7MM WSM vs 7MM/300 WSM

After my last what to do the the 708 post i started looking at these two options .From what i understand the only real advantage of the 7mm /300 is the longer neck , Is it really worth the hassle of necking down or is the standard 7mmWsm fine . The main reason im looking at these two options is i can fit them into my 700 with a bit more room to seat the projectiles out a little further and not have half the projectile in the case like the 284. Which is my main reason for not going with the 284 . The 284 case being just the little bit longer makes quite the difference. I also note that dies for the 7mm WSM are easy to get another bonus in its favor . Would it be fair to say the 7mm wsm is similar in performance to a 280 ackley or has it got a bit more gas ?. I also curious to know your thoughts about its performance . Thanks Wayne

You will also have to open up your bolt face but you probably already know that. Might be cheaper in the long run to sell the 7mm08 and buy a different rifle in a caliber that you really want. Just a thought:thumbsup:

If you're looking at those then probably a 7mmSAUM would fit your action better and you'll have similar ballistics without the faffing around.

buy a browning h/c long range in 300 wsm,,all ready to go at 2k,,there is no substitute for displacement,,size does matter ask any women

Doesn’t answer your question, but as you have considered.284 Win, another option would be to ream your chamber longer to get the case capacity you want (assuming enough mag capacity). That would avoid having to open up the bolt face for a magnum cartridge. My T3 based .284 is longer than standard and sends 162 ELD-X at an easy 2750 with plenty of mag space remaining. Magnums would give more velocity, but also more recoil and throat erosion.

The problem is im using a short action 700 . And i have bedded it, fitted a new trigger, lightweight firing pin, and i know if i sell i'll lose money ,so i thought a re chamber and maybe a bolt face job would do the trick and i would have a something with a bit more grunt than a 708 . If i knew i could get a good one i would bite the bullet and get a Kimber 280ai but i keep hearing that they are still a bit of a lottery . Then i could put the 708 to another use .

I'd go with 7mm saum and get Kiwi Greg to import some ADG brass for it.

@wayno, what specifically do you need the extra grunt for?

You should no issues with a 284, just get the throat set long enough to suit the pills you want to run. Definitely should not have issues with pills seated too deep in the 284. But where you may run into trouble with any of these ideas is that you’re starting off with a used barrel. How many rounds thru it ? A lot of gun smiths won’t touch a job like this because it’s hard on gear and you run risk of a dud. Better off buying a new barrel or rifle. It will save you $$ in the long run

Okay I just found your previous thread. I think you would find that your 7mm08 is going to be more than adequate for 500m. Consider some of the work done by the short-barrelled crowd with heavier, high BC 7mm bullets, and the deadly terminal performance on deer despite relatively low velocity impacts. It's an all-round easier job to have your current chamber extended slightly so you can use long, heavy for calibre bullets, without sacrificing case capacity. Then some smart load development with some of the latest powders and I reckon you would be very surprised what do you can achieve from the humble -08 case.

Mag length is always going to be your constraint and it is a massive pain in the arse to have to single feed. Right there is a reason to look at sticking with what you've got, extending COAL and the chamber to the maximum possible that will feed without getting hung up in the mag.


You need to look at it in terms of percentages. What does all that work and cost equate to in terms of percentage increase in velocity and terminal energy? If it's less than 20% you are wasting your money. There's plenty of guys using their -08 cases in 7mm or 30 cal out to 5 or 600m with no difficulty... its all in the bullet.

Bottom line is today's bullets and powders make for highly effective terminal performance at medium range on our deer species. I shot a few reds last time out at extended ranges with the 143gr ELD-X at impact velocities of 1900-2200fps, you should see the damage. Some large exits and massive bleeds, and some pretty impressive bang flops. Magnum performance comes into its own past 700m, I don't think you need it if you are routinely shooting well below that.

Chainsaw its a rem 700 not a tikka ,so gun smiths dont seem to mind them. The barrel has only had about 130 rounds down it .Flyblown i just would prefer to have that bit extra to comfortably run 160 ish weight bullets .

Yup, and I've just run the numbers in Quickload with the 162gr ELD-M (a bit rough but good enough) and I reckon you're looking at some very expensive incremental ft-lbs. There really isn't that much in it mate. Happy to help with that stuff if you like.

What is the max COAL you can run in the mag?

@wayno when i had my standard 7mm08, i was running 175 smk's @2550fps and was taking large Reds out to 600yds no issue. I was also loading my son's A-bolt with 162 amax @ 2600 with same results.
But at the end of the day, sometimes you just want to tinker (i did...had mine AI'd) so just do what makes you happy;)

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Originally Posted by Flyblown

Mag length is always going to be your constraint...

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Originally Posted by chainsaw

Definitely should not have issues with pills seated too deep in the 284

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hmmmm... now which is it ? Maybe a picture can help here.

Attachment 124187

Even with a short action magazine that has been extended to take up to 77mm ( just over 3" ), bullets like the 162 ELD-M do need to be seated well down in the case to fit.
Also consider the chamber reamer that may be used, as there will be a few out there that are optimised for 180grVLD match shooting and in these situations the jump to the rifling for rounds that can be fed from this same extended magazine will be near on 6mm, and over 10mm for a round that fits to a standard length magazine.

I don't think a .284Win could be recommended in a short action unless you intend shooting light-for-calibre bullets that have an ogive as in the QuickLOAD sourced picture above. Big jumps and reduced capacity is what you will get with LR bullets in a short action for sure. Got to agree with the advice given - optimised 7-08 or SAUM.

@Puffin... see above. Seems to be missing something.

Back to your original post. I reload for my mates short action Kimber 7mm WSM mag feeding 162 ELD-X’s and it’s a weapon. Shoots well inside MOA, pretty hard on the federal brass but the Bertram he got has been holding up pretty well. Expensive brass but for a hunting rifle if you don’t lose them they should last quite a while. It outperforms my 7mm rem mag shooting the same bullet with less barrel length. So if you are keen on a WSM I would say go for the standard 7mm no dicking around necking down or odd ball dies and I’m sure it will be plenty accurate for hunting. After all your not 1000 yard bench rest shooting