This is a discussion on Please school me on 10mm...... within the General Firearm Discussion forums, part of the Related Topics category; Originally Posted by Rockymonster I tried to rent the G20 at my favorite range last week but they were out of 10mm ammo....(have to use ...
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.38 and 357 are rimmed cartridges, and space off the rim. So it’s perfectly safe to shoot .38 in a .357.
10 mm and .40 don’t space off the rim. For a .40 to fire in a 10 mm the extractor needs to hold the rim to keep the cartridge from sliding forward in the chamber. At the very least this increases wear on the extractor every time a .40 round is chambered in a 10 mm. If the extractor loses grip on a .40 when the striker hits the primer, the round could move slightly forward from the bolt face before the primer ignites the main charge, and this gap between the cartridge and bolt/slide face could create a kaboom. Yes, some people do it, but that doesn’t mean it’s safe.
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10mm in 220-230 grain hardcast is very good for bear defense, and Denmark's Sirius sled patrol issues the Glock g20 in 10mm for defense against polar bears. Alaska State Police, and their Wildlife Troopers, are issued 40cal Glocks with the option of 10mm Glocks. They discontinued issuing 357 magnums some time in the last 10-15 years.
Of the people who've used handguns to survive brown bear and polar bear attacks, ALL of them have kept firing until the bear ceased its attack- just like with defense against humans. Empty the cylinder or magazine if needed! Once a bear is on you, logic would say a handgun is much easier to wield than a long gun. I'm sure no bear attack survivors would ever say they wish they'd have had fewer rounds of capacity in their handgun.
220gr 10mm Sectional Density= .203
230gr 10mm------------------> = .212
180gr 357mag (9.1mm)------>= .200
190gr 357mag (9.1mm)------>= .211
(I didn't list the SD of 200gr weight because the rounds won't fit the cylinder length of an S&W revolver)
Last edited by Big Western; October 7th, 2019 at 11:13 PM.
There are no dangerous weapons; there are only dangerous men.--RAH
...man fights with his mind; the weapons are incidental.--Jeff Cooper
There is a reason they try and make small bullets act like big bullets--Glockmann10mm
10mm is fun to shoot. Yes, it is a bit more expensive to shoot and when you use your G29 at an IDPA match people may give you funny looks. :)