Home Forums Hunting & Shooting Long Range Hunting 7mmx300WinMag

BobinNH:

Thank you very much for taking the time to reply and share your data. Sounds like a dandy of a cartridge. Any experience with a 7 STW or 7mmx.300 Wby to compare to the Dakota?

-Ian

The info about the dies is good to know. Thanks for your take on the matter.

I keep jumping back and forth between a big 7mm and the plain 300WinMag or 300WbyMag, as this one is going to be just a hunting rifle.

JBM yields some interesting info:

Allowing for a 7" vital zone and zeroing for Max Point Blank (about 300yds +/-), the big 7mm's look pretty good both near and far.

400yd performance of 300Wby with 155 Scenar at 3,450FPS.
Drop = 6.9"
Wind = 8.9" at 10mph
Vel = 2,630FPS

400yd peformance of a 7mm with 162 Amax at a "lowly" 3,200FPS.
Drop = 8.7"
Wind = 7.5" at 10mph
Vel = 2,590FPS

At this range, the 7mm will drop about 1.8" more but drift about 1.4" less. Impact speeds are nearly the same with the Scenar being 7 grains lighter and starting out a full 250FPS faster. It looks like the .30 cal doen't hold onto its velocity edge for too long, which is interesting considering that few folks shoot game animals out past 400yds. If they do, the comparison gets way uglier. I knew that speed is fleeting but BC is forever, still I didn't realize it would matter as much in instances inside "normal" ranges. That 162 is something....

Jpro: That has always been the attraction of 7mm's....that 162 is the ballistic equivilent of a 30 cal weighing (what?)...200+ grains?,which is really the right comparison.And how much powder do you have to burn in a mag 30 to get that heavy 30 cal bullet to 3200 fps?

Answer.....a lot;along with the recoil.

If you want to go "light" with the 7mm I know the Dakota (Mashburn, 300 WM case,etc)will likely start 120TTSX at over 3500;just a junior version of that 300 Weatherby load you cite.

Actually a garden variety 7RM will start a 140 BT or AB at 3250,and with the 300 yard sighting you list above,will only be down 8-9 " at 400,and about 26" at 500.If you are going to shoot light bullets, I would not bother with a necked down 300 Mag,or Mashburn, etc.It is just not worth the effort and expense of a wildcat.

The Nosler manual shows loads for the 7mmRM of 3300 with a 140, so a 300WM necked down is not worth it;neither is the Mashburn. The real advantage of the larger cases is with the higher veocity of the heavier 7mm bullets.

The figures look correct based on 300 yard zero....even a crummy 160 gr Nosler Partition started at 3200 will only be down about 9" at 400 from a 300 yard zero.

For chuckles, run a 175 Partition (BC 519) at 3100 or so, against a 300 Weatherby with 180's at 3200.It hangs pretty close....and it takes a lot less powder in the 7mm(about 73 gr in my rifle),to get the 175 to speed.

Despite the din over real LR shooting, I have never had to go beyond 400 for my BIGGEST bucks;most were half that distance or under.

Flipping through a few manuals and looking at the 7RM, 7mm Dakota, 7STW, etc., I did find where Hornady's last manual (2006-2007?) showed 3400FPS with 140's and 3200FPS with 160/162's when loading for a 26" factory 7mm Wby Mag. That sounds like a lot of performance from that case, although I hear 3450FPS fairly often from guys shooting factory 270 Wby Mags with 130's. I'd imagine the Mashburn or 7mm/300Win could make those numbers without straining quite as hard, considering the slight bump in case capacity over the 7mm Wby Mag.

Jpro: As usual, you're very observant...

The 7 Weatherby case is about the same size and capacity as the 7RM (although you hear different things from different people on that,all you gotta do is look at the two cases)

The 7Weatherby gets its velocity advantage from three factors:Longer throats(freebore,really), generally longer barrels(most data is 26" as are most rifles),and factory and manual loads at higher pressures.

In contrast to the 7RM,which, while loaded to 06 length as well, is not loaded as "hot in factory ammo;and manual data reflects the same(Federal told me they load to 58-59,000 psi.

Lines can get hazy when conmparing the 7RM, 7Weatherby,and Mashburn.

I have several times had 7RM's made up with leade/chambers cut to accomodate 160's and 175's with bullet base seated to base of neck,ie longer than factory standard.....my loads and velocities then nudged up to 7mm Weatherby vicinity,not quite so high because I was unwilling to load that hot....but close.

The Mashburn is not hugely different than the other two,gaining its' velocities from slightly more capacity(slightly longer case and blownout a bit) than the Weatherby amd Remington,and longer OAL than either...

Also keep in mind that established velocities for the Mashburn, and lots of data that hangs around from Page and Hagel, were from 22" barrels in Page's case, and 24" from Hagel,who also worked with a 28" Ruger +1...

A lot of this is the reason why you see guys on here say the 7RM is not that "fast"...they are not wrong, but are often working with shorter SAMMI throats, short cartridge OAL,and are not loading to Weatherby pressures.It's throats and barrels....

The Mashburn sort of strikes a good balance (from what little I have seen so far)....enough small but important things conspire to provide just enough more capacity to provide the velocities Dober has stated here; and that I am seeing from two rifles back here,in 24" tubes...ie very easily hitting 3075 or so with the 175 gr bullet;and 3150 to 3250 with the 160's.I know Docbill on here is also getting 3250 with 160 and RL25;my pal, Matt gets it in his rifle with Retumbo.

And don't forget that we have powders that Page and Hagel did not....mostly they used WW II H4831; we have things like Retumbo, RL25, H1000.

Jpro, if you will drop me a PM with your email address,I will forward Bob Hagels article from Rifle Magazine on the 7 Mashburn, which is a great read and explains the cartridge and comparisons to the other 7 mags, better than I can. I think you will like it.

That would be much appreciated! Sending a PM......

JPro-if you decide to build a Mashburn feel free to get ahold of me for some load data. My 3rd barrel with the round is about toast and I have a load or two you could try.

If you build it, it'll quickly be one of your favs, especially when you begin to stretch out the ranges a bit.

Dober

In Hagels article, which also appears in the Big wildcat book from Wolfe publishing, he states that when the 7 Rem is throated for 160's seated to the base of the neck the Mashburn and 7 Rem are about 100 fps. different when loaded to the same pressures. The 7 Rem. is a lot better than most think if throated/loaded properly. I use 7 Roy data as my gold standard because the Mashburn is about 4 gr. water capacity different but the Weatherby has freebore. A swap out in my estimation.

Warren Pages obsession was with sectional density and BC and for a kicker he despised recoil because of its deleterious effects on shooter performance. He always sounded SOOO right to me. A technical genius with a PRICKLEY personality.

Dober taught me ....

Appreciate the offer and will certainly keep that in mind. I've got no real "Long-Ranger" in the stable at the moment.

Gotta modify that JPro, everyone needs a big dawg driver in their bag...grin

Dober

Why not the 7MM UM? I have one in a Sako & its a great long range round. Shoots at greater distances than I am capable of.

It's just a bit too much of a good thing, considering the powder appetite and the OAL/magazine constraints.

anybody messed with the 6.5 weatherby?

the guys at mcwhorter custom rifles have been cranking those out. Claiming 3300+ with 140s.

Same for the 6.5/300 win mag.

I bought a McWhorter in 6.5 WBY three weeks ago but I haven't had a chance to chrono it yet. I plan on taking it out this weekend or next to see what she pushes a 140gr. VLD at.

is it possible to take a regular 7mm rem mag and ream it out to 7mm mashburn?

79: What rifle?

Pac-Nor makes barrels for a 270-300WM...I'm having trouble getting that thought out of my head....

I would be reaming out a remington savage or tikka. I like the 7mm rem mag but the last one that I loaded for wouldn't give me more than 2950 with a 160 even with slow powders. I would like 168s to 3000-3100 easily and do it out of a 24 inch barrel.