Quote:
Originally Posted by KLNC
As I've learned more and more about S&W revolvers, I continue to be perplexed by the fact of "oversized throats" on certain revolvers, particularly 25-2s and 25-5s. My question is why did S&W do this? Surely they had the capability of sizing throats properly? What was their thinking?
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They DID size them properly, according to the thinking of the day.
The simple answer is SAAMI standards. (Sporting Arms and Ammunition Manufacturers Institute)
You don't have to take my word for any of this. Go see the SAAMI specs yourself, pages 49-52 in the spec tables:
SAAMI
Formed in 1926, SAAMI established "standards" for the manufacturers. Simply an effort to make sure everyone uses the same data.
One big problem with the SAAMI dimensions-
Up to WW II, Colt used a nominal groove diameter of .454 with an additional tolerance of a few thou for the 45 Colt that could mean a groove dia of .458.
When they brought the Single Action back in 1956, I have always read that they used the same rifling tools they used for the 45 ACP. The SAAMI groove dia for the 45 ACP is .450+.004 tolerance. Now, the SAAMI grovve dia for the 45 Colt is also .450+.004 tolerance!
BUT, they seemed to have kept the old chamber dimensions for the 45 Colt. The SAAMI throat specs for 45 C are .4555 to .4595!
Now, let's look at 45 C ammo specs:
Bullet dia is .456 with a tolerance of MINUS .006.
So totally within SAAMI specs, we could have 45 C ammo with a min bullet dia of .450 rattling out of a max throat which is .4595!!!!!!
That's
9-1/2 thou of SLOP, folks, and TOTALLY within specs.
S&W was simply abiding by the standards. I would also imagine the legal department did NOT want to stray from those standards.
Quote:
Originally Posted by Tom C
I suspect the why is related to WWI and the conversion of the .45 Colt revos to .45 ACP.
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Not really.
By the time of WW I, you could count the 45 Colts that S&W had built on one or two hands.
SAAMI did not exist, so I would imagine they went with whatever the Gov specified.
1917's seem to shoot pretty well. It would be interesting to mike the throats and slug the bores of some.
As far as 25-2's and the 45 ACP-
There are no SAAMI specs for a 45 ACP REVOLVER chamber.
There ARE specs for the 45 AR chamber, and it is the same .4555 to .4595 in the throat.
45 ACP ammo with jacketed bullets can have a bullet dia of .452 with a tolerance of MINUS .003.
Sooooo, it gets even worse here.
We can have a Mod 25-2 in 45 ACP/45AR shooting a bullet that is .449 into a throat of .4595, and be totally within specs!!
SLOP = .0105 (10-1/2 thousandths!!!)
See the problem yet?