Originally Posted by backwoods83
With the reamer blueprints I looked at a 7/300wsm is virtually a 7mm wsm they are the same length all you are doing is necking down a 300 wsm to 7mm. 300wsm blueprint shows 80.4grns capacity, 7mm wsm shows 80.3grns, 7/300 shows 80.1, the only advantages is good 270/300wsm brass verses winchester brand 7mm wsm brass, to work the brass less I'd get 270wsm norma brass and neck it up, your only expanding .007". But yet these with vlds will not fit in a remington sa.
Just to clear it up.
The 7mm WSM is different than all of the other WSMs and uses it's own head space gauge.
The 300 WSM has a body length of 1.802 and the 7mm WSMs body is 1.856 (.054 longer)
The neck is shorter (.244 compared to .298 of the 300) but is not two short.
It is .020 shorter than one caliber .284. And The tried and true 300 Win Mag has a neck length
.044 shorter than the caliber (.308 ) so it has a shorter neck based on the bullet dia than the
All of the WSMs are the same OAL so you can make any caliber from any of the WSM brass if
you want to go to the trouble of resizing and fireforming.
In fact , Norma makes brass for the 270 and the 300 WSM an I had thought about buying some
300 WSM Norma brass and turning the necks and sizing it to 7mm WSM then fireforming it but
the Winchester brass with careful sorting and case prep has worked very well, and the accuracy
at 100 yards with 5 shots in a sporter weight custom rifle was .174 (best) and .212 (Worst)
with a 140 Accubond @ 3307 ft/sec.
I know that the accuracy could probably be improved with a different bullet/powder combination
but For hunting It shoots as well as I can under those conditions.
If I wanted to size down I would go to the 7/08 or the 6.5x47 lapua, Both are capable 1000 yard
Again, just an opinion.
J E CUSTOM