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Posted: 2/17/2005 4:04:34 PM EDT
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I just finished building an M4 look alike with a 16" using a Del-Ton M4 upper (DPMS barrel and DPMS chromed carrier - but with non-chromed key and bolt). The stock is a Magpul M93A. It works beautifully, except for one thing: Using PMP 223 ammo, when the last round is fired, the bolt carrier locks back, but not with the catch on the bolt face, but on the bolt carier. So it is (just) short cycling. Now when I compare the M4 to my Colt 20" A2, there is significantly more resistance when pulling the charging handle back. This doesn't make much sense to me, since the stroke of the bolt/carrier is going to be the same, and so I would expect the same spring resistance. I do have a spare (CAR) spring, which looks about 1/4" shorter. I will try that this weekend and see if it improves things - just dropping it in its still stiffer than the Colt. I am pretty certain that using XM193 it will work just fine, but this same ammo works fine in the Colt. So - question for the cognicenti: Is it normal for a rifle with a carbine stock to have stiffer pull on the charging handle? Does this sound like the source of the problem? I suppose I could always snip a bit off the spring, but that sounds like a last resort type of thing to me. I don't suppose anyone knows how much pull is normally required to cock an AR15??? |
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Just to finish this thread off: I replaced the spring with the slightly shorter one, but couldn't really tell the difference in resistance by hand. I then removed the bolt/carrier and stripped it, removed all the CLP and coated it with Miltec-1, using a hair dryer as per their instructions to heat the metal. After doing this, the bolt/carrier felt distinctly looser. Took it to the range today, inserted one round of PMP ammo, fired, and the bolt locked back correctly. Tried again with 3 rounds, worked perfectly. Ran through a box 5 rounds at a time - perfect every time. Tried XM193 - no problem at all. It probably would have freed up after a couple of boxes or so of ammo using CLP, but Miltec-1 really does seem to work well as a lubricant - especially if applied as they direct. Anyway - problem fixed. |
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I'll give you a little heads up, Your not going to keep the rifle running with having the upper bearing surfaces of the rifle lubed with CLP running wolf ammo. The ammo burns very dirty, and without the cleaning properties of CLP to keep the fouling loose/from causing binding, it's going to be short stroke city. |
I don't shoot wolf - too dirty  A long time ago I bought 1,000 rounds of PMP, and still have some left - its relatively clean. I just use it as plinking ammo. I think my problem is really just break-in, and that I will be able to use CLP after a while with no problem. Remember, it was short stroking by maybe 1/4" at most, so it doesn't take much loosening up to overcome that - and with full power ammo there would be no problem at all. |
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