View Full Version : New ar-15 build, FTF and Failure to lock back
ckimball09
03-26-13, 13:48
I finally got out to shoot my new AR, and alas... i have experienced some issues and call upon the mighty M4C for help. First i will list my specs..
CA Medcon 14.5 barrel, midlength gas system
Troy low pro gas block/tube
URX 3.1 rail
Aero precision upper/lower
Daniel defense ion bonded BCG
Spikes LPK
H2 Buffer and Carbine action spring
CTR stock
Was shooting Tula 223 55gr HP
I use Mobile 1 oil and put it on pretty good so i don't think lube was an issue
Now to the problem... It didn't FTF every single round but i would say 10-15 out of every 30 rounds were FTF. The spent casing ejects every shot. The problem is Failure to feeds and The bolt not locking back after the last round. I had a couple FTF where the bullet got jammed, but most of the FTF were short strokes i think, not even catching a new round. This leads to me believe it has something to do with the gas system?
i have picked up some spent casings and also a bullet that jammed during the feeding process. They have some scrape markings, idk if they are out of the norm.
http://i1358.photobucket.com/albums/q765/ckimball09/IMG_0620_zps3e4dde02.jpghttp://i1358.photobucket.com/albums/q765/ckimball09/IMG_0621_zps5d371f16.jpghttp://i1358.photobucket.com/albums/q765/ckimball09/IMG_0622_zpsf421cea7.jpg
So i beg of you, please help :help: As i want to get my baby up an running...
Also ignore my fingers.. I work with my hands and lots of paint thinner ;p
Try some brass case ammo and new/different magazine for starters and see if it cures the problems. My Aero lower performs as expected for the record.
ckimball09
03-26-13, 14:00
Forgot to mention, i tried 4 different PMAGS all of which work perfectly with my other AR. The ammo is the cheap stuff, but has yet to give me this much of a problem in the past. Next time i go out i will try a few rounds of brass.
IIRC several people that have more experience with steel ammo then I have said that the rifle usually has to break-in for about 1k round before it starts feeding steel reliably.
Quiet-Matt
03-26-13, 14:20
Perhaps a lighter buffer with that barrel and ammo combo.
This is exactly what my BCM/Spikes 16" does with Herter's .223. I tried the ammo in my LPR for S&G and it does the same thing; FTF every few rounds. It even happens if I stagger the Herter's with Federal or PMC x-tac. (I think Herter's is basically re-boxed Tula. I'll check the head stamp tonight and see if that yields any insight.)
It's just weak ammo. Try some higher quality, brass ammo and you should see an improvement.
NeoNeanderthal
03-26-13, 14:33
The rule of thumb is to run the heaviest buffer you can get away with when running shitty ammo. With an H2 your gun might run great with "hot" ammo but not well at all (as you've experienced) with very weak ammo. Ideally youd find a buffer combo that allows your gun to be able to handle hot ammo and yet still reliably feed the weak stuff. With middys the H buffer is a good place to start. Few people need to go lighter or heavier
The short stroking is the big indicator here. That is ether a ****ed up gas system, too weak ammo, or too heavy a buffer. It doesnt have enough "umph" to fully compress the buffer and spring all the way to the rear reliably. Its not even getting far enough to lock back with 4 different pmags.
FWIW i have not heard of anyone running an H buffer with a middy who has found it to be too heavy to function. I know some people run carbine buffers, and others who run h2's though so its gun specific. Got a buddy with an AR? grab his carbine buffer and see if that does the trick with your shitty steel ammo. I'm betting the H buffer will be the best all around buffer for you though.
PS. Compared to me, you could be a hand model.
14.5 middy isn't likely to tollerate that garbage ammo unless the port is obnoxiously huge... like .085-.090.
A carbine buffer might get you into action if you plan on running the doo doo ammo.
The main issue that I see is garbage ammo and a buffer that is too heavy. Use good ammo and an H buffer and you will probably be fine.
ckimball09
03-26-13, 15:32
Got impatient, so i took apart and cleaned my BCG then lubed the heck out of it. Took my buffer + spring out and oiled them a little to go try some brass ammo. I tried the Tula again, S&B 223 55gr soft point, and Federal Fusion 62gr 223 and still it was a no go.. I even got a couple FTE's and a couple Double feeds. but still the main culprit was FTF. It did lock the bolt back once but ONLY once.. here are some more pics of what happened.
http://i1358.photobucket.com/albums/q765/ckimball09/image_zps79654297.jpeghttp://i1358.photobucket.com/albums/q765/ckimball09/photo_zpsd86e084f.jpg
Thanks for the responses everyone, and im sure we can all figure this out :happy:
Looks like that bolt isn't getting far enough back in the cycle. 14.5 middy won't tollerate any gas leakage or weak ammo.
I had a bad gas tube the was too thin and blowing gas forward out of the key. It was giving my 14.5 middy all kinds of heartache. That gun has a .076 port.
My 14.5 middy with an .080 port is much more forgiving.
I think your next step is going to be trying a carbine buffer. It's cheap to do if you or a friend have one, and it won't hurt the gun. Did you install the gasblock yourself?
ckimball09
03-26-13, 15:48
Ordered a Carbine and an H buffer and bcm's extractor upgrade. If that doesnt work should i replace the gas tube? Should i have the BCG checked out?
ckimball09
03-26-13, 15:49
I think your next step is going to be trying a carbine buffer. It's cheap to do if you or a friend have one, and it won't hurt the gun. Did you install the gasblock yourself?
No, i had ADCO pin the gasblock/tube along with installing my URX 3.1 rail
I would trust ADCO as much as anyone. You say the barrel is CA... Is that Centurion Arms? You might want to contact the barrel maker and see what the port size is. That might just lead in the right direction to diagnose the issue. BTW, there have been a couple cases of DD BCG's with leaking carrier keys come about on this forum. Do you have another bolt carrier you can try?
ckimball09
03-26-13, 16:11
I would trust ADCO as much as anyone. You say the barrel is CA... Is that Centurion Arms? You might want to contact the barrel maker and see what the port size is. That might just lead in the right direction to diagnose the issue.
Yeah Centurion Arms, i may just do that. What would be the problem with port size? Gas leaking out? And if so how would that be fixed.
Like Marks said above, the midlength gas system on a 14.5" barrel REALLY likes high pressure 5.56 military ammo. BCM and I assume Centurion size their gas ports to use that ammo. A .076 port will require strong ammo and not be very forgiving to weak ammo. Mark says his is .080 and is fine. Gas port size determines gas flow to the gas tube. The smaller the hole, the less gas and the less gas available to move your bolt carrier. If your carrier key is leaking, gas will leak instead of being used to push the bolt carrier.
I'd make a phone call to Centurion and see what size you most likely have. I'd also just drop in another bolt carrier and use your bolt to check to see if that's the issue.
Are you running an O-ring on the extractor spring by chance? If so, toss it. Also, your BCG still looks pretty dry to me. I don't think it's the barrel. See if you can find a handful or M193 or M855 and run it.
Yeah Centurion Arms, i may just do that. What would be the problem with port size? Gas leaking out? And if so how would that be fixed.
Check your gas rings too.
ckimball09
03-26-13, 17:21
Dont have the O-ring extractor, i will add more lube to the BCG and im about to go try some of my xm855.. I hope the gun can run 223 though, as 556 isnt as easy to get... and i have stocked up on 223.
ckimball09
03-26-13, 17:51
So i gather some xm855 and some of the 223 and went out again... To my surprise the 556 ammo worked flawlessly including locking the bolt back and when i got into the 223 it went to hell again... :angry: Is there a way to fix this? lighter buffer? something? haha
also i forgot to add. here are pics of each shell casing i shot. notice the bent lip on the 2 shell casings of which both are 223. The xm855 shell casing is the middle one and looks normal. Idk if this means anything but just an observation.
http://i1358.photobucket.com/albums/q765/ckimball09/IMG_0623_zps09257eb2.jpg
I run a standard "H" buffer and a blue buffer spring from Sprinco and my 14.5" middies have always run like cheetahs regardless of whether I'm running 5.56 or quality .223.
I won't run garbage Wolf or Tula in my uppers built up of premium quality parts. That is like running diesel in a Porsche twin turbo and expecting it to perform.
If you are dead set on running cheap low power ammo, you are going to have to go to an H or carbine buffer.
Thomas M-4
03-26-13, 20:13
Are you running an O-ring on the extractor spring by chance? If so, toss it. Also, your BCG still looks pretty dry to me. I don't think it's the barrel. See if you can find a handful or M193 or M855 and run it.
I concur with Iraqgunz use some ammunition that has some thump to it don't use weak ammunition trying to diagnose a problem. You may end up just chasing your tail.
NeoNeanderthal
03-26-13, 20:25
If you have stocked up on weak, shitty .223 just get a lighter buffer and use it with your shitty ammo (its like 30 bucks). When you have used up all your "training" ammo you can switch back to your h2 buffer for your quality 5.56. Think of it as a .22 conversion trainer.
ckimball09
03-26-13, 21:58
Got a Carbine and an H Buffer on the way, and the only reason i want to use cheap ammo is because i like to shoot as much as possible and dont want to spend 2-3x as much per bullet. I cant afford to waste my good stuff. So hopefully the new buffer will allow me to shoot any ammo i would want within reason. Thanks for the replies everyone, i will update as soon as i get the buffers in and test them.
assaultrecon28
03-26-13, 23:48
H/ carbine buffer should fix it, if not I'll be surprised
Thomas M-4
03-27-13, 00:44
Got a Carbine and an H Buffer on the way, and the only reason i want to use cheap ammo is because i like to shoot as much as possible and dont want to spend 2-3x as much per bullet. I cant afford to waste my good stuff. So hopefully the new buffer will allow me to shoot any ammo i would want within reason. Thanks for the replies everyone, i will update as soon as i get the buffers in and test them.
You start a new build on full pressure ammuntion after you are confident of proper function then try the lower pressure dirt ammo. It's been said numerous times don't start a high perf build on dirt ammuntion .
It's not that hard to figure out.
Thomas M-4
03-27-13, 01:09
So i gather some xm855 and some of the 223 and went out again... To my surprise the 556 ammo worked flawlessly including locking the bolt back and when i got into the 223 it went to hell again... :angry: Is there a way to fix this? lighter buffer? something? haha
also i forgot to add. here are pics of each shell casing i shot. notice the bent lip on the 2 shell casings of which both are 223. The xm855 shell casing is the middle one and looks normal. Idk if this means anything but just an observation.
http://i1358.photobucket.com/albums/q765/ckimball09/IMG_0623_zps09257eb2.jpg
The bent lips are normal. My suggestion would be to try 500+rds of 5.56 pressure ammo then start working down the pressure to dirt shooting ammunition, on new ammunition.
Don't just replace the Gas tube to replace it. Mine was only about .165" at the gas key. It's supposed to be .180" new I think...
i know I was over Ten Thousands under the dimensions of a new tube, and there was gas/lube fouling all over the tube where it was leaking forward... much more than the usual fouling.
Lighter buffer and more lube should fix it.
"If you're gonna be dumb you gotta be tough"
I had a terrible experience with Tula and will not go down that road again. Good reliable ammo is a must.
Ordered a Carbine and an H buffer and bcm's extractor upgrade. If that doesnt work should i replace the gas tube? Should i have the BCG checked out?
As others have said, when using shitty ammo the culprit is likely the buffer. 14.5 middy is just not the best combo if you want to carry on using cheap ammo (which I don't blame you for at all, there is nothing wrong with it for general practice).
I would hazard a guess that the carbine buffer will help - don't get ahead of yourself with what ifs. Just one word on steel case ammo, Tula is really the worst of the bunch, barnaul ammo such as bear or the newer wolf wpa is much better, especially on such a barrel/gas port combo which is known to be finnicky with weak ammo.
ckimball09
03-27-13, 16:55
As others have said, when using shitty ammo the culprit is likely the buffer. 14.5 middy is just not the best combo if you want to carry on using cheap ammo (which I don't blame you for at all, there is nothing wrong with it for general practice).
I would hazard a guess that the carbine buffer will help - don't get ahead of yourself with what ifs. Just one word on steel case ammo, Tula is really the worst of the bunch, barnaul ammo such as bear or the newer wolf wpa is much better, especially on such a barrel/gas port combo which is known to be finnicky with weak ammo.
Aye, I have no doubt that quality of ammo makes a big difference. But I have high quality brass 223 and it was still getting failures =( so I know it's not because just Tula is garbage(which it is). Trust me
I would much rather put high qual ammo only through my guns but given my current financial status and the rediculous prices as of late it's not possible. Hopefully the lighter weight buffers will help with what's going on. If not then I guess I'll have to sell my crappy ammo and just shoot less.
ckimball09
03-29-13, 17:01
UPDATE:
Got both H and Car buffers in. First i tested it with the H buffer and on the 3rd round got a FTF. So i figured i might as well put the Carbine buffer in. The carbine buffer did run tula better but still had the occasional FTF about 3-4 times out of 30 rounds.. So its somewhat of an improvement but still no where close to reliable.. The FTE's and the double feeds were non existent though.. so i was happy about that.. but now im dissapointed because it has to be a gas problem from what i understand? Given the ammo is also a problem but i think any self defense or fighting carbine/rifle should run ANY ammo(to a certain extent) no matter how crappy it may be... So now im not sure what i want to do.. :suicide:
Ok. Except you're wrong. Tula ammo is crap and inconsistent. When the AR platform came about there was no such thing as steel cased 5.56 ammo. The loading makes all the difference as I have put at least 3500 rounds of Hornady steel case through my AR's and have had ZERO malfunctions.
Run the gun with some real ammo first as suggested several times already.
UPDATE:
Got both H and Car buffers in. First i tested it with the H buffer and on the 3rd round got a FTF. So i figured i might as well put the Carbine buffer in. The carbine buffer did run tula better but still had the occasional FTF about 3-4 times out of 30 rounds.. So its somewhat of an improvement but still no where close to reliable.. The FTE's and the double feeds were non existent though.. so i was happy about that.. but now im dissapointed because it has to be a gas problem from what i understand? Given the ammo is also a problem but i think any self defense or fighting carbine/rifle should run ANY ammo(to a certain extent) no matter how crappy it may be... So now im not sure what i want to do.. :suicide:
constructor
03-29-13, 21:29
If you want to run cheap ammo open the gas port to .082(#45) or .086(#44) using wire sized bits and the standard carbine buffer. When using full power ammo run the H2 buffer.
UPDATE:
Got both H and Car buffers in. First i tested it with the H buffer and on the 3rd round got a FTF. So i figured i might as well put the Carbine buffer in. The carbine buffer did run tula better but still had the occasional FTF about 3-4 times out of 30 rounds.. So its somewhat of an improvement but still no where close to reliable.. The FTE's and the double feeds were non existent though.. so i was happy about that.. but now im dissapointed because it has to be a gas problem from what i understand? Given the ammo is also a problem but i think any self defense or fighting carbine/rifle should run ANY ammo(to a certain extent) no matter how crappy it may be... So now im not sure what i want to do.. :suicide:
Did you run your "high quality brass ammo" you mentioned last time with the lighter buffer to see how that went?
As I mentioned earlier, its unfortunate you have picked a barrel/gas combo that really is not conducive to running low powered, inconsistent ammo. To troubleshoot further, you are going to have to stop using the Tula for a while and see how it goes with better ammo. If it still plays up with good standard western branded commercial brass, the next thing I'd be thinking about is is there some sort of gas leakage (carrier key for example), whether the gasport is partially obstructed through gasblock misalignment, etc.
At the end of the day, if your goal really is to run crap Tula ammo as reliably as possible (and as I already mentioned it is the worst of the worst steel case you can get as loading can be very varied round to round), you'd be better off rebarreling to, say, a 16" carbine gas length system with a barrel from a company that is known to produce barrels that have slightly oversize gasports. Unfortunately it will make for a much 'lumpier' rifle when shooting decent ammo.
But for now - just stop using that Tula and try putting a good amount (i.e. several hundred rounds) of your quality ammo through it and see how that goes.
ckimball09
03-30-13, 01:02
Did you run your "high quality brass ammo" you mentioned last time with the lighter buffer to see how that went?
As I mentioned earlier, its unfortunate you have picked a barrel/gas combo that really is not conducive to running low powered, inconsistent ammo. To troubleshoot further, you are going to have to stop using the Tula for a while and see how it goes with better ammo. If it still plays up with good standard western branded commercial brass, the next thing I'd be thinking about is is there some sort of gas leakage (carrier key for example), whether the gasport is partially obstructed through gasblock misalignment, etc.
At the end of the day, if your goal really is to run crap Tula ammo as reliably as possible (and as I already mentioned it is the worst of the worst steel case you can get as loading can be very varied round to round), you'd be better off rebarreling to, say, a 16" carbine gas length system with a barrel from a company that is known to produce barrels that have slightly oversize gasports. Unfortunately it will make for a much 'lumpier' rifle when shooting decent ammo.
But for now - just stop using that Tula and try putting a good amount (i.e. several hundred rounds) of your quality ammo through it and see how that goes.
Aye, time to sell all my Tula for some decent 5.56. That is my plan for the time being. I wont buy anymore tula after this thats for sure.
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