I've had very good luck with RL-17 in a couple of different calibers where it compares favorably with the 4350's. It would seem to be a good match for the .375's, but I don't find any data for calibers larger than .338 with this powder.

Anyone know of any published data, or has anyone used this powder in a .375 (H&H, Ruger, or any of them)?

Stonecreek,

Here's some data with my 375 AI, 26" barrel. Re17 is my go to powder with this gun.

250 TTSX Brand new Lilja
RE17 EXTREMELY Accurate
77 - 2745
81 - 2917
83 - 2959
85 - 3007
86 – 3040
87 – 3077
88 – 3107 - brand new barrel Very Accurate!!
No PSI Signs – could go higher, if needed.

300 GSC-HV Brand NEW BARREL!!
Re17 – EXTREMEL ACCURATE - ½ MOA
80 - 2729 Super Accurate
82 – 2791
83 – 2823
84 – 2847
85 – 2900
86 - 2885/2907/2892 Krieger//2919/2900 Lilja

300 Failsafe
Re17
83 – 2767
85 – 2880
86 – 2917
86.5- 2900
87 - 2917
88 – 2940/2967 Too Hot!!

300 TBBC all copper non-banded NEW Lilja
Re17
80 - 2713
82 – 2766
83 – 2801
84 – 2814
85 – 2850
86 – 2880 Ok pockets, but maximum

300 TBBC nickel coated/banded NEW Lilja
Re17 SUPER ACCURATE!!!
82 – 2784
84 – 2845
85 – 2855
86 – 2892 Ok pockets
87 – 2915 Ok pockets, but maximum

Thanks for that data. I plan on using Nosler Partitions and Accubonds so the data for monometals is not directly transferable, however it is very helpful and gives me some starting reference.

Stonecreek, these are the loads that go to Africa....375 H&H Ackley Improved. The 300 TBBC load shot completely through a Cape buffalo in Zambia on my last trip...three times.

250 grs. TTSX 88.0 grs Re17 3140 fps

300 gr. TBBC 85.5 grs. Re17 2880 fps

300 gr. GSC-HV 85.0 grs. Re17 2930 fps

A.I.U: Thanks again for sharing your data.

I had a moment today to put together a couple of test loads. Using a Nosler Partition 300 grain with 85 grains of RL-17 yielded 2687 fps out of my 24" barrel. Extraction was slick with no signs of pressure. I then loaded three rounds with 86 grains of RL-17 which yielded an average of 2725 fps instrumental, or about 2735 corrected to muzzle velocity. Extreme spread was only 25 fps and standard deviation a very tight 12 fps. Primers are still rounded and extraction is slick.

These are a bit lower velocities than you are getting with your 26" barrel, but the bullets are also different (as well as likely the primers, powder lots, and cases). But since the velocity is better than 175 fps more than the factory load standard for the .375 H&H I think I'll quit right there and be happy as 175 fps is significantly more increase in velocity than most A.I. modifications yield.

Also, as compared with H4350, RL-17 is a bit denser and doesn't require the compression that 4350 does. What's not to like?

Stonecreek,

I assume you're shooting a standard 375 H&H, not the AI version (AI version has 2 more grs H20 water capacity than a 375 Weatherby). My measured H20 capacity using a fired Remington case is 109 grs. H20.

But, maybe my assumption is wrong and you have a 375 AI, and if so, 2800 fps should be easy to obtain with safe PSI.

Weatherby offers 375 Weatherby ammo giving 2800 fps for a 300 gr Nosler partition. I fired some in my 375 AI and got 2950 fps, but with significant pressure signs. I think Weatherby is using a relative fast burning powder, possibly ~ Norma 203, and their ammo - designed for their rifles - is likely designed for considerable freebore.

My 375 AI has very little freebore - essentially none, and that's how I had the reamer designed. I can put the bullet slightly into the lands with ease. I'm not a fan of freebore.

Your gun may have much more freebore than mine, and that might also contribute to less fps than I'm seeing.

No, mine is the 40 degree A.I. version. I suspect that the difference in barrel length and type of bullets is responsible for most of the velocity differences between your rifle and mine. From the moderate pressure signs I'm sure that I could push it a few more fps, but, like I say, 175 fps more than a standard H&H seems like a substantial gain -- certainly all that I am looking for -- and generating almost on the nose of 5,000 ft lbs of energy. That's a lot of energy from a .375" bore.

I also own a standard .375 H&H, but I've only ever used 250 grain bullets in it (plenty of weight for the elk and black bear taken with it). The 250's seem to settle in nicely around 2800 fps in it.

This is my data with 300 gr Nosler Partitions, but using W760, which I've found to be quite similar - grain for grain - in behavior/performance as Re17.

300 Nosler Part – Not Very Accurate
W760
77 -2546
79 -2660
80 -2688
81 -2755
83 -2793
85 -2807
86 -2844
87 -2850
88 -2891 Pressure signs - STOP

I find this thread interesting, in my 375 Weatherby, max charges with 300gr Woodleighs run at 92gr 760 and 89gr H4350. I guess the 1/2" freebore allows more powder to be used. I can easily get 2850fps with 300gr Woodleighs and over 3000fps with Nosler 260gr.
A I User, don't know why you have an aversion to freebore, my rifle prints tiny little clover leafs without really trying very hard, and when you do tune a load, ragged one hole groups are common, the same is true in my 300 Weatherby and 270 Weatherby. BTW, none are Weatherby rifles, all are built on Win Model 70 stainless classic actions.

Cheers.

416RH,

IMO, guns vary in their sensitivity to seating depth relative to the lands; and thus, when I build a rifle I want the option of getting the bullet close - even a slight jam into the lands.

As you can see from my data, I can still get the PSI up and achieve top velocities without freebore.

Abundant freebore takes away your option for getting close to the lands, if you need to.

By your report, your gun is not sensitive to seating depth.

My 338 Gibbs and my 416 RUM have a bit of freebore and both are accurate - I consider myself lucky.

Stonecreek, I, just this week developed a load for my AI using the 250TTSX.My experience almost mirrors Ackley Improved User's, although I'm running a 24" tube. I called it good at 3133fps(though I used more RL 17)with very low extreme spread on velocity and a sub 1/2" group. I actually got velocities up to around 3170+,but accuracy tapered-off and I was starting to "flatten" the Fed. 215's. memtb