The Real Guns CZ 550 FS Goes 375 Ruger Part II-Handload Development for a Junk Yard Dog

Dennis Olson – Gunsmithing
500 First Street
Plains, Montana, 59859
406-826-3790

He runs a really busy shop, but turn around on this type of project; barrel and action work, fitting and moderate refinishing is very reasonable. Lead time on complete rifles with very fancy stocks and artful metal work runs longer, about a year at this writing. As an example of the first category of work, for a few hundred dollars and a medium action CZ-550FS, I now own an slick, light weight and compact rifle that can be loaded down for deer and loaded up for cape buffalo. I was given no discount for this mention, or any other form of freebee. In fact, whenever I call and give my name, Dennis still responds with “Who?”.

The .375 Ruger cartridge… in context

L-R, .375 H&H, 375 Ruger and the gun’s original 9.3x62mm. The Ruger, shorter than the .375 H&H, actually has greater capacity because the case head diameter is as large as the belt on the H&H case. The .30-06 Springfield is noted in reference to the medium size action that can accommodate the .375 Ruger, in comparison to the magnum length action required for the .375 H&H.

New guns, even with familiar chambers, require requalification of all handloads. Free bores vary, twist rates and chamber differences all contribute to different pressure and accuracy results. Our earlier .375 Ruger handloads were based on the Ruger Hawkeye African with a 23″ barrel, rather than the 20″ barrel Alaskan. Our modified CZ 550 FS has a 20.5″ barrel, but with the same 12″ twist as the Ruger models in this chamber, so we had no idea what to expect.

We did a quick freebore check to make sure all of the bullets we intended to load had adequate leade clearance at the determined maximum cartridge length and that everything would tuck into the gun’s magazine and load and eject reliably. Even the longest bullets with the most blunt ogives were good for 3.340″ with 0.040″ leade clearance. Bullets with more typically tapered ogives; Barnes, Speer, Sierra, GS, etc had sufficient magazine clearance and throat clearance to load to 3.460″ while retaining 0.040″ leade clearance.

The .375 H&H is routinely loaded down below 2,000 fps, which produces .375 Winchester level ammunition with cast and thin jacketed bullets. The .375 Ruger offers a similar opportunity. Why light load a hard charger like the .375 Ruger? Because this is such a small rifle, it would be no problem carrying it for any North American big game hunting, from deer to big bear by loading up and down the powder/bullet range to match the application. So this isn’t a special occasion big and dangerous game rifle. It is a gun that can be rightfully pressed into service frequently.

Impressions… other than on my shoulder

With the exception of the 350 grain loads, the balance of the bullets, thanks to an ever improving ballistic coefficient in the face of a weight induced velocity drop, all have a maximum drop of 8″-9″ at 300 yards, on a 200 yard zero. That’s about as flat shooting as a .30-06 Springfield. The very heavy for bore 350 grain bullets drop 12″ at 300 yards. That’s pretty sensational from a cartridge of this type, especially when shot through a 20.5″ barrel.

This is probably a good example of a heavily constructed 250 grain North Fork bullet pushed to 3,000 fps. The bullet starts out at just under 5,000 ft/lbs of muzzle energy and, even with a modest BC, is still putting out 2,300 ft/lbs at 300 yards. The up and down on trajectory is a maximum of 1.7″ out beyond 200 yards. If I wanted to optimize, I could set zero at 237 yards and be point blank for 277 yards on a six inch target.

The light bullet, light jacket light charge loads that would be excellent for deer size game are so light in recoil, it’s hard to believe it is the same gun. The report is very mild. IMR 4198 and Alliant 2400 were selected for light charges as they work well in these circumstances and burn producing very uniform pressure with partial case charges. They are also good choices for cast bullet loads. I suspect the velocity clustering of the 225 – 250 grain bullets were the result of the short barrel and incomplete burn case full powder charges, but this became less evident as bullet weight increased.

Accuracy was excellent with all bullets tested. The GS Custom bullets shot close to half inch at one hundred yards, all of the North Fork Bonded shot less than three quarter of an inch. The only bullet  that shot greater than one inch after a little load tinkering were the Hornady 235 grain loads, inch and one quarter, but there were very light powder charges.

The Bushnell scope proved to be an excellent choice for this set up. Very bright image, more than enough magnification and lots of eye relief. Adjustments were uniform, the scope stayed put and the rings were just high enough for the sweep of the bolt handle to stay out of the way of the large scope eyepiece.

I’m more than pleased with the gun. It is one I will hang onto and shoot with a great deal of confidence.

The Real Guns CZ 550 FS Goes 375 Ruger Part I
The Real Guns CZ 550 FS Goes 375 Ruger Part II