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Old January 13, 2012, 01:19 PM   #39
SL1
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Join Date: November 8, 2007
Posts: 2,001
JohnSKa,

As I stated in my post about WW-296, the data from Winchester and Hodgdon are from UNVENTED TEST BARRELS, so of course they are higher than velocities from revolvers. Besides the lack of vents to simulate the cylinder-to-barrel gap, these test barrels are also built to SAAMI minimum specifications, which is intended to maximize pressure, and that also maximizes velocity for the same load. The remarkable thing about these data is that they were BOTH test barrels, so you would think that results should be pretty close. But, of course, they were probably different lots of powder and primers, so that could easily make the difference seen.

Many manuals do not report the velocities from the test barrels. Instead, after working-up a maximum load in their test barrel, they fire it in a gun you can buy at your local gun shot to give a more realistic expectation of the velocity that a handloader is likely to achieve. For comparison, look at the table on page 771 of Speer Manual #14. It lists velocities of the same loads when fired from 30 guns chambered in .357 magnum, plus a test barrel. The test barrel was 10" long, so I will compare it to the Contender with 10" barrel. For their 158 grain bullet load, the test barrel produced 1591 fps and the contender produced 1587 fps. So, it seems like a Contender will produce velocities similar to a test barrel. On the other hand, a Ruger Blackhawk with a 10" barrel is listed as producing only 1365 fps with that load. And, in fairness, the way a revolver barrel is measured (not counting the chamber) makes that really a 11.65" barrel. Counting the cylinder length, the S&W M27 revolver with the 8-3/8" barrel is closer in length to the 10" test barrel, and it produced only 1221 fps. So, yes, test barrel velocities are quite optimistic with respect to velocities from revolvers.

And, revolver velocities also vary substantially for the same barrel length, even when made by the same manufacturer. That table in the Speer manual lists velocities from 9 revolvers with 6" barrels. For the same load withthe 158 grain bullet, the velocities range from 1080 fps to 1284 fps. Among 3 S&W M19s the range was from 1154 to 1284 fps, and for 2 S&W M28s it was 1080 to 1178 fps. In fact, the velocity from the revolver with the 8-3/8" barrel was beaten by an S&W of the same model and a Ruger, both with with 6-1/2" barrels, and 2 of the 9 revolvers with the 6" barrels.

That showes how poorly the published velocities in reloading manuals may match YOUR PARTICULAR revolver, and why you might exceed the velocities shown in the manuals for "example" guns (rather than test barrels) without exceeding the listed max charge weight or the actual pressure limit.

One more point. I have an old Lyman manual from the days when the loads were NOT pressure tested. (They were worked-up by those "dubious methods" looking for pressure signs.) But, they did use chronographs to provide velocities from their "example" guns. They also fired factory ammo and measured its velocity to obtain a goal for their "factory duplication load." For the .357 Magnum with 158 grain (lead w/GC) bullet, they obtained 1388 fps from a S&W M27 with 5" barrel using factory ammo. That is 674 foot-pounds. So, shooting the same load from a 6" barrel does not seem to be much of a leap to reach 1412 fps and 700 foot-pounds. And, even today, Buffalo Bore loads ammo to that energy level from a real revolver, as shown on their website.

However, the "factory duplication load" in that old Lyman manual used Herco powder, for some reason. And, it must have been WAY over SAAMI pressure limits of any day. My QuickLOAD program gives 70,000 psi with their load using default parameters and showes a 21% compression. Even enlarging the case volume to what my Security Six produces, I still get a lot of compression and over 60,000 psi. Apparently, Lyman actually shot those loads in their M27 without producing effects that deterred them from publishing that load in 1967. But, I am NOT going to publish it HERE,

SL1

Last edited by SL1; January 17, 2012 at 11:11 AM.
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