40 S&W snap cap in a 10mm chamber?

[IdahoSkies]

Can a .40 S&W snap cap be used in a 10mm chamber like a .270 can be used in a .30-06 or will there be headspace/no go space issues?

Thanks.

 

[rcmodel]

No.
It is too short to headspace properly in the longer 10mm chamber.

You have to use 10mm snap-caps in a 10mm.

Straight-wall pistol calibers like this headspace on the case mouth.

30-06 & 270 headspace off the case shoulder, which are both pretty much in the same place.

rc

 

[jmr40]

I don't use snap caps, so I cannot say 100% for sure, but would be 99.9% sure it would work. I know that lots of guys have fired 40 S&W rounds in their 10mm's without injury. Not something I'd recommend, just saying it has been done. Don't see where snap caps would cause a problem.

 

[1KPerDay]

You can probably use them in a pinch but the only thing holding the snap cap in place will be the extractor, so you'll probably wear out the rims prematurely. Unlike the rifle rounds with shoulders mentioned, the handgun rounds in question headspace on the case mouth. So there's nothing in the chamber holding the .40 back against the impact of the firing pin.

 

[1KPerDay]

dang fast typists...

 

[IdahoSkies]

Thanks. I had that suspicion.

 

[hariph creek]

Most modern centerfire guns don't need snap caps. I'd think any 10mm qualifies as "modern?"

 

[BCRider]

The issue of using the .40 and relying on the extractor to hold the snap cap in place is that the extractor isn't expected or designed to deal with the forward strike of the firing pin. So there is a risk that it could give up the ghost earlier than it would otherwise. If it's a big burly sort of extractor this may never be an issue. If it's a finely shaped little whisp of a thing then it may not live long at all.

 

[MachIVshooter]

The issue of using the .40 and relying on the extractor to hold the snap cap in place is that the extractor isn't expected or designed to deal with the forward strike of the firing pin.

What do you think is different about the force vector on the extractor with the firing pin hitting it versus yanking a case out of the chamber?

Think about it.

 

[Lost Sheep]

What do you think is different about the force vector on the extractor with the firing pin hitting it versus yanking a case out of the chamber?

Think about it.

Firing pin impact is sharper than the extraction force. Though the firing pin impact is mitigated by the snap cap so maybe there is less difference than one would expect.

Ultimately, I don't know, but I would keep an eye on the extractor. Maybe buy a spare.

Lost Sheep

 

[Weevil]

It'll work just fine.

Most chambers tend to be made on the long side anyway to compensate for the slight differences in case length and changes from reloading.

A lot of your rounds regardless of caliber are actually being held in place by the extractor anyway.

This is also one of the reasons why most modern designs use big beefy extractors.

 

[OilyPablo]

Snap cap only?

It will work.

 

[BCRider]

What do you think is different about the force vector on the extractor with the firing pin hitting it versus yanking a case out of the chamber?

Think about it.

It's related to what Lost Sheep posted about the firing pin hit being quite sharp. Consider too how easy it is to slip an empty casing into and out of the chamber. Now stick your finger tip up against the slide's breech face and pull the trigger so the FP stabs your finger tip. There's FAR more kinetic energy in the firing pin strike than the extractor ever has to deal with when extracting a casing.

 

[MachIVshooter]

It's related to what Lost Sheep posted about the firing pin hit being quite sharp. Consider too how easy it is to slip an empty casing into and out of the chamber. Now stick your finger tip up against the slide's breech face and pull the trigger so the FP stabs your finger tip. There's FAR more kinetic energy in the firing pin strike than the extractor ever has to deal with when extracting a casing.

Pin isn't hitting the extractor directly, nor is it an inelastic collision with the primer. Brass has very good shock damping properties, which is why we use brass punches when we don't want the hammer bouncing back at us on a solid hit. As well, the primer is absorbing nearly all of the impact from the FP.

Further, if we want to argue strain on extractor, consider not only the extraction, but ejection. There's a sizable amount of energy present when the back of the case hits the ejector, much more than the firing pin exerts. It is also a less elastic impact.

This is all academic, of course, as extractors are more than capable of dealing with all of the above for a very, very long time.