Granulation in pistol calibers: What's "safe"?

[Old Ironsights]

Assuming I use it only for Pan Prime, I have about 4 lifetime's supply of 4F, and will likely be adding to it as I sift out my next batch of powder.

Can I use 4F in modern pistol cartridges/guns - specifically a Stainless .357 Rossi M92?

Is the pressure spike from 4F too sharp (vs 3F or "Pistol" grade)?

I'm not looking for ultimate accuracy, just a good way to make some plinker loads and use up 4F.

[Bad Flynch]

No way to know for sure without a pressure gun, but the Lyman BP manual lists some 4F loads for cap and ball revolvers. Perhaps if one stuck to modest loads, it might be doable.

Best bet for large caliber revolvers for me has been 2&1/2Fg, made by mixing equal parts of 2Fg and 3Fg grades. It seemed to give better velocities than 2Fg and less fouling than 3Fg.

Goex makes an in between grade, much like the mix, for pistols, but I can't remember the name. Many real old-tyme pistol cartridges like the .45 Colt were factory loaded with 2&1/2Fg.

[KCSO]

I tried 4 f in small caliber loads with the same intent and found that it fouled badly. For some reason I could get 20 shots from a 32 pistol with 3 f and when I went to 4 the groups spread ay 8 shots. The only real proof would be for you to try 15 or 20 and see what happens. The pressure wouldn't be too much for a 92.

[SharpsShooter]

I haven't shot C&B for a long time, but when I did, I always used FFFg. I was taught that it proper choice for 36 cal and above. FFg could be used with the Walker Colt, but velocities were less than FFFg

SS

[Old Ironsights]

Well, I'm looking at cartridges not C&B, and in a Rifle not a Revolver, so the fouling issue is waay different.

I'm mostly concerned with pressures and whether it will be safe.

KCSO: So 4F doesn't "spike" more than 3F?

I've been told by many a Muzzleloader to never-never-never use 4F as a main charge, even in a modern gun like my Firestorm because the sharper spike "causes microfractures". Is that so much BS? I'd like to hope so.

[KCSO]

I only tried it in my 32 H and R in S and W cases. Aside from the lousy accuracy I didn't notice any spike, but I was shooting a 8000 psi load in a gun made for 25,000.

[montana_charlie]

Well, I'm looking at cartridges...in a Rifle

I've been told by many a Muzzleloader to never-never-never use 4F as a main charge,
Old Ironsights,
I am sure you are aware that there are many 'old wives tales' that are accepted as 'Gospel truth'. Horses and guns are two subjects that have more than their share.

I can't answer your questions about 'never-never-never' and 'microfractures' related to 4F but, I would imagine that the old longhunter nearing the end of his trek would happily use whatever grade of powder was left in the bottom of his horn...in a barrel that was not as strong as yours. And besides, the amount you can stuff in a .357 case is not very much powder, really.

The never-never caution may have come about because of using volumetric measures. You can get a good bit more propellant in the measure if it is a finer granulation...possibly resulting in a simple 'overcharge'...especially in an era where 'double charging' was a common practice if one wanted to 'load for bear'.
If you establish your charge size based on scale weight, this difference is avoided.

You had a thread going some months ago with a similar question about 4F...in the same rifle, I assume...but then you were looking at 'plinking loads'. Did you ever do anything along that line of thinking?

In your position, the main concern I would have about 4F 'spiking' more than 3F would be in the 'plinking load' area. With a reduced charge, the presence of an airspace in the loaded round would be my chief concern because of that other 'old wives tale/Gospel truth'...the ringed chamber.

Those who shoot cartridges that perform best with 2F (or larger) always say that 3F (if they try it) is 'dirtier' than the proper grade. 3F should be the proper grade for .357, so I expect that 4F (if used in that case) would be 'dirtier', as well.
But the 'big case' guys, with their 60 to 120 grain charges, don't blow up their guns with 3F...so I doubt that you would experience that with 20 to 30-odd grains of 4F.

But I would watch the airspace...
CM

[Old Ironsights]

Thanks CM.

That's largely what I was thinking, but I was looking for just that erduite a confirmation.

With "full power" 4F BP loads I intend 2 things:

#1 - A compressed load, every time.
#2 - Full length .357 cases (to prevent short-case-chamber-crud-rings)

As for the plinking loads - these would be the plinking loads and I have not yet tried them. However, my "catsneeze" loads are 5gr BP/sub covered with farina to at least 10% compression, and they work marvelously - though my initial batch were loaded in .38sp cases (watching for crud rings).

[NickSS]

When I got rid of my flintlock rifle I had most of a pound of 4F left so I tried it in a 32-20 Winchester low wall I had at the time. I used the Lyman 31108 bullet with my own BP lube and compressed the loads approximately .1 inch. They shot just fine but were a little dirtier than my 3F loads I used most of the time. Never saw any pressure signs.