SR 25 in 6.5cm build help

[BigTex8541]

I'm currently building my first large frame. I have every part with exception to the BCG. I keep debating between JP low mass or JP full mass, both would have the hp bolt. I will be running both suppressed (ultra 7) and un suppressed. Now I've found some of the answers I was looking for, but some of them were outdated back to when all these parts were first coming out. So any fresh input would be greatly appreciated.

List of the essential to the questions parts I have.
Vseven upper
Larue lower
Proof CF 22" .875
Vseven 18" handguard
JP SCS H2 with spring kit
Superlative Arms GB

Questions
1. Low mass or full mass pros and cons?
2. With the SCS which spring are you using in a similar setup?
3. With the Superlative Arms GB are you running in the restricted section or bleed off and why?

I already have a boatload of money into this and I just don't want to make a mistake with the BCG selection. So again your opinions are welcomed.

Thanks, Justin

 

[Desert_Racer]

Full mass.

Don’t be surprised if you have a hard time getting that thing to run. It’s harder to frankengun a large frame AR together and get it to run reliably than an AR-15, or a factory built large frame AR.

 

[BigTex8541]

Full mass.

Don’t be surprised if you have a hard time getting that thing to run. It’s harder to frankengun a large frame AR together and get it to run reliably than an AR-15, or a factory built large frame AR.

Thank you for your input. That's kinda why I went with the adjustability of the gas block and buffer system. Hopefully it will work out.

 

[Desert_Racer]

Just be patient with it, be willing to take the time to test and tune it, and keep in mind that you cannot run anywhere near bolt gun pressure without trashing the brass or blowing primers. Good choice on the HP bolt. The small firing pin is a must.

 

[TheOE800]

Having no experience and also recently bought a Proof 22” 6.5CM, their recommendation is a high pressure bolt, full mass carrier, and adjustable gas. The barrel I have in hand is gassed at 0.086” and I don’t have any comparisons, but that seems conservative.

 

[Huskydriver]

Sfp bolts are a must in my 6.5 builds as well as a +2" rifle rifle gas system....

I will not build a large frame ar without those two if it's going to be a 6mm or 6.5

 

[MPD142]

Not much actually SR-25 about your build...

But in my experience with large frame gassers, Run the FMOS BCG with a High Pressure bolt. I've never played with the JP SCS and tend to run KAC or LMT action springs in all of my builds with buffers ranging from H1, KAC HH, H2, H3 to the MGI Rate Reducing buffer(7.1oz) in my MWS with a factory 24" barrel and Rifle length gas system.

On my Superlative Arms gas blocks I have them all set to restrict gas instead of vent. My logic although I've never actually tested it is that Restriction may give a slight boost in velocity. Maybe someday I'll test my theory.

My latest build is a 16" 6.5 Creedmoor with RLGS, SA adjustable gas block, JP High Pressure FMOS, LMT Spring and H2 buffer.

 

[Evintos]

https://www.snipershide.com/shooting/threads/bolt-carrier-mass-choices.7105427/

SCS - 100% (uncolored) but I also use the AR10 Standard rather than the AR10 SCS-H2 with the Superlative Arms AGB.

Restrict > bleed off. Depending on your suppressor, you'll run out of bleed off adjustment before you run out of restriction adjustment for large frame AR barrels (with oversized gas ports) most of the time.

 

[bigjake83]

Have you confirmed that upper will fit a LaRue Lower??

 

[BigTex8541]

Have you confirmed that upper will fit a LaRue Lower??

Yes sir