inconsistant results

[trophyhusband]

I'm developing a load for my AR 15 that seems to be very picky about ammo. All factory .223 and 5.56 ammo I've shot through it has given me 3-4 MOA. After dealing with a short stroking issue http://www.longrangehunting.com/forums/f111/issue-short-stroking-126805/ I've made two trips out to shoot. Both times I had one load shoot under 1.5 MOA with all others being 3+ MOA. The problem is that it wasn't the same load. What gave me good results on trip one gave me bad results on trip two. On both trips the gun was the same, the conditions were the same, loads were the same. The only thing I can think of is the crimp. I have a Lee factory crimp die. While I can do my best to set it the same each time I really have no way of telling if it really is set the same.

I have an idea of how to approach this but I want to know what you guys think. I'm thinking that I load up all of them using the last load that gave me a good result. I will then set the crimp ever so slight and crimp 5-10 round and test. If I don't get a good group, I increase the crimp just a little and test again and so on. Once I get a good group I can then crimp all the rest of my bullets. Will this work or would I be wasting my time here?

 

[old_heli_logger]

When I see groups like that, I always suspect a loose or bad scope or too heavy a bullet for the twist.
Good luck!

 

[varmintH8R]

I would tend to agree. 1.5MOA seems like a lot to be chasing with a crimp.

How many groups did you shoot with each good load?

 

[trophyhusband]

I too suspected something loose with the scope or mounts. I've now used 4 different scopes and mounts. I even sent it back. They shot a 1.75 inch group at 50 yards and returned it to me.

I've used many different brands of 55 and 62 grain factory ammo and my hand loads are 60 grain. It's 1/9 twist barrel.

With my current configuration I've made two trips to the range. Each time I had 10 rounds each of the following: 21.8, 22.0, 22.2, and 22.4 grains of powder. On the first trip 22.2 gave me the best results and on the second trip 21.8 gave me the best results.

 

[westcliffe01]

Who built the rifle ? What trigger is in it? Do you know whether the barrel nut is really tight ? Is there lots of slop between upper and lower ? Who made the barrel ?

Sorry, just knowing that it is an AR15 is meaningless. That covers the entire spectrum from as bad as an AK to near custom quality.

PS: I sincerely hope you are using military grade hard primers in those reloads ? The AR has a floating firing pin, and using your bolt gun primers can cause you to have a very bad day with slamfires or even full auto burst.

 

[ShootnMathews]

I have limited AR experience but I did try to handload for mine with poor results. All factory fmj rounds shoot 4MOA or less out of my AR which is a Rem R15 w/22" barrel. I use mine for mostly coyote hunting so those are the type rounds I really tested. The two best were Hornaday superformance = 1 MOA and Federal American Eagle AR223 tipped varmint = 1/2 MOA. So the AR223 is what I use all the time now. It's not that expensive but my R15 loves it. Also I gave a handful to my friend who was handloading for his Stevens 223 yote gun with the same results, groups under 1/2 Moa. So if you haven't tried those you might want to give them a go. Sound $14 per 20 here now. $10.50 before he price jump.

I used it two weeks ago with the AR223 ammo to put a one shot kill on a possum at 366 yards. That's AR15 accurate enough for me.

If you think it is something to do with the crimp then buy a stop nut that locks in place for your crimp die. Rcbs and hornaday make them for individual sale I believe.
Jared

 

[firstcoueswas80]

Wow 1.75" @ 50 yards is with in spec? PLEASE post exact make and model as I will make sure to NEVER buy from them!

 

[trophyhusband]

Who built the rifle ? What trigger is in it? Do you know whether the barrel nut is really tight ? Is there lots of slop between upper and lower ? Who made the barrel ?

Sorry, just knowing that it is an AR15 is meaningless. That covers the entire spectrum from as bad as an AK to near custom quality.

PS: I sincerely hope you are using military grade hard primers in those reloads ? The AR has a floating firing pin, and using your bolt gun primers can cause you to have a very bad day with slamfires or even full auto burst.

Its a Bushmaster 16" barrel carbine with collapsable stock. It has the factory trigger in it. I haven't checked the barrel nut but I will. There isn't any slop between upper and lower.

 

[mtwarych]

May I suggest changing your buffer to an H2 or an H3? The heavier buffer will slow the unlocking of the bolt just a bit and should give you a more consistant unlock time and therefore give you more consistant shot to shot. It worked for me. I use an H3 with the same rifle set up as you have. Also, don't crimp the next ladder work ups and don't worry about milspec primers, just make sure to use a primer pocket uniformer so your primers aren't flush but below flush and the slam fire possibilities will go away. Also, what powder/primer combo are you using now?