"Big" just keeps getting bigger.............. loads for the 7 mm RM and the .338-378 WM - Part I

I’ve been dragging my 7 mm RM around for almost 15 years. It’s aRemington 700BDL with a 24″ barrel and a really funky Tasco “distance estimator” 3X9 scope. With inexpensive Remington Core-Lokt® ammo, it can shoot 3/4″ 100 yard groups all day long and the discount store scope has the sharpest image of any scope I own, including my new Leupold Vari-X III. 

When I brought the 7mm RM on it’s first outing on a Pennsylvania hunting trip, it’s presence was met with curiosity, and comments suggesting it was “too much gun” or, “a gun for extreme range shooting”. Today, the 7 mm RM is considered mundane, routinely ranked just a little bit above the .30/30, but mostly below 3,000 newer cartridges, in ballistic performance. Fortunately, I’ve grown really attached to this great shooting rifle, and go on the assumption most animals don’t read gun magazines, so they don’t know the 7 mm RM is now considered ineffective on larger North American game.

I also like the Remington company. Last year, when I began to have difficulty extracting fired cases with 175 grain loads, I sent the rifle back to the factory. It was returned around 6 weeks later in perfect working order, as a “no charge” repair. The indication was “Head spaced okay, polished rough chamber. Extraction checked normal”. Seemed like a very polite way of saying, “Get a chamber brush, dummy, and try using it every couple of hundred rounds or so”. I took it right up to the range, loaded up my cheapo ammo, and shot several three shot groups of less than 3/4″. Life was, once again, very good.

In current literature, the .280 runs close to the 7mm RM performance in factory loads, and in many current reloading manuals. I don’t think the 7mm-08 is all that far behind. But the more I look at older manuals, the more fps I discover. First I thought it might just a case of over enthusiastic reporting in older manuals, then, I noticed the older the manual got, the more larger powder charges appeared in the load tables. Could the 7mm RM be the victim of ever increasing product liability concerns, or just evolving safety standards ?

The 7mm if a shortened, blown out and necked down .375 H&H. It should have enough powder capacity to deliver solid, long range performance over a  120 – 175 grain bullet weight range. One of the goals of this short series, is to come up with a reliable 3,200 fps 145 grain load and a consistent 3,000 fps 175 grain load. Accuracy should be consistent with the 3/4″ groups the rifle currently shoots with Remington factory ammo. I would guess I’ll find part of the answer in one of the early edition reloading manuals, and the balance in slow burning powder like IMR 7828 or Reloader 25.

I don’t know exactly how I arrived at a decision to buy the Weatherby, but I know I’m glad I did. I think I’ve just gotten to the age where I don’t worry about what magazine articles suggest, or what other people think, and I buy what I believe will be fun to shoot. For the guys out there who have decided to carry a .30/06 or a .270, or at least tell everyone else they should,  because “that’s all you really need to hunt anything in North America”, I suppose that’s a valid choice, but they probably don’t know how much enjoyment they’re missing.

The Weatherby is a more practical rifle than my Remington – now there’s a surprise. It’s lighter, has a weather proof fiberglass stock and stainless steel metal parts. I don’t have to worry about wood expanding in wet weather and altering point of impact, or brush scratching up a high gloss finish, or finger tip acid marring a blued finish.

I now know, from first hand experience, the Weatherby doesn’t kick like a mule, with or a without muzzle brake, and it doesn’t bark any louder than other large capacity centerfire rifles. In fact, the .338-378 is more pleasant to for me to shoot than my 7 mm RM. Don’t know why, it just works out that way. Maybe Weatherby, based on a long standing tradition of producing oversize magnum cartridges, figured out how to optimize the rifles that use them.

On the obligatory Fc3 (Freudian cartridge comparison chart), the .338-378 reigns supreme. The .338-378 is based on the Godzilla size.460 Weatherby case. Other Weatherby Magnum cartridges based on the same case are the:.30-378, .378, and .416.  The rest of the Weatherby line is based on various full length, and shortened version of the .375 H&H. The difference in case diameter is .562″ compared to .511″.

Is there a practical benefit to a cartridge case the size of the .338-378 ? I believe so. Case capacity, particularly when filled with the newer generations of slow burning powders, can result in significant velocity gains, without proportional increases in chamber pressure. Therefore, a .340 Weatherby should outperform a .338 Winchester, and a .338-378 Weatherby should outperform a .340 Weatherby. But many articles seem to favor the .338 Winchester over the .340 Weatherby cartridge. They almost always concluded with the statement, “100 fps or so difference isn’t worth it. The .338 is a more efficient cartridge”, or “both cartridges can be reloaded to almost the same performance levels”.

I’m not sure what logic drives these types of comments. 250 fps is a lot of difference, particularly for the .338 caliber and 250 grain bullets. When a cartridge is designed with knock down power in mind, it would seem increased speed and resulting 800 ft/lbs. of increased muzzle energy would be desirable. If you leap frog from the .338 Win Mag to the .338-378, the difference is almost a ton. To most people, if the bullet manufacturer has done his job, velocity and mass mean everything.

KE = velocity2 x bullet weight
        450400

Of course there’s the alternative “Bob’s math project – The study of holistic mass movement prediction systems”, which qualifies a cartridge’s power as an exponential expansion of the gerbil factor, as driven by Bob’s matrix of pre-selected mathematical constants. As an example, a 2 gerbil rating really kicks ass, but a 4 gerbil rating is close to nuclear energy. This system works particularly well for handgun shooters, who are desperate to find any logical basis for calling a handgun “Powerful”.

In some respects, the .338-378 is a puzzle. Here’s a relatively new production cartridge, or not so new wildcat, with probably 25 grains more powder capacity than the .340 Weatherby. Yet the published factory load difference between the two cartridges indicates only a 100 fps pickup by the .338-378, over the .340. But when I went to the reloading manuals, and published data for the cartridges, none put the .340 with a 250 grain bullet over 2960 fps, but several showed the .338-378 over 3160 fps. That difference is another 200 fps and 800 ft/lbs. of energy. Looks like Weatherby is scoffing at it’s own products. What gives ?

And what about cartridge efficiency ? Well…performance cartridges are like performance cars, it always cost increasingly more, to get increasingly less, but the goal remains the same – go faster. So you spend $1.80 more per box in powder to reload the .338-378 over the .338 Winchester. Big deal. Either round would end up in an expensive rifle, to be taken on an expensive hunting trip, where you would probably use one to put away significant size and, maybe, dangerous game. What else would a buck eighty get you that would be worth more than this extra measure of cartridge performance, a Big Mac ?

Contrary to claims of rapid throat erosion, I don’t believe these big rounds are any tougher on equipment then some of the smaller rounds. I just don’t see how a 250 grain slug moving down a stainless barrel at 3,100 fps could ever produce the wear and tear of a high capacity .224 or .243 pushing 3,600 fps – 4,000 fps, especially when the smaller rounds are accompanied by higher pressures and temperatures. If you don’t believe me, get out in your driveway with a pressure sprayer. With a fan of water and less than a 1000 PSI, you can clean your car tires. Narrow the stream at the the nozzle, crank pressure up over 4,000 PSI, and you can cut boulders in half.

So I’m concluding I can find a high velocity, long range .338 round in the Weatherby. A round that’s cost effective to reload, offers significant performance advantages over factory ammo, and is relatively easy on the equipment.Which takes me to the next goal of this series – To create a 250 grain load for the .338-378 that would be 450 fps faster than the .338 Winchester Mag, and at least 200 fps faster than the .340 Weatherby Mag. That would be a MV of approximately 3,150 fps. This is without pushing pressures, and without throwing away accuracy. Between the 7mm RM and the .338-378 I should be covered for hunting anything on North America.

These goals are not without conditions: Free bore in excess of 3″ is to be considered excessive. Rifles must be able to fire 3 rounds in relatively quick succession, without requiring a stock fitted with a hand guard. No acceptable round should result in the interior of any bolt being filled with molten brass and/or primers. Magnetic fields my not play a role in projectile acceleration, nor may the acronym SERAPHIM apply to any phase of the project.

I accept the reality that people will expect qualification and quantification of each step of the process. A log book might accomplish this end but, then again, that would just be me writing stuff down. If I got a little discouraged on an off day, I might decide to just pencil in the results, then flash a picture of the log as substantiation. I also thought I might not get by with “one-one thousand, two-one thousand,…” as a muzzle velocity timing method, so I picked up a small chronograph from Pact. Inc. that I will use to document either my success, or lack of the same.

The Pact was an easy purchase. I thought I would get a few huge boxes, sky screens just sounded really big, but everything came in two small packages. The blue priority stickers means I waited until the last minute to order the equipment, the “second day” designation means I practiced a great deal of restraint. This inclusion of this picture means I have the potential of “running short” with this article.

Packed inside one carton, was a small plastic console, with built in printer. You can probably see the paper tape, but not the columns of numbers. The data basically suggest that if I can push the .338 slug to 5,000 fps, I’d be point blank out to around 3 miles.

As near as I can tell, the most challenging part of this entire process will be getting bullets through these two “V” shaped skyscreens, without actually shooting the little suckers. Since they will only be 8′ from the muzzle, It shouldn’t be too difficult, as long as I take parallax into consideration, don’t shoot too low, and avoid hitting the tripod I borrowed from my camera.

The red bar that holds the sensors and shooting guides is heavy gauge steel. The shooting guides are, intentionally, flimsy plastic to survive a marginal hit, or be cheap enough to replace if hit dead on. While the reloading bench top would definitely be more convenient to work on, I anticipate moving all of this up to the range, just as soon as I have enough ammo prepped for testing.

Why the Pact, and not a Chrony or an Oehler ? Well, the Oehler seemed a little dated, held less shots and strings in memory than I would like, and was relatively costly, for what amounts to pretty average equipment. Chrony did a great job of putting everything into one fold out case, but I honestly wondered why. There’s all of this expensive timing equipment sitting in the bullet path right under the skyscreens, along with the data display, which is out of range for reading. I just thought somebody didn’t have their thinking cap on the day this one was designed.

I did think the Chrony light kit for indoor use, and memory upgrades, might have been a reasonable tradeoff, but then I tried to  place an order: “Do you ship from stock ? …inventory ?”. Response, “What does that mean ?”. “Do you actually have finished units at your location that you will be able to ship, soon ?”. Response – “What model ?”. “Why don’t you tell me what models you have so I don’t have to guess my way through the whole catalog ?”. Conversation, conversation, conversation…..blah, blah. 

“Great, you have the only model in stock I don’t want. That’s okay, can you ship it today?” Response, “We only ship on Wednesdays”.   Of course, how did I forget that Wednesday is the nation’s officials shipping day. “Fine, I’d like the unit to ship overnight on my Fed-X account”. Response, “We only ship UPS and not through customer’s accounts”. Quick interpretation, “We only ship on our UPS number so we can not only bag you on the product, but also get a 50% kickback from an intentionally over inflated UPS shipping charge”

Finally I just said “Screw it”, hung up and purchased from a company that could at least pretend to be happy to get my money. In any comparison of several brands of chronographs, Pact has done very well, and user reviews of the Pact have been very good. I’m sure, just the added security of having the expensive electronics in a box beside me on the bench, rather than out in front of the muzzle, will prove this to be a correct decision.

Regardless the brand selected, I figured inaccurate readings would be the least potential problem. I know that sounds silly when discussion chronographs, but there isn’t much black magic in CPUs and controller chips and, I figured, at an advertised circuit speed of 4 MHz, we’re working with some relatively mature technology. I assume the trick with chronographs is matching sensors, and tuning software, to cover as many ambient light conditions as possible, in an effort to minimize false readings resulting from: clouds, dust, muzzle blast, small birds and bright reflective moly coated bullets. What have we leaned so far ?

• BB’s from a pump Crossman travel at 526.4 fps
• Tuna, accelerated through a straw, drops 1,024″ at 25 yards
• Green peas can be detected by a skyscreen, above 200 fps
• Spit is not detectable at any speed
• Skyscreens are not water proof
• I really need new friends

On that note, I’m going to work up the test parameters and material list for the project, and get to work on the next segment. Hopefully we’ll get a range day in, and collect some baseline performance of over the counter ammo for both rifles. There’s always the chance I can’t get to the numbers I’m looking for, however, may factory velocity assumptions may be all be unrealistic. So if we find out the whole world is actually running slower, we’ll just modify our objectives and look for relative improvement.

Thanks
Joe