Compressed Loads? Are they dangerous?

[lefty_red]

Just what is a COMPRESSED LOAD and is it dangerous?

My GLOCKs like their bullets set deep. I was just wondering if I'm raising my psi's to a dangerous level when I do this.

Jerry

[Oldfeller]

Yes, if you are using any of the higher loadings of the faster powders (like Bullseye, Unique). These can be dangerous if "at ignition" case volume is appreciably reduced.

Especially if your cast bullets get moved unintentionally during auto cycling, unexpectedly seating them way way deeper into your case and further reducing "at ignition" case volumes. Bad news .... big pressure spike.

==========================

Or, if you are an older smarter caster/reloader and you use tightly packed full case loads of slower powders (Herco, Blue Dot, 2400) such that you simply CAN'T push the bullets back any in the case, then no, it won't raise pressure much at all.

Peaky higher pressure autoloaders like 9mm and 40 S&W are safer using intentionally mildly bullet seating compressed larger charges of slower powders.

These are muzzle flashy, inefficent, dirty, noisy (but inherently safer for your gun). They also tend to give better velocity without leading.

==========================

And then there are some of us that use faster powders and taper crimp their case mouths right on into the lead slug deep enough to KEEP the bullet from moving into the case much even if you hit it with a small hammer blow. We balance depth of crush to just give us a barely good headspace lip sticking out.

We like the risk. (we're cheap !!! This saves powder)

<g>

Oldfeller

[Buckshot]

..............Normally compressed (really compressed vs merely having the slug sitting on it) powder charges aren't dangerous. In a rifle they may sometimes produce lower velocities (with REALLY slow powders) or erratic ignition for more spread out SD's and wider velocities.

I think the reason for this in rifle cases with their longer, narrower powder column is simply a matter of mechanics. If compressed, the primer ignition flame and hot gasses have a much tougher time propigating through the charge. Especially if it's a dense ball powder.

The only way to find it out is in testing. A friend did this in the 8x57 loading WC860 for a Turk Mauser. With a charge that the boolit set on (no compression) he got about 75 fps MORE velocity and very nice accuracy with low deviations vs the compressed charge.

.............Buckshot

[Explorer1]

No air space is preferred for high levels of accuracy, the benchrest world modifies cases to hold "just the right amount" of powder which leaves no unfilled void.

Compressed is OK, if not compressed enough to work the bullet back out of the exact position (which can/does affect accuracy by altering jump to or contact with the lands).

That said, this all assumes you are using the correct powder, seating depth, etc. for a safe load.

[swheeler]

Jerry; a compressed load is when the powder fills the case more than 100% of usable space, and when the bullet is seated, it compresses the powder. This is not dangerous if the powder is of a burn rate which allows this and still maintains chamber pressure of a safe level. The loading manuals show many compressed loads that are safe, and they are marked as compressed in said manuals-C or *, whatever symbols used will be noted in foot notes.
BUT what you are asking about handgun ammo may very well be unsafe. If you are using a manual that lists the bullet you are using it should give MINIMUM OVERALL CARTRIDGE LENGTH- use this length in conjunction with the powder you are using and that load is safe. But if you take the same powder charge and the same bullet and seat that bullet to a shorter(deeper seating)overall cartridge length, then you have raised chamber pressure considerably. I can't find it right now, but one of the loading manuals shows pressure test data for the 9mm Luger, and using the same bullet and powder, but seating one .010" deeper increased pressures a large amount- I believe it was over safe SAAMI pressure limits. So if you are taking a published MAX load and using it as published, but seating the bullets deeper in the case, you are shooting a load that exceeds the safe pressure limits. Small handgun cartridges are especially affected because their internal capacity is so small to start with, decrease that capacity even the tinyest bit and pressures skyrocket.
Be safe- Scot
If and when I read across the data again on the 9mm I will post it here- it's in one of the 30+ loading manuals on the shelf- CRS

[lefty_red]

Thanks for the info guys.

The loads I'm talking about is for pistols. I shot my GLOCKs and I use aftermarket barrels for my cast bullets. They come "match grade" and they are pretty tight. So its putting my reloading skills to the test. I'm having to seat the bullets deeper due the tight chambers and my excess lubing. I'm going to start sizing the bullets and only going with the one "toss" of ALOX. That might allow me to seat the bullet out longer.

I'm finding the 40S&W loads like the med-slow powders like BLUE DOT and TRUE BLUE. I treat it like "black powder"! A full case and no air between the powder and the bullet gives me a nice "push" and great groupings.

The 9mm is giving me fits though.

Jerry

[FallRun]

Jerry; a compressed load is when the powder fills the case more than 100% of usable space, and when the bullet is seated, it compresses the powder. This is not dangerous if the powder is of a burn rate which allows this and still maintains chamber pressure of a safe level. The loading manuals show many compressed loads that are safe, and they are marked as compressed in said manuals-C or *, whatever symbols used will be noted in foot notes.
BUT what you are asking about handgun ammo may very well be unsafe. If you are using a manual that lists the bullet you are using it should give MINIMUM OVERALL CARTRIDGE LENGTH- use this length in conjunction with the powder you are using and that load is safe. But if you take the same powder charge and the same bullet and seat that bullet to a shorter(deeper seating)overall cartridge length, then you have raised chamber pressure considerably. I can't find it right now, but one of the loading manuals shows pressure test data for the 9mm Luger, and using the same bullet and powder, but seating one .010" deeper increased pressures a large amount- I believe it was over safe SAAMI pressure limits. So if you are taking a published MAX load and using it as published, but seating the bullets deeper in the case, you are shooting a load that exceeds the safe pressure limits. Small handgun cartridges are especially affected because their internal capacity is so small to start with, decrease that capacity even the tinyest bit and pressures skyrocket.
Be safe- Scot
If and when I read across the data again on the 9mm I will post it here- it's in one of the 30+ loading manuals on the shelf- CRS

What a Great answer! no questions on a cc after reading that

[swheeler]

Thanks FallRun; there is plenty of good stuff rattling around up there in the cobb webs, just hard to spit it out anymore, some days are better than others.

[7of7]

Think about shotguns,... all of those loads are compressed, as you seat the wad on the powder to a particular pressure... in rifle and pistol loading, one needs to pay attention to not exceed the maximum load...
Stay safe everyone..

[Dannix]

One additional note: I'm rusty on some of this, but compression is really only a applicable to some powder types e.g. trying to compress a ball powder is a no-go from what I recall (and others, please correctly if I'm mistaken).

Jerry, careful with BlueDot in 9x19. I've read reports it can be spiky if you push the pressures in that cartridge with it.