Just noticed a possible problem

[A5BLASTER]

Ok first my guns info
JP 18 inch lightweight barrel-rifle length gas
UP two peice adjustable gas block-factory installed gas tube
JP matched bolt
PF M16 profile big
JP SCS gen I stock springs and weights.

I was sorting some spent hornady brass sourced from shooting hornady factory ammo.

When I noticed I had what I would best describe as half moon markings on the caseings, I believe it is from the ejecter.

The marks are located on the case end next to the primer, pics to come if I can get my phone to take a few good pics of what I'm talking about.

My question is I have the extra springs and weights for the SCS should I do some changing out of parts and see if I can tune out these marks.

I'm getting 100% function on feed and ejection and bolt locks back on empty mag 100% of the time as well.

Brass normally lands in the 3:30 to 4:00 o'clock position.

Went back and looked at all my saved up brass and every single case has these marks.

Just wondering if those here with more knowledge thinks I need to fine tune my SCS.

[LRRPF52]

Are the ejector channel marks such that the brass is extruding (flowing) outwards from the case head, or just shadows of where the ejector channel is?

It's pretty typical in a gas gun like the AR15.

I just checked a bunch of my brass shot through several different RLGS recently, and didn't see any of this, but I've seen it before plenty of times.

I get concerned when the brass is flowing away or shearing from the case head.

One of your best indicators of pressure is velocity.

What speeds have you been getting?

[A5BLASTER]

Randomly selected four peices of brass, all show the same marks in the same spot.

[A5BLASTER]

Haven't checked them for speeds, brass is all from factory hornady SST rounds, I uploaded a pic of four peices I just reached in and grabbed.

To me the marks seem to be moving towards the case lip.

[LRRPF52]

I'm not seeing anything alarming there. Can you feel any protuberance from the surface on the marks, or are they flush?

You can try dialing your gas down a little and see if that changes anything.

I know on JP's .223 Wylde RLGS barrels, the port is large, meant to be choked or opened per the user requirements with different loads.

If you're getting a lot of gas volume flowing through, it might be cycling early, but normally your ejection would be different if that were the case.

[A5BLASTER]

Yes if I run my fingernail over the area I can very slightly feel some raised metal but very slight.

I have my gas turned down to the ragged edge now. Hate to go tearing it apart its running 100 percent like it's set up right now.

[A5BLASTER]

Was reading and JP recommends H2 buffer weight for the grendel.

That would mean I would have to change out two of the standard steel weights for two tungsten weights to achieve that weight

[IceAxe]

Is the ejection plunger able to fully recessing into the bolt when pressed?

[A5BLASTER]

Iceaxe handy checked that, thanks for asking will check it shortly.

[A5BLASTER]

Ok checked the ejection plunger it's working 100%, extraction claw looks perfect as well.

[LRRPF52]

It's generally a symptom of early unlocking in a gas gun with a plunger ejector.

The condition is such that the case is still obturated in the chamber and into the bolt face, so if primary extraction begins before you get a chance to rebound, the rotational movement of the bolt will "swipe" the brass that is pushing into the ejector channel, whereas the rest of the brass is held in place by the bolt face.

This is an issue of timing in the gas gun, and one approach is to do as suggested, by adding mass resistance to the recoil system to retard bolt unlocking. I personally use a lot of H2 buffers in MLGS guns.

It can also be a sign of excessive pressure if the case is extruding into that ejector channel, but that isn't what is happening here in my opinion.

[A5BLASTER]

Yea I don't think it's a pressure problem myself LRRPF, I think like you it's just a lil tuning in the buffer weights and springs that's needed.

Think I will break out the replacement weights and springs tommorw and play with it to see what happens.

[LRRPF52]

Make sure to use a heat gun to release the Red Loctite on the screw that holds everything on the center shaft of the SCS before trying to torque it loose.

If you read the distractions, you'll be fine. As soon as I saw the smoke from the Red LT, I knew it had gone molten and was ready to turn.

[A5BLASTER]

Yes sir been sitting here reading over the instructions getting myself up to speed on how to do it.

[cory]

Good luck with that crappy retaining ring you'll need to remove to replace the weights. Have some alcohol wipes to clean all the puncture wounds you're likely to have on your off hand once you're done.

Have you got it setup as a rifle or carbine buffer?