Okay, posted previously about my 605 Clone (16" retro carbine with rifle length gas system). Bought it at a gunshow (I’ve eliminated the vendor and original owners as the sinners here; it was never fired). It came sans BCG, so I put a new LMT one in.
Gun wouldn’t run; fired round was ejected, but the next one wasn’t picked up.
I had a lightly used, vintage Colt BCG and tried that; worked fine.
Put some new gas rings in the LMT carrier group, and now it runs fine as well.
Ideas?
Moon
the short dwell time. sometimes it will cause things to act funny.
but we’d need more info, type of ammo mainly.
try it with some full power nato spec and see how it acts
elia’, I’m sure the short dwell is indeed part of the problem; apparently it was an issue back in the day. Reputedly, Brownells’ replicas have an opened gas port, which was supposed to fix it.
Ammo was NATO stamped '08 Winchester, and I also shot some cheapie imported stuff, after the change of the rings had the LMT carrier group running okay…the oddball stuff worked as well.
I simply like the full sight radius and light weight of the 605-clone (kinda a prehistoric dissipator), whatever the doubts about a FA. And it looks neat.
Moon
They are neat. Little things like maybe a reduced power hammer spring would help. Anything that makes it cycle easier should also help.
My NoDak M16A1 lower already has a Geissele SSA in it (hey, it looksperiod!). The function has improved with the new rings, which do seem to have much reduced resistance.
I thot’ I had a half-circle semi bolt carrier tucked away someplace, but haven’t been able to find it. It seems to me that a lower mass carrier was used back in the day.
Moon
Been having a conversation with the good folks at LMT. They are suspicious of the gas rings, as am I.
A too-tight fit combined with a reduced dwell time for gas?
Moon
That’s not a solution to his problem. That is a band-aid that could lead to light primer strikes in the future.
He has a rifle length gas 16" Gu . The only real fix is a pressure catcher. Suppressor or some sort of booster. Light primer strikes vs ftf gotta weigh your options
Except, see below OP, it runs fine without those things.
Moon, are you still having problems, or does it run?
Wrong on all counts. You don’t fix an out of spec gun by adding more out of spec parts. You find the parts that are out of spec and replace them with parts that are in spec. Period, end of sentence. Anything less is doing things half assed, and half assed solutions could get someone killed if the firearm in question were needed in a life or death situation.
Okay, some things to add. Did a final zero and ran another 20 rounds; 100% function with the LMT carrier group and the new set of rings. Bolt didn’t lock open on the last round.
Thinking about it on the way home; I’m running the rifle buffer that I’d been using with the 20" Colt.
Would it make sense to go to a carbine buffer? I have an ummarked carbine buffer in my spares box; presume that is the lightest version?
Moon
Well, a fine lot of help you fellers are! 
I put the carbine buffer into the 16" carbine, and stopped briefly for a test hop at my local range. I had three mags with two rounds loaded; full function and the bolt locked back after the last round in each mag.
I’ll declare the problem solved.
Moon
To be clear, you are using a carbine buffer in a carbine receiver extension, correct? I think thats what you meant. Reading through, it sounds as though you just threw a carbine buffer in the rifle.
No misperception there, 1168. I put the carbine buffer right into the M16A1-clone lower. As noted, in a brief test hop, ran just fine. Is there an issue there?
Thanks,
Moon
Yes, there’s an issue. a carbine buffer won’t bottom out in a rifle-length receiver extension. You did notice the difference in length between the carbine buffer and the rifle buffer, I hope?
Any visible damage or marks to the lower receiver (at the top under the charging handle) from the rear of the carrier key hitting it?
A better idea to try would be emptying the rifle buffer of its weights, or replacing them with aluminum.
Edit: you might be able to find the correct diameter aluminum rod at Lowes or Home Depot
Military’, I’ll have a look; I was more concerned about buffer weight than buffer length.
1168, don’t really want to bugger up my rifle buffer; it’s a standard rifle buffer and it works fine in the 20" M16A1 upper that usually lives on. How about a source for another rifle buffer, perhaps lighter than normal.
Thanks guys,
Moon
I’ve decided to quit trying to fix something that ain’t broke. Test hopped things again today with the vintage Colt BCG, particularly to see if the bolt would lock open on the last round. It did, so I’ll simply run the Colt group when using the 16", and move it to the 20" when needed.
The LMT BCG will resume its place in storage as a spare…it works in everything else.
Thanks,
Moon