When a standard AR-15 is converted to .22lr through a conversion bolt or replacement upper, the bolt catch stops working.
Magazines that hold the bolt open after the last round (like CMMG mags) are a good stopgap but don't offer the same functionality as a standard AR (and the bolt falls when the magazine is removed).
This is where the Catch22 comes in. The Catch22 is a bolt catch and will work with most common .22lr conversions.
On its own, it can hold the bolt open without a magazine being inserted. When used with a 15-22 magazine and shim, you can have the same last-round-hold-open functionality of a standard AR.
What is the difference between the V1 and V2 Catch22s?
The V1 bolt catch works best for dedicated .22lr ARs as it's a direct replacement for a stock bolt catch.
The V2 bolt catch can slip-on over a .223 bolt catch which is a faster installation and better for ARs that frequently change calibers.
Why would I need an adapter/shim to use S&W 15-22 magazines?
S&W 15-22 magazines are skinnier than a standard AR magazine. Without something to take up the slack in the magwell, the magazine will have too much slop and not work consistently.
What is the advantage of the clip-on vs the stick-on S&W 15-22 magazine adapters?
With the clip-on adapters, you only need one clip regardless of how many magazines you have. The downside can be if you have non 15-22 magazines then you'll need to remove the clip before using them. If you have a number of different types of magazines, then the stick-ons are the better way to go. The shim will be adhered to the magazine so you don't need to change anything when swapping between types of magazines.
How does the catch work differently than the CMMG/BlackDog style magazines for last-round-hold-open?
Magazines that use the follower to hold the bolt open will let the bolt drop when the magazine is removed. The Catch22 uses the bolt catch to hold the bolt open which functions like a .223 bolt catch.
What do I need to have the same last-round-hold-open function as a standard .223 AR?
- Catch22 (V1 or V2)
- S&W 15-22 magazines
- A clip-on or stick-on magazine adapter
What happens if I just use a Catch22 (V1 or 2) with CMMG magazines?
With this combination, the bolt will be held open after the last round by the magazine follower. To keep the bolt open after the magazine is removed, you'll have to manually engage the bolt catch.
The Catch22 V2 slides over a standard .223 bolt catch for easy installation. Use this for non-dedicated .22lr builds where you'll be frequently swapping calibers and still need a functional bolt catch.
CMMG's new magazine doesn't work great with the Catch22. The spring tension isn't strong enough for a consistent lock up. Unfortunately we don't recommend this magazine for LRBHO.
This magazine fits in a standard AR mag well without any shim. The spring tension is a bit weak though and so you will need a lightened bolt catch spring for consistent last-round engagement.
Because the back of the follower can't reach the bolt catch, the bolt catch won't be engaged automatically. The extended part of the follower will hold the bolt open when the last round is fired but the bolt will drop...
The Catch22 was designed around Ceiner style bolts. Because of this, .22Ir bolts that aren't based on that design
might not work. Here is an overview of the most common bolts / uppers.
If you have a question about something not listed here, please contact us below.
•CMMG dedicated upper receivers and conversion bolts
•Palmetto Sate Armory (PSA) and Spike's Tactical dedicated upper receivers and conversion bolts
•Ceiner kit conversion bolts
•Chiappa / ATI dedicated upper receivers
•Taccom 22RF bolts
•CORE15 dedicated upper receivers
•Bushmaster C22 upper/rifle
•Nordic Components V3 upper receivers (rounded bolt)
•2A Armament conversion bolts (does not work with S&W 15-22 magazines)
•Right To Bear (RTB) Bolts
•Tactical Solutions upper receivers (catch might need to be filed down a bit depending on the upper version)
•Bear Creek Arsenal Side Charging .22lr Uppers (the left feed lip on 15-22 mags might need a very light filing for clearance)
•Colt conversion bolts
•M261 conversion bolts
•CZ V22 uppers
•Nordic Components V1 upper receivers (square bolt)
•JP Enterprises upper receivers or bolts
•CMMG auto sear trip kit
•RRA LAR-22 bolts and uppers