300 Sherman Shortmag (SS)

[Idaho Trecker]

That is in Rich's court to answer the throating questions. It's not my place to say. I'm really hoping that the new throat allows some different powders to work for me.

 

[shawnb]

I have some info for you. I have been toying with the 208 eldm bullets and it turns out they pressure out sooner than the 215s i think.

I found that my normal n560 (63gr) 215 load it to much for extraction with the 208s.for the 208s 62.4gr of 560 put 5 shots in the same hole at 100 and had an ok es of 20fps. Any more powder opened up the groups. Velocity was 2825 fps. 62.7gr was 2865, 63 was 2900.

I just got a new scale because i was thinking my old 1010 scale was not as accurate and i think i may be right. I had some still loaded from the 1010 that i havent shot. So i tested them and they were all over the place. Ive shot these into 1.5-2.5" groups at 535 pretty regularly.

I will take this and reload them with the new scale and see if anything improves. Who knows maybe my 1010 was out to lunch with what it was actually weighing compared to a good new scale.

Like you my search for a new powder might be ahead of me.

 

[Idaho Trecker]

I have some info for you. I have been toying with the 208 eldm bullets and it turns out they pressure out sooner than the 215s i think.

I found that my normal n560 (63gr) 215 load it to much for extraction with the 208s.for the 208s 62.4gr of 560 put 5 shots in the same hole at 100 and had an ok es of 20fps. Any more powder opened up the groups. Velocity was 2825 fps. 62.7gr was 2865, 63 was 2900.

I just got a new scale because i was thinking my old 1010 scale was not as accurate and i think i may be right. I had some still loaded from the 1010 that i havent shot. So i tested them and they were all over the place. Ive shot these into 1.5-2.5" groups at 535 pretty regularly.

I will take this and reload them with the new scale and see if anything improves. Who knows maybe my 1010 was out to lunch with what it was actually weighing compared to a good new scale.

Like you my search for a new powder might be ahead of me.

Good to know. It sounds like you may want to try a little slower powder with the ELD.

 

[Idaho Trecker]

Thanks to Rhian again for the great work and fast turn around I should have the 300 ss waiting for me when I get home Friday from work with a new "improved " throat and muzzle brake! As soon as I get out and get some info I'll get it posted. I'm looking at trying some norma mrp and 217.

 

[RH300UM]

Tagging in

 

[welldone]

I have a Criterion Remage chambered in 308. Northland Shooters Supply doesn't sell a Remage barrel in 300SAUM. Has anyone done a 300 Short Sherman using the Remage system? Thinking about reaming out my 308 but don't want to do something unsafe.

 

[elkaholic]

I am going to stick my neck out a ways and predict 3000' useable velocity with a 215......Rich

 

[Capt RB]

Isn't 2900 in the wsm on the borderline?? Wow

 

[elkaholic]

Isn't 2900 in the wsm on the borderline?? Wow

I think 2950' maybe, but not sure?

 

[Barrelnut]

I could get to 2900 in 300 WSM with 215 Hybrid with 62 Gr. RL17 and a 26" barrel. It was the top. Could get to 2960 with 63. Gr. But it is hot and over the top in my barrel.
Using Norma brass.

 

[Idaho Trecker]

I have a Criterion Remage chambered in 308. Northland Shooters Supply doesn't sell a Remage barrel in 300SAUM. Has anyone done a 300 Short Sherman using the Remage system? Thinking about reaming out my 308 but don't want to do something unsafe.

This is the first 300 SS made. A 308 barrel would need set back quite a bit to be rechambered to a 300 SS. The case length of the ss is 1.960". You also would need a magnum bolt face.

 

[Idaho Trecker]

I got the 300 SS back from Rhian with the new throat and the brake. It looks awesome with the brake and it is extremely tame now (not that it was bad at all before). I hurried and put the scope and stock back on last night and ran out to send a few fire forming loads down to smooth everything back out. After the fire forming loads I ran 3 of my most used load of 63.3 grains of Superformance down with the magneto attached. I was somewhat disappointed with the results until I started thinking about it and consulted with Rich. My fist shot gave me an error but next two were 2942 and 2953. Very good ES. This was the exact same speed as before and the bolt was super hard to get open, maybe more so than before. The case head has a very pronounced extractor mark and flattened primer. With a little collaborative brainstorming we hit on the idea of trying some new brass and see how that worked (the brass I used with the Superformance load was on its 12th firing!!! All with full throttle loads.

The results with the newly formed brass was just what we were expecting. Pressure dropped due to the brass being able to contract when sized and not spring back near the web.

I'll post a picture of my results from this morning comparing the initial testing with the new throat. All loads except MRP were one shot over the magnetospeed.

My next session out I will try a load of RL 17 and N560 to see how it compares to before the throating. I will also run higher with Hybrid 100V and see where I max out now.

As of now I am leaning towards 100V, Superformance, or RL22-MRP being the winners. Out of those I'm hoping for 100V since it is the most temp stable of the powders I listed.

Sorry for the long read but lots of information to get out there!

 

[Idaho Trecker]

Forgot to mention this rifle is still extremely accurate! All 8 shots went in 1.25" at 100 yards with 14x scope! 5 of them in .75"!!! All that with different powders and charges.

 

[bigngreen]

I think the throating will make a bigger difference with some powders than others because it's only giving it a soft start so its that first micro second that is being effected. We've been playing with throating for a while, different styles and lengths. A fellow smith and good friend even throated a rifle in the middle of a bench rest shoot, same load shot equally well just took the edge of the pressure, velocity remained very similar.
All things considered that thing is a hammer for such a little package, considering your running 10 or more grains less than a 300 Win mag you'll enjoy a lot of awesome shooting on that barrel.