I've been wanting to try a piston AR for a while so I took advantage of some BF sales to assemble the following. Would appreciate some input on it before I run it.

Upper is LMT shovelnose with a 12.5 LMT piston barrel. Once I realized the front screw has to be completely removed, this part was pretty easy.

Piston LMT bolt carrier with an extra E-bolt I had - this was a REALLY tight fit until I lubed it up. Did not remove the gas rings as I've read different perspectives on this.

Since I've also been wanting a binary lower I went with a MARS-L with a Franklin BFSIII.

Tube is whatever was bundled with my SBA3 and I'm using an Armaspec SCS H2 with no buffer retainer. At first like an idiot I inserted this backwards and couldn't figure out why everything was jammed up and not cycling, but I eventually figured that out.

Buffer is about 1-2mm compressed by the BCG when upper and lower are mated. I've read that a tight fit is recommended so I hope that's about right.

Radian Raptor CH

Gun seems to cycle ok but somewhat stiff so I sprayed all the innards with Ballistol and that helped a bit.

Have a spare PWS tube that I'm thinking of swapping in after reading about carrier tilt in some other threads. Not sure if that's even possible with an SCS.

Will eventually run it with a CGS Helios QD Ti so I swapped the factory FH for a XENO brake.

Anything about this build seem off? I'd prefer it not rapidly disassemble on first use.

What's the perspective on leaving them in?

That it makes no difference.

Wouldn't the additional friction from the bolt rings would apply more force to the cam pin, cam pin track, and upper receiver, both directions during the carrier travel? Further, not only do most piston systems not use the rings, but they also often use a low power spring instead which is quite the opposite.

No idea but I’m glad you mentioned the spring. My carrier didn’t come with one so I’d better look into this.

Considering our conversation above, you may want to take the rings out and see if there's a difference.

Thought you were talking about the firing pin spring on the 308 versions but it doesn't appear the 5.56 version needs that. Anyway, the bolt seems to be moving decently well now but I'll go ahead and pull the rings just to reduce that bit of friction.

Curious as to the difference, if any, so please report back.

As an example, the Adams Arms 5.56 piston kit comes with a bolt spring.

I would remove the gas rings in the bolt, LMT recommends removing them