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Posted: 12/4/2004 10:56:38 PM EDT
I'm finally going to convert my A2 stock to a collapsible using the VLTOR Carbine Modstock Basic Pre-Ban Combo Kit. What if anything do I need to be aware of as far as functioning issues and/ or reliability issues with the shorter stock?? Buffer spring length, buffer weight, extractor spring tension (doesn't the M4 use a different extractor bufffer?), buffer tube length etc.Any common problems with the shorter stock that I need to be aware of, I.e., FTF, FTE etc.? Thanks in advance for your replies. Tack |
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Down and dirty is the carbine stock uses a shorter carbine buffer and a shorter carbine recoil spring that has thicker gauge wire. Using the standard A-2 (or A-1 since they are one and the same) length buffer would limit out the bolts rearward stroke before is could lock on the bolt hold open device. Clipping the standard A-2 11.5” recoil spring down to the 10.75” length of the needed carbine spring to prevent max compressed binding would just lead to the recoil spring being too weak since a lighter gauge wire is used to form the standard spring. When you go for the carbine install, check the new carbine buffer bumper roll pin to confirm that the pin is not hanging out the sides of the buffer and can catch/ bind the spring on the stroke. Also, check the end of coils cuts on the new spring to confirm that it does not have burs that will scrap down the buffer/receiver extension tube insides. Both of these conditions can be simply resolved with the use of a sharp file. Now the last thing to touch on is the ability of the buffer to contain/control the cycling stroke. In regards to buffers, Colt has offered three types of carbine buffers over its history. The first is the standard weight carbine buffer, the second being the H buffer, and the last is the 9mm sub gun buffer. In regards to carbine buffer weights, there listed above, lightest to heaviest. On standard 16" barrel, there is enough barrel after the gas port to allow the gas port to be left relativity small. When the barrel is shortened to the 14.5" length, then the barrel gas port needs to opened up a bit, and the H buffer helps control the cycling stroke better*. Now in regards to the 9mm Sub buffer, this heaviest of the colt carbine buffers is use to help retard the cycle of blow back action that do not use any locking bolt. Simple put, make sure that you install the correct length standard weight carbine buffer/carbine length spring, and check the new parts to make sure that any burs are remove to allow the part to move freely in there respective places. *The reason that I mention the buffers is normally the standard colt carbine buffer is all that is needed. Where the problem arises is regards to barrel/MG’s that the barrel gas port has been drilled larger than normal (16" barrel length). Here, the bolt tends to open too fast, and can lead to bolt rebound/bounce problems. Now regarding this, the only thing that one of the heaver buffers (H type) would achieve is to strengthen the dead blow effect of the buffer when it hit the back of the receiver extension. In regards to slowing the bolt release/unlock, the problem with the standard buffer, or the H buffer, is that the weights free move in side the buffer cavity. Because of this, the only time the buffer extra mass would delay bolt unlock would be if the rifle is aimed downward to allow the tungsten weights to slide forward within the buffer it's self. Simple put, if you need to add mass to the buffer to slow the bolt from unlocking, then you are forced to options that pin/hold the buffer weights to the bolt side of the device, or add weight to the carrier it's self. The 9mm SMG, the MGI buffer, and the Tubbs carrier insert device all do this, and would be the direction to go is in fact that the gas port was over sized from the start, and you are having problems with the extraction of the case from the chamber. |
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