doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Reloading Pressure Question

Hi all, I was wondering what the reloading experts here can tell about pressure increases when a recipe calls for 22 grs of powder, but you throw 22.3. What kind of increases can you expect?

Thanks so much!

Greg

Wow in a 22-250?, 12 gauge 1 7/8 oz, red dot, black xx or just what are we talking about??? Are you a lawyer? You could start by looking at the on line cook books from the powder mfgr's. Before a good answer can be given you are going to have to tell the whole story.

bill

Hi Bill, fair enough, the load is as follows: 12ga, 2 3/4" Cheddite hull, 1 1/8oz payload, 22 grains Green Dot, Cheddite 209 primer, Remington RXP-12 wad. According to Allliant, should have a pressure of 7800psi and a MV of 1200fps.

Hope this helps.

Thanks again!

OK
1 1/8 1,145 Cheddite Green Dot RXP 12 20.5 7,100
1 1/8 1,200 Cheddite Green Dot RXP 12 22 7,800

So if you go up another .3 grains, it will go up X

Is X linear or parabolic?

Call Alliant and see what they say, they are real nice
1-800-276-9337

Are you working to a specific pressure limit?

You are doing great in your endeavor to load a cartridge

MEC bushing #37 shows 23.3 grains, but my bet to you
is that it throws lighter than that. Please assertain using a
proper scale. Next is to use fingernail polish to fine adjust the
bushing to the perfect load. I use RED

Hi Mike and thanks for the kind words. As you jolly well know, I'm very green when it comes to reloading and I'm trying to learn as much as I can and do things right the first time.

Thanks for the tip on calling Alliant, so simple, it's what I should have done in the first place!

With my MEC 600 and using bushing #36, I get 22.3 (weighed on a powder scale BTW) just a hair off the published 22.4 for that bushing. That kind of surprised me, most of the bushings do throw light that I have weighed for other recipes.

The pressure and MV is about what I was looking for in a general hunting load. So I wanted to get it as close as possible.

I like the nail polish idea...I'll give that a try.

Again, thanks for all the help here and on the other forum also.

Stay Well!

Greg

pressure is definitely not linear if it were then increasing the load from:
1 1/8 1,145 Cheddite Green Dot RXP 12 20.5 7,100
to:
1 1/8 1,200 Cheddite Green Dot RXP 12 22 7,800
Pressure would rise to 7620, not 7800. At the same rate the 22.3 would give 7725. I suspect the curve is more or less parabolic with each increase of powder charging giving a greter pressure rise than the last. Even so you are starting a quite low pressure & only getting an increase of a bit over 1%. I seriously doubt the pressure will exceed 8,000.
Pressure can vary depending upon a lot of factors, but I believe shotshells are less influenced by outside factors than rifle cartridges with the pressure being primarily built into the shells them selves. Crimp strength can vary pressure to a greater amount than a tenth or so grain of powder charge.

Greg,
AND when you use the nail polish, put it at the top of the hole and not the bottom
Mike

Greg, when you weigh powder charges and you're trying to hold down pressure and discover than a bushing throws slightly more than the "book" calls for, you're better off dropping down a bushing. That being said, if the given formula with 22 grains has a good safety cushion compared to whatever limit you're shooting for, an extra .3 shouldn't be an issue.

The difference in .3 grs would mean nothing, even if near max SAAMI. In most reloaders your throws would be +/- .3 grs. A precision powder measure is guaranteed +/- .2 grs. Anyone that says their reloader constantly throws the same charge time after time hasn't measured them.