.375 H&H 300g bullets best velocity

[benchracer]

Very soon, I intend to begin an experiment that, for me, will enter uncharted waters.

I am going to experiment with some 300g Cutting Edge bullets in my .375 H&H. It is a CZ 550 with 25 1/2" barrel. According to Hodgdon's reloading data, a max load of H4350 will produce 2640ish fps from a 24" barrel.

Considering that Hodgdon shows the best velocity with 300g bullets to be produced by 4350, would RL17 be worth a try in an attempt to eek out some extra velocity?

Does anyone have enough load development experience with this cartridge to have a good idea of what powders produce the best velocity with heavy bullets?

I realize that the good ol' H&H isn't considered a hot rod cartridge in any circles. I am curious, though, what kind of potential it would have with high bc bullets. I am interested in learning something about the max potential of this cartridge. I think a lot of whether or not this idea is a success will depend on how fast I can safely push heavy bullets and where the accuracy node falls in my rifle.

Because I only have 50 of the Cutting Edge bullets, I will have to be efficient in my testing. I expect to be able to establish my max and find my accuracy load in 30 rounds or less with a single chosen powder, since I won't have to tune the seating depth with these bullets. That will leave me 20 rounds for testing to 600 yards (which is the longest range I have access to).

I have some 300g Hornady Spire Points that I am thinking of using only to test the velocity potential of different powders. Once I have identified the powder with the best velocity potential, I would then use that powder in load development with the CE bullets. I am currently considering H4350, RL17, and Vihtavuori N540.

I would appreciate any suggestions, advice, or criticisms of my thinking and planned methodology on this. I need to make every shot count, so it is important that I have a well thought out plan of attack when I get started.

 

[Lefty7mmstw]

Very soon, I intend to begin an experiment that, for me, will enter uncharted waters.

I am going to experiment with some 300g Cutting Edge bullets in my .375 H&H. It is a CZ 550 with 25 1/2" barrel. According to Hodgdon's reloading data, a max load of H4350 will produce 2640ish fps from a 24" barrel.

Considering that Hodgdon shows the best velocity with 300g bullets to be produced by 4350, would RL17 be worth a try in an attempt to eek out some extra velocity?

Does anyone have enough load development experience with this cartridge to have a good idea of what powders produce the best velocity with heavy bullets?

I realize that the good ol' H&H isn't considered a hot rod cartridge in any circles. I am curious, though, what kind of potential it would have with high bc bullets. I am interested in learning something about the max potential of this cartridge. I think a lot of whether or not this idea is a success will depend on how fast I can safely push heavy bullets and where the accuracy node falls in my rifle.

Because I only have 50 of the Cutting Edge bullets, I will have to be efficient in my testing. I expect to be able to establish my max and find my accuracy load in 30 rounds or less with a single chosen powder, since I won't have to tune the seating depth with these bullets. That will leave me 20 rounds for testing to 600 yards (which is the longest range I have access to).

I have some 300g Hornady Spire Points that I am thinking of using only to test the velocity potential of different powders. Once I have identified the powder with the best velocity potential, I would then use that powder in load development with the CE bullets. I am currently considering H4350, RL17, and Vihtavuori N540.

I would appreciate any suggestions, advice, or criticisms of my thinking and planned methodology on this. I need to make every shot count, so it is important that I have a well thought out plan of attack when I get started.

I've been shooting the 375 h@h for years. I had a m70 that wouldn't hit the broad side of a barn( they are designed with 300 gr pills in mind and have a tapered throat) and I've owned a remmy in 375 for about four years now. It has a straight throat and will shoot moa with any good combo, even at 8# scoped weight.

You aren't going to get either of the 4350's in the case with a monolithic bullet unless you have a very long freebore, and you will be a single shot if you do. I tried my damndest and only got bulged cases. I shoot the 300 tsx in mine and had to go to I 4320 with it, but it shoots moa at 2550 fps. With the 300 dgs hornady I'm using a max charge of I 4530 but never did chrono it. A 270 accubond can be driven to about 2700 fps with I 4320 and it'll scramble you when you touch it off. It shoots well though, at about moa. The best accuracy I've had so far with the 375 is with the 270 speer bt with I 4320 under it; that bullet will cloverleaf.

If you want to break 2600 fps with a 37 caliber 300 grain bullet, you will need to go to a bigger case, but at 2500-2600 fps this round still hits like a hammer.

 

[benchracer]

Thank you, Lefty7mmstw, for sharing your experience with me. What you have to say about the 4350's is pretty interesting.

I have been wondering why the Barnes data shows VV N540 as the top powder for a lot of their loads. It seemed to me that N540 would be a bit on the fast side, but you have me thinking that the probable reason for that has to do with load density/case capacity issues like those you have encountered with the 4350's.

For what I am trying to do, I don't mind if I my rifle becomes a single shot with these loads. I am trying to develop something that would be useful at long range. Maintaining the ability to use my rifle as a repeater would be nice, but not a requirement. I have other shorter range "smasher" loads that still allow me to use my rifle as a repeater when necessary.

You do, however, bring up a good point about throat length. I was thinking more in terms of magazine length myself. Of course, throat length may turn out to be a far more important factor in the final COAL with the 300's. I will have to pay special attention to that before I start my load development.

If I am able to shoot the CE's accurately @ 2600, I will be satisfied with that. I just want to see what is possible using the latest components.

 

[benchracer]

I keep thinking about this. The loading density issues with the 4350's make me think that RL-17 could very well be just the ticket for this application. Hmmmm...

 

[Lefty7mmstw]

I keep thinking about this. The loading density issues with the 4350's make me think that RL-17 could very well be just the ticket for this application. Hmmmm...

Haven't tried rl17 yet myself, but rl15 did rather well with 235 gr and 250 gr pills in my win; considering of course it wasn't that accurate of a rifle. I've got a hundred 300 tsx loaded with I 4320 and a 20 rounder of solids loaded with I 4530. I also shoot a gas check hand cast lyman bullet with rl7 at 2K fps with good results.

 

[benchracer]

I have loaded gas check hard cast 250g bullets myself with excellent results. I used H4198 with those, if memory serves.

I have also tinkered with 250g TTSX and CFE 223 as well. I got tight little cloverleaf groups that would make a varmint rifle jealous. I would be inclined to use that load out to about 500 yards or so on anything short of Cape Buffalo.

I want to find out if the CE 300's will let me really reach out there, though. If I am able to get decent velocities (and if CE's bc numbers are in the ballpark), JBM says the 300's will fly nicely way out there.

RL-15 has come up a lot in my research as being among the top powders for the .375 H&H. I'm just not sure if it is the right match with the heavies to get the best possible velocity. I'm really just guessing, though. I wish I knew more about that sort of thing. I have noticed that the Barnes data keeps showing VV N540 as giving top velocity and accuracy with their bullets. That's the only mono metal bullet data I've seen so far. I am thinking it may be a good place to start with the CE's.

 

[benchracer]

I started load development today. I only did a short workup to establish my max load, using Hodgdon book data, 300g Hornady Interlock BTSP's and H4350.

The Hodgdon data specified a COAL of 3.6", a starting charge of 77g, a max charge of 81.5g (compressed), and a max velocity of 2645 from a 24" barrel.

With the Hornady bullet, COAL to the rifling is 3.830. I backed the bullet off to 3.750 and began one grain above min, loading one round at 78.0g, 79.0g, 80.0g, 81.0g respectively and two rounds at 81.5g. All rounds were capable of being fed from the magazine of my rifle.

The first round crossed the chrono @ 2640 and the last two rounds chronoed 2718 and 2722 respectively. The brass showed no signs of pressure, primers looked good, bolt lift was normal, and the recoil was manageable from the standing position.

With the CE bullets, I initially followed the factory recommendation for seating depth of trim length +1.141", but the seal tite band ended up being seated below the case mouth at this length. Though CE states that it is acceptable for the seal tite band to be seated in the case neck, I decided that I would prefer to have the seal tite band seated just above the case mouth. Seated in that manner, my COAL was 4.004. These loads allowed one round to be placed in the magazine and a second round to be fed into the chamber over the top of the first round.

I loaded one round each at 77.0g, 78.0g, 79.0g, 80.0g, 81.0g, and 81.5g of H4350 respectively. The first round chronoed 2647 and the last round chronoed 2766. As with the first set of rounds, there were no indications of high pressure of any kind.

I am convinced that I could go faster with both loads before reaching max, but I am very happy with the results I've gotten so far. I don't feel the need to push pressures to maximum.

I am also very happy with H4350 so far. The velocity increases between rounds were very predictable and it looks to me like it will produce very consistent loads. I don't intend to experiment with another powder unless I am unable to get acceptable accuracy with this one.

IMO, it was also noteworthy that the CE bullets behaved very similarly to the conventional Hornady bullets in terms of pressure tolerance and velocity. That indicates to me that one can safely use data for same weight conventional bullets and listed powders with the CE bullets.

Now for the next stage of development-- accuracy testing using an OCW ladder. I will post my results with photos in a new thread.

 

[Holmes]

Thanks for the excellent report. Looking forward to the next instalment.

 

[Lefty7mmstw]

2750fps with a 300 grain pill in a 375 H@H is smoking, but you aren't able to keep 'em down to 3.600" are you?? Any accuracy to go with that, or was it just a velocity run up??
My rem has little extra room but I could probably go to 3.650". I'm thinking I still won't be able to use I 4350 there. I have been having good luck with lead core with 4350 though. I'll have to try seated out a bit and h4350 with the TSX, I believe all I had around last time was I 4350 and that's a bit bulkier.

 

[gerryb]

i would have to look at my book but i have used rl-15 with 270 tsx and the 300 tsx in africa many times and have killed animals out to 318 yards. i can't remember velocity but with 270 tsx it was a touch over 2750. i did not find any difference on buffalo up close so now i stick with 270's in H&H and 300's in 375 RUM

 

[benchracer]

My first attempt at an OCW ladder was a bust in terms of generating useable data. I did, however, learn two things:

1. I need to tweak my benchrest shooting form when shooting a rifle with this level of recoil. I didn't feel like I was getting beaten up and I wasn't flinching, but maintaining good follow through is tricky compared to the lighter caliber of rifles I have shot from the bench in the past.

2. I need to keep an eye on my scope mounts. They worked loose during testing without my realizing what was happening. It was only after testing that I was alerted to the fact that they had worked loose by a telltale rattling noise when I uncased the rifle.

Much to my disappointment, I will have to re-group and continue with the experiment another time. I work overseas and won't be home again until the fall. I hope to continue my experiments at that time.

If my experiments do show promise, I plan to have a picatinny rail installed in hopes of keeping my scope from working loose under recoil while in the field.

If I have learned anything so far, it is that attempting precision shooting with a 375 H&H is a whole new ballgame compared to the lighter caliber rifles I have shot with in the past! It is a new challenge and I like it, but it is shining bright lights on shortcomings in my shooting technique!

 

[X-man]

At 2750fps you are too hot for optimal accuracy.
You are going to have to drop it into the 2650fps range to get good accuracy.

Have a hard look at RL-15...the powder of choice...just sayin'!
IIRC I was up around 2700fps with good accuracy with that powder.
Admittedly, it has been 10 years since I loaded for the H&H.

For the long bullets you want to use you should have a look at the 375Rum or even the 375 Wby. I prefer both to the H&H.

Good luck man!

 

[benchracer]

At 2750fps you are too hot for optimal accuracy.
You are going to have to drop it into the 2650fps range to get good accuracy.

Have a hard look at RL-15...the powder of choice...just sayin'!
IIRC I was up around 2700fps with good accuracy with that powder.
Admittedly, it has been 10 years since I loaded for the H&H.

For the long bullets you want to use you should have a look at the 375Rum or even the 375 Wby. I prefer both to the H&H.

Good luck man!

The OCW workup will tell the tale where the best accuracy/velocity combination is concerned. The reason my first attempt failed was a combination of issues with my bench technique and my scope mounts working loose. Both of those issues prevented me from generating useful data. Believe me, BOTH of those issues WILL be resolved before I start slinging $2 bullets down range again.

At this point, I see no reason to change powders. H4350 has done what I am looking for so far. Pending data generation, who knows?

The same cannot be said of the nut behind the trigger, however. I'd change that out, but I don't have another one.

Where chambering is concerned, the whole point of the excercise is to determine the potential of the H&H when loaded to take full advantage of the high bc bullets that are now available. I am looking to explore the limits of what I already have, not justify yet another rifle (as much fun as that is).

 

[X-man]

You can run a 375Wby reamer into your existing gun.
RCBS makes the dies.
Its is much more agreeable for what you want to do.

Trust me dude RL-15 will come out on top in your OCW test and the velocity will be higher.