Just Suppos'in

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plodder

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Just hypothetically imagine that a guy has an AR15 SBR,1 in 7" 7" barrel, Wylde chambered .223 with a SpecWar 5.56 silencer, possibly a carbine buffer & spring (not certain of that) standard non-adjustable gas block. Now suppose that this hypothetical firearm occasionally lets off 2 & 3 round bursts and it also occasionally jams a completely within SAMI spec .223 cartridge loaded with a 55g FMJ projectile prior to reaching battery condition.

If you came across such a firearm would you have a top 2 or 3 list of things to check?
1. Try adjustable gas block
2. Try different combination of spring/buffer
3. Other?

Let's assume that this fictional guy really likes this configuration and does not want to go with a longer barrel.

Just in case I come across a guy like this I want to point him to the right thing to look at first.
 
In that situation, I would advise the owner of the gun to work the problem 1 round at a time until the bolt locks back on the empty magazine.

The problem isn't the potential tripping of the machine gun status (though that is a concern), but more the fact that the rifle would be firing because the hammer is following the bolt. In that case, there is risk that the rifle will fire ever so slightly out of battery leading to a kaboom.

The other thing this will diagnose is if the disconnecter is engaging at all.

Theoretically of course.
 
it also occasionally jams a completely within SAMI spec .223 cartridge loaded with a 55g FMJ projectile prior to reaching battery condition.

This is leading me to believe reloads are being used. If that is correct, that would be my first suspect.

Get a few different brands of factory ammunition and let's make sure the problem is the gun before we work on it.
 
Maybe I missed it but could you be more specific on the type of jam?
Failure to feed?
Failure to eject?
Does it go completely into battery and just not fire?

As Pdsmith said, I always start with one round in the mag to see if it is locking back all the way, that helps rule a few things out (again depending on the type of jam).
 
#1: Yes, this firearm receives a steady diet of reloads and I have checked them with a caliper and a Wilson case gage. They are within specs. Nonetheless, it will be fed a box of store-bought ammo for the next range session to see if problem persists.
#2: It feeds from the magazine but fails to achieve battery position. It will not fire from this jammed position (hasn't yet, anyway!), but the jam is tight enough that it requires the operator to "pogo" the buttstock while pulling on charge handle in order to extract & eject the unfired round.
#3: The same round that just failed to reach battery position, jammed tight and requiring "pogoing" to eject can then be hand fed into the chamber, the bolt released, and it achieves battery and fires as normal.
 
First thing I would do is try factory ammo

Tied for first is to try different (brand) magazines.

When you preform #2 from your post are you hitting the release or manipulating the charging handle?

After you do #3 instead of firing the round eject it and compair it with any other round from the mag, that is unless the bullet stays stuck in the bore and you now just have a case dumping powder all over the place.
 
Sounds similar to some problems I had with a .300 BLK barrel that I had made. It was a 6.5" barrel with what I later discovered to be an incorrectly spec'd gas port. Basically it was a shorter-than-pistol-length gas system and a ridiculously short dwell time because there was only about an inch of barrel between the gas port and end of the barrel.

I'm not saying that your problem is the same, but the same sorts of theory may apply. i.e. it sounds like the gun is undergassed and short stroking. Do you know how large your gas port is? An adjustable gas block won't help if the port in the barrel is too small. You can step up the gas port size a little at a time with a set of numbered bits and a drill press (or hand drill if you're really careful).

I'm not an expert on getting short-barreled ARs to run, but I'd pop off the gas block and measure your gas port before you went too much further.

Aaron
 
from Jmorris:
First thing I would do is try factory ammo

Tied for first is to try different (brand) magazines.

When you preform #2 from your post are you hitting the release or manipulating the charging handle?

After you do #3 instead of firing the round eject it and compair it with any other round from the mag, that is unless the bullet stays stuck in the bore and you now just have a case dumping powder all over the place.

Tonight I had time to try some things:

#1. After thoroughly scrubbing the chamber with a brush & the bolt with CLP I began removed the silencer and began firing alternating 20 round magazine loads of fresh factory American Eagle 55g. FMJ and my home rolled 55g. FMJs powered by Varget. It seemed like it would run forever but the noise and fireball were very impressive.
#2. I always release the bolt by hitting the release. Should I be doing otherwise?
#3. After re-installing the silencer, I only got through about 15-20 rounds before the first jam occurred. It began jamming both new factory ammo and my reloads.

I am beginning to suspect that this 7" SBR with a silencer just runs dirty enough that I will have to scrub the chamber every 20-30 rounds. I have some .223 CFE powder and I may try a batch of that to see if it might run any cleaner & allow me to extend the cleaning times.

Aaron Baker: Thanks for the tip, I will check out the gas port to see if I can eliminate any tendencies for doubles or bursts.

Thanks all for the advice and ideas.
 
With the suppressor attached, does the bolt lock back when you load one round into the magazine and fire it? If not, as Aaron said the gas port may need adjusting/modification (or a different buffer)
 
^^^^ I'm confused: wouldn't adding the can increase gas pressure? I know that with my 300 blackout a "full power" load gets downright jumpy when the can is added because the gas isn't leaving the muzzle as fast. The recoil impulse of the buffer coming back seems significantly higher.
 
^^^^ I'm confused: wouldn't adding the can increase gas pressure? I know that with my 300 blackout a "full power" load gets downright jumpy when the can is added because the gas isn't leaving the muzzle as fast. The recoil impulse of the buffer coming back seems significantly higher.
Typically yes, but it sounds like he's saying it functions without the suppressor but not with it, so trying to narrow down the issue. It's an AR, there's only so many things it can be lol.
 
Try a small base die on your reloads? Have had trouble with brass known to be from a 223 pistol. It needed a small base die to get reliable handloads.
 
I am beginning to suspect that this 7" SBR with a silencer just runs dirty enough that I will have to scrub the chamber every 20-30 rounds. I have some .223 CFE powder and I may try a batch of that to see if it might run any cleaner & allow me to extend the cleaning times.

I think that fouling might very well prove to be the culprit, and specifically running supersonic ammunition with the suppressor attached. I recently received a Daniel Defense DDM4300s with a 10" barrel and have a Dead Air Armament SANDMAN-S mounted. I got to shoot it late last week for the first time. To start off I ran 40 rounds of PNW 220gr subsonic through it without a single issue. My gf shot 20 rounds and I shot 20 rounds and the rifle ran like a sewing machine. She asked about the difference between subsonic and supersonic so I loaded (alternating) six rounds of the PNW and six rounds of Barnes VOR-TX 120gr with the order being sub, super, sub, super etc. The rifle choked on the fith round i.e. after two subs and two supers. I noticed considerably more fouling from the VOR-TX ammunition compared to the subsonic and in particular lots of unburned "gritty" powder particles in the action and in the oil. The rifle is a bit tight since it's new so I'll have more data over the coming weeks, but I think it's telling that 40 rounds of subsonic ammunition ran fine and it took just two supersonic rounds to cause a feeding issue despite in spec ammunition. We all know that suppressors increase back pressure sending carbon and unburned powder back into the action. We also know that supersonic loads have more powder than subsonic loads, and short barrels are less efficient not having enough length to consume all of the powder. This isn't a big issue with longer suppressed barrels shooting supersonic ammunition but it is a potential issue for short suppressed barrels.

Here's a very short video of my girlfriend shooting five rounds. Notice the puff of smoke coming out of the ejection port for rounds 2 and 4 which were both supersonic. Compare that to the lack of smoke for rounds 3 and 5 which were subsonic.

https://youtu.be/deJzGVbVJvw
 
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