Im4Rights

Project 2 Update: On last report, after installing the Armalite carbine buffer kit and opening the gas port to .093, the rifle cycled, but did not lock back on empty mag, so I opened up the gas port to .096 and the rifle cycled properly, locked back, but was over-gassed and kicking like a mule. As this is a budget build, I did some research and decided on a David Tubb 42-coil flatwire buffer spring ($40 all in w/shipping). The 42-coil spring is a little tough to cram in the carbine buffer tube, but it seemed to smooth things out a bit. That,combined with an Adaptive Tactical EX Performance Stock with a vented rubber recoil pad from another of my rifles, has made the shooting experience much more enjoyable. That concludes my build issues, now on to improving my shooting with both rifles. Thanks all!

I installed the Armalite buffer kit as recommended, and at .093 it was cycling, but not locking back, so I took it to .096, not imagining that .003 increase would have such a drastic effect. Live and learn...

Yes, this is what's currently installed https://www.armalite.com/SACItem.aspx?Item=AR10REKIT01. This is gun is a budget build, and I'm not sure I want to spend what they want for that heavy buffer kit. I think the advantage of an adjustable gas block is that I can tune the gas to match the ammo in use, and if the rules ever change to remove suppressors from the NFA, I'd be ready for that too. At this point, I may try a stiffer buffer spring and adjust the buffer weight if needed, or put on an adjustable gas block. If none of those less expensive options work, then I can always try the heavybuffers.com kit. Thanks for your continued assistance! I'll keep you updated.

Project 2 Update: Last I reported, this project was cycling, but not locking back on an empty mag. Parameters were 16" mid-length with 11.75" gas tube, .750 journal, .093 gas port (up from the original .063 port size), with 6 7/16 dwell time, and Armalite carbine buffer/spring. This morning I opened up the gas port to .096 and took it to the range. It cycled fine and locked back on empty mags, but it kicked like a mule. I believe I have gone from slightly under-gassed to pretty much over-gassed. In hindsight, I probably should have tried an H2 buffer first (Armalite buffer is H3). I'm thinking an adjustible gas block is now in order to dial this puppy back a bit. Any suggestions for such a gas block? Here are a couple pictures of my "personal use only" .308 carbine.

Thank you! Will do! Amen! I was worried there for a minute. 👍

Project 1 Update: Amazingly, my analysis was correct, the spring was the problem. After installing an Armalite rifle buffer spring, the rifle is now cycling like a champ and locking back on an empty mag (two different makes). Interestingly, the Armalite spring was longer than the Leapers spring, but it was not as stiff. The rifle is definitely "Minute of Deer" at 100 yards, but I wasn't really trying for group size, more trying to test cycling and lock back. Eventually, my goal with this rifle is to hit a man-sized target consistently at 1000 yards, but a lot of practice needs to occur before I'll achieve that goal, if I'm even able to with my old eyes. 🤔 Here's a picture of the final product. Again, thanks to all for your suggestions. Now, on to Project 2.

Welcome from Tampa! Yes, this site is awesome.

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@98Z5V has a good idea, I'm going to focus on one gun at a time. Get Project 1 running right, then Project 2. So, here are the details on Project 1. Project 1 – Aero Precision M5 upper/lower - Leapers LR 308 A2 stock kit with 5.3 oz rifle buffer - 24" SS Bull bbl (AP/ELD?), with rifle length gas system (tube = 15.125), .935 journal, and .093 gas port (currently) - Dwell time = 11 3/16 by tape measure. Current symptoms: Does not lock back with or without magazine and does not strip and feed a new round from the magazine. It ejects cartridges reliably. The bcg can be locked to the rear manually, and does strip a round off the magazine when the bolt catch is released, or when charged with the charging handle. BCG was well lubed. The BCG and buffer tube are in alignment given no signs of damage at the receiver/buffer tube junction. My analysis (for what it's worth): Not enough gas to get the bcg far enough back to both eject the previous round and feed the new round. Either the .093 gas port is still too small, or the buffer spring is too stiff (assuming 5.3 oz buffer is correct), or the gas block is misaligned. Given, it seems more difficult to pull the charging handle back than it should be, I'm of the opinion the spring is too stiff. I have ordered an Armalite rifle buffer spring and will try that with the current gas port size. If that doesn't do the trick, then I'll go to 0.96 gas port size and try again. I do not want to over-gas the gun and have it beat itself up, but it may be necessary to go larger. Ammo used is PPU M80 NATO 145 gr pill @ 2835 fps per manufacturer. A few pictures. That's oil on the buffer. Let me know if you need additional information Your thoughts are most welcome and appreciated. Thanks! --Tom

Update - I took Project 1 and Project 2 to the range yesterday. Project 1 (24" barrel) improved a bit, but not enough to cycle rounds. I have opened the gas port from 0.089" to 0.093". If that doesn't do the trick, I'm wondering if the buffer spring might be too strong? Anyway, I'll give it another try and report back. Project 2 (16" bbl) performed well as far as cycling, but neither project locked back with or without magazine. Both BCGs and buffer tubes are in alignment with no damage to the lower receivers at the buffer tube. Not sure if this is a common problem among home builds, and I'm not super concerned about locking back; hell, standard AK-47's don't lock back, so there's that. I just want to make sure these guns go bang and shove another round in the chamber until there are no more rounds to feed. Manually depressing the bolt catch does lock the bcg to the rear on both guns. Regards, --Tom

Armalite buffer kit is scheduled to arrive tomorrow. I conducted headspace check with Go/No-Go gauges on both projects and got the expected results. Bolts closed on "Go" and did not close on "No-Go." I opened up the gas port on the 24" bbl to 0.089 and the 16" bbl to 0.093. After installing the buffer kit on the carbine project, I will take both rifles to the range to see if they run. Stay tuned for results. Thanks to all who have offered advise!

Armalite buffer kit on order along with Go/No Go set and variety of drill bits. Stay tuned for updates on these two projects.

Thank you! I'll see what i can find.

Thank you! Re: headspace, I didn't use gauges. I removed firing pin, and it went into battery over a round with the BCG lining up properly with the rear of the upper. I will check with gauges before proceeding. Test fire ammo was 150 Grain Soft Point Federal Power-Shok. However, I want to make sure it will cycle mil-spec 7.62 NATO, so future tests will use that ammo. So, two questions - 1. What port size do you recommend for the 24 in bbl?, and 2. What carbine recoil system do you recommend? Again, many thanks!

Thank you! Re: headspace, I didn't use gauges. I removed firing pin, and it went into battery with the BCG lining up properly with the rear of the upper. I will check with gauges before proceeding. Test fire ammo was 150 Grain Soft Point Federal Power-Shok. However, I want to make sure it will cycle mil-spec 7.62 NATO, so future tests will use that ammo. So, two questions - 1. What port size do you recommend for the 24 in bbl?, and 2. What carbine recoil system do you recommend? Again, many thanks!

Thank you for the info. I was shocked to see this buffer come out of an AP complete 308 lower purchased through Brownell's, but figured they know what they're doing.🤔

Hello 308AR gurus! I am one of those AR-15 builders who thought he could just slap together a bunch of parts, and viola, I'd have a big brother for my AR-15s. Of course, I found out the hard way that is not the case. So, I've been looking over a lot of the info on this forum, and I think I've got my failure to cycle problem narrowed down. "Project 1" was built and failed to cycle, so I thought I better seek some advice to fix "Project 1" before I finish "Project 2." I appreciate any advice you may provide. On to the specifics. Project 1 - AP M5 upper/lower - A2 stock with std spring and 5.3 oz rifle buffer - 24" SS Bull bbl (AP/ELD?), with rifle length gas system (tube = 15.125), .935 journal, and .072 gas port (per my digital caliper) - Dwell time = 11 3/16 by tape measure. Symptoms: Does not cycle, hard to extract by hand after firing, and carbon shadow not very well aligned with gas port. Proposed actions: From what I've read this gas port is too small (even if properly aligned), I think it needs to be .089ish. I need to align the non-adjustable gas block better, and hand cycle the bolt several hundred times. I'm also going to soak the BCG in Mobil 1 in my hot garage for a good long while. Do I have that right? Any other suggestions? Project 2 - I want to start with proper gas port size before proceeding. 16" mid-length with 11.75" gas tube, .750 journal, .063 gas port, with 6 7/16 dwell time. I'll be running a non-adjustable gas block, carbine buffer with std spring and 3.8 oz. buffer. Any thoughts? Many thanks, --Tom "The Second Protects the Rest!"