AR Sponsor
Posted: 7/31/2013 2:19:34 PM EDT
|
Hey all, I just put together a new AR15 and I am having issues with fast cycling. Let me give you details of what I have:
New Frontier LM-15 lower Palmetto State Armory Premium Classic Lower Build Kit PSA 16" Mid-length Premium Stripped Upper - without BCG or charging handle Ultimate Arms Gear Aluminum AR-15 M4 M16 .223 5.56 Rifle Tactical Charging Handle Assembly With Ambidextrous Extended Latch and.... I got an M16 full auto BCG from a group buy on my local gun board, and it seemed like it was good quality, but I can't find a brand marking anywhere on it. I did upgrade the extractor with the BravoCompany extractor. I looked online for the fast cycling issue and everything pointed to needing a heavier buffer. I got a Spikes ST-T2 for it. The original buffer was 2.9 oz on my scale, the new one was 4.2. Put it in, and it seems to cycle even faster. With original buffer, the cartridge would hang up in the bcg, with the new buffer, it just scores across the top of the cartridge (all the way across). I have tried it with multiple mags, and different types of ammo (copper, steel, 2.23 and 5.56). After all this, I threw in my friends AR15 DTI BCG and it worked fine. GRRR, so does this mean I just have a bad BCG? Has anyone every heard of fast cycling being caused by the BCG? Thanks |
|
It sounds to me like it is an under gassed problem, not over gassed. Do the one shot with an empty mag in the rifle test. If the bolt does not lock back you are under gassed, not over gassed. The heavier buffer slowed your bolt carrier down and now it is not coming back far enough to pick up the round, just sliding back and forth over top of it. Before it was picking up the round but just barely and did not have enough travel to get a running start at the chamber, then hanging up. That is how I am reading it anyway.
Check your gas rings on your bolt, and check your gas key on the bolt carrier. If it is leaking gas or your have broken rings then that would explain why the other BCG worked and the one you have does not. My guess is the gas key on the BCG is leaking and you are not getting a good seal. |
| The beauty of having a private range at my house, I went out and fired and you are dead on. (Both of you). My bolt DOES NOT lock back in a one round shoot. What do I have to do to get the BCG to seal? I purchased this thing complete and never messed with the gas key on it. |
| Well, they were. I completely disassembled the BCG late last night, and then cleaned the two surfaces that contact when the key is installed. I am going to look around for the exact type of loctite or other brand that gunsmiths use, as I have the standard red automotive loctite. Once I get that I will put it all around the 3 holes (2 for securing and the one for gas) and then reinstall and torque down the key. I am pretty frustrated, everything was locked down super tight, and seemed to be assembled just right, so not sure why there is a gas problem. The rings also look fine, my only question is are they supposed to be bigger and slightly loose feeling when they are installed? |
|
Don't use Loctite as a sealant. IMO, there NEVER should be red loctite in a BCG... because if you break/crack a fastener, it only makes the removal that greater of an ass ache. It's the stake's job to hold the fasteners.
I'd lap the key and the carrier with compound, Get the correct RTV sealant, torque, and stake. Shoot... I might even consider the BCM carrier key kit if this BCG isn't a known quality unit. |
I was thinking of either that or the Roller Cam Pin Upgrade Kit, since it is now all in pieces parts.  It just stinks because I can't play/sight in the gun since i have been fighting with the BCG for a little while now. I can get a whole new DTI BCG for 110, or go with one of these kits and spend about 30-50 and hope it works. I also need to get some type of sealant, I was thinking Permatex 81158. Does the action get above 450 F?
|
|
I agree, do NOT use lock tite, especially not red, it is a thread locker, not a sealer. Use RTV high temp silicon sealer, like for automotive gaskets, or something similar. If you lap the key to the bolt you do not need sealer but I use just a smidge anyway. Then stake them properly and you will not have to worry about them coming loose. Blue lock-tite on the bolts won't hurt anything but never, ever, use red, but the lock-tite will not take the place of a silicon high temp sealer.
Those roller cams, as far as I am concerned, are a solution to a non existent problem. And with them you need a modified or special key. Why bother? The standard cam works just as well and I cannot see any benefit in them. Of course the maker will claim wonders on cucumbers but I take makers claims with a grain of salt. I prefer standard stuff that I can buy anywhere if something breaks, not something proprietary that might take days to weeks to get. Also check your gas rings to make sure they are not broken or missing. Do not worry about the gaps being lined up or not. When in the carrier the gaps close so while it is OK to stagger the gaps, it is not really needed to do so. Since it works with the other BCG then I doubt your problem in in the gas block or tube. |
AR Sponsor