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Posted: 5/13/2002 7:19:48 PM EST
I have before me two different bolt-carriers.

#1. This one came with my DPMS Panther Bull Deluxe. The carrier nearly completely encloses the firing pin as I thought was standard.

#2. This carrier came with a BM M4 upper recently. It appears different in that the bottom of the carrier exposes the firing-pin right up to where it seats into the bolt. Compared to the DPMS, the BM has less 'meat', having a larger cut-out, and ramping up to the bolt.

If this makes any sense to the reader, I was wondering....

Why or what's the difference?
Link Posted: 5/13/2002 9:21:20 PM EST
From an engineering standpoint the lighter bolt in the M4 would be because of the shorter time for gas pressure to bang the bolt back. A lighter bolt requires less gas to operate.
Link Posted: 5/14/2002 4:17:05 AM EST

""#1. This one came with my DPMS Panther Bull Deluxe. The carrier nearly completely encloses the firing pin as I thought was standard.""

this one sounds to me lyke it might be for a select fire weapon.., burst/auto fire ???????
Link Posted: 5/14/2002 6:09:34 AM EST
There are three different types of semi-auto bolt carrier.  Go to biggerhammer.net to see the difference between the standard semi-auto and the select-fire bolt carrier.

#1)  The standard AR-15 bolt carrier.  This is the "mil-spec" carrier used by Bushmaster and most other manufacturers.  The back end of the carrier has a small area that is circular.  There is a ramp or relief cut on the undersurface leading to the firing pin.  Found in early Colts and most others.

#2)  Colt HBAR bolt carrier.  The back of the carrier is a semi-circle, no complete circle.  No firing pin relief cut.  I don't know why Colt did this?  I guess it made the gun less "evil" like the sear block & all the other Colt BS.

#3)  Colt Sporter bolt carrier.  Found in all new Colts.  The back of the carrier is semi-circular.  There is a firing pin relief cut.  Again, a abberation unique to Colt.

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