375h&h velocity

[James Adamson]

*Please do not copy any of the loads shown below. These loads were carefully worked up in MY RIFLE and may not be safe in another rifle*

Hi all. I finally managed to get my hands on some woodleigh 300gr rnsn and started on some load development last night. Using N140 I loaded up 9 cartridges starting with 3 at 63gr, 3 at 64gr and 3 at 65gr. Today I headed out to test them and was a little disappointed with the velocity, I never got up to 2400fps. With no signs of pressure at all, I headed back in to the gun room and loaded up 3 at 66gr and 3 at 66.6gr. Keeping an eye out for pressure signs I carried on and ended up at 2470fps and the tightest group with 66.6gr of N140. A good honest 1 inch group at 70 yards with open sights. This is .6 of a grain over maximum but as I say there was no signs of pressure, maybe a very slight flattening of the primer but I have seen worse. My question is, should I back off a bit or am I fine? I have no experience with woodleigh bullets and how they perform, I would hate to carry on and find out later that the bullet didn't perform because of velocity being too high or too low. I am hoping that some day I will make it back to Namibia and use this rifle and ammunition on a buffalo hunt, but with everything that's going on just now who knows.
Any advice gratefully received

 

[John Wasmuth]

With open sights at 100 yards it looks pretty good to me. If I recall correctly it’s not much different than the original H and H loading.

 

[Forrest Halley]

Beware groups on steel. It's a short lived proposition before it gets squirrelly. The paint gets blown to hell by the big magnums and there is no repeatable frame of reference. Put some paper about three yards in front of the steel on cardboard. You get a better reference point.
My .375 groups are always larger on steel vs. paper.

As far as being higher than max, don't concern yourself too much as long as few things are true:
• Ammunition is ambient temperature and it's above 80°F.
• Bolt lifts easily.
• Extraction is clean and smooth for the whole magazine.
• Cleaned fired brass isn't showing stress signs.

Don't go crazy with it. There are heavier more powerful calibers. No need to try and 10mm it.

 

[James Adamson]

Beware groups on steel. It's a short lived proposition before it gets squirrelly. The paint gets blown to hell by the big magnums and there is no repeatable frame of reference. Put some paper about three yards in front of the steel on cardboard. You get a better reference point.
My .375 groups are always larger on steel vs. paper.

As far as being higher than max, don't concern yourself too much as long as few things are true:
• Ammunition is ambient temperature and it's above 80°F.
• Bolt lifts easily.
• Extraction is clean and smooth for the whole magazine.
• Cleaned fired brass isn't showing stress signs.

Don't go crazy with it. There are heavier more powerful calibers. No need to try and 10mm it.

There was no signs of pressure, bolt lift was easy and the primer looked fine.
What I might do though is keep the ammo in a warmer room and try again just to be sure, the temperature here is a lot lower than what I experienced in Africa.
My only reason for using the steel target is because it's a 12 inch round target that works perfectly with the bead on my front sight. I have found I can shoot more accurately shooting at that than a square piece of paper or anything else I have tried. 3 or 5 shots then a fresh spray of paint for the next group.

 

[Forrest Halley]

There was no signs of pressure, bolt lift was easy and the primer looked fine.
What I might do though is keep the ammo in a warmer room and try again just to be sure, the temperature here is a lot lower than what I experienced in Africa.
My only reason for using the steel target is because it's a 12 inch round target that works perfectly with the bead on my front sight. I have found I can shoot more accurately shooting at that than a square piece of paper or anything else I have tried. 3 or 5 shots then a fresh spray of paint for the next group.

You're going to want to experiment with warm ammo vs. cool ammunition as pressure and POI will change. Nothing illustrates this more markedly than development of suppressed subsonic loads. You can get a Pfft! for the first few and then begin to crack to sound barrier as the ammunition warms up at the range. Truck dashboard is a very good place to heat up ammunition.

 

[Wyatt Smith]

If it’s available, I would try some different powders and see if I could get the same velocity with a less than max load. Something like H4350 where you can get 75 or so grains for a max load with a 300 grain, should give you less pressure.

 

[sestoppelman]

You are nowhere near maximum for the .375. Any decent load will put you to at least 2550fps and some even more.
Dont know what powders you have access to but IMR4350 or similar with about 80 grs will get you there. Use several different manuals for cross reference. The Barnes manual using only their bullets lists velocities even higher.
My loads worked up years ago using 4350 and IMR4831 were well over 2550fps, nearly 2600, with no pressure signs.

At 2470 fps you are only still in .338 Win mag territory.

 

[machinistbutler]

I found the IMR4350 works great with most 300 grain bullets to get above 2500 fps in the H&H.

I did have a big boat tail Hornady I think that was a bit of a problem to get enough powder in with that huge bullet seated so deep.

IMR 4831 I got a bit too much compression.

Lighter bullets with faster powders such as RL15, 4064 and 3031 got good velocities as well

I have a couple 25 inch barrel, a 24 and a 23 inch 375. I haven't chronyed the 23 inch 375 yet.

 

[James Adamson]

The biggest problem I have here in Shetland is getting powder and primers as it cant be sent in the post. Also there is very little of the hodgdon or IMR powders available here in the UK now, certainly none of the usual ones that would be used in the 375. I use alliant RL19 and RL22 in my 6.5x55 and 30-06 but I have heard they can be very temperature sensitive. I can get most vhit powders and the ramshot powders.

I am not looking to max out the 375h&h, I just want to be sure that the woodleigh bullet will perform as it should at the velocity I ended up at.

 

[Wyatt Smith]

I would try reloader 19

 

[sestoppelman]

I would try reloader 19

Yes, its very similar to 4350-4831 in burn rate, good stuff.