New AR build fail to feed 223 but not 5.56???

[Garyson1311]

And if gives me the same problem I will probably look at the gas block but my Yankee hill block has a pretty big hole and the barrel port hole is pretty small so I felt like my Yankee hill block gave a lot of room for error. Plus the gas tube fit really nicely in the upper and had wiggle on both sides which leads me to hope its straight but we will see!

[Justice06RR]

My first thought is to get different magazines that are reliable. Mags are one of the main causes of failures. So get some Pmags, good GI mags, Lancers, or whatever you can get your hands on. Being limited to one mag is hard to tell because you can't be sure if its the mag or the gun.

Once you figure out its not the mag, then you can troubleshoot your AR. With my builds I usually try to break them in with hotter 5.56 ammo only for the first hundred rounds or so. Nothing wrong with 223, but personally I like to use 5.56 as much as I can.

My last build was a 16-inch Spikes Tactical carbine and I did experience a couple of Failure to fires in the first 40 rounds. Since this is a build, we have to make sure that all parts fit and are installed properly. Things like gas blocks loosening or springs not installed correctly can give you issues. After about 100rds through my Spikes AR, it seems to have smoothen out and it shoots great now.

Good luck and keep us posted. Congrats on your build and it looks like you have a nice rifle there.

[Garyson1311]

Thanks for the compliment

Yeah I think the mag is definitely suspect as its a cheapy. I have 4 USGI mags en route from a buddy who is currently serving. Hopefully they are of good quilty.. If not, I will replace the followers or just get some PMAGS but im waiting until I receive his GI mags because I know there are a few GI mag makers that make good ones.

I am going to only shoot 5.56 for the first 100 or 200 rounds in hopes of giving it a break in period like you and others have suggested.

I am praying the gas block is not the culprit as I REALLY dont want to take off that free float handguard! It looks sweet but was kind of a PITA to install. I didnt want to overtigthen the gas block so I made it "pretty snug" and then I applied loctite to 1 of the 2 set screws. Like I said before, it has a big hole compared to the hole on the barrel but who knows. Hopefully after I get a few hundred rounds down range it'll just break in and work right. If not, im gonna have to explore the gun and find whats not working because I want a rifle that WORKS!

[Justice06RR]

Definitely invest in some good mags. They are becoming cheap again and I've picked up Pmags and Lancers for under $20 last weekend.

Here's another suggestion during break-in of your AR. With good ammo and mags, put one round in the mag and fire that making sure that it locks the bolt back every time. This will ensure you have a good cycling and the bolt catch and mags are working good. If its not locking the bolt back, then you know its possibly undergassed, or your mag is not reliable, or the bolt catch might not be engaging.

After you verify that, you can shoot 2-3rds or so per mag to make sure its stripping the next round properly. If it does that fine, then you can load the mags to capacity.

Once you are 100% sure that your mags and ammo are good, then you can see if your gas block is mis-aligned, or something else is out of spec with the rifle. One of the issues I came across during my break in was improperly installed trigger spring that caused a FTF.

Also once you are done shooting, take the rifle and re-tighten any screws or parts (castle nut, screws on your rails, etc) and inspect that all parts are tight and in place. Check your takedown pins, safety lever, buffer, buffer retaining pin and everything else. Sometimes a part will come loose that you don't notice and causes some type of failure.

These are just some of the things I've learned from troubleshooting my own builds. Hope that helps and happy shooting!

[hagar]

I don't think their is anything wrong with your rifle, the 223 ammo powder might be optimized for longer barrels and not have optimum gas at the gas port for the shorter barrel, maybe that combined with a new rifle that is not broken in yet.

Another thing, did you grease/lube the recoil spring in the buttstock? I have a New Frontier lower on one of my mid length carbines, and I noticed at first that ejection was not as brisk as on my aluminum lowers, it was just barely trickling out, and this was shooting reasonably hot handloads. I did grease mine well, and it improved some. Just lube everything well, and shoot it a lot, might just need a break in period. My one Bushmaster lower has about 15,000 round through it, and it is as slick as a goose.

[Garyson1311]

I am going do a few more single round tests to check for that gas issue. Like I said, I have some usgi mags with green and tan followers on the way so we will see how those work. I think I am going to try and retighten stuff up to make sure.

One thing I did not do is grease the buffer spring. It came wet so I just threw it in there. Maybe that's with taking a look at. I got some xm193 5.56 to try out this weekend and will keep you guys posted. I'm hoping it his needs break in.

[Garyson1311]

Oh and they seemed to be ejecting fine but I don't have much to compare it to.

[Quentin2]

Definitely get good magazines! I would NOT grease the buffer spring.

[Garyson1311]

Interesting. Oil it up?

[Quentin2]

I don't oil the spring at all, though a little oil does run down there when you stand up the rifle with a wet BCG. I don't see any reason to go out of my way to lube the receiver extension. Some folks gunk it up trying to dampen the "sprong" noise though.

As far as the polymer lower needing the buffer spring greased, that's a new one on me. Seems to me it wouldn't matter since the receiver extension, buffer and spring still are metal.

[Metal god]

I don't oil the spring at all, though a little oil does run down there when you stand up the rifle with a wet BCG.

this^

I have never oiled my buffer sping . When I clean my buffer and spring every 500 to 1k rounds it always has some oils on it . I'm sure you've noticed after your gun has been sitting around for a few days or weeks . there is oils coming out between the two receivers by the rear take down pin . It leaks down in to the buffer tube as well .

+1 on using more then just one mag for your test . If you don't have any now , somebody at the range would most likely let you use one . I was having a few problems with feed jam issues . It took me awhile to figure it out but it turned out to be my 20rd Pmags . I have like 7 different makes and or sizes of mags . I have not had one feed jam sense I took the two 20rd Pmags out of the loop .

[Mobuck]

FWIW, I shoot off the bench using the cheapest mags known-Thermolds. Price doesn't always assure functionality. I've never seen commercial .223 ammo that failed to function an AR(that doesn't have problems).
It's quite possible you have some drag on the top round in the mag during feeding. My common test for full bolt travel is to fire one round and see if the bolt locks open-just as the OP did. Three such tests w/o a miss has been good enough for me.
I'm assuming your gas tube is dead center and the gas key slides over it on return w/o any snags. Since you commented about the PITA freefloat handguard, I'd check to make sure the gas tube to key fit isn't part of the problem.

[Garyson1311]

Wanted to give you guys a semi update.

I attained 300 more rounds of 5.56 and went to the range and decided to put some more 5.56 down the pipe before I try some more 223. I also found that my gun as pretty dry after a few rounds (was using CLP) so I tried some Lucas gun oil and my bolt was still wet after a bit of shooting, which was nice. I decided to try to fire a few single rounds of 223 to make sure the bolt locked back and it passed that test a few times in a row with no problems. I did not load a mag full of 223 yet but I plan on doing that on my next range trip because like I said, I wanted to throw some more 5.56 to fix any "break in" issue if thats in fact what it was. I have some different 223 ammo on the way and I intend on trying that ammo and my existing PMC Bronze 223 ammo to see if the bronze really is too weak as people have reported that PMC bronze 223 ammo is weaksauce.

Thanks,
Gary

[Garyson1311]

Double checked gas key by instering bolt really slow and felt no snags. Also did not see any junk near gas block so I am really thinking that I dont have a gas issue. After thinking about it more, the YHM gas block has a HUGE gas hole compared to the one on barrel so if I missed, I woulda had to miss by quite a bit and the thing looks really, really straight.

[Theohazard]

What pretty much happened was that I pulled the trigger on an empty chamber.

I'm not 100% sure what kind of problems you're having. When you say "pretty much", do you mean it functioned like the chamber was empty even though there was a round in it, or was the chamber actually empty?

I've seen under-gassed rifles that would still lock the bolt back on some mags, but still often didn't have enough gas to be 100% reliable. Like others have said, this is sometimes cause by a mis-aligned gas block. An easy way to check gas block alignment is just take off the gas block; now that you've shot it some there will be a ring of carbon around the gas port on the barrel. If the barrel's gas port is entirely inside that ring, you're good to go as far as gas block alignment.

Another issue you see a lot is gas tube alignment; the gas tube is off a little bit to one side or the other, and it snags on the gas key each time and slows (or even stops) the BCG from going into battery correctly. The way to check that is to remove your upper, take out the BCG and charging handle, then take apart the BCG until you're left with just the carrier itself and no bolt or anything. Then hold the upper muzzle-down and drop the carrier into battery; it should just drop down without any snags. If your gas tube is misaligned, it will be slowed down (or even stopped) by the gas tube rubbing on the inside of the gas key.

[Theohazard]

Double checked gas key by instering bolt really slow and felt no snags. Also did not see any junk near gas block so I am really thinking that I dont have a gas issue. After thinking about it more, the YHM gas block has a HUGE gas hole compared to the one on barrel so if I missed, I woulda had to miss by quite a bit and the thing looks really, really straight.

Oops. I wrote my last post without realizing there was a whole second page of responses that already covered what I wrote. However, I still would recommend doing the check on gas tube/gas key alignment the way I described; when you check it with the BCG fully assembled it can sometimes be less obvious what's happening.

[Brass Tacks]

I just replaced the enormous gas block on my M&P15 flat top with a YHM low profile clamp on block. Doing some measuring I found the gas port on both blocks were the same distance from the rear of the blocks. The OE block sandwiched the forearm retainer bracket to the shoulder on the barrel. The bracket was .030" thick. I fashioned a spacer to go between the new block and the shoulder. This put the barrel port and block port in alignment. Without the spacer (or just leaving a .030" gap) the ports would be partially blocked. I have had no problems using PMC ammo in this rifle.