Virginia Gun Owners Forum - VGOF

The short answer is because they are different cartridges in ways that matter.

Of course .22M is much longer, but there are some key differences. The case head of the .22M in several measurements is larger than .22LR. If you put a .22LR into a .22M chamber it wiggles around because the OD of the brass is smaller and the rim is also different. There are other things like a .22LR bullet is kind of mushroomed shaped so that the OD of the bullet and the brass are flush which is unlike most other rounds, including the .22M, where the brass OD is larger than the bullets. Etc.

In a pinch it probably could work, but it isn't advisable. There are guns like this one where they provide a second cylinder so you can shoot either round: http://www.ruger.com/products/newModelS ... odels.html

The chambers are different in ways that matter so you can't do a .357Mag/.38Sp swap.

It's not just a difference in case length. The .22 Mag has a significant taper to the case not present in the .22 LR. You can easily visually compare the difference between the base and rim diameters of the two cartridges with the .22 Mag being noticeably larger.

Firing a .22 LR in a .22Mag chamber often results in a split case. It will almost surely result in a wimpy bullet velocity.

.22 LONG RIFLE
Case type 	Rimmed, Straight
Bullet diameter  .223 in (5.7 mm)
Neck diameter    .225 in (5.7 mm)
Base diameter    .225 in (5.7 mm)
Rim diameter     .275 in (7.0 mm)
Rim thickness    .040 in (1.0 mm)
Case length       .590 in (15.0 mm)
Overall length    .985 in (25.0 mm)
Rifling twist      1-16
Primer type      Rimfire

.22 MAGNUM
Parent case       .22 WRF
Bullet diameter   .224 in (5.7 mm)
Neck diameter     .240 in (6.1 mm)
Base diameter     .241 in (6.1 mm)
Rim diameter      .291 in (7.4 mm)
Rim thickness     .046 in (1.2 mm)
Case length      1.052 in (26.7 mm)
Overall length   1.35 in (34 mm)
Primer type       Rimfire

Yeah, if you want to shoot something smaller and weaker in your .22mag, you have .22WRF.

You can shoot .22LR in a .22WMR, but you may have some ignition issues, and the case will split. Sort of like shooting .32SWL in a Nagant revolver. It's not a great idea.

The .22 WMR is based on the .22 Winchester Rimfire cartridge, which is different from the .22 Long Rifle, Long, and Short cartridge. The ammo companies stopped making the .22 Winchester Rimfire due to the popularity of the other cartridge. Someone started making the .22 Winchester Rimfire a few years ago, but the prices per round were significantly higher than the LR.

Jim