reloading .357 for compensator

[labnoti]

I want to understand loading for a compensator better. In particular, the S&W Performance Center revolvers that come ported from the factory or with add-on compensators, and in .357 Magnum.

So the way I understand it now, the compensator is driven by the mass of gas at some velocity. Looking at the mass of powder used in a load should be a good indicator of how much gas it can fuel the comp with, but we also have to consider the portion of the powder that's burned before the bullet base exits the muzzle. This is primarily a concern with slow powders in short barrels. I can estimate this with Quickload.

I understand book-listed pressure tells me little about compensator performance because the pressure can spike to the listed maximum while the bullet is still in the chamber and then drop very low by the time the bullet is passing the ports. So while pressure is a factor in driving comps, we'd need to know muzzle pressure rather than maximum pressure. Again, I can estimate this with Quickload. The pressure at the port(s) and the mass of gas flowing through them should give a good idea of how much the comp will work, but for practical purposes, this is best estimated from things simpler to measure like the relative mass of powder and % burned.

My immediate concern is determining when a load is going to be ineffective at driving a comp. I know I can load full charges of H110 and that will provide plenty of gas, but I have come to favor less massive powders for a variety of reasons -- powders like Longshot, BE-86, and HS-6. The book loads for these powders still have more mass than loads for Autocomp. Is that a good indication they'll work well with a compensator?

If you've loaded for comps, what can you tell me about it?

 

[ATLDave]

Based on your post, you absolutely understand the concept and issues.

In USPSA/IPSC, guys shooting open guns are trying to feed compensators with either their 38 super or 9mm Major ammo. Common powders used by such shooters, and which are considered to feed a compensator enough gas to make it work well, include:

• AA #7 (the classic)
• Silhouette
• HS-6 (what I use in my 9mm Major)
• VV 3N37 and 3N38
• CFE

There are others, but these are the most common. With the extra "boiler room" the .357 case gets you, I might also give AA#9 a whirl. Remember that more powder behind a lighter bullet will work the comp more than a heavy bullet loaded to reach the same momentum calculation.

One other point: if you've never played with a compensated handgun before, don't expect there to be no recoil. You will flatten the gun a lot... but it will still come back at you about as hard as without a comp. But the flipping/jumping component is being countered. Even with a highly-effective comp, it does not ever feel like a .22lr if you're throwing a 100+grain projectile at 1300+fps.

 

[fxvr5]

My immediate concern is determining when a load is going to be ineffective at driving a comp.

Virtually all powders will be effective in reducing muzzle rise by some amount because gas pressure when the bullet exits will be greater than ambient air pressure. It's only an issue of which powders are more effective. In this case, as you've noted, gunpowder charge weight effectively predicts how effective a powder will be in reducing muzzle rise. More charge weight (to push the same bullet to the same speed) means more gas/pressure for the compensator.

This article might help a little; https://www.shootingtimes.com/editorial/compensators-pressure-gas/99170

 

[forrest r]

You have a lot going on with 357's & comped/muzzle braked bbl.'s. Barrel length's play a huge role in how affective the comp is. Barrel lengths play a huge role in how affective the powder is. Awhile back I did a little testing with 3 different powders and a cast 158gr hp looking for peek performance in a 586 l-comp revolver.


I won't say what the loads were but I will say that stating they were full house loads would be an under statement. They were flat out hot. The powders were 2400, H110 & MP-300. I was mainly interesting in what the loads would do in the 3" bbl'd l-comp (actually the bbl is 2 1/2" with the last 1/2" of the bbl being the comp itself.)


I also tested the same loads in 357's with 4", 6", 8" & 10" bbl.'s.
In the 2 1/2" bbl 2400 out performed H-110 & the MP-300 having higher velocities. Just not enough bbl for the H-110 & MP-300.
In the 4" bbl.'s (2x) all the powders were pretty much equal velocity wise.
In the 6" bbl.'s (2x) the H-110 & the MP-300 started to pull a head velocity wise. +/- 50fps over the 2400
In the 8" bbl the H-110 & MP-300 really started to shine doing +/- 70fps over the 2400
In the 10" bbl the H-110 & the MP-300 were very impressive doing +/- 90fps over the 2400

The dw's get a lot of range time with the heavy bbl shrouds and muzzle breaks. The 4" & 6" dw's chambered in 357.


Those dw's get a steady diet of full house loads of power pistol pushing 158gr to 170gr bullets. If I were you I'd be taking a hard look at power pistol for your comped & muzzle braked 357's. Power pistol does extremely well in short bbl.'s, it has excellent velocities in not only low pressure rounds like the 38spl/44spl/45acp. Velocities in the 357's are impressive.

Those are the 2 powers I mainly use in my comped/muzzle braked 357's. 2400 & power pistol