270 Sherman Shortmag (SS)

[Idaho Trecker]

It's early Christmas! The 170's showed up today! I'll get some measurements and bullets seated later tonight and will get some more info up. It looks like the bc was reduced from the original. 703 estimate and are now listed at .662. I was hoping for more but performance is what will matter.

 

[bigngreen]

Dang, looks like the BC worms got to this one the same as the 195's, I was hopeful cause its still listed as .703 on eol.

 

[Idaho Trecker]

Ya that is quite a significant drop in bc.... now marshal drops the info that he got new dies for his new designed 175's now i'll be waiting for those to come out next.

 

[bigngreen]

Just when you think you have it all worked out someone drops something awesome, I'm waiting till after shot show to go nuts!

 

[Longtooth32]

Ya that is quite a significant drop in bc.... now marshal drops the info that he got new dies for his new designed 175's now i'll be waiting for those to come out next.

I also got my Berger 170s today…Any link to Marshal's new 175 .277 info?

Thanks...

 

[Idaho Trecker]

Finally made it out a couple times to play with the 170's with my SS.

The first outing I loaded 3 groups of 3 with the same lighter charge of rl 26 and just test seating depth to see what my rifle liked. Here is what I ended up with:

27.41 inHg 35 Degrees

3.037" 2.982" 2.927"
2810 2824 2818
2812 2835 2814
2845 2829 2812

The lengths are OAL. My rilfe grouped best with the mid length load which was .057" off the lands.

On a bright note I finally did bite the bullet and got a Magnetospeed so I have some piece of mind with my speeds.

The next day I went out and ran a quick pressure test with the 170's and the mid seating depth. I just fired one shot at each charge of 62,63, and 64 grains to see where I topped out. Here is what I got:

62..... 2964
63..... 3018
64..... 3103

After firing these my practical max is going to be around 62 grains of RL 26.
63 grains was stiff bolt lift and 64 almost needed a stick to slam the bolt open.
The 62 and 63 grain load were practically the same hole at 100 yards.

 

[Idaho Trecker]

Another interesting bit of info I thought I would offer up from testing the SS and the Sherman are the speed differences which blew my mind until I started thinking about it and talked with Elkaholic.

Even though I only fired one round of each with 170 bergers and RL 26 here are the results:

270 SS 270 Sherman

62 2964 2973
63 3018 3000
64 3103 3067
65 didnt shoot 3117

For every load the SS was faster than the Sherman which was not what I expected especially when considering my SS has a 24" barrel and Sherman a 27".

Definitely goes to show how much efficiency, design, and working pressure count for.

 

[elkaholic]

Another interesting bit of info I thought I would offer up from testing the SS and the Sherman are the speed differences which blew my mind until I started thinking about it and talked with Elkaholic.

Even though I only fired one round of each with 170 bergers and RL 26 here are the results:

270 SS 270 Sherman

62 2964 2973
63 3018 3000
64 3103 3067
65 didnt shoot 3117

For every load the SS was faster than the Sherman which was not what I expected especially when considering my SS has a 24" barrel and Sherman a 27".

Definitely goes to show how much efficiency, design, and working pressure count for.

To be fair, the SS is more efficient for sure but it also has less capacity so an equal charge would mean more pressure in the SS which also means more velocity. On the other hand, 3 inches of barrel length is approx. 65'. Loaded to equal pressures, they are pretty much on par but the SS does it with less capacity (thus the efficiency). Hope this makes sense......Rich

 

[bigngreen]

This thread is making me so happy

 

[elkaholic]

This thread is making me so happy

I'll be happy when I get all my 270 SS parts together and you make it shoot as well as my last!........Rich

 

[Idaho Trecker]

Seeing these speeds with a 24" makes me want a 28 or 30" heavy gun just for target or sitting on canyon rims. Whenever marshal comes out with his 175 it may be the real game changer for the 270 since berger lowered bc compared to their original estimate.

Looking forward to seeing your rifle put together Rich.

 

[elkaholic]

Seeing these speeds with a 24" makes me want a 28 or 30" heavy gun just for target or sitting on canyon rims. Whenever marshal comes out with his 175 it may be the real game changer for the 270 since berger lowered bc compared to their original estimate.

Looking forward to seeing your rifle put together Rich.

I was thinking the same thing the other day! If this lightweight doesn't work out for some reason, it may get a facelift

 

[marshal]

Projected to be late spring.

 

[elkaholic]

Projected to be late spring.

Bring it on!