Shooting 40 cal HST from my p220 legion 10mm

mattyb said:

Hey guys I took my P-220 legion to the range to break it in. Is it okay to shoot .40 cal to break it in? No issues at all from full power 10mm, range 40 cal or range 10mm.

Semper Fidelis View attachment 456042

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Why ? You are probably asking for truoble. Plus It's Probably Dangerous Too.

Both cartridges headspace on the case lip.
By shooting the shorter .40 in it you’re pretty much only relying on the extractor to hold it in place. May wind up with some rounds not going off due to the looseness.

I shoot 40's in my 10mm's all the time. I have a thousand or so thru my Wilson CQB and another couple hundred thru my Fusion Commander. I shoot them in IDPA with 40's. I would not recommend them for carry but it is no problem.

Head space is only a concern with bottleneck cases, this is no different than shooting 38's in a 357 except the normal extractor tension holds the case against the breech face. It is no harder on the extractor than any other shooting, this is apparent when one understands the operation of the pistol. I have challenged many people and still have seen no evidence of damage from firing 40's in a 10mm.

If the case really did a hard stop against the end of the chamber any slight variation would stop it from fully chambering.

If anything, the .40 S&W is lower-power than the 10mm and should put less stress on the pistol. The only trouble I could see would be proper cycling of the gun with a recoil spring designed for the more powerful 10mm round not allowing full slide movement with only the .40 energy. However, I have not heard of this being a problem with any brands. Glock guys do this all the time.

i do shoot 40 in my glock 20s, 29s, 40 mos..... no issues with the Sig whatsoever

Firearms Collector said:

Why ? You are probably asking for truoble. Plus It's Probably Dangerous Too.

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Do you know that it is dangerous? I have hundreds of rounds of .40 through my G20.

i havent thousands of rounds through my other 10mm pistols. All my 10mm 1911s were broken in with 40 cal ammo

Intermittent use may not create a problem, but when you get "flame cutting" erosion at the shorter cases "mouth" you may start getting extraction issues later, with the longer cartridge.

More prevalent with a high intensity cartridge like the .40 S&W, than milder .38 Special in .357 Magnum, or .22 Short, in .22 Long Rifle.

...and if the chamber is not cleaned well after using some of the less expensive and dirtier ammo out there, you start to get deposits on the ledge where the 10 is supposed to headspace. Then you start having trouble with 10mm feeds if it gets bad enough.

IMO, 40 in a 10 is a "can if I HAVE to for some reason" kind of solution. But it is more risky than the 38/357 example due to failures due to the extractor missing the case rim, and the fact that the headspacing issue due to build up could show up at a very bad time... unless this is a range toy only.

For me, it is just not worth the risk. It is like buying a vette and filling it with the cheapest oil I can find to save a buck.

If you can afford a Legion 10mm you should be able to afford the correct ammo for it. As for the Glock 10mm, run all the .40 you want, won’t matter one way or the other.

I cannot imagine the pressure peaks that you are generating when the bullet passes over the excessive gap space accelerating into the leade and then is suddenly slowed by friction as it engages at too high a speed into the rifling.

But that is the point. Without measuring the internal ballistics, you simply do not know what pressures you are generating when you are doing this, and how close you come to the barrel's tolerance for over pressure.

I do it all the time. No problems at all.

It seems to work after a fashion... but why. A while back a guy at our range came over to me when he saw me shooting Sig's (like that matters). well his 220 10 was having problems going into battery, well while I was looking at it he said I don't understand I just shot a few boxes of 40 out of it and it worked fine. Uh...

I was just taking to a buddy of mine about this. I’m new to this idea but he is also talking about his Glock. No problems though on his end. But I tend to agree with the above. “Only if you have to”