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Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by ICANHITHIMMAN, Apr 24, 2008.
Is there a 7mm built on a 300 win mag case that is factory produced? If so what is it called?
That would be the 7mm Remington Mag.
There are no other factory cases based on the 300 Win Mag.
The 7mm Rem Mag is the 338 Win Mag necked down.
the 300 WM is considerably longer (.156 in body & .12 OAL) than a 7mm RM.
The real answer is "no"
No, it's not a 7mm Remington Magnum. I have one of those and have been investigating getting mine bored out to a 7mm/300 Winchester (7mm-300 Winchester). BTW, a 7mm/300 Winchester is pretty close to the original (or at least the most famous of the originals) called 7mm Mashburn Super Magnum which was made famous by Warren Page. (If I don't have the Mashburn Super Magnum part right feel free to correct me, there were several 7mm Mashburns and I may have my facts mixed up).
My opinion is that a 7mm/300 Winchester would be a fantastic cartridge that would come close to splitting the difference between a 7mm Rem Mag and a 7mm STW capacity wise and would provide velocities closer to an STW than the standard 7mm Rem. It would also allow the case capacity to be expanded while keeping the OALs short enough to allow bullets to be seated to the correct length in a standard model 700 magazine box and provide access to all of that wonderful match grade 300 Winchester magnum brass.
If anyone knows a gunsmith that has a reamer for this and/or can provide me with more information on where to get dies for one of these it would be greatly appreciated.
I have a 6.5X300 Win Mag.. Redding was the supplier I used.. It was recomended by my smith. Just make sure they get the Win Mag part right.. My first dies were 6.5X300WSM.
Now I just need some time to build a load.
There already is a cartidge that splits the difference between the 7 Rem Mag and the 7 STW. Its called the 7mm Weatherby Mag. No specialty chamber dies needed. Reloading dies are readily available. Norma makes the brass.
Want something more powerful than the STW? 7-300 WEATHERBY Mag. It has been out for a while so reamers and dies should not be hard to find. Again, Norma makes Weatherby brass.
Do I have a thing for Weatherbys? You bet. Roy Weatherby knew what he was doing when he developed his cartridges.
I am in the process of having a 7mm rifle built based on the 300 WM case. This cartridge is not simply a necked down 300 WM though. The neck length is .284. I wanted at least a bullet diameter's length in the neck of the case. The diameter at the shoulder is .492 as opposed to .489 for the 300 WM. The length of the case to the shoulder is 2.183 as opposed to 2.196 for the 300 WM. The angle at the shoulder is 30 degrees instead of 25 for the 300 WM. The capacity of the case will be just a hair less than the 300 WM.
I think it will be a great case and so does Pacific Tool and my gunsmith George Vais.
Dies are being built by Hornady and will be done in about 5 more weeks. The reamer is being built by Pacific Tool and will be done in the next week or so.
That seems pretty elaborate. What are the advantages to doing what you're doing instead of just necking down a 300WM?
I'm with Rocky on this one. I am old school I guess and wonder why everybody is trying to re-invent the wheel. The 7mm weatherby gets right between the 7mm rem mag and the STW. Ain't a whole lot of room there but it gets right between them. I have two 7mm wby's and get 3450 fps with a 140 grain bullet without the need for a brake on it. Your not going to change those numbers much with what your talking about. If you want more then go with the STW or 7mm-300 wby. I have 5, 7mm STW's and my 7mm-300 wby will outshoot all of them which I can't understand because the STW has more case capacity. Just a fast barrel 7mm-300 I guess. The 7mm wby sounds like exactly what your looking for to me.
Thanks for the information. I've considered the 7mm-300 Wby because it's far more standard than the 7mm-300 Win. but I have no experience with Weatherby cartridges so I kind of look at them the same way that I do a Macintosh. I have several questions about these?
Are the Weatherbys as accurate?
Are the case bodies roughly the same diameter so that they'll feed through the magazine without altering the rails?
Are the lengths of the cartridges roughly the same as the 300 Winchester so that I can seat the bullets out where they need to be instead of jammed into the cases?
How expensive is brass and does it last as long as other brass?
Do the double radius shoulders cause any trouble when sizing the brass?
Are Weatherbys accurate? As much as any other factory rifle. My 40+ year old 7mm Weatherby with who knows how many rounds down the barrel still shoots around 1 MOA with Soft Point hunting loads. My 30-378 Weatherby get less the 3/4 MOA. I had a .243 Vanguard "youth" model that shot 1/2 MOA (unless I f*&#ed up). Weatherby even has a whole line of Vanguards called SubMOA that guarentee it when using factory Weatherby ammo.
300 win mag - body dia .513 - c.o.a.l. 3.340
7 wthby mag - body dia .512 - c.o.a.l. 3.360
300 wthby mag - body dia .518 - c.o.a.l. 3.560
If you buy an original Weatherby in 7mm, you won't have to worry about jamming the bullet into the lands. Most Weatherbys are very long in the throat. If you go with a 7-300, just make sure the reamer is to the dimensions you want.
You can buy either Norma or Weatherby stamped brass, but, Weatherby brass is made by Norma Precision anyway. As you know, Norma makes argueably the best brass. Midway has 300 Wthby Norma brass for $120/100, Rem for $60/100 and Hornady $94/100 and has 'Quality Cartridge' brand 7-300 Wthby for $45/20. If you want some 7 Wthby brass let me know. I have a bunch of once fired.
As far as the double radius and sizing, I assume you mean necking down the 300 to 7mm. I've never heard of it causing any problems. I have had no prblems with either neck or full length sizing my brass for reloading, but like any belted magnums, expect it to eventualy form a bulge above the belt.
Does this help?
Cross, Weatherby's are exceptionally accurate holding the thousand yard record group with various versions through the years. I have shot weatherby calibers since the 60's and during the 70's the 7mm-300 was about the hottest thing in 1000 yard competition holding the world record for quite some time. The 300 also was a good one and did well. It is just one of the all time inherently accurate rounds. I have at least one of every weatherby caliber except the 460, plus wildcats off the various cases.
One thing I could never understand all through the years was why everyone was trying to design something to compete with the weatherby's. Why didn't they just get a weatherby? I am a Weatherby fan but also a fan of about everything else so I am not biased. Most of my rifles are not Weatherby calibers anyway. After 50 years their is still nothing off a standard magnum case that will outshoot a Weatherby. The 7mm STW wildcat is probably about the best argument. The big nock all through the years was the cost of brass and no selection other than wby/norma brass. Cost was a big factor with a lot of people and they went with lesser chamberings.
The reason they were never as popular is because of expensive brass. The brass is excellent quality made by Norma. The expense is the reason the STW began to do well and the 7mm-300 wby started to slide. They are essentially the same thing with different shoulders and the STW holds a little more powder. However I have 5 STW's and only two will outshoot my straight 7mm wby. None will outshoot my 7mm-300 wby. Also any of my wby's will shoot more accurate than any of my STW's but I am sure that is just law of averages from a small sample. If I had a hundred of each they would probably average out because one should not be any more or less accurate than the other. Just depends on that particular rifle.
Case bodies are the same diameter. The length and seating depth depends on which magnum action you have. Some actions made just for the 300 winchester length stuff are to short for seating out the 7mm-300 but are fine for the standard 7mm wby. Heck, they are to short to seat out the 300 winny on some. They will work you just can't seat way out there. With the rem 700 or win mdl 70 action the one made for the 375 H&H is the one you would want for the 7mm-300.
If you use to much lube and full length size the wby shoulder is more likely to dent on the radius. I always neck size mine, no problem. The other is not a problem either because you shouldn't use that much lube anyway. If your action is long enough to seat out the 300 winny then it is probably long enough to seat out the 7mm-300 although the 7mm-300 is longer so check. You should not experience any feeding problems. With most of the shorter magnum actions sold in 300 winny you can't seat way out there.
Hey guys don't forget about the the 7mm Dakota. It will do everything the weatherby can without any problems.