.375 H&H reload prob????

[Flapjack23]

I have a couple issues with a some loads I worked up. I loaded three round per charge looking for accuracy to see where my gun shoots well at. All rounds showed reasonable accuracy (the last has vert. stringing), but my questions have to due with velocity. I loaded all four groups with Rem brass and Win LRM primers. Powder IMR 4831 and loads from Nosler fifth ed. guide. Bullets Nosler Accubond 260 Gr. My results as follows:

1. 76.5 Gr. powder 2396 FPS
2. 77.5 Gr. powder 2450 FPS
3. 78.5 Gr. Powder 2496 FPS
4. 79.5 Gr. Powder 2511 FPS

Manual lists 76.5 Gr. Powder at 2605 FPS abd 78.5 Gr. powder at 2669 FPS.

My results are well below published velocity. No difficulty extracting with any loads, primers showed increased levels of "change" as powder increased. Last load (79.5 Gr.) filled the case up. Heaviest load primer was similar looking to factory load primer.

Any clues as to why my velocity is lower than published? I'd like to be in the 2650-2750 FPS range but don't want to compress the charge or exceed the max listed of 80.5. Any comments welcome.

Thanks,

Andy

[Brian Pfleuger]

Any clues as to why my velocity is lower than published?

Because you're not using the gun the publisher used, the powder lot the publisher used or the primer lot that the publisher used. Also, is your case length identical? Case capacity? Seating depth? How far off the rifling is the bullet?.... All those things and more can effect your velocity..... temperature, distance to chronograph....

[edward5759]

My pressure gun from H&S has a barrel length of 28"
It's a copper crusher type.
I’ve done pressure testing at different altitudes that makes a difference also.
Are you loading on a Rainey day? Trapped moisture makes a difference
are you shooting the cool?
A lot of difference in what you will have and the manufacture.
Don't worry about velocity changes of 3,4,5,percent go with ACCURCRY
ed

[Scorch]

As others stated above, there is a difference between your rifle and the test gun the factories use to test bullets and loads. Typical barrel length for factory pressure guns is usually 26" or 28". Each extra inch of barrel length will give about 50-60 fps velocity gain, so if you are shooting a rifle with a 24" barrel, you may see as much as 200-250 fps of difference in velocity between your loads and published data. Even if the test gun specs are exactly the same as your rifle, there are also differences in case volume between the major manufacturers, which will affect pressure, and therefore velocity. This is one reason I prefer the Hornady and Lyman loading manuals over others, they use actual rifles.

[edward5759]

My 45/70 barrel is 32" long on the test gun.
other than some trap door ive seen very few barrels that are 32" long.
Ed

[Scorch]

Where do you work, Edward? Bullet company or powder company?

[Unclenick]

The SAAMI compliant pressure barrels all have a minimum chamber, so pressure in them will be higher than in a randomly selected commercial chamber. The pressure is dependent on the volume the case expands to in your chamber. The Nosler manual uses a 24" Lilja barrel that will have that minimum chamber. If your chamber is bigger or if your barrel length is shorter, it will make a difference. Your chamber probably has a longer freebore than theirs. That gives more opportunity for gas to bypass the bullet before it obturates the bore, and that lowers peak pressure and velocity.

You are using Remington brass, and Nosler is using Winchester brass. Winchester usually has the most room in most chamberings, but that might not be so in any particular case, so they may have less powder volume due to the brass? This does not seem likely to me, but I thought it should be tossed into the mix to check.

You are using a WLRM primer, they are using a Remington 9 1/2. If the Remington primer is warmer (and Remington's magnum primers tend to be on the warm side) you could see 100 fps difference from that.

You are assuming your chronograph and theirs match. Lots of chronograph velocity reading errors occur, mostly due to lighting conditions or not having the chronograph far enough away from the muzzle to avoid being triggered by muzzle blast that gets to the first screen ahead of the bullet, but doesn't trip the second screen. When that happens, the second screen waits for the bullet to get there, thus producing slow readings. I would use at least the 15 foot distance to the center between your sky screens that many of the manual publishers do. If you want to be sure, borrow a second chronograph and put it just behind yours to see how the readings compare? Ideally you would see a few feet per second less on the second unit. Figure about 1 fps loss per additional yard with that 260 grain Accubond near the muzzle.

[GeauxTide]

I haven't loaded for the 375, but all the information I've read in the manuals and Pet Loads have a common theme. The expansion ratio of the 375 (case capacity to bore size) is good, so faster powders would be in order to get the max velocity. For instance, Nosler 6 give charges of RL-15 from 69 to 73gr, giving velocities of 2648 to 2793.

[Unclenick]

That's a good point. A lot of folks report better accuracy from IMR4350 than from anything faster with that cartridge.

Also, I would comment that incrementing the load in 1 grain steps could cause you to skip an accuracy sweet spot right inbetween two of those loads. Even with the magnum case capacity I would not increment by more than half a grain per step. Try Dan Newberry's method for finding you optimum charge.

[edward5759]

Some of the 375 H&H are pre war European chambered. these rifles Will give varied results as well, Depending on who chambered them.

4064 has given me the best results in my rifle with the 270 grain bullet when dealing with accuracy.

Some people say "I want". I want the rifle to shoot 4350. I want the rifle to shoot the barns bullet. I want is what will make the rifle fun, or a bastard.

Work with the gun and what it wants to shoot, not what you want to shoot.
Ed

[ForneyRider]

My brother used IMR 4064 for 270gr, and IMR 4350 for 300gr. I used Varget for Hornady 225gr bullets with good success. Made a nice reduced load at ~2550fps.

I got poor velocity when trying to run R25 in 7mm Mag. When I swapped back to R22, I had no issues with velocity.

[Flapjack23]

I think I might be better off trying a different powder. Accuracy was reasonable with all loads, but velocity was a little lower than I would like.

Thanks,

Andy

[crimsondave]

I have reloaded extensively for the .375 H&H for years. Of all the rounds I have chronoed, you will not do better than Reloader 15 for velocity. IMR 4350 is the only other one close. I have found however, in most bullet weights I get better accuracy out of the IMR 4350 in my model 70. However, the 260 gr Accubond was the exception. RL 15 had the highest velocity and best accuracy in my gun with that bullet.

Just a little extra tidbit you didn't ask for, if you need a good whitetail load for the .375, try the Speer 235 gr loaded with a "light" load of 81 grains of IMR 4350. Very accurate, and will not tear up the meat.

[Flapjack23]

I'm thinking I might try to find some RL 15. Most powder is pretty scarce around here. Crimsondave, what find of velocity were you getting with the RL 15? I'm hoping for 2650-2750 with good accuracy. I'll be poking deer this fall with it, then back to the .300. Would like a load I can be happy with for larger game.

Andy

PS. What is the right forum to discuss terminal ballistics?

[greensteelforge]

I have reloaded for 18 different cartridges over the years, and never owned a chronograph, or any other testing equipment other than lots and lots of targets. I check penetration for this round with logs, and have yet to have a load come out underpowered. The .375 H&H is one of the most forgiving rounds I've ever loaded, and routinely groups exceptionally well with a wide variety of bullets, powders, primers and brass (even mixing loads for a group came out surprisingly tight). Put together a load that you like to shoot, test it out on something that will help you gage how it will perform terminally, and enjoy one of the nicest to shoot, most versatile big game rounds out there.

[crimsondave]

I got around 2700 fps with 75 grains of RL 15. You did not ask me, but I will tell you that you don't want to shoot deer with this load. I ruined half the loin on a deer with a similar load. The load you are talking about here is not underpowered for any game in the Western Hemisphere. It is also not the most pleasent load to shoot for the heck of it.

I agree with greensteelforge, this is probably the easiest caliber to reload I have ever reloaded. I've gotten good groups from both slow and fast powder at different bullet weights. What blows my mind is how little the trajectory changes with different bullet weights! It does require tons of powder, though, LOL!