressed, although I do not have this bullet on Quickload to verify.

My thoughts are is that you pick a safe/max upper limit and go 5% low and shoot groups of 4 or 5 at the target in increasing increments of 1%. Precision on the target is the acid test, not velocity. Groups of meaningful numbers like 4 or 5 takes into account the statistical nature of shooting.

So, shoot one or two groups of four rounds with the following powders loads:
31.6
31.3
31.0
30.7
30.4
30.1
It's the tightest average group size you want at the highest velocity, in the safe range.

You won't see meaningful variations in velocity with powder increments less than 1%. 1% is 0.3 grains in your case.

Unfortunately with an AR, because it is so minimalistic (fragile) relative to other actions using typical overpressure signs as benchmarks is often too late. That swipe mark on the base is probably already three increments too hot.