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Old July 21, 2013, 06:56 PM   #11
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Join Date: July 20, 2005
Location: Indiana
Posts: 10,167
Most published 357 mag ballistics are from 7.5"- 8" test barrels. Firing them in 6",4",or 3" barrels would be equivalent to shooting a 300WM from 18",12" and 9" barrels. The velocity numbers are going to be considerably slower, especially with barrels under 4".
If you're looking at loadings with heavy bullets designed and marketed for hunting perhaps, but with 158gr or lighter JHP loadings most manufacturer's numbers are from four inch barrels. The following loadings all have their advertised velocities from 4" barrels per their manufacturer's websites:

Remington 110gr JHP
Remington 125gr JHP
Remington 158gr JHP
Remington 125gr Golden Saber
Winchester 110gr JHP
Winchester 125gr JHP
Winchester 125gr PDX1
Winchester 145gr Silvertip
Speer 125gr Gold Dot
Speer 158gr Gold Dot
Cor-Bon 110gr JHP
Cor-Bon 125gr JHP
Cor-Bon 140gr JHP
Cor-Bon 125gr DPX
Glaser 100gr Pow'RBall
Glaser 80gr Blue
Glaser 80gr Silver

In addition, Federal does not list their test barrel length, but chronographed velocities from BBTI and other sources seem to indicate that they're using 4" barrels as well. The only major manufacturer I'm aware of which does use long test barrels for almost all it's .357 Magnum ammo is Hornady which lists 8 inch vented test barrels only for all its .357 Magnum ammo except the 125gr Critical defense which is listed from both 8 inch and 2 inch barrels.

As to the difference in actual velocities, barrel length measurement must be taken into account. Because a semi-auto's barrel includes the chamber, a .40 with a 3" barrel would only have 2.15" of usable barrel length due to the .850" taken up by the case. If we measure a .357 Magnum barrel the same way, it would only have 1.71" of usable barrel length due to the case taking up 1.29" of it. If we assumed that a .357 Magnum revolver had a 2" barrel and a cylinder 1.6" long so as to accommodate cartridges loaded to the maximum OAL of 1.59", that would give us a usable barrel length of 2.31" due to the chamber throat.

Just to keep things simple, we'll use BBTI's 3" barrel velocities for both cartridges and assume that the decreased usable barrel for the .357 Magnum is offset by the lack of a barrel/cylinder gap (BBTI's 3" .357 velocities are consistent with what I've seen routinely chronographed from 2-2 1/2" revolver barrels). Also, let's compare the loadings with the closest bullet constructions and weights: the Federal Hydra-Shoks.

From the 3" barrel, the .357 Magnum 130gr and 158gr Hydra-Shoks chrono'd 1194fps and 1122fps respectively. This gives us 411fpe for the 130gr and 441fpe for the 158gr. By comparison, from a 3" barrel the .40 S&W 135gr and 155gr Hydra-Shoks chrono'd 1080fps and 1065fps for 349fpe and 390fpe respectively. Now, we could certainly expect a .40 S&W with a longer 3 1/2" barrel to produce somewhat better velocity and energy figures, but many .357 snubbies have barrels anywhere from 2 1/8" to 2 1/2" which would improve that cartridge's numbers as well.
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Last edited by Webleymkv; July 21, 2013 at 07:20 PM.
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