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How much velocity and maybe accuracy would be lost shooting 38 spl +P from a 640-1 cylinder with a 2 1/8" barrel?
38spl +P velocity from a 640-1 357
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Compared to what?
I'll take a 4" 686 for comparison.
Mechanical accuracy of the 640 should be fine, but the longer sight radius of the 686 should help shooter accuracy.
Loss of velocity is extremely dependent on the powder and bullet used in the +P .38. My near-max .357 hunting handload of WIN296 under a 158gr JSP suffers great speed loss in a short barrel. A .38 125 gr over HP38 less so.
I would expect about 875fps from your 640 with the Speer Short barrel 135gr +P .38 Gold Dot. More importantly, the bullet will expand reliably at that velocity. That would be my firt choice in defense loads for it. The "old tech" 158gr HP lead would be my second choice, but speed will be in the low to mid 800s.
I'll take a 4" 686 for comparison.
Mechanical accuracy of the 640 should be fine, but the longer sight radius of the 686 should help shooter accuracy.
Loss of velocity is extremely dependent on the powder and bullet used in the +P .38. My near-max .357 hunting handload of WIN296 under a 158gr JSP suffers great speed loss in a short barrel. A .38 125 gr over HP38 less so.
I would expect about 875fps from your 640 with the Speer Short barrel 135gr +P .38 Gold Dot. More importantly, the bullet will expand reliably at that velocity. That would be my firt choice in defense loads for it. The "old tech" 158gr HP lead would be my second choice, but speed will be in the low to mid 800s.
Based on my limited tests with a few short-barreled S&Ws and C****s, you probably WILL lose a little velocity with a .357 cylinder. However, I believe that there are other factors, also, that vary from gun to gun, so it's hard to be sure. I doubt that it would be more than 50fps, but if you really want to know, borrow a chronograph.
As far as accuracy, I wouldn't count on learning anything. There are many other factors, almost all of them more important than chamber length. I would generally rank choice of grips well above chamber length.
Hope this helps.
As far as accuracy, I wouldn't count on learning anything. There are many other factors, almost all of them more important than chamber length. I would generally rank choice of grips well above chamber length.
Hope this helps.
From my chrono measurements, there is more gun to gun variation due to cylinder gap and other minor barrel variations than you can measure from a .357 cylinder to a .38 cylinder. My .38 IDPA loads ( a mild +P) are fastest in my 4" model 686 compared to other .357s and a model 67 .38.
As we say in data analysis, any difference is lost in the noise.
ArchAngelCD
Moderator, SWCA Member, Absent Comrade
I did some work with .38 Special +P loads and here is some of the data I collected. I have more but this is typical of most of the data.
4" M686 --- 2" M640
927.0 - AV - 888.9
955.1-- H -- 897.1
905.4 -- L -- 876.6
49.7 -- ES -- 20.5
20.7 -- SD -- 7.9
17.0 -- AD -- 5.9
4" M686 --- 2" M640
927.0 - AV - 888.9
955.1-- H -- 897.1
905.4 -- L -- 876.6
49.7 -- ES -- 20.5
20.7 -- SD -- 7.9
17.0 -- AD -- 5.9
ArchAngelCD
Moderator, SWCA Member, Absent Comrade
You're welcome, glad I could help.
