Any advantages of the 300/7mm wsm?

[OKbow87]

I am in the process of building my second ever custom rifle and wanted to get some feed back from some guys. I was wondering what the advantages or disadvantages of a 300/7mm wsm would be over a standard 7 wsm. The one thing I can see right off the bat is that the 300 case has a longer case neck which is always nice, and that brass will be easier to find. Are there any other advantages or disadvantages? One of my main questions that I haven't been able to figure out is if I will gain or lose case capacity and how velocity will be affected. My gunsmith is having to order a 7mm wsm reamer throated for 168 vld's, so I got to thinking if there was a true advantage why not go ahead and get the 300/7mm wsm. The gun is being built on a stiller predator long action and a hart #7 1:9 twist. Any other advice on the gun or caliber is welcome also. Thanks ahead of time to everyone who responds.

Colin

 

[Shortmagman]

I don't own either, but from what I have read the 7mm WSM should offer a slight advantage in volume since the neck is shorter. However, the shorter neck is also a disadvantage as you have stated. So its the short neck with greater volume or the long neck with reloading advantages. I don't think you can go wrong with either.

 

[TCKev]

Here's an article I just read on this subject.

Vince B's 7mm WSM Record-Breaker (7 Win Short Mag)

 

[tjonh2001]

all i can say is that my 7mm wsm is an awsome gun. i would highly recomend this caliber. i havent found a problem with finding brass.

 

[JeffVN]

longer neck with the 300 WSM brass, only a touch less case capacity (longest neck is on the 270WSM brass). I shoot the straigh 7WSM. A bit more neck would be nice, but is not affecting me as far as I can tell. I long-throated my current rig to get teh boat tail junction above the neck/shoulder junction and you could easily do the same to maximize capacity in the 7/300WSM

JeffVN

 

[gunsmith]

Thank you, TCKev, for that article. Well written by a humble champion, and very informative.

 

[geargrinder]

7mmWSM brass can be made from 270WSM or 300WSM brass with a simple neck size and fireform.

I use Norma brass in mine.

 

[gunsmith]

Colin - the question probably breaks down to which slug seats well - you may need to choose the option with the longer neck, as that alone could make the difference in accuracy down range. I'd probably start out selecting the slug with the highest BC I could find in that caliber and see how well it seats in the shorter neck before building the gun.

I ran some math on the chambering differences. I sincerely doubt the miniscule powder charge increase is a noticeable advantage. You could possibly cut the deeper chamber and keep two bolts of different lengths to see which performs better.

I DO NOT RECOMMEND THIS PRACTICE TO ANYONE, as mistakenly choosing the long bolt or the with the long bullet or the short bolt with the short bullet could cause a disaster, but it is a way a VERY CAREFUL fellow could check out both cases with one gun. If I was that curious myself, I would paint one bolt red and one bolt green, taking only one bolt and one (the appropriate one) set of ammo to the range on any one day.

If you are making a claw extractor, you will likely need to make one for each bolt, a red one and a green one. If you do try this, PLEASE don't get blown up! A world record group ain't worth it! You're probably better off building both guns.

JeffVN's point is very good - you could long-neck the chamber and use the 270WSM brass and never really regret anything.