How do these devices, when mounted to an AR, not deform the receiver, barrel, or rail mounts with their recoil? I always thought it would be cool to add one to my AR, but I keep imaging the recoil enlarging the receiver holes or ripping off the rails. Does this ever happen?

If they had enough recoil to damage the mount, they would damage the shooter as well. 40mm seems like a monster, it does shoot a heavy projectile but velocity is low and it feels more like a shove than a sharp snap. Think about how small those screws are that hold a scope, rings and mount onto a magnum rifle.

I don't know all the ways all these mount up, but if a little research on your desired model dosnt show problems, I wouldn't worry about it.

Prince Yamato wrote:How do these devices, when mounted to an AR, not deform the receiver, barrel, or rail mounts with their recoil? I always thought it would be cool to add one to my AR, but I keep imaging the recoil enlarging the receiver holes or ripping off the rails. Does this ever happen?

I can't speak to the breaching shotguns, but I can to the grenade launchers:

While the projectiles are heavy, the velocity is low. M781 chalk rounds run about 240 FPS. The HE grenades, and pretty much everything else beside crowd control stuff (rubber balls, foam batons etc) run at the same low velocity. They produce less recoil than a 12 gauge according to my shoulder.

40mm and 12ga underbarrel mounts don't have anywhere near enough recoil to be an issue whatsoever.

CanOfWhooppass wrote:If they had enough recoil to damage the mount, they would damage the shooter as well.

This was my favorite answer. Flesh is FAR less tolerant than 6061Al. Even if hole fit is sloppy.

Never used an undermounted, but a standalone 40mm launcher feels like a 12ga except a little more smooth. Kind of like .40 cal to a .45. More power behind it but not too snappy. Depends on the round you're using too. Some of the crowd control stuff with a bunch of small projectiles is pretty sissy to shoot.

I had 2 LMT 40mm.

One rail mounted, one barrel mounted.

I sold the rail mounted one. I could not find a rail that would take abuse of repetitive use. Now I was actually using the thing probably 25 to 30 chalk and other rounds at a time, but all the free floated rails I had would bend over time.... Larue and KAC included.

The barrel mounted one is solid as a tank. Perfect on a 14.5 " LMT barrel. Also great with the Stand-alone KAC mount.