Pistol powders that cannot be compressed.

[justindad]

Are there any pistols powders that should never be compressed in any cartridge?

[Nobade]

As far as I know, none of the really high nitro powders have any compressed loads except in shotguns. Even in something like 25 acp.

[Kosh75287]

I used to reload .357 Magnum cast loads with (then) Hercules Herco. It seemed to work a little better, when compressed.

[cwlongshot]

Generally Ball powders do not compress well.


It is advised not compress Trail Boss.

CW

[justindad]

Do the ball powders not compress well simply because spheres don’t pack in any tighter, or is it due to the burn performance?

[racepres]

I have avoided Compressed loads for my entire Experience (about 1978). There is always a Powder that compression is Not a Requirement...so.... That is how I go.

[Larry Gibson]

Blue Dot can show erratic pressures if compressed in handgun cartridges, particularly the magnums. That is erratic, not high or spiking pressures.

See pressure test data in; https://castboolits.gunloads.com/sho...s-Alliant-test

[jdgabbard]

Generally Ball powders do not compress well.

I always thought that the powders that did compress were typically ball, or flattened ball. Such as H110... That's just one example, but it was the impression I had.

[45_Colt]

Accurate Arms #9 in the .357 SIG is a compressed charge. This is a ball powder with nitro added. Being compressed also helps reduce set-back.

To add: this is a 90% ball powder, with the remaining being a flattened ball.

45_Colt

[justindad]

I’ve done compressed charges of Enforcer in .357 Sig. The max charge is about 0.1” from the mouth of the case. I had to elongate my OAL because the powder pushed the bullet out a bit.

[justindad]

Has anyone ever seen AA#7 compressed? I’ve read about people compressing HS-6, but I haven’t seen the load data.
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I’ve loaded a few different cartridges with Silhouette that were very near compressed, but never quite there. That powder is used in almost no cartridge with a roll crimp. Makes me think Silhouette would go unpredictable if there was a >95% case fill.
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What about Long Shot?

[winelover]

I use AA#7 for 9mm and like it so much that I purchase in 8# jugs. It's used for high end loads. However, since I seat and crimp in separate stages, upper end powder charges will allow the bullet to gain in OAL>>>demonstrating too much compression. IIRC, that happens above 7.5 grains........depending on bullet design. BTW, I don't load anything heavier than 138 graines, sided and lubed.

Winelover

[TurnipEaterDown]

Compression can be a hinderance, or a great aid. Depends on application.

High recoiling rounds in a magazine rifle: helps avoid set back. Post number 9 alludes to same benefit in Auto Pistol.
High compression in a revolver, neither fish nor foul. May allow higher performance depending on powder & cartridge. May get you reformed bullet noses on seating.

Have read that 4895 isn't recommended for compressed loads, then I find it specifically recommended in the 416 Taylor in the A Square manual. There are several 4895s however. Probably depends on application as well as powder specifications.

I wouldn't compress a a powder that I haven't cross referenced to other applications while wildcatting, but I have done so before and do will do again at those times when I have cross referenced a powder when I have no data in my intended use.

There is a comment in the thread about ball powders that have flattened ball in the mix.
This is just burning rate control. The granules will also not all be of identical size. The flattening is done in the pliable stage of manufacture to increase the surface area of a larger size sphere. It is actually rare in my experience to find a canister spherical propellant that doesn't have some flattened granules.

The surplus WC820 I have is very uniform spheres, and this also contributes to terrific metering. Needs to be kept in mind though that bulk powders for military are made to hit a specification range, and then loads adjusted after the burning character is understood. The specification range to characterize the powder is broader than canister.
Canister powders for reloaders are made to a tighter specification range so the already published data is "good" -- they adjust the powder to the data range already published.
The adjustment for military lot loading can be large compared to canister for reloader powder lot changes. They deal with specification range being broader by characterizing each lot.

I know nothing about a warning against compression in general while using Ball/Spherical powders, but then none of us know everything.

[stubshaft]

trailboss!

[Messy bear]

Good question. It seems that many common loads in higher pressure cartridges wind up compressed. I have loaded as such for years. So we know it’s ok with many powders.
But the only ones mentioned so far are blue dot and trail boss. I would surmise that titegroup would be one also but don’t know for sure.