I've got a Pre-64 model 70 Magnum length action that was previously chambered in 375 H&H, and I want to rebarrel it in a 300 Magnum.

Now the question is...

1) build a 300 Win and throat it so the bullets could be seated to 3.562" ?

2) or build it in a 300 Weatherby?

Kind of depends on what you are after.

If you want a most performance .30, the .300 weatherby or .300 RUM.

If you’re more after an American magnum that you can use anywhere the .300 win mag will give you the option of factory ammo, but with a long mag box you could get a bit more performance.

If it’s just a hunting tool, I’d do the bee (or RUM option, which is what I did) for most point blank range.

A .300 win (or .300 H&H) will probably preserve resale value best.

Pretty much what Dr. Butler says.
Depends a bit on what your intended use is. I had a lighter weight 8 1/2 lb .300 Win Mag 24” barrel pre64 Mod70 glass stocked when I was primarily sheep and mixed bag hunting including grizzly. Then I went to one of D’Arcy Echol’s short throated .300 Weatherby’s on a G series Mod70 with a 26” barrel done up by Gene Simillion with one of D’Arcy’s Legend stocks and parts. I still have that rifle and it’s been primarily used alot for western hunts for elk and mule deer. My son used that rifle in Zimbabwe for 8 animals. I have a wood stocked Dakota 76 .300H&H with a Krieger barrel that weighs 9.2 lbs and it doesn’t seem to kick more than many .270’s. The main theme I have found on all the .300 Mags is they all have been accurate and the recoil at the bench is tolerable so you can really take the time to dial them in.

The 300 Win Mag should feed OK without any rework.

However the 300 WBY will require rework of the magazine box or a whole new special guard unit, plus rail work

The 300 RUM, lets say you do not want to go down that path with a Pre 64 action

J Wisner

A pre-64 M-70, if it's going to be rebarreled, screams to be done in 300 H&H. Anemic in factory loads but a screamer in hand loads.

I'll second Todd's recommendation to do a 300 H&H if you have a .375 length action. I agree resale will be much better if that's a "thing" with you. On the other hand I have all the .300 variants and there is not a nickels worth of difference in what the terminal performance is on big game. Go with your gut...

quote:

Originally posted by J Wisner:
The 300 Win Mag should feed OK without any rework.

However the 300 WBY will require rework of the magazine box or a whole new special guard unit, plus rail work

The 300 RUM, lets say you do not want to go down that path with a Pre 64 action

J Wisner

Thanks, Jim!

THAT'S the answer I was looking for... the path of least resistance for feeding.

Yes, I'll add new bottom metal (Blackburn or Sunny Hill.)

If I stick with the 300, will I need a 300 H&H follower, or is it the same as the 375?

Would the RUM require no rail work?

quote:

Would the RUM require no rail work?

The RUM requires rail work, custom mag box as well as opening up the bottom of the receiver. I just finished a 28 Nosler (similar to the RUM) on a pre-64 and ended up with several days into making the box and making it feed.

quote:

If I stick with the 300, will I need a 300 H&H follower, or is it the same as the 375?

It will feed with the same follower. The .300 H&H will be your easiest option. It may require minor tweaking but will likely feed without any changes.

I do not recommend using a 30-06 length belted magnum cartridge in a 375 H&H magazine box. The reason is, you may encounter rim lock. I have had 230 grain rounds slide in a 375 H&H, the top round behind the lower. The stupid belt on the top round caught the rim of the lower and prevented the top cartridge from moving. I had to pull the bolt back, push the stack down, which usually cleared the jam.

The belted magnum is a poor cartridge design for many reasons beyond this.

A 300 Win Mag is shorter, unless you can find the short magazine conversion parts, and the bolt stop short action parts, don't go that route. If the rifle proves unreliable in feed with a 300 Win Magnum, you have an expensive boat anchor.

I suggest, go 300 H&H Magnum. Great cartridge, smooth feeding, very accurate.









lubing the cases for first firing. The base to shoulder distance is not standardized for belted magnums. I do not want the front of the case sticking to the chamber, because the sidewalls will have to stretch for the base to reach the bolt face. This can cause case head separations on the first, second, or third firings. It is better to have the case slide to the bolt face, the shoulders fold out for a perfect chamber fit, and have a perfectly fireformed and stress free case.

Then after, bump the shoulders back about 0.003" in a sizing die.






Of course if you want velocity, and more velocity, I want to ask, what do you get with more velocity? Do the animals drop any deader? Does the increased velocity allow shooting at distances beyond the marksmanship level of the shooter? Does more really mean more?

I will claim that to drive bullets the same speed as a 300 H&H, the 300 Win Mag has to run at higher pressures, because the case is smaller. And things go bad faster at high pressures. It is an advantage to do the same job, at lower pressures.

No question, lots of wise people voted for the 300 H&H for a lot of good reasons, have to love the wisdom and experience of the AR community

Thanks for the input, but the 300 H&H is a non-starter.

I've owned a few, and they were fine, but I'm too heavily invested in Win Mag components.

quote:

Originally posted by new_guy:
Thanks for the input, but the 300 H&H is a non-starter.

I've owned a few, and they were fine, but I'm too heavily invested in Win Mag components.

New guy,
Not really sure what you are saying?
All 300 Mags pretty much use the same components; primers, bullets, powders. The only variables I see are a set of loading dies and simple brass.

300 Win. Mag. MK 248 Mod.1 chamber.
Coupled with a 1-8 or 1-9 twist barrel.
78gr of Retumbo puts a 230gr Berger out at 2900 to 3000 fps.
Coal is In the area of 3.560

quote:

Originally posted by 4WD:

quote:

Originally posted by new_guy:
Thanks for the input, but the 300 H&H is a non-starter.

I've owned a few, and they were fine, but I'm too heavily invested in Win Mag components.

New guy,
Not really sure what you are saying?
All 300 Mags pretty much use the same components; primers, bullets, powders. The only variables I see are a set of loading dies and simple brass.

I should have said brass and dies.

30-06---save your shoulder and powder and in reality give up very little.

I think leave that pre-64 action for a .375 and just buy a .300 Winnie. I saw one at a local establishment a few days ago. Old style Interarms Mark X .300 Winnie in really nice condition for $700 plus tax. You could put one of Wisner's 3 position safeties on it, spend the rest of your stash on a real nice scope or new binocs, and go hunting.

quote:

Originally posted by carpetman1:
30-06---save your shoulder and powder and in reality give up very little.

Magnum length with H&H bolt face. 06 cannot work.

300 Weatherby, I have one so I am bias, but I like it.

quote:

Originally posted by new_guy:
I've got a Pre-64 model 70 Magnum length action that was previously chambered in 375 H&H, and I want to rebarrel it in a 300 Magnum.

Now the question is...

1) build a 300 Win and throat it so the bullets could be seated to 3.562" ?

2) or build it in a 300 Weatherby?

Neither, build a 300 H + H

I can’t say how much work was required, but my custom .30 mag is a .300 RUM on a pre 64 M70 that Jim Kobe did for me. It feeds great, and is very accurate as long as I don’t push for absolute max velocity.

I would assume if you are having this made, they will make it feed.

My goal was with the .300 RUM I had a MPBR that was as far as I feel comfortable shooting at unwounded game. I was getting set up for Sitatunga hunting and the shots were possibly going to be up to 400 yards.

I thought about the .300 weatherby, but Jim talked me out of it. I had no interest in the .30-378, which was the only real larger option, and that wouldn’t fit in a pre 64 M70 anyhow.

Jim did really try to get me to use the .300 H&H as it is the classic cartridge, but I insisted on MPBR.

I’ve used this rifle on Sitatunga in Uganda and Mountain Nyala as well as elk and deer.

If you are after the goal of max PBR, the .300 Wby will be better than the .300 WM.

If you are married to the .300 Win, and want a P-64 really, I’d get a ‘06 length action as that is a bit more correct, but would cost you the mag box length.

The Weatherby or the .300 RUM are the long case (non Rigby) options for max velocity.

The RUM will require more work to get it right, but a top flight maker will get it to work flawlessly. It just might cost a bit more.

For my hunting, of your options, I’d go with the weatherby. If this is more a general use rifle, I’d get it in the H&H as that isn’t as overbore and specialized.

If you really are just after a bit more range and want a .300 win mag, then that’s the choice.

Most folks getting a nice pre 64 are after a classic rifle. I wanted a classic looking gun that did what I needed in the field. It costs more, and is definitely not an investment… but I’m happy with mine.

You are at the point of deciding what makes you happy. A custom rifle is a pretty big investment of money, so the more off the beaten path your desire is, the more you need to be sure that is what you really want. I will admit that most likely the resale of mine will be only a little more valuable than the cost of the action when I die/have to liquidate my collection of hunting guns.

I used to have a 300 RUM. I have a 300 WBY now. And I'm doing load development for my friends 300 Win Mag.

I have a NICE 1909 Argentine in my project cabinet. If I did a 30 caliber, it would be a 300 H&H. The 300 H&H is a very classic catridge for the pre-64 Win. Have been looking at a few to buy. You won't regret and the H&H really shines with with 200 and 220 gr bullets.

Another vote for the 300 H&H, with a tad of nostalgia, but I can reload mine to within 100 fps of the 300 Wby (another good caliber btw)...I like the taper of the H&H as a hot load will not stick as a rule, and they feed real smooth, but they eject even better...Don't headspace them on the belt, neck size fired cases until they feed lightly snug in "your gun" and brass last consideralby longer..

Just a great option for the handloader, not so much for the non handloader.

Im of the school that the 300 Win mag has too short a neck, and the 30-338 is what it should have been to start with...The RUM and those monster 30s are more blow than go, you don't get much for the buck...As we say in the horse business, its just proud flesh..

New Guy,
If you already have a ton of 300 Win brass, in these days of limited and super-expensive supply, I think that makes it a no-brainer.

My 300 Win is built on a Rem 721. With a 26" barrel, I'm shooting 180gr Noslers at 3250. It shoots flat and strikes a mighty blow.

Im a 300 H&H fan,always have been, but if you dont' reload, the 300 win mag is a poor choice, but most of the big 30s to the wby are fine..LIke the above poster stated, availability of components makes the win mag a intelligent choice.

+1 for the Holland's .300!

Not a fan of the Wby at all. I tried. Had 4 and dumped them all. Too much recoil for minimal gain and mediocre accuracy. No matter how hard I tried I couldn't get cloverleafs
with the Wby. If I wanted to I could actually shoot groups with either of my 2 Wins that could fit inside the Wby- both shoot one ragged hole. One built by Charlie Sisk on an M70 Classic, the other put together by Jim DuBell on a Pre War Mod 70. Same holds true for my 340 Wbys, one I sold, the other is being re barreled to a 3-7-5 H&H.

That being said if I were to build another 300 I would build an H&H to go along with my other Wins.

I think the majority of hunters advised you well - the solution is the 300 H&H. If you had the standard length action, I would opt for 308 Norma Magnum.

Its very easy to convert a std pre 64 to a mag action. My old 300 H&H was built on std action pre 64 by Dennis Olson, and I stocked it..Have done several to 300 H&H..