Sent a DD V2 Carbine upper to ADCO to have the barrel shortened to 14.5 and have a BCM Gunfighter Comp perm attached. Now I’m having failures to lock back on empty mag with lower powered ammo like PPU and Winchester 223. This is with a VLTOR A5 RE and standard buffer. I also tried it on another lower with a Carbine RE, H2 buffer, and Sprinco blue spring.
The problem has been resolved somewhat with an A5 H1 buffer. It only fails to lock back when I hold the weapon away from my shoulder, but this doesn’t seem right to me.
I shoot 855 or 193 exclusively, and haven’t had any problems with those rounds, but I use the weaker stuff when I test changes to the operating system. My biggest concern is how the weapon will functions when really fouled. I’ve only run 150 rounds through it so far.
I also noticed that my DD V3 16" midlength has more recoil, and no problem cycling anything on either lower or with any buffer up to Carbine H3 and A5 H3.
I made the comment on my work order to make any modifications to the gas system necessary for reliability.
The buffer I originally tried was the VLTOR A5 H2. Now I am using the A5 H1 which is a little better.
The lightest buffer I currently have for any weapon is a LMT carbine H2 which I tried in a lower with the proper buffer tube, and that wasn’t any better.
This is kinda disappointing because this was going to be my “go to” rifle.
Wouldn’t an H2 buffer slow the bolt more, exacerbating the malf? I had the same issue running Tula through a mid length barrel with an H2 buffer. I put a CAR buffer in now when I shoot Tula, cycles perfect.
yeah, I have a Green Sprinco in there now. I don’t know if they are any stronger than normal rifle springs, but I was thinking about putting a standard rifle spring in. I don’t have any currently, because I had to buy the parts for this buffer assembly in pieces.
Like Iraqgunz said, though. I thought the gas port was the same size, and I shouldn’t be having to tune the rifle like this. It was was perfectly fine before I had the barrel chopped.
A CAR buffer is never an acceptable solution. The port must be measured. I find it hard to believe that the port is too small… that almost NEVER happens.
I’m starting to wonder if DD uses a smaller gas port for their 16" carbines vs 14.5" carbine barrels. If nothing else I may remove the FSB to measure the gas port and if necessary open it up to .063
I e-mailed ADCO but got no response.
Ryan, I typically shoot Lake City 5.56. I was just using Winchester White Box and Prvi to test. My DD 16" mid-length didn’t have any problem locking back with those rounds.
How is a CAR buffer not an acceptable solution? H, H2, and H3 are solutions for over gassed rifles, why not use a lighter buffer if the bolt won’t hold open? Over gassing is a cure now?
ETA: I didn’t suggest opening up the gas port because it seemed to already be determined the gas port was the correct size.
He is running an A5 RE… Carbine springs or buffers will fuck shit up.
Do your homework before making recommendations. He did the right thing by going to the A5H1 buffer, I would keep the green SpringCo rifle spring and add a LMT enhanced auto carrier…
I don’t think it’s an issue of gas escaping but the port size MAY need to be looked at. By shortening the barrel the dwell time, or the length of the gas pulse, has been shortened. Without any way to increase the length of the gas pulse, the only alternatives are to either enlarge the gas port slightly and deliver a stronger pulse to the carrier, or reduce the resistance of the buffer/spring to allow the carrier to move more easily.
The barrel-maker I use for my 6.8 used to ship barrels with a larger gas port for better function and to avoid issues with short-stroking back when Remington 6.8, etc, was mostly what was available. As SSA and others stepped up to the plate and developed more for the SPC II chamber they reduced the diameter of the gas port and made sure that customers would know to expect problems with the lower-pressure ammo.
Winchester white box (especially a .223 loading) is going to be pretty weak as I recall. Again, if it was me, I would be looking at the port. I remember reading that some DD carbines had the .058 port size.
Now the question is how crazy will I be if I drill it out myself. A 1/16" drill bit is about .0625
If I can find a 1.6mm that’s about .063"
I have a spare BCM gas tube and taper pins, so I’ll go ahead and replace those too.
I don’t have a drill press, but the existing gas port should act as a pilot and keep my straight. I’ll just put a wooden dowel in the bore, so I don’t punch too far. My primary concern would be leaving any burrs in the bore.