New to Forum, Looking for Load Info on New 338 Build

[LeddSlinger]

I am new to the forum. I have a lot of experience with hunting, long range shooting, precision reloading, minor gunsmithing, and even dabbled in a couple 1K BR matches, but always looking to learn more

Anyhow I thought I'd begin my debut with a couple pics of the new 338-375 Ruger rifle I just got done building, and perhaps pick the brains of some of you that may have experience with this caliber. Looking for load data specifically, but any other input is much appreciated. I have the 250gr Berger Elite Hunter bullets on hand and that is the only weight I plan on shooting out of this rifle. Will be used mainly for hunting deer and elk.

Haven't fired one round through her yet, so I still need to break the barrel in then begin load development. Case capacity of the 338-375 Ruger is 1 gr of H2O more than the 340 Weatherby, so I believe I could start with medium load data pertaining to that caliber and work my way up. But would appreciate any info on loads used specifically for the 338-375R. Thanks Folks

Action: Remington 700 Stainless Magnum, lapped and blueprinted to barrel.
Barrel: Brux Stainless .338 1 in 10", Rem Sendero contour, finished at 26"
Stock: Bell & Carlson A2 Medalist, full aluminum skeleton, black with gray web
Optics: Bushnell Elite Tactical 4.5-30x50mm
Other: Timney "flat trigger" @ 1.5 lbs, Badger Ordinance .316" recoil lug,
Blackhawk one piece scope base, Burris Tactical rings, bipod, sling,
PTG Speedlock firing pin assembly and bolt shroud,
Full action bedding with Devcon Steel Puddy

PS: I know, I know...I need to cut my grass lol!

[LeddSlinger]

Looks like I came to the wrong place for advice on this gun. Almost 260 views right now and not a single post.

I suppose it is a newer wildcat that has yet to become known amongst the general shooting world...

[Jimro]

Leddslinger,

Yes it is a "newer" wildcat, but ballistics will be similar to 340 Wby, give or take a standard deviation. Considering internal volume is so close to 340 Wby that is where I would start too. The 250gr bullets should do you well.

Hodgdon has two loads for 250 gr bullets for the 340 Wby,

250 GR. SIE SPBT Hodgdon H4831 .338" 3.560"
78.0 2487 83.0 2784

250 GR. SIE SPBT Hodgdon H4350 .338" 3.560"
73.0 2570 76.0 2724

Alliant also lists two powders.

Federal 3.61 24 Fed 215 Reloder 19 83 2,788
Federal 3.61 24 Fed 215 Reloder 22 85 2,781

Norma lists one powder.
Norma MRP Max 86.0 Min 82.0 2877 2730

Be aware that Weatherby rifles are notorious for having long freebore to mitigate pressure, so your custom wildcat chamber will probably show signs of pressure sooner.

Looking at the data, it looks like Norma MRP will give you the most velocity, although on a burn rate chart it is nestled right between H4831 and Re22, so no clue why it has 100 fps over the other two. MagPro might be another powder to try (I have no 340 Wby data for it) as well as Power Pro 4000-MR.

Good luck on your load workup.

Jimro

[LeddSlinger]

Good point on the freebore issue. I will be sure to monitor for pressure signs very carefully during load development.

I have a lot of different powders I will be trying including MagPro. Others I will be trying are;
RL - 17
RL - 19
RL - 22
RL - 25
IMR 7828 SSC
IMR 4350
Hornady Superformance

And maybe a couple others I'm forgetting about...

Will all be tested with various magnum primers as well. I have Remington 9 1/2, CCI 250, and Federal GM215M.

I think MagPro will be a definite contender. However, in my past experiences with other chamberings that prefer slow powders, where MagPro works well, RL-17 works even better for velocity and consistent accuracy. But all experienced shooters and handloaders know that every rifle can be a completely different animal so everything is nothing more than an assumption right now.

[Jimro]

I wouldn't bother with Re25 or 7828SSC unless you bump your bullet weight up to 300 grains. Even Re22 might be a tad slow unless you are using something like a 270 JLK or Lost River.

Re17 has got to be the most temp sensitive powder on the market, it produces great velocity but that comes at the price of temp stability. For long range shooting you might have to make a temp/velocity chart to make sure your come ups are accurate to drop those big bullets on target.

I don't know how MagPro or Norma MRP go for temp stability, but H4831 has a good reputation. I'd sacrifice 100 fps at the muzzle for less than 20 fps shift between cold and hot conditions.

Jimro

[hooligan1]

Hell with the mowing let's go shooting dude, If it shoots half as good as it looks it'll be Fire!!! Nice rifle man, no foolin.

[LeddSlinger]

Thanks hooligan. I can't wait to start throwing fire down the tube

I think you're right Jimro. Some folks I've talked to have mentioned trying Retumbo, but I'm almost positive that will be way too slow. I'm thinking the RL-17 to RL-22 is going to be where it shines as well.

I've used RL17 in my 6.5 rem mag and a lot of other calibers with excellent accuracy and speed results, but it is fairly temp sensitive as you stated. However the velocity differences I've seen from 30-70 degrees has often ended up hitting the target at less than 1/2 MOA of difference all the way to 1000 yards.

I developed one load with the 140gr Berger VLD in my 6.5 rem mag at 32 degrees in the winter months using RL17 and when I took it to play at a 1K benchrest competition the following summer, I only had to adjust my scope with two 1/4 moa clicks. So the difference in impact with varying temps I have seen with RL17 has been very minimal. But that's just my personal experience...

[Jimro]

Leddslinger,

More probably what happened is you had higher atmospheric density during the summer which caused increased drag which compensated a bit for the change in muzzle velocity.

For example a 142gr SMK at 2775 fps at 39 degrees, 10% humidity, and 28.92 mmHg only strikes 0.3 MOA less than the same bullet launched at 2805 fps at 89 degrees, 80% humidity, and 30.92 mmHg. That represents a 1fps/degree temp sensitivity and wildly different atmospherics (about a pound psi difference).

If you use the same atmospherics for the 40 fps change the difference is 0.7 MOA, at 1k.

However, the real danger isn't in target shooting, it is loading a safe load in the winter and experiencing an overpressure event in the summer. Probably not much of an issue if you are pressing up against a max (or beyond max) load.

Jimro

[LeddSlinger]

Very true. It probably had to do with atmosphere.

I never did have any problems with pressure spikes using RL17 so far. Have my 140 bergers loaded pretty hot too. Pushing them at 3130 fps from a 26" barrel.

However, I did experience large swings in pressure using RL22. That was the powder I used before RL17 came about. I had that same bullet in the same rifle going 3210 fps when I developed the load in 40 degree temp. That same load in summer months wouldn't gain a lot more speed, but brass life would fall to 2-3 firings before primer pockets loosened enough to render the brass useless. And accuracy would fall off from 1/3 MOA to a little over 1 MOA. So when RL17 came about and proved to me that it was much more stable, I glady changed my load.

My load with RL17 is only 1/2gr under the point where I began to get loose primer pockets and brass life and accuracy has remained the same under all conditions. So I don't believe RL17 is as temp sensitive as some of the other Alliant powders.

RL17 has also proven to be a very good powder in my Dad's 300 WM and my father-in-law's 6.5-300 WSM. I had great luck with it in my 6.5x47 Lapua too, but load testing is not complete with that rifle.

And in my experiences, the larger the case capacity, the less they seem to be affected by slight increases in pressure. Much like where .2gr difference in powder charge with my 20 VarTarg can make a pretty big difference with certain powders, but it will not affect a large charge in a 300 win mag very much if any at all. Of course that has to do with powder burn rates as well...