Having some issues and could use some help.

[wisconsinteacher]

I have an 16" AA barrel that I put on a upper that I have built. I have been shooting 123 Amax's with XBR 8082. My brass is fire formed IMI 7.62 brass that I shot out of this rifle. I am also using CCI primers.

My goal is to shoot .75" groups consistantly. Here is some of the data I have been able to get from my shooting.

24.5gr=.221" The next time out = .996"
26.0gr=.386" I stuck with the 26.0gr to keep velocity up. The next 6 times out with the same charge I got .809, .661, .722, .429, .991, and today 1.005" I don't understand why the groups are growing with the exception of a few groups.

Today I shot
26.0=1.005
26.1=1.735
26.2=1.658

I know the rifle can shoot better but I am stumped as to what I need to do????

Any thoughts, tips, or ideas.

I am using a Vortex Crossfire 6-24x50. I am starting to wonder if something is up with it and how it is holding zero while I am shooting.

[seatleroadwr]

Try another bullet. Amaxs don't always shoot well in every rifle. My rifle does not like them but it loves Nosler 123 grain bullets and Sierra 107s

[wisconsinteacher]

I can do that because I ony have 1 Amax left. Does my grain weight sound like it in the ball park for IMI 7.62 brass?

[LR1955]

I have an 16" AA barrel that I put on a upper that I have built. I have been shooting 123 Amax's with XBR 8082. My brass is fire formed IMI 7.62 brass that I shot out of this rifle. I am also using CCI primers.

My goal is to shoot .75" groups consistantly. Here is some of the data I have been able to get from my shooting.

24.5gr=.221" The next time out = .996"
26.0gr=.386" I stuck with the 26.0gr to keep velocity up. The next 6 times out with the same charge I got .809, .661, .722, .429, .991, and today 1.005" I don't understand why the groups are growing with the exception of a few groups.

Today I shot
26.0=1.005
26.1=1.735
26.2=1.658

I know the rifle can shoot better but I am stumped as to what I need to do????

Any thoughts, tips, or ideas.

I am using a Vortex Crossfire 6-24x50. I am starting to wonder if something is up with it and how it is holding zero while I am shooting.

WT:

Assuming you shot these at 100 yards and measured them by hand, your groups probably have a mean of .75 inches or less.

The extreme spread is .2 inches. That is less than one bullet diameter and the variances are probably more due to your skill in taking measurements that small than anything else.

Bottom line is that you don't know the mean and you don't really know if they are getting bigger or smaller.

If you want to find out, shoot them at 200 yards.

LR1955

[wisconsinteacher]

LR1955, I am shooting them at 100 yards and use a digital caliper to measure from center to center of the 2 shots in the group that are the greatest distance apart. I understand what you mean by shooting them at 200 yards but am a little confused about no knowing what the mean is of the group. Again, thank for the help and please keep the info coming.

[A.D.D. AR]

WI teacher- I use hornady and AA brass and CCi 450 primers, (AA chamber) my most accurate load is right at 28.2 gr XBR- I can't recall offhand how much to reduce the charge when using formed 7.62 brass, but i would try going up .2 grains at a time
to see if that helps- in my experience with XBR it seems to be "picky" about the "sweet spot" (shoots a little erratic, then you hit the accuracy node, then if you go above that, accuracy falls off fast) Maybe someone with experience using 7.62 brass
will chime in, but I would try a ladder test & go higher .2 grains at a time.
-mike

[rasp65]

WT My WW ff'd cases have 2 grains less water capacity than Lapua.

[jurassic]

LR1955, I am shooting them at 100 yards and use a digital caliper to measure from center to center of the 2 shots in the group that are the greatest distance apart. I understand what you mean by shooting them at 200 yards but am a little confused about no knowing what the mean is of the group. Again, thank for the help and please keep the info coming.

http://en.wikipedia.org/wiki/Mean

[A.D.D. AR]

thanks rasp for the info! - WI teacher- ok, probably not wise to go above 26.2gr in the ff'd 7.62 cases. Look at other areas: what is your C.O.L. ? do you have an oal gauge? Are you sure your powder measure is right on? what primer?
Is the neck tension different between batches of brass? Seems like that load should work great from an AA chamber if the col is right. OR- maybe the barrel nut backed off, or its a scope/ mount issue? Just some ideas.
-mike