I was looking in the Lyman 49th edition and it lists the max load for IMR 4350 at 81 grains for a velocity of 2629 for a Swift A Frame 375 H&H.

It seemed quite high so I called IMR and they said the max load should be 76.5 - does anyone have any suggestions - I am going to pull the bullets. Based on Lyman book I did the starting load at 77 - I am wondering whether that is even safe.

I am shooting a Winchester Model 70 that was made a few years ago.

The A frame is very accurate and I am trying to duplicate the Remington Factory Loads that I have had for a few years. Any help would be greatly appreciated.

I'd pull 'em and drop a couple/three grains. Then work back up. I suspect you will be fine, though.

I load 77-79 grains of H4350 under the A-Frames for about 2575 FPS

Rl 15

Got better groups with H4350 over R-15 for A-Frames. 78 grains for 2575 fps in my CZ. R-15 was really good with 300 gr Barnes. 69 gr for 2530fps out of my Model 70.

I use 78.0 grains of IMR4350 with 300 A-Frames, which gets around 2550 from the 22" barrel of my semi-custom Mark X Mauser, and sub-inch groups. I use 81.0 grains with 300 Partitions and Siiera GameKings in the same rifle, for just about the same muzzle velocity and accuracy, but A-Frames tend to produce somewhat more pressure, due to the pure copper jacket.

Have tried H4350, R15, Varget, Big Game and some other newer powders over the nearly three decades I've owned the rifle, but so far none has done as well as IMR4350. Have also tested the load at zero degrees Fahrenheit, and it only loses a few fps, probably because it's pretty compressed.

I would chrono your 77 gn loads and see if they are within IMR's expected velocity for the 76.5 gn Aframe load. One half grain may be within pressure max depending on brass and primer. Is the IMR load at max SAAMI pressure? Velocity equals pressure, usually. Might not use the 77 gn load in high temps just to be safe.

Here's my suggestion. Your concern seems to be that you both started and finished at too high of a charge level and you are concerned about the safety?

I wouldn't pull down the loads right away; I'd load more with even lighter charges and start with those first. It may very well be that the Speer data is high for your rifle, but it can also turn out to be just fine. It would be a shame to pull down loads, just to turn around and load them again if IMR comes in on the whimpy side. Speer's data was right for some rifle, and your's may follow suit.

Worst case scenario you end up pulling the loads down a little later.

Thanks for the help guys - I started learning with smaller calibers and working my way up -

I will follow the advice given.

The original 76 and 76.5 did not group as well as the Remington Loaded Ammo which is no longer made.

I am trying loading the bullets to .020 off my lands and using the Lee factory crimp die - they are at 3.6" which makes the crimp just below the cannelure - the Lee instructions say this is OK but I would appreciate some guidance here.

I am going to try an work up to 78 as Mule Deer suggested.

One of the items I failed to mention was that .375 H&H chamber-throat dimensions can vary somewhat, which isn't unusual in older cartridges. This definitely affects maximum powder charges from rifle to rifle, which is one reason some handloaders (including me) pay more attention to the chronograph than specific powder charge.

There's also the basic fact that a controlled-expansion 300-grain .375 bullet at even 2400 fps on Cape buffalo, or water buffalo.Not long ago Berit Aaagard Pace used exactly that sort of handload in Finn's M70 .375 to take both kinds of buffalo, quite neatly. Which once again demonstrates that a good bullet placed correctly is more important than a few extra FPS or foot-pounds.

I worked up to 81.0 grns of IMR4350 with 270 gun TSX bullets which is a highly compressed load but didn't see any pressure signs. Accuracy wasn't as good so I went back to 79.0 grns. I'm not sure if a 270 TXS is as long as a 300 A-Frame.

I tried R-15 and got better velocity, but accuracy suffered. My rifle just likes IMR4350.

I just re-read the original post and had assumed you were using 300 gun A-Frames, but it doesn't say that. I tried to 81.0 grns of IMR4350 with both 270 gun TSX and A-Frames. From your posted velocity, I think you used 270 gun bullets. I got about the same velocity as you did.

My Lyman's manual (49th ed.) shows a max load for IMR4350 with 270 gun A-Frames of 77.7 grns, but for 300 grn A-Frames the max load is shown as 81.0 grns. That's puzzling isn't it?

Yes - I was referring to a 300 Grain A-Frame - The folks at Swift were extremely helpful when I called and I ended getting under 1 in groups and am very happy - I have not had a chance to chrono it yet - I was very impressed with the level of support they gave me. And will start trying their bullets in my other rifles.

I don't have access to my pictures, but 76gr of H414 F215 primers and 300gr Swifts get me consistent 3/8-1/2" groups and 2550 fps out of my 24" Model 70.

I was going through a doubled gallon freezer bag of my 375 H&H ammo yesterday, 300gr Partitions, 300gr BBW #13 solids, and a small ziplock with 20 rounds of 300gr SAF's, note inside said RL-17 and 2626 fps, bet that would work too. love finding things I forgot I had.

I think I have 3 boxes of Remington Factory Loads?

I would chrono the factory loads and stop when you reached that velocity. R15 has been my go to powder and is less bulky than 4350. I always ran out of room with 4350 and heavy bullets before top velocities were achieved, but this is some what a moot point as the rimmed 375 and others have performed well at lower velocities for decades.
Another when I get around to it project is to re-work my 375 loads with R16 for less temperature variance and maybe more velocity. R16 is right between 15 & 17 but almost a duplicate of 17. It is denser than 4350 so I hope it will work out it should.

I use H-4350 and the 300 grain SAF in my .375 H&H Intertarms Whitworth. From the 24" barrel it's getting 2630 fps.

Thank me anytime

I looked up the load data: 78.5 Grains H-4350 and a Remington 9-1/2 mag primer.

Jorge is that group shot with both the 300 grain SAF and Hornady RNSP?

yessir. In actuality it's two A Frames and one old style 410gr Hornady SOLID. I still have two boxes of the old steel clad ones..

I believe that powder and W760 are one and the shame. I had very good luck with 760.

correct on the powders.

[quote=jorgeI]yessir. In actuality it's two A Frames and one old style 410gr Hornady SOLID. I still have two boxes of the old steel clad ones..[/quote]

Like these?



Top bullet is a Hornady .375" 300 grain solid.

Bottom bullet is a Hornady .458" 500 grain solid.

You have lovely hands Elk!

Gunner, ya noticed.

Maybe Nurse Rached (as in One Flew Over the Cuckoo’s nest).

She’s his keeper and handler while he’s under house arrest and close management.

DF

must be something in that NM soil ; ]

Thanks,you like the nail polish to?

Why yes, yes I do, SNORK!

Thanks!

Cant wait for you to get squared back up banging hard on all eight cylinders and hunting Africa again my Friend!

Gunner,you're not the only one!

Should find out in March what is going on between my ears.

All the Luck to ya Buddy.

Thanks Gunner.