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Shooting & Reloading - Mausers, Big Bores and others >> Big Bore Rifles

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mauserand9mm
.400 member

Reged: 03/09/09
Posts: 1039
Loc: Queensland, Australia

375H&H mag - load observation
#336975 - 24/01/20 09:26 PM

I bought a chronograph fairly recently and it's a good thing because it gives me more reason to go through the gun safe and fire some rifles that had become otherwise dormant.

I put some of my 270gn handloads through my 375H&H CZ550 and recorded the results thinking nothing of it - average of 2858ft/sec with a SD (10 shots) of 13ft/sec. I've since found out that that is actually a fairly "healthy" velocity. Loads are far from hot (primers look good, cases extract easily, brass lasts a long time etc). I guess this must me due to the longish barrel.

Anyone else have chrono results for comparison?

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DarylS
.700 member

Reged: 10/08/05
Posts: 26998
Loc: Beautiful British Columbia, Ca...

Re: 375H&H mag - load observation [Re: mauserand9mm]
#336983 - 25/01/20 03:53 AM

Long barrel certainly helps, but also, many of today's powders are much better than those of 20 years ago.

As P.O.Ackley once wrote, brass longevity is the final judge on a load's integrity.

The .375H&H is a 60,000PSI cartridge.

--------------------
Daryl

"a gun without hammers is like a Spaniel without ears" King George V

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Rule303
.450 member

Reged: 05/07/09
Posts: 5061
Loc: Woodford Qld

Re: 375H&H mag - load observation [Re: mauserand9mm]
#337009 - 25/01/20 09:28 AM

I think I chronied some of my 300grain projectiles from the CZ550 375H&H but that was some years ago. Those results will take a bit of finding. So, from memory they were a bit slow but I was using AR2206 as recommended by some blokes I know. AR2209 got the bullets up and moving a bit better.

I'll see if I can find that data.

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mauserand9mm
.400 member

Reged: 03/09/09
Posts: 1039
Loc: Queensland, Australia

Re: 375H&H mag - load observation [Re: Rule303]
#337021 - 25/01/20 12:26 PM

I use AR2208 for most loads in the 375. Others recommend AR2209 but I can't fit enough into the case. My loads are quite a bit over ADI listed loadings but they are okay pressure wise. ADI show 50,000 cup for their maximum loads (not sure how these equates to PSI).

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Rule303
.450 member

Reged: 05/07/09
Posts: 5061
Loc: Woodford Qld

Re: 375H&H mag - load observation [Re: Rule303]
#337068 - 26/01/20 08:25 AM

Found the data. AR2209 gives me just above listed max velocity with the 300grainers. Can still stuff another couple of grains in. With monometal bullets I need to go back to AR2206H to get enough powder in and getting book velocities.

I need to experiment with BM8208 with the monometals.

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DarylS
.700 member

Reged: 10/08/05
Posts: 26998
Loc: Beautiful British Columbia, Ca...

Re: 375H&H mag - load observation [Re: Rule303]
#337091 - 27/01/20 06:20 AM

Yes - the longer monometal bullets will require faster powders taking up less space.
There should, however be no problem in achieving "book" speeds.

In 1912, the ballistics were: 2,600fps for 270gr. and 2,400fps for 300's.
Those are the ballistics, with which the .375 earned it's African all-round game killing reputation.

--------------------
Daryl

"a gun without hammers is like a Spaniel without ears" King George V

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Postman
.375 member

Reged: 25/09/13
Posts: 846
Loc: Canada

Re: 375H&H mag - load observation [Re: DarylS]
#337097 - 27/01/20 11:09 AM

Using 300 grain TSX, I get ~ 2400 FPS out of my 375 H&H 20” bbl Sako Kodiak. I get a similar velocity out of my 26” barrel Heym .375 Flanged Magnum. My loads are near max according to modern/current reloading manuals. No signs of abnormal or high pressure. I’m a conservative reloader. I do not hot rod my rifles. What would be the point? If you want or need more power than a given cartridge was designed to provide, I prefer to simply acquire a more powerful cartridge. I value my fingers, hands, eyes and general good looks

and have no desire to rearrange my physique for an extra 50 or 100 FPS.

Edited by Postman (27/01/20 11:11 AM)

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Rule303
.450 member

Reged: 05/07/09
Posts: 5061
Loc: Woodford Qld

Re: 375H&H mag - load observation [Re: DarylS]
#337107 - 27/01/20 07:02 PM

Quote:

Yes - the longer monometal bullets will require faster powders taking up less space.
There should, however be no problem in achieving "book" speeds.

In 1912, the ballistics were: 2,600fps for 270gr. and 2,400fps for 300's.
Those are the ballistics, with which the .375 earned it's African all-round game killing reputation.

Yes however modern book velocities are around the 2600fps mark for the 300grain. Modern powders and I am more than happy with these velocities. Like the earlier loads they simply work.

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Postman
.375 member

Reged: 25/09/13
Posts: 846
Loc: Canada

Re: 375H&H mag - load observation [Re: Rule303]
#337111 - 27/01/20 10:51 PM

Quote:

Quote:

Yes - the longer monometal bullets will require faster powders taking up less space.
There should, however be no problem in achieving "book" speeds.

In 1912, the ballistics were: 2,600fps for 270gr. and 2,400fps for 300's.
Those are the ballistics, with which the .375 earned it's African all-round game killing reputation.

Yes however modern book velocities are around the 2600fps mark for the 300grain. Modern powders and I am more than happy with these velocities. Like the earlier loads they simply work.

This seems about right, based on what I see with my Sako Kodiak rifle assuming a loss of ~ 50 FPS per inch of (shorter) barrel length. Also, most reloading manuals tend to use 26” test barrels, another factor to contemplate.

Edited by Postman (27/01/20 10:55 PM)

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