I was reading someone's post on a Glock 20 and the guy mentioned how his 20 reliably functioned 40s&w rounds.  I figure this is not really something that should be done and it would put extra stress on the extractor ..  I'm sure you guys have heard of this being done... What are your thoughts?  Disaster waiting to happen?  No big deal?

Myself, except for shooting 38spcl in a .357 mag firearm, I can't see doing this,  But I can't see the danger of doing this either, although it just doesn't sound right.

Quote from: dsonyay on April 27 2014 12:23:20 PM MDT
I was reading someone's post on a Glock 20 and the guy mentioned how his 20 reliably functioned 40s&w rounds.  I figure this is not really something that should be done and it would put extra stress on the extractor ..  I'm sure you guys have heard of this being done... What are your thoughts?  Disaster waiting to happen?  No big deal?

Myself, except for shooting 38spcl in a .357 mag firearm, I can't see doing this,  But I can't see the danger of doing this either, although it just doesn't sound right.

It won't put any more stress on the extractor, it's the same case... and if your shooting a few , I wouldn't worry about it.
A 38/357 case rests on the case ridge at bottom of case... The major diff is the 10 chamber is made for the case front edge to sit and also help position the whole bullet... since the 40sw case is shorter and the aol of the bullet less, there's a chance that a lot of rounds can possibly damage/wear this chamber ridge.

Since a 40sw barrel are drop in and only about $100, its a safer , better fit.

Long standing debate about the safety of this practice.  The short answer is it is a bad idea.  The longer answer is that it is very platform dependent.

The Springfield Omega, with it's big beefy dual extractors, works great with 40 S&W.  I believe the factory manual for that gun even says it is a supported practice.  To the best of my knowledge no other gun maker supports shooting 40 S&W in a 10mm barrel.

Reports are that Glocks generally function fine with 40 S&W.  There are some ugly articles about some other platforms ability to handle 40 in a 10mm chamber.

It really comes down to the size and strength of the extractor.  Since both cartridges nominally headspace on the case mouth, when shooting 40 in a 10mm chamber, you are relying on the extractor to hold the cartridge in place.  If it doesn't accomplish the task, then you might get a light strike, or you might get a primer blow out.

I personally consider the cost of a second barrel cheap insurance.

It's been a long time and all the info from "hot" rifles to 105 mm tank (M-60 and M-48 A2) guns is starting to jumble up in my head, but the term "throat erosion" comes to mind when I hear about people doing this.  Logic would indicate that the .38/357 would be an indicator that there is not much if any problem, but it's something I would be concerned about in the hotter 40/10 rounds.  Just don't think it's a good practice.

Please don't.  As stated above, you may have no issue with some platforms.  If you do have issues, it amount to a bad day.  Why risk it?

Yes it works!  But it can cause problems, like as the bullet is fired from the shorter casing and passes across the end of the 10mm chamber cut (a little over an 1/8" jump) bullet material can be sheared off and rolled up on that edge.  This can build up and will require a good cleaning, if done enough times some wear can occur on the edge.

The extractor is trying to hold the cartridge in place and the cartridge can come out from under the extractor leaving the cartridge loose inside the chamber.  The extractor could suffer issues if it tries to jump over the case rim.

Much easier to use a conversion barrel, then switch back when the 10mm ammo is needed.

I have always looked at this situation as a last ditch or emergency usage only - it is good to know you have this option.

Doug