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Posted: 11/17/2011 12:53:40 PM EDT
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I'm currently hand loading for my DPMS AP4 308.
After working up several different loads I made a batch of Federal brass, CCI primers, 41.5 IMR 3031 with 165 grain Nosler Accubond. This seemed to be the load I was getting the best accuracy from out of that rifle. While firing some of the new batch, I had five cartridges that did not feed properly into the chamber. The bolt appeared to be all the way forward but the cartridge was not all the way into the chamber. I had to "mortar" the cartridges out of the rifle. The rifle is not short stroking and I tested different mags with the same result. What I did find, was that cartridges that were not feeding properly appeared to have a slightly larger extractor groove. I assume the bolt is not grasping the larger groove properly, thus causing the cartridge to get hung up and not chamber correctly? Is this common to have different sized extractor grooves? Do I just need to check that each time and only use the smaller grooved brass? The brass I was using was suppose to be once fired federal match. |
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When you resize the "once fired" federal match brass, make sure it is driven all the way up in the sizer die and the ram "cams over". If you do not have a case gage, break down the AR and use the chamber for a gage. The case, after inserted all the way by finger, should fall back out when the barrel is tilted up.
Brass with enlarged extractor groove diameters should be inspected closely to determine if other case head diameters (rim, ref. diameter at the 0.2 datum, etc.) have become enlarged also. I have not experienced the variable extractor groove diameter with 1X LC and Win .308 brass. |
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Quoted: I'm currently hand loading for my DPMS AP4 308. After working up several different loads I made a batch of Federal brass, CCI primers, 41.5 IMR 3031 with 165 grain Nosler Accubond. This seemed to be the load I was getting the best accuracy from out of that rifle. While firing some of the new batch, I had five cartridges that did not feed properly into the chamber. The bolt appeared to be all the way forward but the cartridge was not all the way into the chamber. I had to "mortar" the cartridges out of the rifle. The rifle is not short stroking and I tested different mags with the same result. What I did find, was that cartridges that were not feeding properly appeared to have a slightly larger extractor groove. I assume the bolt is not grasping the larger groove properly, thus causing the cartridge to get hung up and not chamber correctly? Is this common to have different sized extractor grooves? Do I just need to check that each time and only use the smaller grooved brass? The brass I was using was suppose to be once fired federal match. Federal is soft brass. Your 'larger grove' is very possibly a sign that the brass has been fired repeatably, the head is stretching, and you're more likely to have a case failure. I'd be very leery of that brass, because it is so soft it stretches easily and the primer pockets open up. If you decide to continue to use it, be sure to have a broken case extractor handy because you'll likely need it. |
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Quoted:
Quoted:
I'm currently hand loading for my DPMS AP4 308. After working up several different loads I made a batch of Federal brass, CCI primers, 41.5 IMR 3031 with 165 grain Nosler Accubond. This seemed to be the load I was getting the best accuracy from out of that rifle. While firing some of the new batch, I had five cartridges that did not feed properly into the chamber. The bolt appeared to be all the way forward but the cartridge was not all the way into the chamber. I had to "mortar" the cartridges out of the rifle. The rifle is not short stroking and I tested different mags with the same result. What I did find, was that cartridges that were not feeding properly appeared to have a slightly larger extractor groove. I assume the bolt is not grasping the larger groove properly, thus causing the cartridge to get hung up and not chamber correctly? Is this common to have different sized extractor grooves? Do I just need to check that each time and only use the smaller grooved brass? The brass I was using was suppose to be once fired federal match. Federal is soft brass. Your 'larger grove' is very possibly a sign that the brass has been fired repeatably, the head is stretching, and you're more likely to have a case failure. I'd be very leery of that brass, because it is so soft it stretches easily and the primer pockets open up. If you decide to continue to use it, be sure to have a broken case extractor handy because you'll likely need it. I think I'll be inspecting the cases a little closer and staying clear of Federal brass. I've read that their brass was softer. |
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