doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Pressure Variables with BP Loads

The thread on loading brass hulls got me thinking about the pressure variables when loading plastic hulls with BP. Most manuals have disclaimers warning reloaders not to mix and match various components and I have read that different hulls and primers are two of the variables that can increase or decrease pressure.

My load for most of my BP SxS is 1 1/8 shot with equivalent volume of shot. My hulls are 3.5 inch Kent cut to 2.5 inches and skived. Primers are Win 209. I put in the powder, 1/4" dry wad, 1/4 lubed wad, plastic shot cup with the compression component cut off, compressed with the powder tube of a Mec 600, shot, over shot card then rolled crimp. If I started to changed the type of hull and primer what pressure increases might I expect?

Well I'm not a ballistician but black powder burns at a much more consistent rate than does smokless under varying conditions, confined or un-confined. I don't think varying your components is going to cause you any problem with black unless you use something which doesn't seal & lose your pressure. An equal volume of black to 1 1/8oz shot is a comparatively mild load of a bit less than 3 drams.

Blackpowder is very generally very consistent with very low Standard deviation in velocity compared to smokeless powders. But I don't think that is your question. I think you are asking for a scale of pressure changes as you vary the case capacities and primers. I don't think the primer change will make much difference as black ignites so well with even the least of the primers. Case capacity might make some difference because the room for gases to expand in will function same for black as for smokeless - but your working pressures with black are so much lower than with fast burning shotgun smokeless powders that change should be well within the guns safety margins. I know where you can get definitive answer though. Contact Tom Armbrust and have him test the loads for you.

WHY blackpowder, unless you like the smoke?
As noted in Sherman Bells articles of Black vs Smokeless 7625 has exactly the pressure curve that black has. I shot black in my 10 ga Duck hunting a couple of weeks ago just for fun, but if you are worried about pressures, go to 7625.
I have the chart I can add here if interested

Because for a lot of people, the reasons are the same as why we choose to shoot 120+ year old guns. It goes hand in hand.

For some, shooting smokeless in an old gun is like having a Model A and somehow pulling out the engine and transmission, and replacing it with a fuel injected, computer controlled...whatever. Outside the car looks the same, but it would have completely lost it's soul. To each his own.

Then why are you useing plastic with your wads ? I've shot nitro and BP in my cartridge guns for 20 years. Been shooting muzzleloading smoothbores for 40 years and never used plastic wads. It's like putting a modern engine in a Model A. If you're loading equal amounts of powder and shot there will be no problem with any primer or hull. But please, throw away those plastic wads, they weren't made when BP was used in guns. Paul

I agree that using plastic wads in a BP load causes melting of the plastic and bore buildup in my experience.

I shoot a lot of BP in MUzzleloaders and extra washing and cleaning of a breechloader is a unnecessary nuisance to me.

First I am not worried about the pressure caused by blackpowder vs smokeless. My concern was if I change the type of hull or type of primer can I expect to have different pressures. Some hulls are more constrictive because they have thicker plastic and are constructed differently and primers are all over the place in how hot and how long they burn. It makes a significant difference with smokeless powders but I'm not sure about black powder.

The plactic cup I use in my loads is just that, a cup. It is used to form better patterning, similar to a paper cup that some use. With the way I reload there is no plactic build up in the barrels as the plastic is buffered from the powder by 1/2" of fiber wad.

And for cleaning, I would clean my guns regardless of whether I use blackpowder or smokeless. I really don't find one more cumbersome than the other. If cleaning the blackpowder takes slightly more time all it means is I get to fondle a 100+ year old gun a little longer :>)

Stallones,

I would be interested in your reloading chart using 7625.
Thank you.

There is one "VERY MAJOR" difference in black powder & 7625. I found it out the hard way one cold day in a duck swamp with a load taken directly from the old DuPont handloaders guide @ about 7K psi. After my Son & I broke ice across about 100 yds of open water to get to the woods where it was still liquid all I got with those loads of 7625 was squibs. I have never again loaded 7625 as a low pressure replacement for BP. Perhaps different components would have made a difference, but these were from "The Book" not some cooked up load of mine. The first duck I shot at, a mallard drake, the recoil was extremely light & the sound quite low. The duck flinched a bit but kept flying with essentially the same results, but that thime he did come down on the water Swimming. My son took a shot & killed it. Lead was still legal & I was shooting 5s in a 12, my son was shooting 6s in a 20. When we got home we did an autopsy, his 6s had penetrated nicely, while my 5s were in or just under the skin. I don't really know what brought him down to the water, unless they just disrupted his balance a bit.
Black, Would have Gone Off.