Failure to lock back, failure to feed

[jwfuhrman]

I posted about my buddies 18in Rifle gas SS410 upper awhile ago on some issues it was having.

We have it narrowed down to not locking back/or feed the next round with ANY ammo. Handloads, XM193, XM855, any ammo will not lock back or feed.

Doing the 1 round in a mag test for locking back and 2 in to see if it will strip a round off, it will not.

I'm assuming this is a gas issue. The gas port is at .096 currently. We tried different lowers, different buffers, different buffer systems, different buffer weights and it still wont work.

What is the next step?

[mtrmn]

Saw this issue in another thread (maybe on another forum) and the screw holding the stock on the buffer tube was too long. It would not allow the BCG to come back far enough.

This is, of course , if you don't have the normal collapsible stock and you have the rifle-length buffer tube.

[mtrmn]

Also, you may have a rifle-length buffer spring in a carbine-length buffer tube

Sorry-----re-read your post and I see you tried different lowers:confused:

[jwfuhrman]

Ok really? A ****ing rifle buffer in a carbine buffer tube? Who is that ****ing stupid?

Can we get actual intelligent help please?

[DirectDrive]

Have you verified that the gas system is clear ?

Gas port open ?
Gas block open ?
Gas block properly aligned with gas port ?
Tube installed properly ?

Is tube dragging on gas key ?

How about trying a different, known-good BCG ?

[jwfuhrman]

checked all of the above, tried 3 different good BCG's.

It has done this since it was factory new.

The upper is a factory made BCM upper. He's emailed BCM twice in the last 2 months with no reply and calling doesn't work either.

[Tweak]

can you pull off the FSB?

What is the inside diameter of the gas tube?

[polymorpheous]

Since you've ruled out all of the usual suspects...
I guess I would start with the cheapest part and replace the gas tube.

[mtrmn]

Ok really? A ****ing rifle buffer in a carbine buffer tube? Who is that ****ing stupid?

Can we get actual intelligent help please?

Re read my post-I clearly stated buffer spring

And you can jump up an armadillo's ass

[jwfuhrman]

can you pull off the FSB?

What is the inside diameter of the gas tube?

Low pro gas block.

Have not checked that. He's got his rifle back with him, 2hrs away. Will advise him to do this.

[jwfuhrman]

Since you've ruled out all of the usual suspects...
I guess I would start with the cheapest part and replace the gas tube.


Already have done this, twice.

I'm starting to wonder if he just got a lemon.

[jwfuhrman]

Re read my post-I clearly stated buffer spring

And you can jump up an armadillo's ass

:rolleyes: :suicide:

[Brahmzy]

I'd be opening up a can on BCM. FIX IT. Not your problem. If you built it, your problem. If they built it, their problem and they need to FIX IT.

[DirectDrive]

Gas port size seems big enough....although you have a little reduction in dwell with an 18" rifle gassed rig.

I'd try a reduced power buffer spring before doing anything permanent, though. With a CAR (standard) buffer, of course.

http://dsgarms.com/ProductInfo/WOL16502.aspx

It's hard to find clear and concise info on gas port sizing.
Here is a link to a thread where a guy is trying to get an 18" rifle-gassed rig to run.
The interesting part is at the bottom of the page where he goes to .101 diameter and gets it to run.
He started from .093 and went up in .002 increments.
http://www.uzitalk.com/forums/archive/index.php/t-45226.html

[jwfuhrman]

He is using a rifle buffer system(MagPul PRS stock).

[Tweak]

Already have done this, twice.


If he's already replaced the gas tube twice then there is no reason to check it, odds against three being too small are pretty low.

I'm assuming that you can lock the bolt open with the face of the bolt behind the bolt catch.

You say the gas port is fine and that the block is lined up and you've tried other BCGs and tubes so have him send it back.

Have him call BCM, maybe his emails aren't making it through some spam filter.

[Cincinnatus]

That's weird that it won't lock back OR feed on any ammo type instead of just one or the other.
Let us know what BCM says once your buddy finally gets through.

[jwfuhrman]

I should re hash my first post.

It will feed Nato spec ammo, handloads and factory loads like American Eagle 55gr, but just not lock back.

It will not feed Hornady Steel cased ammo(both Steel Match and TAP Training), Precision cartridge(imported zinc cased), UMC(that doesn't surprise me on that), or something other stuff.

Maybe I will open it up farther then in .002 increments till it works.

[DirectDrive]

He is using a rifle buffer system(MagPul PRS stock).
In his last two posts he talks about an H buffer and then settling on running a CAR buffer.
I believe that this rig is similar to yours.

OIC, your buddy is running PRS.....

Might be worth a shot to try a reduced power spring before committing to changing the gas port.
It sounds like you're close.

Here's a better link to Wolff Springs
http://www.gunsprings.com/index.cfm?page=items&cID=2&mID=1&dID=79

[Scorpion]

Did you try changing out the FSB? If it isn't undergassed, maybe there's an obstruction in there (maybe a burr or something).

[Iraqgunz]

I understand that you are trying to assist. However, him saying I have emailed them twice doesn't cut it. Let's follow the standard course of action since nothing else has worked thus far.