Converting to a Radial Delayed Blowback PCC Upper

calicojack · Nov 14, 2021

So I did order the CMMG BCG and 8" barrel for 45 APC; now I need to find a Glock pattern lower and a 3.5" extension (straight and can worthy) to pin and weld.

outrider58 · Nov 14, 2021

teratos said:
It’s my purpose in life…

It's always best to be killed by a professional. You get my vote!

teratos · Nov 14, 2021

calicojack said:
So I did order the CMMG BCG and 8" barrel for 45 APC; now I need to find a Glock pattern lower and a 3.5" extension (straight and can worthy) to pin and weld.

Have fun!

drking2 · Nov 14, 2021

I’m ordering parts now

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woodline · Nov 14, 2021

OP I would suggest adding a VLTOR A5 length buffer tube to whatever lower you get (it’s going to have to be CMMG compatible, so . . . Probably a CMMG one). Will add about an inch to OAL and make your muzzle device search less miserable.

teratos · Nov 14, 2021

fbi_surveillance_van said:
OP I would suggest adding a VLTOR A5 length buffer tube to whatever lower you get (it’s going to have to be CMMG compatible, so . . . Probably a CMMG one). Will add about an inch to OAL and make your muzzle device search less miserable.

Good idea! The New Frontier lowers are widely said to work just fine with the CMMG uppers in .45. I know they work great in 9mm.

woodline · Nov 14, 2021

teratos said:
Good idea! The New Frontier lowers are widely said to work just fine with the CMMG uppers in .45. I know they work great in 9mm.

You just remove the fixed ejector from the lower?

teratos · Nov 14, 2021

fbi_surveillance_van said:
You just remove the fixed ejector from the lower?

Yes. 2 Allen screws.

teratos · Nov 14, 2021

Here she is. Though it’s 9mm.

woodline · Nov 14, 2021

teratos said:
Yes. 2 Allen screws.

Nice, glad the compatibility issue seems to be working itself out. I keep hoping PSA will work an exclusive with CMMG to make an RDB PCC that takes PSA/Scorpion mags.

outrider58 · Nov 14, 2021

fbi_surveillance_van said:
Nice, glad the compatibility issue seems to be working itself out. I keep hoping PSA will work an exclusive with CMMG to make an RDB PCC that takes PSA/Scorpion mags.

I'm working on an MP5 mag compatible lower. Just waiting on part...

woodline · Nov 14, 2021

outrider58 said:
I'm working on an MP5 mag compatible lower. Just waiting on part...

That will be really cool, but I think a Scorpion mag CMMG RDB compatible lower would sell better.

calicojack · Nov 14, 2021

teratos said:
Yes. 2 Allen screws.

Noted.

calicojack · Nov 14, 2021

fbi_surveillance_van said:
OP I would suggest adding a VLTOR A5 length buffer tube to whatever lower you get (it’s going to have to be CMMG compatible, so . . . Probably a CMMG one). Will add about an inch to OAL and make your muzzle device search less miserable.

Thanks, and also for the tip about the ejector.

alucard0822 · Nov 14, 2021

teratos said:
There are 4 slots for springs in the buffer. It comes with 4 weak and 4 strong. There are 4 holes where the springs go. I went with the factory set up (1 weak, 1 strong) and it works great. I may play with those some more. Marked reduction in recoil/muzzle climb compared to a straight blowback. I went from a 9 ounce tungsten buffer/.308 spring to taking the weight out of my 9mm BCG and using the included system. Huge difference.

I did take the weight out. It’s a different gun. VERY happy. Now that I have the system working, time to take it apart, and polish what I can.

I’ve put a lot of time into recoil reduction on 9mm carbines. I need to get the RDB system out with this side by side. RDB is great for Glock pattern guns. This is a great alternative. I really wanted something to run in a Colt pattern lower, because I have a Colt pattern pre-13 SBR registered at 22”. I can’t reproduce it now.

Awesome, was thinking about getting one to try out. If it works with a short stroke setup, might have some ideas

dbledoc · Nov 14, 2021

teratos said:
Playing with it right now. I’ve been going nuts with this thing. I figured it out, and I’m a f’ing idiot. I was playing with a RDB system before this and that requires you to take out the ejector on a Colt pattern lower. Guess what homeboy forgot to put back in?

This thing runs great.

Do you think it would work in a 10 mm?

teratos · Nov 14, 2021

dbledoc said:
Do you think it would work in a 10 mm?

They don’t specifically mention 10mm on their website. They mention .45 and .40 and etc.

I really don’t see that it would be a problem. I took the weight out of my 9mm bcg, and recoil is very soft. I was thinking earlier I might do a 10mm with this once my 9mm builds are finalized.

jrumann59 · Nov 15, 2021

Now that I have my NFA trust set up I will have to pay more attention to these threads, I want to make an SBR PCC, with can.

calicojack · Nov 15, 2021

drking2 said:
I’m ordering parts now

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Did you go with Scheel or CMMG?

drking2 · Nov 16, 2021

calicojack said:
Did you go with Scheel or CMMG?

Scheel

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Converting to a Radial Delayed Blowback PCC Upper

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