JP 223 with New Suppressor Issue

[Lsume81]

I have a JP SCR-11 223 small frame rifle. It has the VMOS bolt carrier, a Gen2 Silent Captured Spring with H2 heavy buffer and two piece Adj Gas Block with detent & 0.750 bore. Gun has performed well with the factory settings. I removed the break and installed a CGS Hyperion Ti suppressor. On the first shot with the suppressor the spent cartridge was expelled as normal and the next cartridge loaded. But the bolt carrier did not fully close on the new cartridge. The bolt would not close or open with the charging handle. I took the gun home and looked it over closely but could not find anything obvious from the outside. So I got the bolt moving and was able to use the charging handle to extract the unfired cartridge. The cartridge was very scratched on the casing and there was grit on the cartridge and the bolt. I fully cleaned the action and barrel. There was some grit in the action but nothing unusual in the barrel.

In reading all the JP information I have the setup they suggest to be able to run a gun that operates properly with the suppressor either on or off. I plan to go back to the range and shoot the gun without the suppresser to conform proper operation again. Then install the suppressor again. Any suggestions on what to do if the same issue happens again?

 

[srt-4_uk]

You using reloads?

 

[UpSideDown]

Why were you not able to get the next round out of the bolt? Was the bolt engaging the rim of the cartridge or wedging against the side of the case?

What is this grit you saw inside? Carbon or something else? Did you shoot it prior to this?

 

[msgriff]

I'd load one round in the mag, charge and shoot. You should get "last round bolt hold open", if not, adjust your AGB. If the action looks filthy, clean and/or repeat with one round in the mag. When the debris starts to lessen, load a few rounds in the mag and shoot. If after a few rounds it gets real dirty again, clean and repeat. It should clear up after the Ti suppressor "breaks-in".

 

[Lsume81]

Ammo is Winchester 5.56 62g green tip M855.

I shot 10 rounds prior to putting on the suppressor. I cleaned the gun the week before after a trip to the range. I was not clear in my explanation. The bolt was initially jammed in the partially closed position. Once I got the bolt moving it ejected the unfired cartridge as normal. Both the bolt and the cartridge were covered in fine grit.

I suspected it was from the suppressor, but was not sure. This is my first suppressor. It seemed like the gun might have worked normally if the grit had not jammed the loaded cartridge.

 

[UpSideDown]

Where is this grit coming from? AR's typically get pretty dirty, especially with cans, but it's normally a non-issue. Where was your bolt when it was jammed? Was it all the way forward but not fully rotated closed?

 

[Lsume81]

I had just cleaned the gun prior to this trip to the range. I was using a generic "Bolt" for the carrier and the bolt. So the bolt was fully closed with a new round in the chamber. The bolt carrier was 3/4" closed and did not have the trigger cocked. The round was jammed in place and I was unable to move the carrier with the charging handle. I got the carrier moving by gently applying pressure with a screwdriver. Once it was moving I used the charging handle to eject the round in the chamber. When I took the gun apart I found the grit on the carrier and cartridge. All this happened after one round through the new CGS suppressor.

 

[srt-4_uk]

The round was stuck because it didn't fit in the chamber. Either the round was damaged badly going in or the blowback crud from the suppressor caused the round not to fit. That's why you had to pry it out.
JPs have tight chambers. I chamber check all my reloaded 223 ammo. Rounds that pass LE Wilson gauges don't pass in the JP gauge. Factory ammo doesn't have a problem passing but added blowback from the suppressor will cause problems.
Did you turn down the gas at all?

 

[mettee]

Try reducing gas slightly, and adding all the mass you can to the buffer weight.

The JP does have a tight match chamber that won't last as long shooting suppressed before it fouls up and makes it hard for the next rounds to go into battery.

The grit may be unburnt powder that made its way back through the gas system. Once the bcg leaves the gas tube there is a gas release.

 

[Lsume81]

Thanks for all the fantastic information. I won't be able to go to the range again until after Christmas. When I do I plan on the following procedure based on your information and suggestions.

1. Shoot 10 rounds unsurpassed and check for any grime or grit in the action. Also confirm lock back on final shot.
2. Install suppressor.
3. Load single round and fire checking for lock back and any grit. If there is grit, clean action and perform single shot test again until action stays clean.
4. Once single shot tests continue to give lock back and grit is not present, move to multiple shots. Probably try 5 rounds to see if operation continues as normal.

I will be prepared to reduce the gas if needed to achieve proper operation.

If you have any suggestions for modification of this procedure just let me know.

Again, thanks for all the good information.

 

[srt-4_uk]

It isn't going to be crap in the upper receiver, it'll be crap in the chamber.