Does anyone have any info on the 300 Winchester mag improved?

I own the 300 RUM and I also own the 300 WIN.
but I do not own 300 Win. Mag IMP.

I guess this was an older cartridge. I know of an old Sako chambered in it. It has a 40 degree neck. The Navy at one time used an Improved 300WM out to 1500 yards. There is not much data on it.

P.O.Ackley was doing his experiments on case design back in the 40s and 50s.

I think by the time the .300 Win mag came out in the early 60s the gun companys had a handle on the improved design and designed the .300 with little room for any improvement.

If you think about it a .300 Wetherby is a .300 H&H improved. The only thing that Wetherby did to create his .300 was to use Ackleys model of the improved case and imploy it on the .300 H&H and of course add the venturie shoulder.

The military has used .300 win mags for sniper rifles since Vietnam. My collage rifle coach told me storys of head shooting NVA with his .300.

I can see the Navy or any other branch of the service playing around with an improved win mag design but I doubt that it would get much traction and I would say thats probably why you can't find much info on it.

Hum…I seem to recollect that the biggest improvement that one of the US sniper groups wanted to make to the 300 WinMag was to turn the belt off, turn the rim diameter down, and recut the extractor groove so that the cartridge was a true rimless cartridge. I recollect that at the time it had something to do with feeding reliability and greater accuracy by headspacing on the cartridge shoulder rather than the cartridge belt as the factory rifles were delivered to them. I believe this was reported in the American Rifleman magazine.

capoward- That may be what jpat was talking about. I did'nt see that arcticle in AR.

I did watch an eppasode on the history channel about snipers. It showed them reloading there .300 win ammo and headspacing to the shoulder by neck sizing. Each lot of ammo that had been reloaded was marked to the spcific gun for use.

The thing with the guys working in these armorys is that their there 8 hours a day working on this stuff and it's really hard for all of us to keep up with it.

Are all standard .300 Win Mag rifles headspaced off the belt? Or for that matter all belted cartridges? Is their potentially clearance around the shoulder/neck area of a cartridge that spaces off the belt? I'm sure its super minimal but it makes me curious... I full length resize all my brass too.Never looked at just neck sizing.

quote:

Originally posted by carnold724:
Are all standard .300 Win Mag rifles headspaced off the belt? Or for that matter all belted cartridges?

Yes, but the careful hand loader will not set the shoulder back treating it like any other case that headspaces from the shoulder.

An answer for Jpat could probably be found in some obscure footnote, but as far as I'm concerned the improved 300 Win mag is called a 308 Norma magnum. Remington went one better and eliminated the unnecessary belt on their Ultra mag series.

so just how short does the neck get on a 300 Win Mag, once you 'improve' the shoulder?

its neck is short enough to begin with.

Norma had the design(Nils Kvale) but winchester is the bigger company.

Nils Kvale made a cartride for recambering 8mm mausers with magnum cases without rim. They selled tools and cases for the US market.