I like jelly, but I don't like this kind of jam...

[Redtbird]

Hope this is in the right place.

I need some help figuring out what is wrong with my AR-15. It is a New Frontier lower and an RGuns upper, chambered in 5.56.

It has serious problems with jamming. The cartridge being ejected gets turned backwards with the base facing the breech. Then, as the bolt is coming forward, it picks up the next round from the mag. However, as the spent cartridge is in the way, the new round gets stuck under it.

Sometimes I can drop the mag and then gravity clears it. Other times, mostly, I have to wiggle the spent cartridge loose and then drop the mag.

This happens at least once on every mag.

Tonight at the range, I was working with a friend who has more experience in these matters than I do. He looked over my AR before we even went to the firing line, and pronounced it clean, clear and ready to go.

I started with the first mag, and after about 8-10 rounds, it jammed. We cleared it and started again. Then, a few shot later, I got a “horizontal stovepipe”. This cleared easily.

On the second mag, he gave me one of his Pmags(?). I have been using A.C.S. mags bought from Natchez Shooters Supplies. We even switched ammo. The same jam happened with his mag. So, next we switched out the bolt carrier, his in my rifle. Same thing. We even switched complete uppers, and got to the 14th round before it jammed.

Basically, we built a “Franken-Rifle” and it still jammed. Out of 60 -70 rounds fired, there were 5-7 jams.

Any thoughts, ideas, suggestions from INGO experts on this? Has anyone experienced anything like this?

 

[CQB]

What Gas system length?
buffer weight?

 

[Redtbird]

What Gas system length?
buffer weight?

Leaper's A2 stock with correct buffer.

How would I measure the length of the gas system?

 

[Hop]

So the problem stays with your rifle length lower correct? What spring did you use? Correct buffer is a rifle buffer correct?

You say you swapped carriers but did you mean bolt carrier group? The whole things not just the carrier.

 

[Mgderf]

May sound like a stupid question, but is the bolt 180 degrees off in the carrier?

 

[Leo]

I have seen that when people use one of those clip on case deflectors. Never seen it on a plain rifle. Do the cases that make it out ok have a dent in the middle of the body? Stick a piece of foam rubber weather stripping on the brass deflector bump and see if it is hitting that and bouncing back. The foam with change the direction of bounce back.

I have been successful tuning the ejector plunger to set my brass where I want. My match guns set the brass in a pile one foot to the right and two feet forward. Drive the 1/16th inch roll pin out and remove the ejector plunger (be ready to catch it, the spring will launch them) , cut two or three coils from the back end of the ejector spring at a time. If you switched the bolt and bolt carrier group, that would seem to eliminate a too strong of ejector spring. Changing ammo would seem to eliminate that variable. Strange problem.

 

[cwillour]

How long is your barrel & how far in front of the upper receiver is your front gas block? That will tell us what length gas system you have.

I know you said you have the correct buffer for the A2 stock, but could you put the length up for us just to rule it out?

I know is might sound strange, but can you tell if there is any extra drag when you cycle the action? Is it possible the receiver extension isn't straight out the back and could be causing some issues?

 

[Redtbird]

So the problem stays with your rifle length lower correct? What spring did you use? Correct buffer is a rifle buffer correct?

You say you swapped carriers but did you mean bolt carrier group? The whole things not just the carrier.

The new A2 stock is from Leaper's, and is a UTG RB-T469B Model 15/16 Standard A-2 Stock. This buffer spring is longer than the spring in the collapsible stock on my friend's AR.

First we swapped the entire bolt carrier group. Then, we swapped the complete upper, with my friend's BCG in it. The only original parts then were my lower. Still had the same problems.

 

[Redtbird]

May sound like a stupid question, but is the bolt 180 degrees off in the carrier?

No. First thing my friend checked.

 

[Redtbird]

How long is your barrel & how far in front of the upper receiver is your front gas block? That will tell us what length gas system you have.

I know you said you have the correct buffer for the A2 stock, but could you put the length up for us just to rule it out?

I know is might sound strange, but can you tell if there is any extra drag when you cycle the action? Is it possible the receiver extension isn't straight out the back and could be causing some issues?

Buffer measures 5 7/8". Buffer spring is 12 3/4 inches long, or 2 1/4" longer that the spring for the adjustable stock.

Barrel measures at 16 1/2 inches.

I had the same jamming problem with the original adjustable stock too.

Doesn't seem to be any drag, and the friend I was working with yesterday agreed the rifle was in good shape, except for the jamming problems.

 

[cwillour]

Buffer measures 5 7/8". Buffer spring is 12 3/4 inches long, or 2 1/4" longer that the spring for the adjustable stock.

Barrel measures at 16 1/2 inches.

I had the same jamming problem with the original adjustable stock too.

Doesn't seem to be any drag, and the friend I was working with yesterday agreed the rifle was in good shape, except for the jamming problems.

If the barrel is 16.5", you likely have a carbine or mid-length gas system (distance from the receiver to gas block will tell which one.)

Do I understand that you changed the receiver extension? (buffer tube) If so, how about the trigger &/or mag catch?

Any unusual wear/rub marks on your BCG?

A few pics may help, as might a close inspection of the lower next to another (known good) unit.

 

[SEIndSAM]

Since the problem is with your lower, there is either something wrong with your buffer/tube/plunger or your BCG is dragging across your hammer/trigger group.

Is there any dents in your buffer tube? Is your buffer tube on straight??? Make sure the castle nut is tight.

Try using your friends spring & plunger and see if that helps.

Is your hammer spring correctly installed??

 

[Redtbird]

Since the problem is with your lower, there is either something wrong with your buffer/tube/plunger or your BCG is dragging across your hammer/trigger group.

Is there any dents in your buffer tube? Is your buffer tube on straight??? Make sure the castle nut is tight.

Try using your friends spring & plunger and see if that helps.

Is your hammer spring correctly installed??

There are no dents in the buffer tube.

The buffer tube is on straight.

With the A2 stock, there is no castle nut. There is a screw in the top of the butt plate that holds everything together.

My friend's AR had a collapsible butt stock.

The hammer spring was installed at the factory, not by me. I would imagine it is all right.

 

[HamsterStyle]

Imagining that it is alright isn't good enough. I would check it out for sure. Compare it to your buddies known good lower to be sure.

 

[Redtbird]

If the barrel is 16.5", you likely have a carbine or mid-length gas system (distance from the receiver to gas block will tell which one.)

Do I understand that you changed the receiver extension? (buffer tube) If so, how about the trigger &/or mag catch?

Any unusual wear/rub marks on your BCG?

A few pics may help, as might a close inspection of the lower next to another (known good) unit.

Yes, I changed it from having a collapsible butt stock to an A2 butt stock.

Did not change neither the trigger nor the mag catch.

We did not notice any unusual wear on the BCG. My friend, who has built several ARs, gave it a thorough check.

Will try and get some pics.


The place where I bought it, Black Star Tactical, in Moores Hill, IN, has suggested I send it back to them so they can go thru it and diagnose the problem. Later today, I will go to my storage unit and see if I still have the original box for it.

 

[Hop]

I haven't heard of it happening before but maybe that rifle length receiver extension spring is too stiff. It wouldn't hurt to put the rifle buffer on a scale and weight it either.

 

[cwillour]

Yes, I changed it from having a collapsible butt stock to an A2 butt stock.

Did not change neither the trigger nor the mag catch.

We did not notice any unusual wear on the BCG. My friend, who has built several ARs, gave it a thorough check.

Will try and get some pics.


The place where I bought it, Black Star Tactical, in Moores Hill, IN, has suggested I send it back to them so they can go thru it and diagnose the problem. Later today, I will go to my storage unit and see if I still have the original box for it.

Since you mentioned it having the problem before changing the receiver extension (IIRC), I might put that aside for now. Barring the threading for the extension being slightly out-of-alignment (resulting in an out-of-alignment extension, which may or may not be obvious to the naked eye) I am inclined to believe the issue is up front on the lower.

There are some reports online about some of the polymer triggers being wider-than-spec and dragging on the BCG. Similarly there are some reports of the mag catch having issues or being slightly mis-located and causing FTE issues. I might have missed it, but were all the mags polymer or did you try an aluminum mag as well?

Also, how is the front take-down pin? Any play?

 

[jonny4523]

You know, if I were you, I'd just junk the whole lower. Buy a quality lower from Palmetto State Armory and be done with it. With as cheap as they are right now, it'd be a no brainer for me.

 

[Redtbird]

Since you mentioned it having the problem before changing the receiver extension (IIRC), I might put that aside for now. Barring the threading for the extension being slightly out-of-alignment (resulting in an out-of-alignment extension, which may or may not be obvious to the naked eye) I am inclined to believe the issue is up front on the lower.

There are some reports online about some of the polymer triggers being wider-than-spec and dragging on the BCG. Similarly there are some reports of the mag catch having issues or being slightly mis-located and causing FTE issues. I might have missed it, but were all the mags polymer or did you try an aluminum mag
as well?

Also, how is the front take-down pin? Any play?

The mags I am using are A.S.C. mags from Natchez Shooters Supply. They are 20-round, gray aluminum, with a grey follower.

When the upper is fully seated on the lower, there is no discernible movement between the two parts.

I opened it up and put a small piece of tape on top of the trigger. Then I cycled it 10-12 times, pulling the trigger each time. First I used Scotch tape, and then replaced it with silk surgical tape, as it is a bit thicker than the scotch tape. I noticed no rub marks, scuffs or anything that would denote the trigger and the BCG having any contact.

While at the range, I did try a 30-round polymer magazine, and had the same type of jam with it.

When changing the butt stock, the buffer tube screwed on very easily and is definitely not cross-threaded.

 

[Hop]

How hard is it to pull the charging handle to the rear? Does it feel like it drags?

Screwed in easily doesn't guarantee it's perfectly in line with the upper.