180gr load for 7.5 Swiss


PDA






Rick Finsta
May 2, 2009, 12:14 PM
I've done some searching, but haven't been able to find anything on a particular load I'm working up, so I wanted to run some ideas past you all and see what you think; I'm just starting off and I'm prety much working with whatever I could find, as there isn't a lot out there (as you all know).

I'm using Prvi Brass, Federal 210 primers, and Winchester 180gr. CL-SP bullets with a flat tail. I was going to start low on the powder with 39.2gr of IMR 4064 and work up from there to find a sweet spot. OAL is 2.850", which fits my chamber with this bullet, but the variation in the soft points means that I'm really not sure how far off the lands this gets me.

My questions are:
1) Is it safer to have the bullet further back (possibly causing overpressure due to smaller case volume) or further forward (possibly necessitating "soft seating")? Do I have a .020" or so range that will be safe?

2) Anyone else know if I'm being way to cautious on the powder charge starting off? I don't have a lot of materials and don't want to waste them on a load that won't work.

Thanks in advance for your help. I am going to be finishing up my OAL guage (it's like the Hornady unit but without the stupid 36tpi thread so I can make my own shells) and then I can get more accurate with the OAL, but I'm wondering if I'll be safe in the meantime.

If you enjoyed reading about "180gr load for 7.5 Swiss" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
NCsmitty
May 2, 2009, 04:33 PM
Rick Finsta, welcome to THR.
I do not have a Swiss rifle or load for it, but I did do some research and have been reloading for many years.
A trusted site lists 42.6gr of IMR4064 as a maximum load using 180gr Sierra giving 2500fps.
It's my understanding that the Swiss chambers are not too long and care should be taken not to seat too far out. You are correct in that different brands do vary in bullet shape. A record of each type of bullet and the COAL needs to be kept.
Perhaps you already know this, but I find a minor sizing of a case so the bullet can move and then chambering will give you the reference point for that particular brand. I seat nearly all my target loads .020 off the contact point.

You are not being too cautious with your choice of a starting load. You'll have to try it to see if it will shoot in your rifle.
The Hodgdon site, and they own the IMR powder line now, does not list a load for IMR4064.
I'm guessing you have a manual to reference your starting load.
FYI, IMR4350 is the powder of choice to duplicate the Swiss match loads. It's slower burning and works well with the long barrels.
I hope I helped with my information.

NCsmitty

NuJudge
May 2, 2009, 06:12 PM
The problem with Swiss K31 chambers is that the rifling starts just ahead of the case mouth: the Leade is really short. Bullets used in the K have to start tapering immediately ahead of the case mouth. This requires deep seating with many bullets.

I've only used 180gr bullets in the 7.5x55 in Factory ammo. All my reloads have used 165 and 150gr bullets, but the latter never shot well forme. For 165gr bullets, I really like powders in the speed range of 4831 in the K31. The 165 that shot best for me was the Remington SPCL.

Matt Dillon
May 2, 2009, 06:22 PM
Pierre St. Marie is a pretty well known authority on the Swiss rifles, and I have loaded a couple thousand rounds of 39 grains of IMR 4064 underneath a 173 grain pulled M72 projectile, (one of Pierre's suggested loads)and they shoot very well out of my rifle.

Rick Finsta
May 2, 2009, 07:18 PM
Cool, guys thanks for the replies. Most of the heavier bullets I've seen loads for are boat tails, so I wasn't sure how the flat tail would compare as far as volume taken up.

Should I move up from 39.2gr, or down? I know these usually are very close to .308 Win for load data, but usually with a charge that's knocked down a few grains. I guess I can just take my first five shots and look for pressure signs on each one to be safe.

NCsmitty
May 2, 2009, 07:32 PM
If you've already loaded some with your 39.2gr of IMR4064, they should be fine. If not loaded yet, Matt Dillon's recommendation sounds good too.
The load that I listed, stated for use with either boattail or flat base bullets.

NCsmitty

Rick Finsta
May 3, 2009, 07:36 PM
Range Report:

I loaded up 20 rounds which were identical other than the powder charge: Prvi FL Resized and trimmed brass, Fed 210 Primers, Remington (oops I think I said Win. before) 180gr PSP CL-WC bullets (.308) seated at 2.850".

I loaded five of each to 39.2, 39.6, 40.0, and 40.4 grains, respectively, and ran them through the rifle. There was a definite closer grouping going from 39.2 to 40.0, but it looked about the same from there. I'm going to have to borrow my buddies scope as with the scout aperature on this thing the best my eyes can do is about 2MOA at 100 yards, and GP-11 does <0.75" groups when scoped, so now that I know the safe range I can move from there!

THANKS for the quick replies - I needed a morale boost before shooting my first loads. The guys at the highpower match this morning looked at my cases and said they all looked great, so I think I'm all set!

If you enjoyed reading about "180gr load for 7.5 Swiss" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!