LMT FA BCG issue

[Shooter McGavin]

I have a LMT upper with a AXTS Raptor Ambi charging handle and a LMT full auto BCG.

The BCG fit in fine but the issue is when I pull back on the charging handle the bolt catches on something and sticks after about an inch to an inch and a half. It seems to be catching on the bolt release. That's the only thing I can see that would impede the movement of the bolt inside the upper.

Does anyone have any similar experiences or possibly a remedy?

[danieljmaunder]

I have a similar issue with a Les Bauer Semi BCG and a PRI gas buster. still trouble shooting, i am about to yank the bolt catch and swap it out. if that works i'll let ya know

[danieljmaunder]

I have a LMT upper with a AXTS Raptor Ambi charging handle and a LMT full auto BCG.

The BCG fit in fine but the issue is when I pull back on the charging handle the bolt catches on something and sticks after about an inch to an inch and a half. It seems to be catching on the bolt release. That's the only thing I can see that would impede the movement of the bolt inside the upper.

Does anyone have any similar experiences or possibly a remedy?

Update, bolt catch was not the culprit. The firing pin retaining pin was loose and was catching on the inside of the receiver.

[Shooter McGavin]

My issue has to be the bolt catch. When I hinge the upper open the bolt slides right out.

I can't see what else it could be.

[Cincinnatus]

Do it with another BCG, too?
Is it your forward assist snagging?

[AM-15]

With your hammer in the cocked position you will feel some resistance at about the 1.5" ish area where the carrier is contacting the top of the hammer pushing it down.
Rifle unloaded, dryfire so hammer is resting on carrier, slowly pull back charging handle, at a point you will see the trigger move forward and set.
Is this the area that you are feeling the issue ?

Clarence

[DreadPirateMoyer]

With your hammer in the cocked position you will feel some resistance at about the 1.5" ish area where the carrier is contacting the top of the hammer pushing it down.
Rifle unloaded, dryfire so hammer is resting on carrier, slowly pull back charging handle, at a point you will see the trigger move forward and set.
Is this the area that you are feeling the issue ?

Clarence

This was exactly what I came here to post. Are you guys experiencing this sure you're not feeling the BCG contact the hammer, even if cocked?

[Shooter McGavin]

Do it with another BCG, too?
Is it your forward assist snagging?

I swapped out the bcg with a RRA BCG and experienced the exact same problem.

I checked to see if the forward assist was protruding to the inside of the receiver and it is not.

[Shooter McGavin]

With your hammer in the cocked position you will feel some resistance at about the 1.5" ish area where the carrier is contacting the top of the hammer pushing it down.
Rifle unloaded, dryfire so hammer is resting on carrier, slowly pull back charging handle, at a point you will see the trigger move forward and set.
Is this the area that you are feeling the issue ?

Clarence

Hey Clarence...I dry fired the rifle and slowly pulled back on the charging handle. It doesn't move far enough back to reset the trigger. I would imagine that if it is hitting the hammer it would give when applying more rearward pressure on the charging handle.

What I am experiencing is a dead stop.

[Leaveammoforme]

Hey Clarence...I dry fired the rifle and slowly pulled back on the charging handle. It doesn't move far enough back to reset the trigger. I would imagine that if it is hitting the hammer it would give when applying more rearward pressure on the charging handle.

What I am experiencing is a dead stop.

Is the rear end of your carrier hitting the lip of the receiver extension?

[TommyG]

Buffer retainer out of whack somehow and snagging it?

[Shooter McGavin]

I thought about that but when the upper is locked into the lower the rear of the bcg abuts the receiver extension. If it were interfering I wouldn't be able to pull it back at all. Rihht? Could it be a wrong spring and buffer?

[Shooter McGavin]

Buffer retainer out of whack somehow and snagging it?

Thought about that too but the buffer retainer lines up perfectly with the channel on the bottom of the carrier.

[AM-15]

You never mentioned your lower and what is in it.
You would not by chance have a rifle buffer in a carbine stock ?

Clarence

[Shooter McGavin]

I bought a LMT lower receiver group with an A2 stock and took the spring and buffer from that along with a mil spec carbine buffer tube to install a Magpul MOE stock.


https://imagizer.imageshack.us/v2/320xq90/r/922/Ka5jhc.jpg

[SeaDonkey]

Do you have different complete upper you can test on the culprit lower?

Also, test the culprit upper on a different lower.

[SeaDonkey]

A2 buffer spring and buffer are longer/larger than carbine. That is your issue.

[AM-15]

I bought a LMT lower receiver group with an A2 stock and took the spring and buffer from that along with a mil spec carbine buffer tube to install a Magpul MOE stock.


https://imagizer.imageshack.us/v2/320xq90/r/922/Ka5jhc.jpg

Rifle buffer about 6" long
Carbine buffer about 3.25" long
That is why the carrier only moves about an inch and stops.

Clarence

[Shooter McGavin]

Well...there you have it.

The education of a noob continues. :)

Is it just the spring? Can I use the same buffer?

[AM-15]

The 6" buffer is what is stopping the carrier.
You need a carbine buffer at minimum and might as well get a spring.
What length gas system on the upper ?

Clarence

[Shooter McGavin]

The 6" buffer is what is stopping the carrier.
You need a carbine buffer at minimum and might as well get a spring.
What length gas system on the upper ?

Clarence

I bought a LMT 14.5 " upper receiver group like this one.

https://dsgarms.com/lmtl7d1

I think it's a carbine length tube.

I replaced the A2 front site with a LaRue low profile gas block. I kept the barrel and gas tube.

[AM-15]

Just some added information.

It is a good thing that it went in this direction and not a carbine buffer in a rifle length tube.
That would have done some damage if fired.

Take your time and get it corrected.

If carbine length gas then depending on the ammunition you use, would go carbine or h1 buffer and spring.
I keep a Carbine, H1 and H2 handy with a few springs.

Get it resolved and enjoy the rifle.

Clarence

[Shooter McGavin]

Take your time and get it corrected.

Clarence

I intend to.

I have been building this since October, as funds allow.

I have been function checking along the way and so far this is the first issue that has presented itself.

It has not been fired yet. There is a gunsmith at my range. I think I'll have him give it the once-over before I fire the rifle.

[Shooter McGavin]

Any reason I would need a "h" carbine buffer rather than a regular carbine buffer?

[Cincinnatus]

Any reason I would need a "h" carbine buffer rather than a regular carbine buffer?

Yes. Longer service life, longer dwell time, etc. Essentially, you want the heaviest buffer that will still lock back reliably with the ammo you intend to run.

[Shooter McGavin]

Yes. Longer service life, longer dwell time, etc. Essentially, you want the heaviest buffer that will still lock back reliably with the ammo you intend to run.

Good information.

I'll order accordingly.

Thanks.

[Shooter McGavin]

37978

Well there you have it.

The difference between a carbine buffer and spring and a rifle buffer and spring and the cause of my problem this past week of not being able to charge my rifle.

Here's a pic for all of those that are learning like me.

[AM-15]

All is well that ends well.
Glad we could help :smile:

Clarence

[Shooter McGavin]

I suppose in all fairness to LMT I should change the name of the title of the thread to something like "idiot behind charging handle doesn't know the difference between a carbine and rifle sized buffer"

There is nothing wrong with the LMT BCG. :)

[Shooter McGavin]

All is well that ends well.
Glad we could help :smile:

Clarence

I really appreciate the assistance.

I love learning.