Would like to understand this group !!

[Ganderite]

Testing at 100 is a waste of time and money. The minimum is 300 and i prefer 500 if it is not too windy. For a whole bunch of reasosn, 100 yards mean nothing if it is long rnage you are trying to prepare for.

The Chrony is probably quite accurate.

I choose a bushing 3 thou smaller than the loaded neck.

5 shot groups are not nearly as useful as 10 shot groups at predicting match results.

Neck tension is a huge variable - that is why I use the 3 thou under bushing.

 

[CyaN1de]

0.071 am i missing something here ? isn't that 71thou or 1.82mm, i'm new to the moa thing i thought 1moa at 100yds was approx 1 inch please educate me or point out the obvious i missed!!!

Edge to edge measurment of the group minus bullet diameter gives a good approximation of group size so a 1" edge to edge group = 1.00 - .308 = .692" which is close enough to .692MOA. If you shot that at 300 you would divide the result by 3 (400 divide by 4 etc....)

I think the yardage multiplier is right if not, someone will chime in.

 

[Charles]

Many thanks to all of you guys !!!

I have now alot off things and variable to test.
I never realized the importance of neck tension and this is something i will check in my next reloading session.

I was very concerned with the run-out but not the tension.
At least i know that all my round do not exceed 0.003 of run-out, all checked with a sinclair gauge.

First, i will shoot my load at 200 yards and see if the groups want to open and if i can notice a average.

Mystic you say that after triming i have to neck turn, for what ?


Ok guys i will keep you informed with my results
Thanks again

 

[Mystic Precision]

Neck turning is to machine off a thin layer of excess material in the necks so that the neck thickness is even and concentric. Also, ensures the bushing or collet die works effectively based on the orig desired neck thickness..

As brass flows, it flows in irregular patterns so the necks will change in thickness. If you were using a certain bushing die, the amount of sizing/neck tension will change as the neck thickness and ductility changes.

Ideally, we want to keep all cases as identical as possible so some fussing to maintain even and consistent neck thickness, with consistent ductility will lead to best accuracy.

Jerry

 

[J.S.G]

Hey Charles, you may have your numbers wrong. A .071 would look like one bullet hole. A .171 would look similar to your group, which would still be outstanding. Great shooting there!

 

[Charles]

Thanks again Mystic for the infos. I have a K&M neck turner who sit in the dust and i think this is time to try this technic.

However, i have not a match chamber and i wonder if the neck turning is justified in this case, there will be a big clearence ...

J.S.G Yeah you have right. The problem was i have measured the hole and substract .308. Now i know that i have to measured not the hole but the mark of the bullets and substrack .308.

 

[Oscar Makonka]

Hey Charles, you may have your numbers wrong. A .071 would look like one bullet hole. A .171 would look similar to your group, which would still be outstanding. Great shooting there!

If you look at the group and notice the two outside shots you can see that if the shots in between them were not there the two outside shots would not even touch so the group is minimum .308" plus add whatever space there would exist between the outside shots. group looks like about a half inch to me.

 

[Mystic Precision]

Charles, in your case, the goal is not to remove alot of material. Just adjust the cutter so it cuts maybe 70% of the circumferances of most cases. You are just removing the high spots.

Turn a few necks and you will see what I mean.

If the neck thickness is more then 14thou, then removing some material is not a bad idea. I prefer necks around 12 thou to 10 thou but that depends on the chamber as well.

The K&M is a nice tool and will serve you well.

Neck turning is a small thing to improve your consistency but all these little things can lead to better performance.

Jerry