Sizing down 375 h&h to 300 h&h... possible?

[Majo]

Hi there!

Long time reader, first time posting...

First of all, nice to be here and thanks in advance.

Question is easy... could I size 375 h&h (i have a bunch of once-fired cases) to 300h&h? I’m waiting to get a new (to me) sako finnbear... brass is expensive and hard to find, so will be nice to have a backup plan...

By the way, any feedback on the 300 holland will be nice. I’m considering to load sierra 165 game king hpbt (#2140) at mild velocities... but may be better to step up to 180-200 grains... I don’t care about recoil, but don’t need too much bullet for reds and boars in Spain... not planing to go to Africa yet

Thanks!!

 

[GuttormG]

Yes, it can be done. Annealing the case, good lube and maybe in several steps.
RCBS has/had a forming die to do this.
Propably much easier to make from 7mm Rem.mag or 300 win mag

 

[sierraone]

There you go....someone on this forum always has the answer. But you suggested it yourself, if you do go to Africa with it to hunt, go with the heavier bullets for that caliber. The smallest caliber I have hunted with in Africa was a .375 HH, although I do own a .300 HH but only shoot it locally. Dead accurate but I shoot factory 180 grain ammo. Congratulations and good luck!

And welcome to our forum!

 

[fourfive8]

You'll need to start close to the 300 HH length of 2.850". Otherwise you'll end up with cases that are too short. 375 HH and 8 MM Remington Mag are two of the standard belted mag lengths that are 2.850". Another potential problem to consider is that reducing the caliber increases neck wall thickness. May or may not be an issue. Best bet is to use 300 HH brass from the beginning.

Here in the US at least it is available but you have to look around. Gunbroker sources average $50-75 per 20 or less if once fired. The Redding 300 HH Form and Trim die is about $50. I have no idea of availability for any reloading tools or components in Europe. New PRVI/PPU 300 HH brass is available here so would be one possible European source.

 

[TOBY458]

Yes, it can be done. Annealing the case, good lube and maybe in several steps.
RCBS has/had a forming die to do this.
Propably much easier to make from 7mm Rem.mag or 300 win mag

7mm Rem Mag and 300 Win Mag are a shortened version of the H&H case. So he unfortunately wouldn't be able to make the longer 2.85" case for 300 H&H from these two calibers.

 

[GuttormG]

Case length, forgot that!
300 weatherby will work, a rad shorter but it doesn't really matter (0,6m)

 

[Majo]

Thank you for the replies.

300wm/7rm will not work.

300wby may work... but I just have 150-200 pcs 375 h&h that could use if this work ok.

I like to use good quality brass... so will probably go with norma 300 h&h brass. I can source them in Germany for 88€ (105 usd) for 50 pcs. Not cheap but they should last me (unfortunately LOL) a couple years...

Keep the good info in the “30super” coming!

Cheers

 

[TOBY458]

Case length, forgot that!
300 weatherby will work, a rad shorter but it doesn't really matter (0,6m)

I just wonder if the sharp shoulder of the 300 WBY would be easy to remove? That sloping shoulder on the H&H is definitely much less defined than what the WBY has. Would be interesting to try.

 

[wswolf]

Hi there!

Long time reader, first time posting...

First of all, nice to be here and thanks in advance.

Question is easy... could I size 375 h&h (i have a bunch of once-fired cases) to 300h&h? I’m waiting to get a new (to me) sako finnbear... brass is expensive and hard to find, so will be nice to have a backup plan...

By the way, any feedback on the 300 holland will be nice. I’m considering to load sierra 165 game king hpbt (#2140) at mild velocities... but may be better to step up to 180-200 grains... I don’t care about recoil, but don’t need too much bullet for reds and boars in Spain... not planing to go to Africa yet

Thanks!!

I just tried sizing a .375 H&H case, which has been fired several times, in a .300 H&H die. A normal amount of lubricant was applied by rolling the case on a case-lube pad.. The sizing did not require great effort and the case formed perfectly. The length of the case increased by .025".

My favorite loads include 180 Nosler Partitions with H4350, H4831, Reloder 23, or Reloder 26 and 200 Partitions with Reloder 23, Reloder 26 or Ramshot Magnum.

Cheers

 

[Majo]

I just tried sizing a .375 H&H case, which has been fired several times, in a .300 H&H die. A normal amount of lubricant was applied by rolling the case on a case-lube pad.. The sizing did not require great effort and the case formed perfectly. The length of the case increased by .025".

My favorite loads include 180 Nosler Partitions with H4350, H4831, Reloder 23, or Reloder 26 and 200 Partitions with Reloder 23, Reloder 26 or Ramshot Magnum.

Cheers

Thanks for the info! Good news, then...

I’m worryed about neck thickness when sizing down from .375... may need turning...

Planning to load sierra prohunter RN 180 and the Gameking HPBT 165 too... over N160/N560 btw...

 

[Newby]

Necking down should lengthen the cases a little, not shorten them.

Neck wall thickness may be an issue, and should definitely be checked; but the only way to check this is to take some measurements before necking down, and again after necking down. Outside neck turning would sort that out if the necks end up too thick.

 

[Majo]

Necking down should lengthen the cases a little, not shorten them.

Trimming is not an issue... quick and easy.

But I was referring to turning the necks... let´s see if WSWOLF came by again and share some more feedback with us!

 

[fourfive8]

If all else goes well with sizing down... neck wall thickness can be checked with a ball mic. and that number can be compared to regular, new factory brass. The critical thing, however is that the loaded round have enough clearance between the neck and chamber wall for "easy" bullet release upon firing. Most consider .002-.003" to be OK but marginal with .004"-.008" in the range of average or normal for chambers designed for reliable hunting or tactical applications. Too little can drastically increase pressure. It only takes one out of a batch!! and not all brass thicknesses are uniformly equal within a batch. Also, any excessive sizing will work harden the brass in the neck and can shorten useful life of the case.

An easy check for chamber neck clearance-- Measure the neck diameter of a fired round, preferably one that has been fired a few times and/or with a full pressure load. Add .001" for brass shrink back after firing- that is about the diameter of the rifle's chamber neck. Compare that number to a loaded round. That difference will be an approximation of total clearance.

Of course you can anneal the neck and shoulder prior to sizing down to help in the sizing operation and to delay the effects of work hardening. If after reforming you find the neck wall thickness is too great, the necks can be turned down. Neck turning is not difficult but requires another couple of tools. It is tedious to do correctly, is time consuming and one of my least favorite case prep operations.

 

[wswolf]

Using a RCBS Case Master tool I got the following neck thickness measurements:
New Hornady .300 H&H - .012 to .013"
New Norma .300 H&H - .012"
Winchester .300 H&H formed from .375 H&H - .013 to .014"

Probably not a problem unless you have a particularly tight chamber.

fourfive8 wrote a post worth remembering!

 

[Arzie]

Well I have about a 150 rounds of .300 H&H brass that I want to get rid of and need some .375 H&H brass.

 

[Bob Nelson 35Whelen]

Yes, it can be done. Annealing the case, good lube and maybe in several steps.
RCBS has/had a forming die to do this.
Propably much easier to make from 7mm Rem.mag or 300 win mag

@ GuttormG
The 7mm and 300 are to short to form into 300 H&H.
You should be able to neck the 375 down to 300 in one pass on a good press. Keep a close eye on neck thickness but this can be easily fixed by dreaming or neck turning if needed.
Bob

 

[Bob Nelson 35Whelen]

I just wonder if the sharp shoulder of the 300 WBY would be easy to remove? That sloping shoulder on the H&H is definitely much less defined than what the WBY has. Would be interesting to try.

@TOBY458
I've tried necking down a 35 Whelen AI to standard Whelen with no success due to the shoulder. It came close but no cigar.
Bob

 

[tarbe]

Smart move to keep the Sierras at mild velocities. 308 level should be ok for the most part.

 

[Sabattiboy]

My 375 wildcat is based on the 300 WM case and up to the shoulder break is 300 WM. I went with a 30º shoulder then let the neck length shorten when necked up to 375. They came out 0.020 shorter then 2.620 standard 300 WM cases.
A couple of years ago, probably more like 4 years ago, 300 WM brass got hard to find so bought a bag of Remington 375 H&H to try. They had a lot of body taper to blow out and 0.250 to cut off. I used 14 grains of RedDot with a cotton wad to blow them out then fired with full charge loads. The cases were a little heavier then those made from 300 WM cases.
The most aggravating part was having to cut off that extra 1/4 inch. In desperation I discovered I could stick the case neck in a 1/2-13 threading die and use it for a cutoff guide with a jewelers saw then finish them with a case trimmer.
Someone said their kingdom for a horse. I'd give my kingdom for a lathe and mill.
And annealing the 300 WM cases was needed from that much neck expansion.
I found the new case neck position on the 375 H&H cases left about 1/16 length at the neck/shoulder joint that needed a few thousands turned off. It caused no problems if it was not done and I only discovered it when skim turning to true up the necks.
Then Ruger made a 375 that fit a standard action length and obsoleted my brainchild.
If I wanted to reset the barrel one turn it could be rechambered to the Ruger 375 and shoot factory ammo.

 

[Majo]

My 375 wildcat is based on the 300 WM case and up to the shoulder break is 300 WM. I went with a 30º shoulder then let the neck length shorten when necked up to 375. They came out 0.020 shorter then 2.620 standard 300 WM cases.
A couple of years ago, probably more like 4 years ago, 300 WM brass got hard to find so bought a bag of Remington 375 H&H to try. They had a lot of body taper to blow out and 0.250 to cut off. I used 14 grains of RedDot with a cotton wad to blow them out then fired with full charge loads. The cases were a little heavier then those made from 300 WM cases.
The most aggravating part was having to cut off that extra 1/4 inch. In desperation I discovered I could stick the case neck in a 1/2-13 threading die and use it for a cutoff guide with a jewelers saw then finish them with a case trimmer.
Someone said their kingdom for a horse. I'd give my kingdom for a lathe and mill.
And annealing the 300 WM cases was needed from that much neck expansion.
I found the new case neck position on the 375 H&H cases left about 1/16 length at the neck/shoulder joint that needed a few thousands turned off. It caused no problems if it was not done and I only discovered it when skim turning to true up the necks.
Then Ruger made a 375 that fit a standard action length and obsoleted my brainchild.
If I wanted to reset the barrel one turn it could be rechambered to the Ruger 375 and shoot factory ammo.

Sounds like a very nice project!!

By the way... i finally get 50pcs of shiny brand new Norma 300hh cases... and a box of factory Hornady 180 gr interbond... I have plenty of cases now... just run a few rounds to try the rifle, some factory and some Sierras 180PH over a mild charge of VV N160. Looks nice!

I´m giving the rifle some care (action bedding, change scope, etc) so no really started with load development...

I keep my supply of 375HH cases for my BRNO 602 375 rifle and the "emergency" of urgent 300hh cases needs...

Will keep you posted...