We have 40sw ammo so why the watered down 10mm?

[Lester Polfus]

If a .40 and a 10mm are throwing a 180gr load at roughly the same velocity, is there any kind of recoil advantage to the 10mm? Would the 10mm have less of the typical .40 snappiness in recoil? Is there less pressure in the 10mm for that same bullet /velocity?

Yes. 180 grain 10mm loads that are loaded to .40 S&W velocities (roughly 950 to 1050 FPS) are very nice to shoot out of a Glock 20, as are .40 S&W loads fired through a .40 conversion barrel.

As I bring the Glock 20 online as my primary "Field Pistol," I'll likely get into the practice of carrying something like the Hornady Critical Duty load on our way back and forth from the back country.

Honestly, the Glock .40S&W guns should have been built on this frame, or some hybrid combination of the original 9mm frame with a heavier slide, ala the .45 GAP guns.

[GJM]

When using a 40 conversion barrel in a 20/29, is there any issues with magazine length and the shorter .40 cartridge?

[Lester Polfus]

I've never owned a 29. I used an Olympic Arms conversion bbl in a Gen 2 and a Gen 3 Glock 20 many thousands of round without issue. I had access to virtually unlimited free .40 SW cases and I was pinching pennies so it really helped me out. If I intentionally limp wristed it, it felt like it was on the verge of failure, but I never got it to fail.

I haven't bought a conversion barrel for the Gen 4 I bought last November and probably won't, so I can't comment about that. Now I'm just loading 10mm ammo by the bucket and the UPS guy is cussing me every time he has to come to the door.

[DAVIDF]

I also had no issues with a Gen 3 Glock 20 and a Lone Wolf .40 conversion barrel. Even very light Tula .40 loads worked with the stock RSA. The stock magazines seem to work excellent with the .40 loads.