Does a Gas Check Affect Pressure?

[John Patrick]

I’ve been looking at load data for 38spl, 38spl +P and 357 in preparation for loading some Rim Rock 158gr SWCHP-GC bullets to come as close as possible to the BB 38spl +P load using the same bullet.

Lots of data for 158gr lead bullets but I haven’t found any for a gas checked bullet.

FWIW, Modern Reloading Second Edition (Richard Lee) shows standard pressure 38spl data with a nominal velocity of 1013fps (barrel length unknown) with a 158gr lead bullet using True Blue. And I have a pound of True Blue.

Thanks for any help!

ETA: Also will be loading coated 158gr SWCs to similar performance for field and practice use.

 

[rockquarry]

I’ve been looking at load data for 38spl, 38spl +P and 357 in preparation for loading some Rim Rock 158gr SWCHP-GC bullets to come as close as possible to the BB 38spl +P load using the same bullet.

Lots of data for 158gr lead bullets but I haven’t found any for a gas checked bullet.

FWIW, Modern Reloading Second Edition (Richard Lee) shows standard pressure 38spl data with a nominal velocity of 1013fps (barrel length unknown) with a 158gr lead bullet using True Blue. And I have a pound of True Blue.

Thanks for any help!

ETA: Also will be loading coated 158gr SWCs to similar performance for field and practice use.

Gas checks probably affect pressure but minimally. Some years ago, I called Lyman with a pressure question. I spoke with one of the technicians that actually does pressure testing and he was very helpful. I don't know whether or not those guys are still that accessible, but that's where you'd get your best answer.

 

[mtgianni]

Get a hold of a Lyman manual. IIRC, there is little difference between the 358156 gc bullet and the 158 gr 358477 plain based.

 

[John Patrick]

Get a hold of a Lyman manual. IIRC, there is little difference between the 358156 gc bullet and the 158 gr 358477 plain based.

I have a couple, will look again. Thanks.

 

[Ivan the Butcher]

There used to be two types of gas checks for sale. Lyman's were "Slip on" and Hornady's were "Crinp on". Depending on how much bullet lube got squeezed under the Lyman Gas Check, it would fall off after exiting the barrel. I tried to stick with Hornady's because of that. I think that only Crimp On are made anymore! Both types are applied at the time of sizing and the casting must be made for a gas check with a smaller diameter notch at the bottom. In the 80's, I shot bullets designed for GC's, but none installed (usually at 800-900 fps) without any loss inaccuracy. This saved me the 2/3 cent ($5.99/100) per bullet. Now Midway still sells them but from $50/1000 to $90/1000.

Ivan

 

[John Patrick]

Get a hold of a Lyman manual. IIRC, there is little difference between the 358156 gc bullet and the 158 gr 358477 plain based.

I found the two bullets in 357 load data in Lyman’s 50th Edition and their Pistol and Revolver Handbook 3rd Edition.

358156 (you write GC) is 155gr. 358477 is 150gr (obviously not GC based on the base.) There is some difference in data, but nothing obviously attributable to the GC rather than the weight difference.

Oddly, both books have 38spl data for the 358156 (GC,) but not the 358477 (non GC.)

My takeaway is keep off maximum +P loads for 158gr lead bullets, in case the GC is a factor in the data differences, rather than the 5gr weight difference.

Thanks for the help!