Harveyshot

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As stated earlier, I bought the Armalite 10A bolt catch and it has worked great but I've only used Hexmags with it. No steel ammo, range won't allow it.

I just must have been lucky on my one and only LR-308 build. It's an 80% polymer lower and I bought parts from a bunch of different sellers and except for the bolt catch all eventually worked out in the end with no drilling or modifications to any of the parts, just some tweaking. The buffer assembly I bought (Luth-AR LR-308/AR-15 MBA-2 Skullaton Stock Assembly A2 Tube .308 Rifle Buffer And Spring Dark Earth MBA-2FK308 | Cheaper Than Dirt) didn't specify the buffer weight only that it was 'standard' but it worked. I did buy an adjustable gas block made by Sadlak Ind. and that, I think, made all the difference. Once I opened it up, all the FTLs and FTEs went away. The Armalite AR10A bolt catch replaced the one in the LPK. It has a 20" barrel from CDC and rifle length gas. I would have been up poop creek if mine had required drilling. Yes, the red dot optic color doesn't match the rifle but that's what happens when you order from the picture without reading the description. It 'looked' FDE. (sigh) Hope your 308 works out well, James.

The third one I bought was the one that finally worked the way it should, the AR10A bolt catch from DSG Arms.

Final Update Installed the Armalite AR-10A bolt catch, lubed everything excessively and went to the range. The first 20 or so rounds loaded and ejected without fail but the bolt wouldn't hold open after the last round. It was a choice of bc (3rd one) still not catching or not enough pressure to push the bcg back far enough to be caught. I opened the gas block a little more and lo and behold, it locked open! After that the rifle performed flawlessly (me, not so much). Happy camper. A big thanks to all that helped.

I built an 80% (aluminum) AR-15 six years ago and enjoyed the research, milling and drilling of something I'd never done before. Now that I'm retired and looking for things to do, I decided on an 80% (polymer) LR-308 for the same reasons. I've finished (after much anguish of waiting for parts in the mail, ordering wrong parts, etc.) and it's on to the next project. Thinking 80% AR-15 lower and dedicated .22 upper.

Received the two adjustment screws from Sadlak with no bill. I'll be sending them $25 and hope that covers it.

Update on the bolt catch problem. Finally got the Armalite AR-10A bolt catch from DSG Arms. First of all, the pin hole in the Armalite bc is slightly smaller than the holes in the other two bcs I have. Therefore the bottom edge of the Armalite hole is slightly higher than the lower’s pin hole bottom edge. I could not get the screw/pin to go through the bcs hole. So, out of non-destructive ideas, I got the Dremel out and ever so slightly lowered the groove in the lower just below where the plunger sits. It worked! The Armalite bc moves and sits better than the previous bcs. It also catches a tad more of the mag’s follower. Range time will be the test but that will have to wait for now. And kudos to Sadlak Industries. I lost the adjustment screw to their gas block and emailed them about a replacement. They immediately replied telling me not to fire the rifle with that screw missing and that they would send me one. According to them, it’s a hard to come by stainless steel set screw. I told them I would pay them if they would send me two. I probably should get a spare gas block for instances like waiting on the mail.

Never tried a .45 but if you’re working on a .308 bolt you likely have a .308 case lying around somewhere.

Sounds like a great way to check the sights. I’ve taken a 3-8x scope from another rifle and put it on the 308. I’ll try that method before going to the range. From my minimal experience, a non-magnified red dot is pretty much useless at 100 yards unless your target is big.

Thanks for that link, jtalien83, but it just added to my confusion. I’m starting to think I’ll have to buy one of every make and model and try them all. That little nub on my current bc, that the follower pushes up, barely makes contact with the follower. I think the 10a might be a viable choice because it ‘looks’ like that nub is wider and more towards the end of the bc but they are hard to find.

Question: 10A or 10B? Looking at the differences between them from a page on this site, it looks like the 10A would work better. But what do I know.

Aero Precision. Never actually tried out their bc on a functioning rifle, just didn’t like the way it moved so little and sat cocked in the lower. Does everyone’s bc sit that way? Ordered a Luth-AR bc and it did the same. Although, when trying the bc out a few weeks ago (just manually operating the bcg), it worked. All the parts we’re pretty much dry. I’ll try the Armalite one and hope for the best. Thanks.

Funny thing, I did lose the gas block set screw. I’ll check with Sadlak about the size.

Back from the range with an update. After about 50 rounds, she almost did perfectly as far as feed and eject go. Near the end there were a couple of ftf and fte. Broke it open and oiled it some more. Didn’t help. Then I remembered DNP saying start it with the gas block wide open so I opened it quite a bit (didn’t want to lose that screw at the range) and that seemed to work. So thanks everyone for all the advice. The remaining problem now is the bolt catch that isn’t catching with an empty mag inserted. I would put two rounds in a mag and fire off both but no catch. Did this many times. At first it would catch if I used the charging handle but at the end it wouldn’t. When I look at it with the gun open it just doesn’t seem right. If you can see it in the pic, the catch is barely making contact with the follower when the mag is fully inserted. The one pic shows it with the mag almost fully in. There are other pix of the catch in the original post. I’d appreciate anyone showing their bolt catch. Thanks.

Tube depth is 9 5/8”. I’ll give it a good cleaning, lube it seven ways from Sunday and hit the range tomorrow. I’ll update afterwards. Thanks again, everyone.

The buffer tube I.d. Is 25mm Spring o.d. Is 25mm, 38 coils, length 13” Buffer length: 5 1/4” weight: 5.4 o

Here is a shot of the area around the gas port.

As I start the tearing down, here are some findings. Gas port size: larger than 5/64 and smaller than 3/32 which is what it should be according to posts here and other places. 0.0935”/#42 falls between the two fractions above. Here is a pic of the gas tube in the upper. Seems to end in the right place. But I think the real culprit may be the bcg lubrication. The bcg was dry and the bolt would barely move in and out of the carrier. So much for thinking I lubed it enough. Man, these DI systems are extremely dirty. And that was after only about 30 rounds. Excuse my ignorance but my only AR experience is with an AR-15 I built six years ago with a gas piston system. I would have done that with this one but they’re just too expensive. On to the buffer assembly.

Ok, Magwa, maybe my using the word ‘specs’ is wrong but they should know what size hole they drilled for the gas port.

Jeez, if you can’t depend on manufacturer’s specs, you’re just ordering blind. I’ll dig through my drill bit collection and see if I have one that small before spending more money on my ‘budget’ build. Thanks.

Alright, thanks. I’ll try to get those measurements. Port size may be difficult since I have nothing that will measure it. I’ll have to rely on barrel manufacturer’s specs. As for gas block alignment, the set screw on the bottom is in the barrel’s dimple. So if it’s slightly off , how do you tell? As for the range screw up, most of my range time has been with handguns and iron sights. Never realized a new red dot sight could be that far off. A learning experience, indeed.

The excitement of finally firing my LR-308 build after months of waiting for parts in the mail was soon tempered by ftf/fte problems. But first the good news, it didn't blow up in my face on the first round fired. I was using Winchester 7.62 and .308 ammo as pictured. All the 7.62s failed to eject. All the .308s ejected but failed to feed the next round. But ALL would feed and eject using the charging handle. So it would seem to point at short stroking due to gas pressure or buffer problems. I'm using an adjustable gas block and kept screwing OUT the adjustment screw (I'm assuming OUT is what you do for more pressure) but did little or no help. It's possible the gas block hole is misaligned with the barrel port but the set screw is in the dimple on the barrel. I lubed the bcg quite heavily. I've also included pix of the fte and the ends of some of the 7.62 and .308 cases, if that helps. The ends of the 7.62s seem to show some heavy extractor markings. The problem with working on guns is if you don't have a place to shoot on your property, you have to go to the range to test any fixes you did to find out if they work. My nearest range is 40 miles away and that slows down the progress. And you have to take all your AR tools with you. One other thing, the bolt catch would sometimes work and sometimes not work. if it worked, the catch release would not work. I've had doubts it and replaced it already but no better. When installed, should the catch lie flat on the lower's surface? With pin inserted, it doesn't. See pix. Below are links to the parts I'm using: Sadlak Adjustable Gas Block Aero Precision Upper ALG Defense Trigger AR-Stoner Gas Tube Hexmag Magazine CBC 20" Barrel Mercury BCG Luth-AR Buttstock/buffer/tube/spring A side note: the red dot optic was so far off I wasn't even hitting the paper at 100 yds. It was shooting so high a range employee came to me to let me know I was hitting their rails above the targets (indoor range). Oops. I couldn't see where they were hitting. Moved the target to 35 yds and finally got one on the paper and was able to adjust the optic to hit where I aimed. Thanks for reading this long post. Any advice will be appreciated.

That it did.

While building my LR 308 I kept reading about headspace checking which was new to me so I researched it ad nauseum and decided it was worth the effort. I have only built one AR 15 (80%er) six years ago and decided to build a 308 for something to do in retirement. It’s a P80 80%. Since this will probably be my one and only 308 build (a budget one at that), I couldn’t see spending $50+ on a ejector removal tool for a one time headspace check. It’s a simplistic tool that looked homemade doable. Two pieces of scrap wood, a cut down 7.62 case and a vise did the trick. It takes a little bit of finagling to hold the bolt in place while tightening the vise but it worked well. I rented the headspace gauges from Reamer Rentals. $27 to rent is better than $70 to buy since it’s a one time use.