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Posted: 10/8/2012 9:59:20 AM EDT
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I rebarelled an RRA with a new 11.5" Daniel Defense Barrel and Trek-T Supressor
Now I have a problem where every 10 rounds or so under rapid fire a spent case sticks in the chamber. The bolt will travel back and ram the next round into the empty case. Several times it appears the bolt has ripped the edge of the case off. Other times it appears to slow th bolt down enough for the bolt to leave scratches on the next round in the magazine and sometimes not feed the next round correctly. The problem gets worse as the gun gets hotter. If I fire slowly with a couple of minutes of cooldown every 3 rounds, I won't experience the problem. The bolt will lock back on an empty magazine every time. This may be because the gun cools down while I arrange 1 or 2 rounds in the magazine to test this. Other details -Magazines are Magpul -Ammo is reloaded LC brass, AA2230 powder (26.? grains, I don't have my notes with me), 55 gr montana gold bullets. I can't be the first, but can't seem to find exactly what I am experiencing. |
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11.5" barrel with supressor,
Suppressor increases the back pressure that the gas system is seeing, and speeds up the unlock, causing the spent case to be more pressure bound to the chamber at extraction (hence why the extractor is slipping off the rim on the way back). 1. Might want to think about increasing the buffer weight to try to slow the unlock back down to normal when suppressed. 2. The increased back pressure of the suppressor is going to cause more gas back through the chamber after the spent case starts coming out, so increase the tension on the extractor with something like either a Colt back insert M-4 or Wolff extra tension extractor spring. 3. Get used to running the rig on the tad wetter side with CLP. CLP has an active cleaning agent in it, and will help to break down the blown back gun powder fouling before it has a chance to build up in the action (small portion of it will also be migrated to the new case/chamber, and help to keep the fouling from building up there as well). 4. Chamber brush with CLP by hand to clean the chamber is a must every cleaning!!!! Not only is the chamber going to foul quickly, but the void in the barrel extension as well (will save you a lot of time instead of trying to use a Q tip to get in there and clean it that way instead). So to sum it up, try to get the unlock back in check so the residual bore pressure on the spent case drops down to normal'ish before the B/C goes to unlock. If you try a few different buffer, may find that somewhere between a H2 and H3 will allow the rifle to function fine both suppressed and unsuppressed. Also to point out, if you have a standard buffer, then just buy a H3 buffer alone. The differance between a standard buffer and H series is the discs within the buffer. Being a standard buffer has three steel discs, while a H-3 buffer has three heaver tungsten discs instead. Hence with two buffers, 3 steel discs, 3 heaver tungsten discs, you can swap discs around to come up with an H-1 and H-2 buffer as well. Increase the tension on the extractor via a stronger spring so when the action does go to unlock on the faster side, the extractor does not slip off the rim. Granted that at some point if the action is unlocking too fast and the chamber fouls up bad enough, your going to rip a rim off a case, but cleaning and CLP used as lube should save you from getting to that point. Run the rig on the wetter side with CLP to help from the rifle choking out on fouling. |
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You were on the money. I got an H3 buffer and the problem went away. I ran it dry and it was a jamming machine. I ran it wet and it runs like a top, but boy was that thing gunked up big time.
The brass still ejects about 2:00 though. Is that an indicator of future issues? There appears to be alot of carbon buildup. I've never worried about it before, but what I have now is relatively alot. Is there anything that needs to be done? |
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With the can, you going to have blow back no way around it. Just keep the rig CLP lubed, and the cleaning agent in CLP will keep the fouling from sticking/building up to the point of choking out the rifle.
Forward ejection, are you sure that is not due to the spent cases off the deflector. If not off the deflector, then maybe off the back of ejection port window instead. Here, just pull the charging handle all the way back, and confirm that the face of the bolt does not retract back past the back of the ejection port window. Other than that, maybe a weak ejector spring, or ejector binding in the bolt face channel, or even a edge bur on the grabbing claw of the extractor that is not allowing a clean release of the spent case rim at rearward stall. And you might not have a clue what a real mess is. Run a MP-5SD for a few hundred rounds, then get back to use once you spin off the reflex can and have to clean the mess up. Even better, run the +p ammo that the rifle was designed to run, and see just how much more that ammo throws up into the can/back into the delayed blow back system. Don't get me wrong, with the amount of volume that the reflex can has, it does a great job, but think that it may have just been better if HK would have spun a large diesel motor oil filter to the the barrel instead ( over size oil filter would be around $10, and quicker to just change it out, then the effort and solvents need to clean the suppressor/rig instead. |
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