powder crush

[Link]

I did a search and I might have asked this question. What is the effect when crushing [compressing] powder.
ty Don

 

[K22]

Lyman has an extensive discussion (a page and a half) on this subject in their Reloading Handbook. It is too long to recite here. In other words, it is not a subject that can be adequately addressed with a few words, at least according to them. I trust they know what they are talking about, they have been in the reloading business a long time. Hint, it's important.

So, the next time you are at a gun shop that has this book, you may want to read the section on Compressed Powder Loads which should accurately address your questions rather than just getting opinions on want Billy Bob Joe does or does not think.

 

[Larry Koch]

I thought about using a coffee hand grinder to shorten Imr 4198 so you can get another grain of powder in the 30 br case.

 

[Preacher]

Depending on how much it's crushed, but it will change the burn rate, allowing more surface area to deal with.

 

[Link]

I asked GOOGLE - this is what i got.

Normally a pistol or rifle shellcase is considered full, or 100% loading density, when the powder charge sits at the base of the bullet when the bullet is fully seated. It is possible with some powders and cartridges to increase the powder charge slightly above this point, such that when the bullet is seated it actually compresses the powder charge slightly. This condition is known as a compressed load.
Hodgdon notes in its reloading data if the subject charge is a compressed load. A full case, or lightly compressed charge is an ideal condition for creating loads with the most uniform velocities and pressures, and oftentimes, producing top accuracy

 

[Homerange]

Hodgdon notes in its reloading data if the subject charge is a compressed load. A full case, or lightly compressed charge is an ideal condition for creating loads with the most uniform velocities and pressures, and oftentimes, producing top accuracy

As do most other reloading manuals.
The rest is very true and what many of us target when developing a load.
Pun intended.

 

[TheCZKid]

On a side note, one detrimental side affect on a compressed load can be cracking your seating stem where it hits the bullet. I accidently did that, twice, with a Forster seating die, as it won't take the pressure.

 

[Doom]

I thought about using a coffee hand grinder to shorten Imr 4198 so you can get another grain of powder in the 30 br case.

The burn rate of extruded powders is determined in part by the geometry of the grain. Do not do this.

You may be joking about this but it is not a joking matter.

 

[Larry Koch]

The burn rate of extruded powders is determined in part by the geometry of the grain. Do not do this.

You may be joking about this but it is not a joking matter.

Yes you are correct. Burn rate is also affected by the coating on the powder. However I think one grain or two shorten enought to fit in a 30 Br case. With a little caution, and slowly could be the ticket until H4198 is reinvented. We are not using weak actions and barrels.
To much caution and Columbus would never sailed across the sea.

 

[Jager]

Heavily compressing a charge, such that the individual kernels actually begin to shear or break apart, would accelerate the burn rate of the powder. I'd venture that that would introduce a highly variable wildcard into the mix.

That's not what usually happens, though, when we handloaders normally talk about a compressed load. What we're doing is simply compacting the charge - reducing the pockets of air between and around the kernels.

A lightly compressed load is, for me, ideal. Because it eliminates powder geometry within the cartridge case at the moment of ignition - itself a variable.

A heavily compressed load, or a more moderate compressed load in combination with very light neck tension, holds the potential of introducing inconsistent COAL. That's probably the biggest thing to be mindful of with compressed loads.

 

[Doom]

Yes you are correct. Burn rate is also affected by the coating on the powder. However I think one grain or two shorten enought to fit in a 30 Br case. With a little caution, and slowly could be the ticket until H4198 is reinvented. We are not using weak actions and barrels.
To much caution and Columbus would never sailed across the sea.

The deterrent you refer to is a surface coating on the kernel of powder not a mixture with the nitrocellulose. It is applied after the kernels are extruded and dried and covers the entire powder kernel. Anything you would do to reduce the grain size will not uniformly cut each grain the same and will expose various surface areas with no coating. You will have little to no control over the burn rate of the resulting powder. Increasing the burn rate of some of the powder will also increase the burn rate of the balance of the powder because the pressure will increase faster.

The concept you are thinking about is called a duplex load where powders of two different burn rates are loaded. It is not a mixing of the powders but progress loading in the case and requires that the powders stay segregated.

Playing with propellents and explosives with proper data, instrumentation and caution is foolish.

 

[markm87]

You may be joking about this but it is not a joking matter.

I use tweezers and small scissors to cut IMR in half. Takes 3 weeks to make a single round.

 

[dellet]

Different powders, different answers. Then there are mechanical issues to consider.

Tubular powders or doughnut shaped like trail boss are designed to allow the flash through the center. Crush them and the burn rate changes.
Trail Boss is basically a little sponge and I don’t think it’s possible to “crush” but you can compress it and it bounces back. Highly compressed loads have a tendency to push the bullet out over time without a stout crimp.

Compressed flake powders are another powder tough to crush, but seem to get unpredictable ES numbers, pointing to erratic ignition if compressed enough.

Ball powders, especially the finer ones, if dropped with a tube or slow trickle, are almost impossible to crush or compress. You’re more likely to deform the bullet than get much compression. Ruining the seating stem is common and if you really get after it, bulging the case so it won’t chamber is possible.

There is a big difference to the feel of seating with an arbor press, that you lose with something like a Big Boss II, where you may not realize when the bullet hits the powder. Based on some data I’ve seen, you can’t trust the published data to tell you when it’s a compressed load. So feel can be important, and a lot of people shoot compressed loads without ever knowing. It’s always good to check.

Most people learn the hard way, and enough people out there can generally answer for a specific cartridge and powder if you ask. But a generic answer is pretty much impossible.

 

[Laurie]

Heavily compressing a charge, such that the individual kernels actually begin to shear or break apart, would accelerate the burn rate of the powder. I'd venture that that would introduce a highly variable wildcard into the mix.

That's not what usually happens, though, when we handloaders normally talk about a compressed load. What we're doing is simply compacting the charge - reducing the pockets of air between and around the kernels.

A lightly compressed load is, for me, ideal. Because it eliminates powder geometry within the cartridge case at the moment of ignition - itself a variable.

A heavily compressed load, or a more moderate compressed load in combination with very light neck tension, holds the potential of introducing inconsistent COAL. That's probably the biggest thing to be mindful of with compressed loads.

I wrote a piece for 'Target Sports' e-zine on this a while back based on Internet, loading manual, and reloading books research, the last name going back many years in some cases. Findings were very much as @Jager 's post above. (And like him, I have a preference for lightly compressed loads.)

https://www.targetshooter.co.uk/?p=3543

The reloading manual research in the feature uses the 338 Federal for which nearly all quoted maximum loads are compressed (up to 115% in Nosler #9's case), and only one factory case is available, so all testers perforce used same capacity brass.

Of particular interest was a piece I found from the old US NRA handloading tome on the results of research done for the NRA on compressed charges of IMR-4350 log powder which produced findings of nil MV /pressure increases as compression appeared and rose, but reduced ES/SD values (.......... except when charge settling methods were used when ES/SD values increased).

An interesting issue I commented on in the piece is ball powders which in my early days of handloading, you were usually warned off using in compressed loads, but no longer, Nosler in particular listing many very heavily compressed maximum charges. The sole exception to this that I could find is Norma's manual which still warns against the practice with this type, and goes further saying a small airgap must be left under the bullet base.

 

[Laurie]

On a side note, one detrimental side affect on a compressed load can be cracking your seating stem where it hits the bullet. I accidently did that, twice, with a Forster seating die, as it won't take the pressure.

I've heard of this with Forster seaters, but never had any problems myself despite using this make for years and over multiple cartridges.

Where it definitely is a major issue, but few users realise it, is the Redding Competition seater die. The maker's online blurb on the Competition dies and instructions have a mention somewhere in the small print that it is unsuitable for such loads.

I found this out the hard way using a 'Competition' seater on mag length 69gn SMK 223 Rem cartridges where most powders end up compressed some heavily to the point of feeling kernels 'crunch' through the press handle.

 

[Larry Koch]

Don't go outside today might rain. If you try to compress a load to much the bullet will pushed it back out some, or you will not fully seat it. Or both.

 

[swd]

I’ve shot many thousands of light to moderately compressed in my main F Open rifle with zero issues for about the last 8 years. All have been upper end high node loads and need a drop tube to get all the powder in and are still compressed. My brass lasts just about forever. As long as you’re not destroying kernels, which may change burn rates, it just seems to be a non issue.

 

[Webster]

Yes you are correct. Burn rate is also affected by the coating on the powder. However I think one grain or two shorten enought to fit in a 30 Br case. With a little caution, and slowly could be the ticket until H4198 is reinvented. We are not using weak actions and barrels.
To much caution and Columbus would never sailed across the sea.

In 50 years I never shot a compressed load. Columbus knew it might be his last boat ride.

 

[Homerange]

In 50 years I never shot a compressed load.

Nor had I until a few years back wanting to push 130's quick from a 308.
Consulted the manuals and a max load of Varget (ADI 2208) 50gr was listed as compressed.
Shot a small cloverleaf 3 shot group from a sporter weight rifle @3000fps with 6fps ES.

You never know until you try......
YMMV

 

[swd]

No scary pressure spikes or voodoo magic happens when you compress a load within normal safe load data parameters. It’s not like pushing a bullet into the lands where you do see an immediate rise in pressure and have adjust for it. This seems to be one of those issues that guys that have never done it are scared for no reason other than they’ve never been there and then share their fear of the unknown..