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1/12/2026 4:11:21 PM EDT
[Last Edit: Erik72][Edited] [#1]
yeah 10-4.....John at Keystone Accuracy drilled & tapped his CMMG bolt on the left side and milled his UR to accomodate.  But he's a gunsmith and can do what he wants.  He's still in business but has been difficult to get to respond over the last couple years as he was going through a divorce.  Anyway, I suspect any competent smith could do the same.  I'll see if I can find a link to a video or photo that showed what he did.

his is a LH upper but you get the idea.
https://youtu.be/j4QEo_bLufc?si=9Q5g-Ltlf9AvY2yb
1/14/2026 12:27:03 PM EDT
[#2]
Another vote for RTB (which is basically CMMG).

1/26/2026 11:02:29 PM EDT
[#3]
Quote History
Originally Posted By 45-Seventy:


I put around 40k rounds through CMMG type AR22 builds in Steel Challenge. They’re alright but for reliability I’d go for Tippman or M&P-15/22. I went with the later and they’re trouble free as long as you replace the magazines when the feedlips spread.
View Quote


the bore buddy versions are the best of the "cmmg/ciener" variety.  or at least replacing the bolt parts with bore buddy, then the weight kit to tune for ammo / eliminate bounce.  forget cmmg mags use mp15/22 mags with bettermag adapter.

and yeah mp15/22 mags have a lifespan, but its easily tested via the "erection" test (can you easily flip the first round up)

that being said, for someone starting steel / rimfire challenge today you'd be hard pressed not to just get a 4lb tippmann rcr.
1/27/2026 6:08:42 AM EDT
[#4]
Quote History
Originally Posted By deanwormer:


that being said, for someone starting steel / rimfire challenge today you'd be hard pressed not to just get a 4lb tippmann rcr.
View Quote


Checked their web site and only see full size rifles.
Looking more for one with 3-4 inch barrel.
TBD
2/3/2026 9:20:51 AM EDT
[#5]
https://www.rimfirecentral.com/threads/complete-rtb-22lr-ar-upper-new.1344513/

Here's a brand new 4.5" RTB upper for $199

2/4/2026 8:05:13 AM EDT
[#6]
Quote History
Originally Posted By Erik72:
https://www.rimfirecentral.com/threads/complete-rtb-22lr-ar-upper-new.1344513/

Here's a brand new 4.5" RTB upper for $199

View Quote


Thats pretty cheap. With all the scammers on the boards nowadays, wonder if its too good to be true.
TBD
2/4/2026 8:46:12 AM EDT
[Last Edit: TW200][Edited] [#7]
1,000's and 1,000's of rounds through my 7.5 barrel S&W M&P.
Perfect trainer for real AR15 556.
Highly recommend 5 stars.

S&W M&P 7.5 inch barrel. 25 Yards 10 inch plates
Glock Derangement Syndrome > Trump Derangement Syndrome.
Plastic Fantastic Fanatic.
I love my little pro gun Viking wife.
She has the world's bluest eyes.
2/4/2026 9:05:57 AM EDT
[#8]
Quote History
Originally Posted By JThompson:Thats pretty cheap. With all the scammers on the boards nowadays, wonder if its too good to be true.
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He's got 21 5-star reviews on their classifieds board.  Much like the EE here.  You F up once, you run the risk of no one trusting you.  I've been a member on that forum for years.  Pretty good bunch of folks over there.
2/4/2026 10:52:05 AM EDT
[#9]
Quote History
Originally Posted By TW200:
1,000's and 1,000's of rounds through my 7.5 barrel S&W M&P.
Perfect trainer for real AR15 556.
Highly recommend 5 stars.

S&W M&P 7.5 inch barrel. 25 Yards 10 inch plates
View Quote


Definitely looks like fun.
TBD
2/5/2026 7:31:19 AM EDT
[Last Edit: Sailormilan2][Edited] [#10]
Quote History
Originally Posted By JThompson:


Definitely not interested in a left handed upper.
Just wanted the charging handle on the left side of the receiver.
Have 2 builds with it and so much better than the usual charging handle.
No one has them in stock anymore.
View Quote


Ambidextrous stripped uppers can be found relatively easily. I have several. I like them better than the rear charge, and I think they work better with scopes.
The issue is a bolt with the handle/knob on the left side. A standard AR bolt is too hard to drill. I’ve tried.😊 Note: I have not yet tried to drill a 22lr bolt. So, I have no idea how hard they are.
I like the idea of having one lower that one can use multiple uppers on. One upper being a 22lr for cheap practice.
2/5/2026 8:32:09 AM EDT
[Last Edit: 11b4v][Edited] [#11]
FPNI.  I'm a big fan of CMMG and the versatility over others.  I've put tens of thousands of ammo through two uppers I've assembled using CMMG SS conversion and dedicated CMMG barrels and they run very well.  Any hiccups I blame on the "seconds" I buy from a big name LGS.  Mags are Black Dog Machine.   Franklin Binary triggers on both.   I've got an "artisan" steel airsoft folding stock that's indiscernible from a Sig/JMAC on the SBR pictured below.

Many options out there to choose from, or as ARFCOM always says; “Get both!”
Attached File

Some Men fear war. Some wars fear Men-75th Ranger Regt.

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