Help with a 270 WSM build for Berger 170 EOL's

[codyadams]

Howdy guys!!

I'm helpin my buddy with a build, he has a Winchester Model 70 Black Shadow chambered in 270 WSM, and it has been beaten up pretty good, and he wants to get it fixed up. He is getting a stock for it, a B&C I believe, and he is going to go with something like a medium to heavy sporter contour, to keep the gun around the 10 lb range. he is getting a 1 in 8 twist to mainly shoot the 170 EOL or possibly the 165 matrix bullets. he has about 400 rounds of brass, all the dies, and everything else, and the ballistics of this combo is pretty good, so he is sticking with this caliber.

We want to get the most performance possible out of this rifle, and to do that we need to be able to load these long. The magazine box on this gun can accept rounds up to about 3.1", maybe a tad less. So my question is this....

What is the OAL and CBTO of a 270 WSM loaded with a 170 EOL, when the bullet is loaded so the bearing surface just uses up the neck, so as the only part of the bullet below the neck is the boattail of this long pill? I want them to look like the 28 nosler cartridge on the right in the pic I'm adding (stole the pic from google). I'm trying to figure out where they will be seated at 3.1" or slightly less, and how long the throat needs to be to load these right off the lands and still fit.

Thanks in advance guys!! and any input on this build would be appreciated as well!! take care

 

[codyadams]

on the right....

 

[Edd]

Based on the Berger spec sheet and the SAMMI drawing.

OAL will be 3.060" and CBTO will be 2.330".

 

[JTB]

This was actually one of my projects. I just seated a 170gr eol in the case I was going to be using (no powder or primer of course) until it had an extra 0.125 in the magazine and sent the blank to pacific tool. They made a custome reamer that worked perfectly to give me the maximum case volume with that bullet in my magazine. It is a great shooter. I actually extended the magazine slightly and customize the bullet ramp on the action to get a little more OAL but not necessary

 

[sedancowboy]

Edd has it exactly right 3.060 COAL for the 170s. I have built the same gun on a Montana Rifle Co action which is based on the Winchester action my SA Box is 3.125 I load my 170s at 3.120. Shot a .250 group today with 68 grs of Retumbo.

 

[Danny1788]

Edd has it exactly right 3.060 COAL for the 170s. I have built the same gun on a Montana Rifle Co action which is based on the Winchester action my SA Box is 3.125 I load my 170s at 3.120. Shot a .250 group today with 68 grs of Retumbo.

Your jamming .060" into the LANDS? That's pretty far into the lands how much neck tension do you run to be able to keep the bullet from being pushed back into the case?

Or are you saying your throat is setup to work with your 3.125" mag box and you load to 3.120" if so how far off the lands are you?

 

[sedancowboy]

I am not jamming into the lands. I have a long throat and am about .015 from the lands. The 270 WSM is a great cartridge and made better with a faster twist barrel and chambered to get the bullet up out of the case.

 

[Floundertrap]

Great post gentlemen, I'm looking to build the same using a savage short action, 8 twist brux, wsm bolt head and an AI mag sized for WSM rounds; it's in a chassis. I believe the mag length for the wsm is the same as the .308, and if so that only gives me 2.897 COAL by my mic. I have asked for internal dimensions of the WSM magazine from AI, but I'm guessing they'd be close to the. 308 mag dimensions.

Question: Can I get what I need out of that mag length and use my existing chassis or would I be money ahead using an internal mag box and conventional stock setup to get the mag dimensions you guys are getting above? It will be a hunting rifle and it'll save me a good chunk of change to use my existing chassis if it makes sense.

 

[codyadams]

Great post gentlemen, I'm looking to build the same using a savage short action, 8 twist brux, wsm bolt head and an AI mag sized for WSM rounds; it's in a chassis. I believe the mag length for the wsm is the same as the .308, and if so that only gives me 2.897 COAL by my mic. I have asked for internal dimensions of the WSM magazine from AI, but I'm guessing they'd be close to the. 308 mag dimensions.

Question: Can I get what I need out of that mag length and use my existing chassis or would I be money ahead using an internal mag box and conventional stock setup to get the mag dimensions you guys are getting above? It will be a hunting rifle and it'll save me a good chunk of change to use my existing chassis if it makes sense.

Not sure on mag length of the AI, but some of the AICS mags allow up to 2.970", which is wjat I use for my .260 AI. A good option may be to look at the .270 Sherman Shortmag, unless you are already set up on brass and reloading gear and don't want to try something different.

 

[Floundertrap]

Not sure on mag length of the AI, but some of the AICS mags allow up to 2.970", which is wjat I use for my .260 AI. A good option may be to look at the .270 Sherman Shortmag, unless you are already set up on brass and reloading gear and don't want to try something different.

Thanks Cody, I'm not set up yet, so i have options I guess. I have the action and chassis, I swap the chassis between 2 savages at the moment, one of which I plan to rechamber. I looked into the Sherman briefly, but I want to say the cost of brass or something reaffirmed my choice on the 270 WSM.

 

[elkaholic]

Thanks Cody, I'm not set up yet, so i have options I guess. I have the action and chassis, I swap the chassis between 2 savages at the moment, one of which I plan to rechamber. I looked into the Sherman briefly, but I want to say the cost of brass or something reaffirmed my choice on the 270 WSM.

I understand that concern but consider that 50 Sherman brass will last as long as your wsm barrel and it's quite a bargain.

 

[Buddro]

JTB Do you have any of the specs on your build? I'm trying to figure out what I can fit before I start ordering parts on a build and what kind of coal people are getting with the heavier stuff.

 

[JTB]

JTB Do you have any of the specs on your build? I'm trying to figure out what I can fit before I start ordering parts on a build and what kind of coal people are getting with the heavier stuff.

I am using a M70 WSM so I can stretch out the OAL to about 3.1" in stock configuration. I have modified the magazine/action slightly to allow another .100" or so but the current configuration is utilizing an OAL of 3.105 which positions the 170gr EOL's 0.015" off lands in my rifle. Current using 67.2gr Retumbo for 3060 from 24" barrel (1:8 twist)