Advantages of 300/7mm wsm?

[okbow87]

I just want to start off by saying I have been looking at this site for close to two years now and finally decided to join up.

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

 

[Forum Boss]

Norma makes the best brass, by far. Currently Norma makes 300 WSM brass, and 270 WSM brass, but not 7mm WSM brass.

Brass availability and the slightly longer neck weigh in favor of the wildcats. For full-length sizing you can use 300 WSM dies with a smaller bushing.

Norma

.270 WSM - Product #26907
300 WSM - Product #27676

If you really want to run the standard 7 WSM dimensionally, you could just use the .270 WSM brass and fire-form it to 7 WSM dimensions.

.270 WSM shoulder dimension is .5382
7mm WSM shoulder dimension is .5377

So you might have to full-length size the .270 brass first.

 

[Ackley]

I run a 7mm/300 wsm lets just say I wouldnt have one again,necking down had to be done in 3 operations and then neck turn,after a couple of firing I got brass migration whivj ment i had to neck turn again,I have a new barrel waiting so I will go std 7mm wsm minimun SAMMI spec

 

[Thorbird]

I am in the same position on considering the 7mm WSM, but had wondered the same about the 7/300 WSM after reading about the shorter neck. It is very interesting to hear that someone with one would go with a standard 7mm WSM if they could do it over again. I was also thinking about the 7/270 WSM so that you would just be able to neck up? From what I have learned, you have to get a reamer with the right throat as you mention, and it looks like you have settled on the 168 grainers. The 9 twist should work for that from what 168's, but you might look into a faster twist. 8.5 or 8? On loss of case capacity, I don't think it is an issue in terms of velocity, but I have heard that bullets forced back into the case can create higher pressures, and that cartridge is already at like 65K PSI. The berger bullets like to be jammed into the lands, and that is more pressure.

 

[Jeffvn]

I run a straight 7WSM, and use the 180 Bergers long-throated way out there. Yeah it has a shorter neck overall, but I don't have to play with necking up, necking down, or getting a custom reamer. ,not to mention I bought a ton of teh stuff before prices on brass jumped like crazy - so 7WSM is my chambering of choice for a long time)

Were I to do it again, I would go with the 7 SAUM. Capable of the exact same velocity,with a 28" or longer barrel) as everything else mentioned in this thread using a 7mm 180 Grain Berger, but doing so with a lot less powder. It has a nice long neck, and is easy to load from a magazine if you are so inclined.

I forgot to add that I shoot a 9 twist barrel, and it worked fine for 180 Bergers running as slow as 2,800 fps at sea level.

JeffVN

 

[okbow87]

Jeff... what do you think about the velocity in a 26" barrel with the 168's between the wsm and saum. My gunsmith just built a saum that he is very very happy with but he is only shooting them about 2960 out of a 26" tube. He has been hinting that he would like me to try the saum instead of the wsm but im not quite convinced because I am expecting something more along the lines of 3100 with the wsm and be able to find brass easier than the saum. Do you think thats about right?

 

[Thorbird]

I have heard or read that there is a velocity node that Walt Berger mentions for his bullets, and pushing beyond that node, can hurt accuracy? I cannot say from experience, but maybe someone here can?

I have also heard the saum mentioned for its efficiency and neck. Hopefully you will be able to get brass for them over time, or maybe it will become so popular for competitive purposes that brass will continue to be produced.

 

[Jeffvn]

Yep; you can get the WSM brass easier then the SAUM.

3,100 with the 168s in a WSM from a 26" barrel, possibly, but you will be pushing the pressure enevelope, at least I know mine would be at that velocity.

I'm thinking that if you could get 2,900-2,950 fps out of the 180s, the results would be as good or better then the 168s, but I have no experience with the 168s. My personal preference is to stick close to the 2,950 node that almost every cartridge seems to like.

this is my rig wearing its 26" barrel. Shot it configured this way for F-Class and did just fine,including shooting off of the bipod). She now wears a 28" barrel for pure F-Class work, but I swap out back to the 26" for just ringing steel to and beyond 1,000 yards - looks exactly the same.

JeffVN