Home Forums Hunting & Shooting Custom Rifles & Wildcats 300 H&H Necked To 7MM

I've been googlin' around for quite awhile now to see if this has been done without any changes to the body but so far have come up empty handed.

Thoughts anyone?

Without "improving" the case, it would seem to be very similar to a 7MM Remmy. If you improve the case, it would be 7-300 Wtby.

No desire to improve.Just looking to see if it's out there and who has the reamer without going to the trouble of having one made.

Thanx, 284

284LUVR,

The 7mm Mashburn Magnum configuration is as you describe. I think Dober shoots one...jim

The .275 Holland & Holland Magnum was produced. A friend has a pre war M70 custom barreled for that round.

"The .275 Belted Magnum case is 2.50" long with a standard magnum rim diameter of .532". The neck has an outside diameter of .325" and accepts standard .284" (7mm) bullets. Cartridge overall length is 3.42", which means that long bullets do not need to be seated as deep in the case as with modern 7mm Magnum cartridges.

Original British factory loads gave a 140 grain bullet a muzzle velocity (MV) of 2650 fps and a 160 grain bullet a MV of 2700 fps. The Western (U.S.) factory load used a 175 grain bullet at a MV of 2680 fps and muzzle energy of 2810 ft. lbs. These loads seem pretty tame by modern standards because they were limited by the lack of suitable powders."

I got the above quote from Chuck Hawks site. I see the low velocity of the 140 gr.

Now THAT is a cool round! If I were doing a full lenght 7mm, though, I would go STW or RUM.

More 275 H&H here.

I should have included in my above post that I would like to keep the 2.850 case length but to do that it would seeem that the shoulder would have to be moved back or lose something in the neck area.The above 275 has a case length of 2.500.

I plan on rebarreling my 300 H&H and have always like liked the long streamlined look of the round as well as its greating feeding.

Maybe I'm looking for something that does not exist.

A friend has a 7mm/8mm Remington mag reamer but that isn't what I am looking for.

Thanks guys and keep 'em coming.

The .280 Halger Magnum might interest you. Its of magnum length, has body taper and is really a better round than any of the H&H's as it headspaces on its shoulder.



.280 Halger Magnum

I bet getting brass for that baby is fun.

Terry

Well, the original 7mm Mashburn Magnum was on the .2.85" case, and there was a second version on a shortened case. There numerous variations on shorter cases. Mashburn reamers are available.

I would find a photo of an original Mashburn case to see if that taper is what you like. The shorter cartridges usually have less taper than the original H&H case.

jim

It seems like the 7mm STW would provide then very best means to an end in this particular case.

Why take the long way around the barn?

AD

The .275 H&H and the .244 H&H were a necked down .375 H&H as the .300 H&H had a different, more shallow shoulder angle. FWIW I know a collecter here in the Denver area that has a pre-war M-70 from the Winchester custom shop chambered in .244 H&H. Has Original custom shop letter and invoice etc... It is something to behold, but in the end is nothing more than a collectors piece.

Some of us just love that long tapered case and its a one of a kind nothing else resembles it except maybe a 22 hornet,one of the easiest chambering rounds I know of and pretty dog gone good shooter to boot,YE HAW for the 300 H&H magnum,there were some guys about a year ago working on the idea of necking it down to 7mm and even 6.5mm either here or on accurate reloading,they were looking for guys to jump in and split the cost of the chamber reamers and what not,they even had model cartridges up to inspect in pictures and they even looked like their ol pappy the 300 H&H,it had my curiousity up...............

284 luvr-sorry it's taken me a while to get to you on this, that darn making a living thingy can get in the way can't it...!

I can email you a pic if you like of the 7 Mashburn Super version that I use, and it was the most common one used of the 3 by far.

And if you wish you could then put up a pic on here for others.

Long and the short is that I could make cases out of the old H&H , that's how they used to pre 300 Winnie. Once the Winnie came out people just used that case to begin with.

From there it is a easy two stage forming die and a full length resize and then a fire form. Although my fire forming load (IMR4350 and a 139 Horn flat base) is so darn accurate and runs at 3220 fps that I could just hunt about all with this load.

I don't know if any of this will help you but I'll help if I can.

Dober

(if you wish, pm me your phone # and I'll give you a call)

Dober, PM on the way.

Might be fun for the rest of the crew to see the pics if you can post but I will include my e mail addy as well.

Savage 99, Thanks for the great pic and the links.

I sure do like the 300 H&H and the shape of that cartridge leaves me weak in the knees.

I'm going to rebarrel my old Model 70 and as I have an affinity for the .284/7mm bullets I thought I could kill two birds with one stone.

If I have to have a reamer and dies made I will but I'm sure this has been done before.

I have spent some time thinking about your request and 7mm cartridges in general as I like that bore diameter as well.

Let me ask you a few questions and then perhaps we can zero in.

Is your action set up now for a 3.6" long magnum cartridge or would you spend the $$$ money to make it so with no problem?

Do you mind the headspace problem with factory belted magnums?

Do you mind form die work and case prep to this extent?

On one hand the 7mm Mashburn Super has history behind it what with Bob Hagel and Warren Page along with others favoring it.

On the other hand there are factory rounds, none of which please me 100%, that are a lot easier to "just go hunting with".

I don't have any final suggestions. Just respond if you will.

Savage 99

My action is indeed a mag length action.

If I can't find an existing example of what I am looking for, it would be very simple to modify the reamer as to NOT cut for a belt or to have a reamer made in that configuration.

No big deal to remove the belt from the brass on a lathe.

Used to have a 240 Weatherby set up that way and have seen several 300 winchesters set up that way.

Having said that, the belt really isn't an issue for me.

Just thought a nice SLEEK 7mm version of the 300 H&H would be fun to do and it would probaly wind up being similar in velocity to a VERY VERY hot loaded 7 Remington mag .