7.5 Swiss Recipes?

Potshot21

Potshot21

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Howdy folks,

I have myself a bunch of once-fired Prvi boxer primed brass and I'm looking to put it to good use in my K-31!

I'm looking for loads that would closely replicate GP11 ammo, but anything you've had good experiences with would be appreciated.

I picked up a box of Hornady 178 grain HPBT match bullets to try, not sure if GP11 was boat tail, but 178 grain is right at least.

On a side note, the K-31 is one sweet rifle! Very quickly becoming one of my favourite rifles in my collection!

Thanks!
 
As with most reloaders, we pride ourselves with being able to load ammunition that can be superior to the factory loads and be tailor fitted to each rifle. That being said, I have a heck of a time trying to create a load that can measure up to the original GP11 loading. Creating a soft point hunting round is pretty straight forward but the accuracy of the surplus GP11 for long range target shooting is on par with top quality match ammo.
 
I did some reading on SwissRifle forums and have settled on trying RL-17 and the Hornady HPBT that I have.

But this whole thing of COL has me second guessing myself. I've never loaded without the dimensions coming from a manual, and as I don't have any published data, I'm trying to wrap my head around measuring the dimensions myself.

I hear mixed reports on the hornady gauges and modified cases, and am leaning more towards cutting the case neck on a piece of brass and gently chambering it with a bullet seated out to see how far it gets pushed back.

Don't know enough about it though so I'm still trying to work up the nerve to try it.
 
Good method to find where the lands on your rifle make contact with the bullet you want to use.
Your real C.O.L should be shorter than that contact point, or you will have difficulty closing the bolt on your reloads.

Before all that, make sure your empty brass will chamber.
Recommend full length sizing. Some dies might give you problems with the shoulder profile being slightly off.
Cam over the press if it can.
Nothing to be worried about.

Reason listed C.O.L. for 7.5x55 is too short for K31 is that the k31s were not readily available until the 2000's.
Most of the American load data was base on the 96/11 and 1911 rifles with their much longer throats.
 
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diopter said:
Reason listed C.O.L. for 7.5x55 is too short for K31 is that the k31s were not readily available until the 2000's.
Most of the American load data was base on the 96/11 and 1911 rifles with their much longer throats.
Click to expand...

Thanks Diopter, this confirms what I think I understood from reading the Swiss Rifle forum. Although it wasn't as clear on there, they did talk about throat dimensions being different between the 1911 and K-31. I do believe my hornady manual used a 1911 to get its data from, so that leaves me to discern my own seating depth with given projectile.

If anyone wants to confirm, my plan now is to slit a case neck with a thin dremel cutoff wheel, insert a bullet very shallow in the case, and gently chamber and extract the round and measure COL. I'll do it several times to confirm measurement, then seat my projectiles to measured COL less .020" to leave some room for jump to start.

Does this sound right?
 
Do it and/or use this as a guide:
https://www.tapatalk.com/groups/the...ggest-hurdle-for-7-5x55-in-the-k31-t6627.html

The profile of the bullet you want to use is the most important deciding factor to decide it's C.O.L. in the K31's short throat.

bulletshapes4.jpg


http://bulletin.accurateshooter.com/2007/07/283/

Original GP11 bullets taper all the way from the front to the boat tail.
Considered a "bore rider", as in sides that contact rifling are not same diameter.
At case mouth it is .306"± to boat tail's .308"±
 
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GP11 on left, Berger 175gr VLD on right.

P2210238-closeup.jpg


You can see the taper on the GP11 and that the Berger does have parallel sides.
 
First of all, thank you very much Diopter, great info posted above!

Well I can definitely say the Hornady BTHP projectiles I have are secant ogive and differs from the VLD posted above.

I tested out the Hornady bullet in a case I cut with a dremel, and after measuring 6 times I got a consistent COL of 2.955" every time. So I'll load some up with a COL of 2.935" to test.

From one of the posts regarding RL-17 on SwissRifles, it looks like most guys were getting good results around 49-50 grains, so I'm thinking of starting lower at 46.5 grains and working my way up 0.5 grains at a time until I get to 50 while checking cases for pressure signs.

Just another question I'm curious about is sizing. I see most people recommend full length sizing. I'm wondering what the advantage is over bumping the shoulder back a few thousands?

Also if anyone can see anything wrong with my above plan, please speak up! Like I said, I'm treading in new territory here and happen to like my face and rifle in one piece!

Thanks again for all the great info and help!
 
Straight Pull rifles are very much like semi-autos in that the case has to chamber easily for reliability.
You don't want to have to hammer on the bolt handle with your hand just to lock the bolt.
Eventually, you will have to full length size your brass anyway, since the sides will bulge out after a few firings making the chamber sticky with those fatter cases.

I'm using 50gr of RL-17 myself.
Same P.O.I as GP11 at most practical distances since it is the load for GP11.

https://www.canadiangunnutz.com/forum/showthread.php/1143157-K31-Ammunition-Question
 
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Just bumping an old thread rather than starting a new one. I just received a K11 and a pile of the new manufactured RUAG 7.5x55 brass. I have a selection of match 308 bullets from when I was building a load for my Tikka that I'll end up using up in this rifle if it proves accurate. But before I do that, I was going to build some plinking rounds to get familiar with the rifle. Has anyone loaded using bulk CamPro 308 projectiles using IMR4064 and run them through your Swiss rifles?
 
Out of my reloading manuals, the newer Hornady one I have lists 7.5x55 Swiss. It showed ~38gr as min and ~42 max for IMR4064 for a 150gr FMJ. I loaded up 20 using the 147gr Campro FMJ along with 40.0gr of IMR4064 to hopefully sight in the rifle with next weekend. Now that I am looking back on this thread at Diopter's link above from CamPro, it lists 43/46grains for Min/Max in 308 for that round

Next, I had taken the new production brass and resized/trimmed it. Seating the bullet seemed fairly easy, almost too easy? To test, I used an unprimed sized case and seated a projectile in there then "scientifically" used a bullet puller hammer to remove it. It still took 3 whacks, so I assume it's holding tight enough. I've never crimped the 308 or 8mm I reload; do you folks generally crimp 7.5 Swiss?
 
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