Short 223/556 Barrels and CMMG 22lr Conversion

Product support and suggestions and all other things related to BoreBuddy products

Moderator: Renaissanceman

Post Reply
Kit
Posts: 17
Joined: Tue Jun 15, 2021 1:03 am

Short 223/556 Barrels and CMMG 22lr Conversion

Post by Kit »

Just wondering if anyone has experience with using very short 223/556 barrels with the CMMG 22lr conversion kit. I've run the kit with success in 556 barrel lengths down to 7.5". I'm considering a dedicated 22lr build with a 4.5" 1:7 twist 556 barrel using the CMMG 22lr conversion kit. Considering this route rather than an actual 22lr barrel as the barrel is available and significantly less expensive than the CMMG 22lr shorty when in stock and available. The other cost savings comes from not needing to purchase the 22lr adapter to change out with the faux 223/556 extension that comes on the bolt in the CMMG kit. My only hesitation is effectiveness. Doing the math, a 4.5" barrel with a typical 223/556 round having case length 1.75" +/-, leaves about 2.75" of rifled barrel to spin and stabilize the projectile. This is one of a whole lot of reasons a 4.5" barrel is terrible for 223/556. The faux 223/556 casing on the conversion bolt is the 1.75" +/- case. My theory is using the CMMG kit with the 1:7 twist 4.5" barrel might actually be beneficial for 22lr stabilization due to decreased ability to spin and over stabilize resulting from only having about 2.75" of rifled barrel for the 22lr projectile to traverse. That said, theories are sort of like opinions and opinions....well everyone has them and they aren't really facts. It could be this is a terrible idea that will result in 10" groups at 25 yards, I just don't know. So, if anyone has experience with something like I've described, or a theory/opinion to share about potential effectiveness, I'd be glad to hear what you have to say.
User avatar
Renaissanceman
Posts: 52
Joined: Thu Sep 10, 2020 4:38 pm

Re: Short 223/556 Barrels and CMMG 22lr Conversion

Post by Renaissanceman »

Get a 4.5" dedicated barrel and collar and don't look back.
Kit
Posts: 17
Joined: Tue Jun 15, 2021 1:03 am

Re: Short 223/556 Barrels and CMMG 22lr Conversion

Post by Kit »

You just provided the confirmation to do what my gut was telling me. Longer wait, little more cost, and a whole lot more precision.

I have been looking for a dedicated 22lr barrel for a while in a lot of places. The CMMG AR 22lr barrels have been out of stock everywhere for a long time. Even the companies they co-brand with like 'Right to Bear' have been out for a long time. I wish they'd make less new caliber items there's no ammo for, concentrate on the calibers people actually want and have ammo for, and get down to manufacturing. They have great products however sometimes it seems like they out think themselves.....how strong can the demand be for something like 4.6 x 30. I have yet to see that ammo on a shelf.

You guys should go in the barrel manufacturing business.
Chuckh350
Posts: 2
Joined: Fri Apr 08, 2022 4:01 am

Re: Short 223/556 Barrels and CMMG 22lr Conversion

Post by Chuckh350 »

Opticplanet had 11 4.5” with barrel/bolt combo yesterday. Only retailer I could find. I spent a long time looking too.
Kit
Posts: 17
Joined: Tue Jun 15, 2021 1:03 am

Re: Short 223/556 Barrels and CMMG 22lr Conversion

Post by Kit »

Funny you should post this. I have a couple of the CMMG 22lr conversion bolts so all I needed was the alternate collar and just yesterday I saw the 4.5" 22 barrel available as a stand alone item on a 3-4 week back order so I pulled the trigger and ordered it. I'm just hoping this isn't one of the Optics Planet ruses where they say something is one way and then it turns out another with my barrel getting sent out in August. Fingers on both hands crossed.
Chuckh350
Posts: 2
Joined: Fri Apr 08, 2022 4:01 am

Re: Short 223/556 Barrels and CMMG 22lr Conversion

Post by Chuckh350 »

They are out now. When I posted that, I looked again they had 5.
Kit
Posts: 17
Joined: Tue Jun 15, 2021 1:03 am

Re: Short 223/556 Barrels and CMMG 22lr Conversion

Post by Kit »

Optics planet runs on this drop batch program of some sort. You can look for the same thing 4 times in 1 day and 2 times it's in stock and the other 2 times it's on extended back order. Twice in the past 6 months I went on their site, logged in and looked for something scarce, once an FDE 2.5x primary arms prism and the other time a specific line of the BCM Foliage Green pistol grip and a matching BCM trigger guard. Both times I logged out, logged back in, and did the search again and both times the items were then in stock. That newer extension of their site, DVOR I think, is also a good place to look. Sometimes they put stuff on their as specialty offerings for a week or 2 before they put it on the Optics Planet site. Anyways, I paid for the back order CMMG 22lr 4.5" barrel when they said 3-4 weeks....just keeping my fingers crossed at this point.
Post Reply