THE COMPLETE 9MM AR15 BUILD/INFO THREAD

[instaramen]

Nope, glock cut for glock mags, colt cut for colt mags. Some BCGs are cut for both and can take both.

[afteractionreport]

No, I believe they're marketed as "glock cut"

I believe a few companies offer 'hybrid' models but I have no experience with those.

[afteractionreport]

I do know that stern defense offers bcg cutting services for a small fee....check em out

[ar15barrels]

Can you use a BCG designed for Colt Mags with Glock Mags?

Generally No, but there are some bolts that claim to work with BOTH.
Glock mags have a smaller opening between the lips than colt mags so the part of the bolt that pushes the cartridge needs to fit within the lips.
Glock mag presents a single centered cartridge at the top of the magazine.

Colt mags are based on uzi mags.
Uzi mags present two cartridges at the top of the mag, one on one side and the other slightly below on the other side.
We call this staggered feed which is how AR-15 magazines feed.
After the top cartridge is pushed out of the magazine, the next cartridge appears on the opposite side.
The part of the bolt that pushes the cartridges needs to be wide enough to catch the cartridges on BOTH sides of the magazine.

[ugimports]

Thanks everyone. I'm curious how the hybrid BCGs work given how different the mags operate..

[ar15barrels]

I'm curious how the hybrid BCGs work given how different the mags operate.

They make the part of the bolt as wide as possible while still fitting through the magazine lips.
It's a compromise on both mag types.
If the glock mag is offset to one side, the bolt could rub the magazine.
If the colt mag is offset to one side, feeding problems could occur on one side because so little of the bolt is catching the cartridge case.

[sigstroker]

I think the latest PSA bolts are supposed to work with both. I know my old Glock mag bolt won't fit in a Colt mag gun because the Colt mag ejector is higher than the Glock mag ejector and the Glock bolt ejector slot is too small.

[deckhandmike]

My recent build used a new frontier Glock lower. Palmetto state upper with an 8oz heavy buffer and has been flawless. Haven’t got it shooting bugholes yet but was feeding it a random mix of ammo out of my can. Everything was cheap and it all cycled.

[AlHO1966]

What's a good price for a side charging, LRBHO upper? And what sellers should I watch for a deal? I have too many builds going to pay full price! :-)
Thanks,
Billy

https://www.newfrontierarmory.com/product/pistol-caliber-side-charging-upper/

This is the one I run... I think they went on sale for $200.00 throughout the year. Works great!

[DirtyJimmy]

Digginit

Really nice thread. Lots of info. Many informative links. Thanks one and all for building and posting. And fixing, and posting again.

[Tom_SoCal]

Really nice thread. Lots of info. Many informative links. Thanks one and all for building and posting. And fixing, and posting again.

Bumping thread for informational purposes.

[Caligula36]

Good thread.

Has anyone used the KE Arms, KE-9 9mm lower? What upper did you match it to?

[naz]

The key details of my build are:

[Caligula36]

Anyone using the CMMG delayed blowback system with their own combination of a non CMMG receiver?

[Rinzler]

is New frontier Armory Glock mags G-9 Billet Lower (Gen 2) legal to transfer to a local FFL in California?