AR15.Com Archives
 Bolt won't chamber a round...
orientalexpress  [Member]
4/3/2012 9:14:33 PM EST
Just put together a colt socom barrel in a spikes upper. A friend of mine was sold me a brand new smith enterprises chrome bolt from brownells http://www.brownells.com/.aspx/pid=41509/Product/AR-15-M16-COMPLETE-BOLT I bought an lmt carrier that's not chromelined to go with it. When I go to chamber a round the bolt won't close. You have to pull back on the CH handle 2-3 times to get it seat. Hitting the FA does nothing. I tried locking the action open and letting it slam home with by releasing the bolt release. I tried the BCG in another upper same result. I tried a different BCG in the upper I just put together and ran through a mag , flawless. Tried swapping carriers bolts. Could the mixture of chromelined and nonchromelined parts be causing an issue? Once you get a round in the chamber you can shoot aboutn3 rounds before it does the same thing. All I can figure is that it's either out of spec, the chrome is causing it to be slightly out of tolerances, or it needs to be broke in. My friend offered to give me my money back but for $25 I think I'd rather try to get it working and if not chalk it u as a loss. Suggestions?
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C_1  [Member]
4/3/2012 9:18:48 PM EST
Did you try the Smith bolt with the running carrier? And did you try the LMT carrier with the running bolt? That should help you with finding the culprit.
bhouse1545  [Team Member]
4/3/2012 9:19:14 PM EST
I don't know much on this but it sounds like your bolt and the barrel are not head spaced correctly this could be a very dangerous thing when going to shoot get it checked out by a gunsmith.

Edit could also be that the bolt is out of spec too just saying
orientalexpress  [Member]
4/3/2012 9:26:39 PM EST
Originally Posted By C_1:
Did you try the Smith bolt with the running carrier? And did you try the LMT carrier with the running bolt? That should help you with finding the culprit.



Yes and yes. Im 99% sure it's bolt related. I have 2 of the lmt carriers both brand new. This past weekend was the first time I had gotten to use either of them. Before I had taken them to the range I swapped the carriers to see if maybe one of the carriers was causing the issue. Both resulted in the same result. The night before I had went shooting was the first time I had tried to chamber a round since its the first time I'd be able to shoot since putting together. I was thinking maybe the chromelined bolt didn't like the nonchromelined carrier but I really fail to see why it would cause a problem.
Obo2  [Member]
4/3/2012 9:27:11 PM EST
See how it locks up with no round in the chamber. can check with go no go gauges all though a gunsmith may do it for you relatively inexpensively or free compared to buying the gauges. Sounds like the bolt if out of spec (Lugs too big, bolt face not deep enough) somewhere since you said it was showing the same issue in a different upper. If it is the chrome lined bolt there's not a whole lot you would be able to do without destroying the chrome which would take some effort in and of itself.
orientalexpress  [Member]
4/3/2012 9:30:35 PM EST
I didnt mention this specifically or make it super clear but it only does it if chambering a round.
Obo2  [Member]
4/3/2012 9:34:44 PM EST
Then most likely bolt headspace is off nice paper weight or go get your $ back... well strip it down make sure ejector doesn't have something clogged under it. Make sure you can fully depress ejector.
C_1  [Member]
4/3/2012 9:34:54 PM EST
Originally Posted By orientalexpress:
Originally Posted By C_1:
Did you try the Smith bolt with the running carrier? And did you try the LMT carrier with the running bolt? That should help you with finding the culprit.



Yes and yes. Im 99% sure it's bolt related. I have 2 of the lmt carriers both brand new. This past weekend was the first time I had gotten to use either of them. Before I had taken them to the range I swapped the carriers to see if maybe one of the carriers was causing the issue. Both resulted in the same result. The night before I had went shooting was the first time I had tried to chamber a round since its the first time I'd be able to shoot since putting together. I was thinking maybe the chromelined bolt didn't like the nonchromelined carrier but I really fail to see why it would cause a problem.



So you ran a different BCG and it worked? But when you put in the LMT/Smith BCG combo, it doesn't want to chamber a round? And you tried the Smith bolt with a known running carrier, and the LMT carrier with a known running bolt? If so, it sounds like the Smith bolt is out of spec.
orientalexpress  [Member]
4/3/2012 9:40:39 PM EST
Originally Posted By C_1:
Originally Posted By orientalexpress:
Originally Posted By C_1:
Did you try the Smith bolt with the running carrier? And did you try the LMT carrier with the running bolt? That should help you with finding the culprit.



Yes and yes. Im 99% sure it's bolt related. I have 2 of the lmt carriers both brand new. This past weekend was the first time I had gotten to use either of them. Before I had taken them to the range I swapped the carriers to see if maybe one of the carriers was causing the issue. Both resulted in the same result. The night before I had went shooting was the first time I had tried to chamber a round since its the first time I'd be able to shoot since putting together. I was thinking maybe the chromelined bolt didn't like the nonchromelined carrier but I really fail to see why it would cause a problem.



So you ran a different BCG and it worked? But when you put in the LMT/Smith BCG combo, it doesn't want to chamber a round? And you tried the Smith bolt with a known running carrier, and the LMT carrier with a known running bolt? If so, it sounds like the Smith bolt is out of spec.




The only thing I didn't do was use the non running carrier with a known working bolt. I was thinking about what someone posted earlier about the ejector.

C_1  [Member]
4/3/2012 9:46:58 PM EST
Yeah, I would strip the BCG down and make sure everything is installed correctly, including the ejector and cam pin. Check head space, oil it up, and try to chamber a dummy round.
ErikS  [Member]
4/4/2012 12:13:43 AM EST
Reloads? FL resized? Tight chamber?
SkipD  [Member]
4/4/2012 12:38:09 AM EST
What ammunition is being used when the problem is encountered?

If you take the BCG out of the rifle and drop a cartridge into the chamber with the muzzle pointed down, does the cartridge go all the way into the chamber under its own weight? Remember that about 1/4" of the cartridge base will be exposed when the round is fully chambered. If you lift the muzzle, the round should fall back out of the chamber.
TGagnon  [Member]
4/4/2012 1:02:22 AM EST
Why don't you just get a 5.56 head-space set? Sounds like you have multiple AR15 rifle systems that you like to tinker with. It would be a safe bet to just get a simple head-space set use it every time you change out a bolt, carrier, extension, or barrel. Best of all head-space sets retain there value so even if you decided you didn't need it and sold it down the road you wouldn't be out much. And you would have the added benefit of being able to verify the safety of all your chambers and your friends chambers without having to go to a gunsmith.
FMJ  [Team Member]
4/4/2012 2:11:48 AM EST
LMT makes non chromelined carries ?
H53EXPERT  [Member]
4/4/2012 3:20:56 AM EST
It sounds to me like something is interfering with the bolt rotation. Especially with it being an intermittent problem. Try a different cam pin, and you didn't force the cam pin into the wrong side of the hole in the bolt, did you?
orientalexpress  [Member]
4/4/2012 6:49:45 AM EST
Originally Posted By SkipD:
What ammunition is being used when the problem is encountered?

If you take the BCG out of the rifle and drop a cartridge into the chamber with the muzzle pointed down, does the cartridge go all the way into the chamber under its own weight? Remember that about 1/4" of the cartridge base will be exposed when the round is fully chambered. If you lift the muzzle, the round should fall back out of the chamber.


Yes a round can be dropped I and out freely. The ammo used was factory loaded. Out of about 100 rounds 60 was ppu 5.56 20 federal bulk .223 and 20 Pmc .223. All with the same result. I'll check the cam pin and measure it when I get some free time. I did look down in the receiver last night and I didn't notice any unusual wear marks.
CRsmoker250  [Team Member]
4/4/2012 7:07:39 AM EST
Not trying to be a jerk but did you verify the bolt is in the carrier in the proper orientation? It happens....
orientalexpress  [Member]
4/4/2012 9:25:03 AM EST
Originally Posted By CRsmoker250:
Not trying to be a jerk but did you verify the bolt is in the carrier in the proper orientation? It happens....


Yeah I'm sure ounces the bolt seats on the actual round it seats properly. If it was in wrong it wouldn't eject at all.
Gregory_K  [Team Member]
4/4/2012 11:08:14 AM EST
what kind of ammo?

Any changes to the lower?

Sure the bolt is a 556 one?

headspace?

If the gun cycles and locks up just fine with no ammo, but fails to work when ammo is added, I would look at your mags and ammo.

Would a rifle buffer in a carbine extension cause this kind of issue? or a rilfe spring in a carbine extension?
AR18  [Member]
4/4/2012 11:23:09 AM EST
Do you have pics of the problem?
pun  [Member]
4/4/2012 11:34:48 AM EST
I didnt know LMT made unlined carriers...sounds like a bolt problem.I like chrome bolts and use les baer or original Colt ones.
Cycline3  [Member]
4/4/2012 1:17:36 PM EST
extractor spring so tight it wont go over the round? take it out and see if it works without extractor, in not youre back to looking at the bolt.
orientalexpress  [Member]
4/4/2012 7:22:37 PM EST
I tried 3 different style mags 2 pmags, an older pmag, a new one, and a usgi mag. Ammo doesn't seem to be the problem and neither does the lower. I don't have a set of gauges.... Yet. I'll try pulling the extractor when I have some time. I know the spring isn't a bcm, or Wolf power spring. It does however have an o ring.
bdawg998  [Team Member]
4/4/2012 9:34:16 PM EST
Originally Posted By pun:
I didnt know LMT made unlined carriers...sounds like a bolt problem.I like chrome bolts and use les baer or original Colt ones.


I'm pretty sure that he's saying he's running a chromed bolt in a standard phosphated carrier. The word "lined" is throwing everyone off.
Pain  [Team Member]
4/5/2012 1:03:49 AM EST
check your gas tube?
smokingun45  [Member]
4/5/2012 5:31:51 AM EST
Originally Posted By orientalexpress:
It does however have an o ring.


Try taking the o-ring off the extractor spring.

orientalexpress  [Member]
4/5/2012 5:47:42 AM EST
Originally Posted By bdawg998:
Originally Posted By pun:
I didnt know LMT made unlined carriers...sounds like a bolt problem.I like chrome bolts and use les baer or original Colt ones.


I'm pretty sure that he's saying he's running a chromed bolt in a standard phosphated carrier. The word "lined" is throwing everyone off.


Yeah that's right right I probably didn't word it the best way. I dont think it's the gas tube, I thought maybe the same thing but I pulled the upper off and slid the bcg to make sure it wasnt banging the side of the gas key or something. Last night I was trying to get it exhibit the same symptoms but out of 40-50 tries of me chambering a round it only did it once. Where initially it would do it everytime.
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