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Ivantherussian03
10-17-2006, 12:45 AM
I am using the Lee loading manual for 7.5X 55. With 180 grain bullet my max powder load of H380 is 40 grains. I am wonder if anyone has another reloading book, or experience with this cartridge? The powder load seems light. Everything else the same, my 8mm mauser takes 46 grains powder. Is my logic flawed, or should I stick with the manual?:Fire:

Wayne Smith
10-17-2006, 07:32 AM
Ivan

Sierra doesn't list H380 for this combination. They list IMR4350 as both the hunting load and accuracy load, strongly indicating that they like 4350 for this round! Hunting load is 47.6gr for 2498 fps, accuracy load is 45.8gr for 2320 fps.

Check Hornaday's website, they have thier loading manual on-line.

versifier
10-17-2006, 10:09 AM
Ivan,
I suspect that they inadvertantly listed a reduced boolit load instead of the intended jacketed load, as that is one of Lee's favorite powders with cast. He makes the point more than once that he developed many cast loads, but there was only space to print .30-30, .308, and part of the .30-06. While there is lots of great data in there, like anything, it was compiled by human beings who make mistakes.
You are following the safe rule, to compare the proposed load with two published sources, and if they don't agree, check a third. (And if that doesn't check with either, jump up and down and yell loudly to relieve frustration before calling for help. :mrgreen: )
NRA's Handloading only lists IMR 3031, 4064, & 4895.
COTW lists IMR 3031, 4064, & 4350.
FWIW, I think you are correct, and after checking with Hornady, I would start with 40gr of H380. But if it were me, I'd also be checking out the IMR powders starting with 3031 anyway. Odd that Sierra doesn't mention it, they usually have an exhaustive list of powder choices. I wonder why....

Ricochet
10-17-2006, 03:17 PM
FWIW, the case volume is nearly identical to the .30-06.

swheeler
10-17-2006, 09:48 PM
Hodgdon Manuals #25 and #26 both show a max load of 40 grs with 180 bullet, and I assume this is where Lee got their data, since they don't have a ballistics lab and as far as I know don't contract one to develope data for them- it is compiled from all the published data available from other manuals.

versifier
10-17-2006, 11:24 PM
Then I guess Ivan better start with a lighter charge. And I'd still go with a test run of 3031.

Bass Ackward
10-18-2006, 06:31 AM
Quickload (a computer program) says the pressure ceiling for that cartridge is 55,000 psi. If true, that ocurs with 55 grains of H-380 using a 180 grain Sierra round nose. Of coarse this is using standard seating depths which affects case volume.

It also shows 23,000 psi with the 40 grain load. IF I change the metal composition factor for resistance to lead from copper, the pressure drops to 18,500. Just so you know.

Try and get your hands on a chronograph if you can.

Ivantherussian03
10-19-2006, 12:49 AM
At the risk of revealing complete ignorance, but wanting to learn more.

I am plain vanilla reloader. I buy the ingredients, and make cartridges that work in my weapons. I take the cook book and follow it.

Correct me if I am wrong. I get the feeling I can really dial in my rifles with some more experiementation and reseach. You guys are telling me IMR 4350 works well with K31, more soo....than say H380?

So what powder works best is mauser K98? Or my Remington model 721?

So, different bullets ( copper jacketed vs lead) react different to powder loads because of the differing metal compositions?

Wow, there is alot to this stuff:coffee:

versifier
10-19-2006, 12:53 PM
Ivan,
When you fire a round and the bullet/boolit travels up the bore, there is friction between the driving bands of the boolit or bearing surface of the bullet and the lands of the barrel as they distort the metal of the projectile. The harder the metal, the greater the degree of friction and the higher the pressure, if all other variables (charge, case, primer, OAL, and projectile weight) are the same. Both projectiles will most likely have different muzzle velocities (the cast being higher due to less friction dragging on it) and they will show different points of impact with the same sight setting.
Each barrel is different. The interior surfaces will be smoother in one, the grooves may be deeper, etc. If you took a bore scope and looked at two production barrels that came out of the rifling machine consecutively, they would look different, maybe very different due to differences in the sharpness of the drills and reamers used to prep them and the skills of the machine operators for both operations. Barrels can be as different as fingerprints.
As to what combination works best in your rifle, only the rifle itself can tell you that. The most we can tell you is what has worked for us in our rifles, and if we have noticed any general trends that might be helpful to you. My "go to" powders for medium capacity cases are IMR 3031 and RE-7, both of which have given me good results in many rifles: a general trend. Sierra techs liked IMR 4350: most probably a general trend, but possibly the preference of an individual barrel. Frank Barnes liked IMR 3031, 4064, & 4350, definitely a general trend as he was an experimenter and wildcatter who worked with literally thousands of cartridges in his long and productive life. But none of these can be used to say exactly what will work best for your rifle. The only thing that can is actual experimenting with your rifle, one powder at a time. With a rifle as well made and cared for as a K31, this is not going to be a difficult job. :) And it just might be H-380 that your rifle likes best, too, you never know until you try. As long as you keep aware of the pressure signs by watching the fired primers, you won't get into any trouble, and you'll be busy enough to stay out of other kinds.
I have an article on the process, but it is geared to real first timer newbies, and you don't sound to me like a newby, just a safe "cookbook cook" with some years of experience who wants to know more and is ready to learn it. You ask the right questions and are honest when you don't understand something, rare qualities in a person. No part of it, taken by itself, is really difficult (except some of the math, and that's often way over my head), but there is a lot to learn about it and it takes years to get comfortable with it to the point that we can go into the unknown safely. Cast boolits are part of that unknown area, as bullet makers generally wish we didn't exist and cut into their potential sales and profits, so we have to make our own data (and find our own "general trends"). [smilie=1: The good thing is that we are usually dealing with reduced (sometimes greatly reduced) loads and that means we are working within a very safe envelope pressure-wise, so we have a lot more leeway to experiment than a wildcatter working on the top edge of the safe pressure zone. The downside, if it is a downside, is that we have a lot more possible choices in powders than the high end wildcatter, and a much greater range of velocities to play in.
And no, you aren't wrong, you really can dial most rifles in with a little research and experimentation, and your K31 is a perfect rifle to begin with. The K98 is another good choice if the bore is in good shape. A bolt action .30-30 is another good prospect, like a Savage or a Rem788, extremely cast friendly.

Wayne Smith
10-20-2006, 07:30 AM
Also be aware that it is generally the cartridge size that determines the correct powder, or rather the cartridge capacity and the bore diameter. The make of the rifle may relate to the type of rifling and wether or not that partricular rifle may or may not be a good cast boolit gun, but it's the cartridge capacity that sill determine the powder and amount.

This is why Richochet mentioned that the case capacity is almost identical to the 30-06, and the bore diameter is essentially the same. Given that the peak safe pressures between the typical rifles in each caliber are different, with caution you can use 30-06 data as starting points in the 7.5 Swiss. Most rifles chambered for the 30-06 are safe at 55,000psi, I believe that the K31 tops out at 45,000psi. This means that you only use the beginning loads listed for the 30-06 and carefully monitor velocity and pressure signs, knowing the safe velocity you are aiming for in your rifle.

As an example of this process in a very different caliber, I have a .405 Win. in a Win. '95 and some of Bullshop's 350gr bullets for it. No data for the bullet, but data for jacketed loads for 300gr and 400gr bullets. A little math and I have starting loads for the 350gr. and I'm only aiming for about 2000fps out of this rifle with this bullet. At an average of 1950fps I have no pressure signs and the rifle is not a bitch to shoot, either. I'm satisfied and have no intention to push it any further except maybe to tweak accuracy, if necessary.

NickSS
10-20-2006, 05:00 PM
Stick with the manual at least at the start. You can then work up in pressure until you see pressure signs then back off a bit. As for cast loads I never try for max pressure but max accuracy. I personally like AA 3100 for the 7.5 X55. I use 45 gr for jacketed 180 gr bullets and 40 gr for cast 185 gr bullets both loads work good in my rifle.

mike in co
10-20-2006, 07:18 PM
i shoot a berger 135 bullet with vv n135 powder......
you just never know what may work...