Thehotrodpig

Update. I have a couple hundred rounds through the gun now and it has run flawlessly. Shot it back to back with a buddy's Rainier Arms 16" mid gas ar and there was a noticeable difference in how flat shooting my gun was over his. That is with my gas all the way open too. Shot it Saturday at 100 yards to see what groups I could get out of this new Criterion barrel. With the large dot of my Tac30 scope I was still able to shoot several sub 1" groups with my cheap Remington green box ammo. I think with a more target friendly reticule this gun has some serious potential. That Criterion barrel seems to be a good value. Overall for my first dedicated 3 gun build I think I have a very functional budget gun rifle. I want to thank all of you (especially you Tom) that helped me work through the build and sort out the gas issues. Now I need to just finish fine tuning the comp and possibly pull a little more gas out of it and I will be dialed in. https://docs.google.com/file/d/0ByL2EF4qKSUZbzNmMkQyRFVRalU/edit

Yes "u" is not yet classified.

I know your fancy font is cool and different but it's really hard for tired eyes to read. So much so that I often skip what you have to say, which is unfortunate.Of course it doesn't show up in a quote.....

Yes I do Tom, thanks to you and others that have walked me through the tuning process. I have assembled several cookie cutter ar's and never had an issue. Like you said they were basically just like Legos and they worked fine but none shot as flat or smooth as this gun. I enjoy the tuning and understanding why and how parts interact with other parts. I am not done though. Time to play with the gas a bit more and mess with my muzzle brake to see if I can get it to shoot even flatter. I will update is I get further. Thanks again. PS, I still would be interested in replacing the spring. Tubbs, jp or?

Just went down to my range and ran 10 or so 2 round mags through it. Combo of old worn out GI mags and new pmags. The gun picked up every round and locked back on every empty mag. I know it wasn't a thorough test session but it was promising. My neighbors don't complain about the pistols but when I break out the ar for too long they start to complain a bit. This is with full gas locktighted in place. The receiver and bcg are new and when I cleaned them after last testing they were pretty sticky. I think that my issues could be related to a stacking tolerances type deal. New receiver, bolt, bcg, gas port perhaps on the small side, perhaps I didn't get the gas system perfectly aligned or blown out. I also did not have the gas adjuster locktighted in place before. I also might have found the sweet spot on the buffer weight at 2.9oz. I don't know for sure but I'll continue to test and report back. Thanks again for all the help you guys have been. I appreciate it.

Thank you Tom, you have been very helpful. I have learned a lot with this build. I now have the buffer weight at 2.9 oz, just under what the jp buffer is at 3oz. I assured the gas is aligned and clear and I cleaned and lubed everything. I also confirmed the gas block is open and lock tighted there. I'm going to function test it in a few minutes.

No, if had done so the holes would have been off by approximately .020. I measured the two holes from the shoulder and from the end of the block and placed the block accordingly.

Ok, so I took the gas block off and the block and tube were free of obstructions. The hole in the barrel appears to be right around .091. It was difficult to get a perfect measurment with my calipers but I am pretty close. Does this sound like it is on the small size? The barrel is a criterion 18" hbar with rifle gas. .750 under the block.

I don't really know the history of the spring since it has been sitting around with my a2 stock for the last decade. If I wanted to put a new spring in there to reset my baseline, what should I try? Standard a2 spring or one of the fancy aftermarket types? Is there a recommendation for my app? Not a custom shorter one at this time.

I might try putting my car lower on this and see what happens. I prefer a fixed stock on my 3 gun rifle but the car lower might have to work. I am going to start first with removing the gas block, measuring the port and assuring that the tube and gas block are clear of obstructions. I do remember noticing that the hole in the barrel was very small compared to the large hole in the gas block. Thank you everybody for all the help and advise. I will get back with my findings.

That makes sense. I will measure the gas port size tonight if I have a chance. Would it be advised to play with springs at this point?

I did that last night. No obstructions and the screw is not protruding into the tube.

Thank you Tom, that is great info. I will check the port size. You are correct, our department runs colt carbines. I already checked the buffer tube for obstructions and there were none. I still don't understand why it ran fine with a standard carbine buffer and not with an empty rifle buffer. The carbine buffer was heavier and yes I know I shouldn't have done that.

This is a new build. Never tried a standard bcg in it yet. It ran with a heavier carbine buffer (my rifle buffer was empty). Yes I know that it was not wise to try a carbine buffer in a rifle tube. I've been appropriately scolded and will never do it again. I will check the buffer tube tonight for obstructions. That seems like the best advise yet.

Shouldn't I be able to get the gun to run with this ammo I have? All my other ar's along with our entire departments ar's run with this ammo. An AR with a lighter bcg tuned properly (which it obviously is not) should have no problem running with ammo that standard ar's eat up right?

Thank you but we covered that a couple posts ago.

Ya I realize now the short buffer was a no no. Did some more reading last night when I got home. I didn't put many rounds through it that way and luckily it doesn't look like I damaged anything. I will check on the screw length and obstructions. If I had a screw that was too long would there be some sort of witness marks on the buffer?

So I put together a rifle and am having issues tuning it. 18" criterion rifle length gas barrel Adjustable gas block New Jp low mass bcg, jp enhanced bolt A2 stock Rifle buffer. Stock a2 spring So I started out with a stock rifle buffer. No matter how much gas I ran it would still short stroke and failed to pick up next round. Next I slowly removed weights from the buffer and reliability increased the less weight I had in it. Eventually I removed all weight and it runs great but does not lock open after the last round. Just to see what happened I grabbed a buddy's full weight carbine buffer and threw it in. It is heavier than my empty rifle buffer by a bunch (technical term). The gun ran flawlessly and locked open on an empty mag but makes a weird wobbly spring vibration when it cycles. Rounds are Remington umc green and white box 55g stuff. I get it free from work so I really want to stick to this ammo at this point of my 3 gun endeavor. From what I can tell there are no gas leaks and the block is property lined up and spaced off of the barrel shoulder. I am a little confused as to what I have going on here. All I can guess is that the rifle buffer is bouncing back faster than the mag follower can move up and the shorter carbine buffer is going further back allowing the follower to get there. Am I close? I am still at a loss as to why the rifle buffer never reached a point of reliability as I progressed through the weight removal. I foresee the "just get a jp low mass buffer" response which I am not against doing but I really want to understand what is going on before just buying more parts. Thank you in advance for any help you may offer.

Well thanks again, for me that's a pretty decent first classifier with a revolver.

Thank you. How did you come up with this?

Dawson fiberoptic. They should have one for just about any cut you need.

Just shot my first match ever in revolver with my 625. 13.78 sec 60 points 4.0639 hf Anybody know where that puts me percentage wise?

I don't know the difference but I'm running the dawson metalform mags in my sti trojan 9mm and have never had a hiccup. Several thousand rounds with all kinds of loads and lengths. Even run dirty. They have been perfect so far.

Great choice. I love my sti trojan in 9mm. 45 version is in my future.

Thank you. That is exactly what I needed. Pretty happy with the gun?