Being that the Ruger AR-556 has an un-shrouded BCG, I am hearing horror stories about the firing pin and firing pin retaining clip are getting chewed up. Can anyone confirm this and elaborate on it? I really don't want to buy another BCG, but, if my 556 BCG is going to do this to my firing pin, can anyone suggest a fully shrouded BCG? I don't want to spend a lot of money, just a replacement that is a know brand for not too much money.
Shrouded BCG VS Un-Shrouded BCG
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AlexanderA
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The un-shrouded (beveled) bolt carrier has an interesting history. Around 1970, Colt identified a problem with uncontrolled automatic fire (hammer follow-down) if the disconnector was removed in its then-current AR-15's. (It's unclear whether the ATF complained to them or not, but I'll bet they did.) As a result, Colt took the AR-15 entirely off the market until it could do a redesign of the offending parts. (Incidentally, that hiatus in the availability of the AR-15 gave a market opening to the Armalite AR-180, which filled the void.)
Colt's solution was the beveled ("un-shrouded") bolt carrier, combined with a notched hammer. In this design, if the disconnector was removed, the hammer would snag the firing pin and hopelessly jam the gun. With these changes, the gun was reintroduced to the market.
Some time later, this whole problem was found to not be as significant as first thought, and Colt (and other manufacturers) went back to the original "shrouded" bolt carrier, apparently with ATF's blessing.
It's pretty clear that the shrouded bolt carrier is more desirable, in terms of reliability. Just be sure to have a functional disconnector.
The key thing with an unshrouded (beveled) bolt carrier is to use a firing pin with a small-diameter collar. If you use the standard large-diameter firing pin, the hammer may still snag on it even if everything else is functioning normally. I suspect that that might be the problem with these Ruger guns -- someone is substituting a standard firing pin for the small-diameter one. Or maybe the mistake was made at the factory -- who knows?
Colt's solution was the beveled ("un-shrouded") bolt carrier, combined with a notched hammer. In this design, if the disconnector was removed, the hammer would snag the firing pin and hopelessly jam the gun. With these changes, the gun was reintroduced to the market.
Some time later, this whole problem was found to not be as significant as first thought, and Colt (and other manufacturers) went back to the original "shrouded" bolt carrier, apparently with ATF's blessing.
It's pretty clear that the shrouded bolt carrier is more desirable, in terms of reliability. Just be sure to have a functional disconnector.
The key thing with an unshrouded (beveled) bolt carrier is to use a firing pin with a small-diameter collar. If you use the standard large-diameter firing pin, the hammer may still snag on it even if everything else is functioning normally. I suspect that that might be the problem with these Ruger guns -- someone is substituting a standard firing pin for the small-diameter one. Or maybe the mistake was made at the factory -- who knows?
Well written AlexanderA
The ensuing jam wasn't Hopeless but it would require you to completely dissemble the rifle to clear it and hopefully taught you a lesson that made you put the disconnector back in place.
I don't recommend M16 heavy firing pins be used in semi automatic rifles using full auto full shroud bolt carriers as the ATF still considers the "More than two parts constitutes an attempt at full auto fire capability" as far as I know
The ensuing jam wasn't Hopeless but it would require you to completely dissemble the rifle to clear it and hopefully taught you a lesson that made you put the disconnector back in place.
I don't recommend M16 heavy firing pins be used in semi automatic rifles using full auto full shroud bolt carriers as the ATF still considers the "More than two parts constitutes an attempt at full auto fire capability" as far as I know
AlexanderA
Member
At one time, the ATF published a list of full-auto parts that it considered taboo in semiautomatic rifles: the bolt carrier, hammer, trigger, disconnector, and selector. (It goes without saying that the auto sear was also a no-no.) The large-diameter firing pin was not on this "magic 5" list.
Later, at the behest of Colt, ATF took the full-auto bolt carrier off this list. The thinking was that the full-auto bolt carrier by itself, and with no other FA parts, could not result in automatic fire. Colt apparently had inventories of FA bolt carriers, and did not want to go to the trouble and expense of milling off a portion to bring them to semiauto specs. The letter to Colt (which was made available to the public) did not mention the firing pin.
The additional weight of the large-diameter firing pin, IMO, would not be significant. The main reason to use a small-diameter firing pin would be to avoid possible interference with the hammer if using a beveled (un-shrouded) bolt carrier. Otherwise, you could use whatever firing pin was available.
Later, at the behest of Colt, ATF took the full-auto bolt carrier off this list. The thinking was that the full-auto bolt carrier by itself, and with no other FA parts, could not result in automatic fire. Colt apparently had inventories of FA bolt carriers, and did not want to go to the trouble and expense of milling off a portion to bring them to semiauto specs. The letter to Colt (which was made available to the public) did not mention the firing pin.
The additional weight of the large-diameter firing pin, IMO, would not be significant. The main reason to use a small-diameter firing pin would be to avoid possible interference with the hammer if using a beveled (un-shrouded) bolt carrier. Otherwise, you could use whatever firing pin was available.
briansmithwins
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I have personally seen this in my friend's rifle. He was wondering why he kept breaking firing pin retaining pins and why the firing pin looked chewed on. The problem naturally went away when he replaced the Colt bolt carrier.
BSW
AlexanderA
Member
It's a good idea to replace the "beveled" or "unshrouded" bolt carrier. Failing that, be sure to use a small-diameter firing pin. With the small-diameter pin, it's impossible for the hammer to snag on the pin (as long as the disconnector is in place and functioning).
Quentin
Member
The Ruger SR-556 also has an unshrouded firing pin. Harder to correct since it's a piston AR. Why would Ruger go this route when most AR manufacturers went to shrouded firing pins years ago. I guess their lawyers had to find something to do after writing safety graffiti on barrels!
Deal breaker for me.
Deal breaker for me.
AlexanderA
Member
What's a "shrouded" or "unshrouded" firing pin? How does that relate to the large or small collar diameter?
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