RE: Magazine Length for Winchester Model 70 Safari Classic in 375 H&H Mag

[sandman0921]

I just posted reloading data for my Ruger M77 Hawkeye in 375 Ruger using RL 17 and 300 grain Barnes TSX bullets. That load development is coming along well, and I'm set to load up another batch of cartridges with varying seating depths to fine tune group size...

Having some time off has sparked an interest in some rifles I've put away in the safe for a while, and needed to develop hand-loads for, but have put off. As I've posted before, I purchased a used Winchester M70 Safari Classic in 375 H&H Magnum a few years ago that was one of the New Haven, CT guns made in 2002. I had it completely reworked including action truing, re-barreling (in the same cartridge), new NECG front/rear sights and barrel band sling swivel, as well as re-bluing all of the metal to match. I had previously installed a Timney trigger and Williams bottom metal before I sent it off. It was also previously re-stocked by Accurate Innovations in a beautiful piece of AAA/Fancy English walnut. Everything looks beautiful and this rifle really is a classic now, however, I overlooked one important thing, and I wish I had thought of this before getting the rifle back. The factory magazine box is too short.....

As I said before, I hand-load, and my intention was to load this rifle as an all-around African rifle utilizing the Barnes TSX 270 grain bullets in order to gain a little more range if needed. I was going to utilize Alliant RL 15 for the powder. Today, I began by checking chamber measurements with a Sinclair Seating Depth Tool to determine the max COAL when the bullets are seated all the way out to touch the lands. As a starting point, I then seat the bullet 0.050 inches deeper, as recommended by Barnes technicians, as a starting point to give the long Barnes TSX bullets adequate jump to the lands. I do the same thing for all of my rifles regardless of caliber, because....well just because I'm OCD when it comes to reloading, and I want to know my individual rifle's measurements.

SAAMI specs call for a max COAL of 3.600 inches in the 375 H&H Magnum. And, with Winchester M70 Safari Classic rifles being factory produced rifles, the maximum length of a cartridge that will fit inside a Winchester M70 Safari Classic rifle in 375 H&H Magnum is 3.60 inches, absolutely nothing more, at least by my measurements. However, in re-barreling this rifle, my max COAL could be 3.771 inches, and my starting seating depth was going to be 3.721 inches for the Barnes TSX 270 grain bullet. Not gonna happen.......

So......I've had to set my Redding seating die to produce a max COAL of a hair under 3.60 inches so that my rifle doesn't effectively become a single-shot rifle. I only wish I would have though of this while my gunsmith had the rifle, and we could've fixed it. I know Barnes TSX bullets like a lot of freebore to start, and we'll see how these loads do, but I wonder if almost 3 times more jump to the lands as is recommended by Barnes (to start) is going to effect accuracy? Maybe.....maybe not....only testing will see. But, I wanted to recommend to everyone, if you are getting a custom rifle made, magazine box length is definitely something to think about if you hand-load.

There is a solution. For the Winchester Model 70 Safari Classic in 375 H&H Magnum, Wyatt's makes an extended length magazine box that will supposedly allow for a max COAL of around 3.825 inches or so. However, it requires milling off about 0.125 inches of the magazine cut-out on the bottom of the receiver, as well as shortening the factory bolt-stop by 0.110 inches. They do make a replacement bolt stop that has been shortened. An easy fix, for a competent gunsmith as long as you let him know before hand that you may want to load for cartridges that are longer than SAAMI max lengths. I'm not sure if other manufacturers like Duane Weibe, etc. make extended length mag boxes.....

For right now, I will probably let it ride and see how the rifle performs utilizing the OCW technique of Dan Newberry. If accuracy is not up to par, I may send the barreled action back to my gunsmith to let him perform the modification for a Wyatt magazine box. However, I have to temper my expectations with the realization that this is not supposed to be a bench-rest rifle capable of shooting bugholes at 1000 yds. Anything at 1 MOA or under, and I'll be happy.

Just thought I'd share this as food for thought in case someone was going the route of having a custom rifle made. It's a question you may definitely want to ask your gunsmith.......

 

[PHOENIX PHIL]

My M70 .375 was made after the FN purchase and was made in the SC plant. So perhaps not a good comparison for expectations, but it's the one rifle I've done absolutely nothing too. It is as it was when it came out of the box. The loads I have for it fall in line with expected velocities and are very accurate.

So yes.....give it an honest go before putting more $$$ into it would be my recommendation too.

 

[sandman0921]

Phil,

I agree. My expectation is that it will shoot just fine.......at least that's my hope because otherwise I've invested a lot of money into a rifle that looks much nicer, but performs no better than it did prior to the upgrades. Like I said, I have to remind myself that this rifle is not a long range tack driver......I will be completely satisfied if I can maintain MOA or less (which should be easily accomplished) at 200 yds.

This was really more of a "Mea Culpa", and demonstrating that despite thinking you have thought of everything regarding a rifle build, sometimes the little things sneak up and bite you. My hope is that if an item like this (extended length magazine box) is important to someone building a rifle, that this will trigger them mentally to say, "I need to make sure my gunsmith knows this....".

If you're shooting factory ammo, then magazine length shouldn't be an issue. However, if you are a handloader, then it very well may be if you want to seat your bullets out closer to the lands, and thus extend the COAL past max SAAMI specs. Like I said, I could really see this being important in, for instance, a rifle being designed as a long range sheep rifle, etc. When shooting past 500 yds, every little bit of help as far as accuracy counts......

Of course despite the fact that I have "rung steel" at 500+ yds, I don't ever take a shot at an animal at that distance. My own limits I set mentally every time I go into the field......

 

[njellis]

I did the exact same dadblasted thing, with a new M70, rebarrelled by Lee Christianson and trued/fitted/restocked with a D'Arcy Eccols Legend Stock, through Hill Country Rifles. Wouldn't you know, I forgot all about the magazine? Oh well, we'll see how those barnes bullets shoot when jumping an extra .15 to the lands.

 

[sestoppelman]

Probably shoot fine, but it seems to me this is the kind of thing the smith should point out to the customer. Like "do you really want all that throat with a short mag box?"

 

[ZG47]

Probably shoot fine, but it seems to me this is the kind of thing the smith should point out to the customer. Like "do you really want all that throat with a short mag box?"

Precisely. Did you go for a nonstandard chamber?

 

[sandman0921]

Precisely. Did you go for a nonstandard chamber?

ZG47,

No, I didn't specifically ask for a "non-standard" chamber measurement, and simply left that up to the gunsmith. I don't think a long throat/leade is as uncommon as one might think. For instance, Weatherby Mark V rifles are very well know for having long throats, ostensibly to minimize people from causing over-pressures with the hot Weatherby loads. It's well known enough that Nosler puts a disclaimer in the pages of their reloading manual with their load data for the Weatherby cartridges to say don't even try because the COAL will be too long for the magazine boxes. Another rifle I have, which is a bone-stock Winchester Model 70 Supergrade in 270 Winchester that was made by the FN plant in Columbia, SC, has a very long leade. I don't specifically remember how much, but I think it is well over 0.15 inches long based on repeated chamber measurements. I do know that to seat the Hornady (0.277) 130 grain SST's to within 0.010 inches of the lands, which was going to be my starting point in load development, the COAL was going to be way over the maximum allowable OAL for the factory magazine box. I've also seen discussions on reloading forums the CZ 550 rifles have this trait as well.

Probably shoot fine, but it seems to me this is the kind of thing the smith should point out to the customer. Like "do you really want all that throat with a short mag box?"

sestoppelman,

I suppose so but I'm sure a lot of gunsmiths are guilty of not thinking of this, or at least not worrying about this phenomenon, as well. I really don't know. I imagine that the chambers are cut to SAAMI specs with the thinking that shooters will use the standard COAL? Even in some of my long range mountain rifles, I don't really ever remember discussing this with the gunsmith (a different one). Luckily the magazine boxes accommodate the COAL that I want......

It may be that since this is a 375 H&H Mag, and not intended to be a rifle designed to shoot animals/steel to 500+ yards that it doesn't come not play. Not being a gunsmith, I don't know. I have yet to start load development with this particular rifle, as I am still in the process of fine-tuning the load for my Ruger M77 Hawkeye in 375 Ruger.

Once I start, I will update the forum, but my hope is that it won't matter too much. As long as the rifle can shoot MOA/sub-moa, I'll be fine. Previously before sending it off, I could get close to MOA but reach it, and certainly not best it....

The main point of posting this was for those that are considering, or in the process of, having a custom rifle made, if you think a longer COAL might be important, it would be worth considering discussing this with your gunsmith.....

 

[Ray B]

I had a 300 H&H M70 rebarreled to 375 with no changes to the action. As noted, the OAL is 3.6". My go to loads are the Sierra and Bitterroot 250 grain bullets, so I can load just short of 3.6 and have effective accurate loads. To get more horsepower, primarily to shoot the Sierra 350 gr HPBTM bullet, I went with a 375 RUM, but as noted, lengthening them way out results in a single shot- but for targets at 1000 yards, single shot is not a problem.