Posted: 8/23/2004 4:33:22 PM EDT
I reload for the AR to get max accuracy.
-Resize, Decap, and seat.
RCBS Rock Chucker
Misc headstamp brass
Cases are all trimmed to size
When I was at the range, I loaded the mag and was shooting fine all day long. I was getting very good accuracy (1.5" to 2" from a Bushy commando and 20" HBAR). But when the ceasefire was called, I had a very tight seated round in the chamber...oh, it would eventually come out...but the handloaded rounds were in the chamber pretty tight and took some effort on the CH to get them out.
Any suggestions what might be causing this, and how I might solve this problem?
It doesn't happen with factory loads.
It doesn't really cause that much problem...it just bugs me.
It could be that you have the sizer die set too far off the case holder during sizing that you are not setting the shoulder back far enough, to crimping the bullets too much and flaring/mushrooming the shoulder.
Since it sounds like you are loading from the mag, then I can't see that you are running the bullets to a longer OAL that is allowing the bullet to engage the lands on loading. But, if you have a short-throated Match barrel set up for longer ogive bullets, this may be happening.
If nothing else, get a gauge to do a random test on a few rounds as you reload. The gauge is nothing more than a mock chamber to give you idea if the ammo is being sized, and crimped correctly.
Judging from your list of equipment I would bet on the brass. Once a case has been fired more than a couple of times it begins to get softer and when that happens along with the added heat of sitting in the chamber it will swell against the walls tighter than factory new rounds that are not as soft. Of course you won't have the problem in bolt guns or firing slowly in semi because there is not the amount of heat. This is just what I have experienced and i have reloaded thousands of rounds and ran them in bolt actions,semi's, full and single shot break opens and only had the problem when heat was involved.
Brass is annealed from the start. This allows the necks to be formed with collapsing the case wall. Over the life of the brass, the side walls will become thinner from the multitudes of fire forming stretch, and at some given point, the case will split (normally at either the mouth, or at the web from being set back too many times). Now when referring to brass, the more that it is shot, cleaned, and resized, it actual becomes more brittle (solvents play a big role).
The fact that we are talking about a case that has only been sized and not fired yet, in order for the brass metal to even begin to flow/stretch from contact heat, you would have a barrel/ heat on the verge of cooking off the round.
As I posted above, most likely his problem is that the brass being either sized or crimped wrongly causing the problem. Now granted that he may have fouled the chamber to the point that the cases may have been sticking (lack of lube), but my guess since he was shooting for groups, he never allowed the either the chamber, or the barrel to foul to this point.
Also, when considering brass, unless the cases have been fired threw a M-249 with a way worn out chamber that causes the brass to only last a few reloading, the primer pocket is the first to go. Since the question did not come up regarding either bright rings at the base/web, splitting necks, nor blown primers, this leads to me believe that his brass is still in it's useful life, and should still be good for several more reloadings before it needs to be trashed.
Bottom line is that some brass is better than others, and the deciding factor is the softness/ integrity of the brass from the start. The factor regarding this is determined not by the case sidewalls, but the rim it's self. If the brass is not up to par, then on the first firing, the extractor is going to tear the hell out of the rim. Granted that the this may be due to the case over expanding (loosing it's elasticity during normal working pressures), resulting in it plasma forming to the side chamber walls, leading to the rim torn extraction problem, but this problem shows it self in the first firing of the brass. To sum it up, his brass could have been defective/worn, which would cause an after ignition problem, but not when the round is only setting in the chamber waiting to be fired.
Note: When firing for groups, you don’t even begin to get the barrel to any considerable amount of heat the can either cause excessive throat erosion, nor to the extreme of ammo cook off concerns. Long before these problems, the barrel is going to start to over whip, and destroy the relationship of the barrel harmonics and the load tuned to correspond to it.
P.S. Feel free to respond. Often the best advice given here is when we as a group take point/counter point stands, and go well beyond the initial discussion, to expand the subject to the multitudes of aspects of not only the rifle, but the ammo that can lead to the original problem.
If you are already setting your sizer die hard against the shell holder, you probably will need to try a small base sizing die that will return the brass a little closer to the unfired dimensions.
If you are neck sizing, or otherwise not pushing the shoulder back as far as possible, you should consider trying to push it back a little farther. I size my cases for 5.56 semi-autos as far as I can using a SB sizer die.
I turn my sizer die down to the shell holder, then back it off a quarter turn.
That may be the cause of the shell not fully sizing the shoulder. I'll try to turn the sizer all the way down. I'll let you guys know what comes of this after i make a few new rds and field test.
Make sure to check the gap with a case in the sizer under pressure.
When full sizing, I set the die to just kiss the holder under sizing pressure, which accounts for any slop in the press pins.
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