Advice needed

[GunDogRandomness]

I'm working on the finishing touches on a pistol build and I have seen an issue I hope can be easily fixed. This is only my third build so I am not an expert. Here is the problem:

Once fully assembled I wanted to check for functionality and loaded a round in a mag to make sure it would chamber properly. While the round did make it into the chamber the BCG was only about 80% forward. Not even far enough that the forward assist would be able to help. I have to lock the bolt to the rear and turn the rifle vertical to extract the round. My first guess was an issue with the BCG but I have used it in another rifle without a single issue with nearly 500 rounds.

Would headspace be an issue? The upper parts I am using are a Spikes BCG, Spikes upper, and an Aero 10.5 barrel. I am going to try switching to my BCM BCG this evening to see if that helps. If anyone has any other ideas let me know.

Thanks in advance for any assistance!

[Dstrbdmedic167]

Headspace is one thing you can check. You can also try different ammo. I had this issue with an aero barrel in the last and was due to out of spec ammo.

[UWone77]

Could be a number of things, but I would start where you were going... try another BCG and see where you're at.

[Dstrbdmedic167]

Just make sure you do one thing at a time and check to see if the problem is fixed. Don't do a bunch of things at once then when it's fixed your still left wondering....

[WHSmithIV]

You might find that you need to ream out the barrel extension. What one manufacturer told me when they called me was that with new barrels there is often some grit left over in the barrel from the manufacturing process. I was having a similar problem - not quite the same in that the cartridge did fully seat in the chamber but wouldn't extract. I wrapped some 0000 steel wool around one of the bits of my dremel and simply ran it in the chamber for a little bit then cleaned the barrel again and it cleared up the problem.

[BoilerUp]

Does the bolt properly lock into the lugs of the barrel extension (without a round in the chamber)? Do the feed ramps on the receiver line up properly and tightly with the feed ramps on the barrel extension? If the answer to either or both of these is "no" then the barrel extension indexing pin actually may not be properly lined up into the slot on the upper receiver fully seated all the way back.

Is the bolt NiB coated? I've read stories on the interwebs where coated bolts won't lock into the barrel extension due to the extra thickness.

[Computalotapus]

You might find that you need to ream out the barrel extension. What one manufacturer told me when they called me was that with new barrels there is often some grit left over in the barrel from the manufacturing process. I was having a similar problem - not quite the same in that the cartridge did fully seat in the chamber but wouldn't extract. I wrapped some 0000 steel wool around one of the bits of my dremel and simply ran it in the chamber for a little bit then cleaned the barrel again and it cleared up the problem.

If you gotta do this IMHO then just get a new barrel and from some place reputable


Does the bolt properly lock into the lugs of the barrel extension (without a round in the chamber)? Do the feed ramps on the receiver line up properly and tightly with the feed ramps on the barrel extension? If the answer to either or both of these is "no" then the barrel extension indexing pin actually may not be properly lined up into the slot on the upper receiver fully seated all the way back.

Is the bolt NiB coated? I've read stories on the interwebs where coated bolts won't lock into the barrel extension due to the extra thickness.

These are both easy to verify. Always look at the little things before jumping to the big conclusions of what might be wrong.

[UWone77]

If you gotta do this IMHO then just get a new barrel and from some place reputable



These are both easy to verify. Always look at the little things before jumping to the big conclusions of what might be wrong.

Pretty much spot on.

This is likely an easy fix, as simple as the extractor. Like Comp said, start small and eliminate one possible issue at a time.

[Eric]

Clean and lube generously, to include the use of a chamber brush.
Strip the bolt, firing pin and cam pin from the carrier. Does the stripped carrier fit the upper, move freely and does the gas key on the carrier correctly match up with the gas tube? Do the M4 style feed ramps on the barrel extension match up with the cutouts in the upper?

[JHoward]

Make sure it's not hitting the gas tube as well.

[DutyUse]

Make sure it's not hitting the gas tube as well.

that was my thought too

[Stone]

"and loaded a round in a mag to make sure it would chamber properly" Did you load it on a closed bolt then charge the rifle or was it locked to rear and you dropped the bolt catch?

[JHoward]

Mine would only hit with an uploaded mag in.

[WHSmithIV]

Make sure it's not hitting the gas tube as well.

Actually, by the description, that could actually be the problem - the gas tube not lining up into the gas key would certainly stop the bolt from going forward.

[DutyUse]

This might have already been asked but you used a carbine gas tube right? And not a pistol length?

[Fathom_Arms]

Check the gas tube. Also scrub our chamber with a chamber brush.

[Gaspipeshooter]

Does the bolt go home and everything cycle freely when the pistol is empty? It might be the ammo you are using...

[Jerry R]

Just a couple of questions:

Does the rifle correctly pass all function checks without ammunition?
Will a loaded or dummy round freely, and completely, drop into the chamber by hand? Pull the upper, remove the BCG and drop one in.
When you "turn the rifle vertical" does the round fall out, or do you have to pull it out? If you have to pull it out, how much force is required?
If you ease the BCG slowly forward on an empty chamber, do you feel any resistance or binding as the carrier moves in the upper?
While checking the last question, watch the key through the ejection port. Does the tube easily enter the key without "moving"; i.e., does the key have to move it to complete the cycle?

Think through the answers as you perform the function checks, it might help you narrow down the issue. What would cause the rifle to pass/fail the specific question. As others have said, small steps and eliminate one thing at a time. Hope this helps.

[John Moses]

+1 On the gas tube. My best guess is that you did not properly line up the barrel nut to the upper. Depending on the Barrel nut used (you didn't mention if it was the stock style) I bet you have the Gas tube cocked to the side. Diassemble the upper, and verify the gas tube is not crooked in the upper. Next guess would be an Extractor issue. You should be performing these tests without the Lower attached. Simply place the Charging handle and BCG in the upper and see if you can get it to seat. My biggest question is, how did you get the Upper onto the lower in the first place if the bolt will not go all the way forward?

[DutyUse]

He must have figured it out or thought we didn't have the right answers because he posted 5x and hasn't been back since starting this thread lol

[GunDogRandomness]

My apologies for the delayed response. I have a six week old son at home and finding time to tell the wife I'm going out to the workshop is about as rare as sleep these days...

I can't thank everyone enough for the quick responses. I took the advice and checked each idea one at a time to help identify the issue. Just as several of you thought it seems to have in fact been the tube. I was using a standard barrel nut and it was just slightly pushing the tube to one side inside the receiver.

I stripped the upper last night and reassembled to correct the issue. On checking again once complete the issue seems to be fixed! Now I just have to find some time to get it to the range for real testing.

Maybe if I wasn't sleep deprived I could have figured it out without the advice. Good to know there is such a great wealth of knowledge out there. Thanks again!

[DutyUse]

Sleep what's that? Ha just drink another 5hr.. Try a newborn AND a potty training 2.5yr old AND 4 dogs AND full time work.

Just teasing bro I know it's rough, hang in there it's worth it. At least your family's not sick like mine... Always could be worse. Glad you got the upper fixed :)

Now go burn some mag dumps and report back ;)

[BoilerUp]

Thanks for getting back and positing the resolution. I like learning from other people's mistakes!

And I've got two toddlers underfoot, so I know how it goes. Glad you got it figured out.

[Iraqgunz]

For the record. According to the technical manual, you can manually tweak the gas tube. All you need to do is use a large flat tip screwdriver and place it between the receiver wall and the tube. Simply tweak the tube, the direction it needs to go. Usually it is very minimal adjustment. It's also a good idea to check the alignment with a stripped BCG so that you can tell if the carrier key is the binding point.