300 Sherman Shortmag (SS)

[shawnb]

Very interested in the results. In my saum h4350 was to fast. And 4831sc reached pressure before a full case as well. Im using n560 right now and can get 64grs in my case as a max charge and the 208eldm was moving at 2940. Seems fast but thats where it was verified. Ive lowered the charge to 63 as a safe max.

Its throated for the 215s so the 208s could see a little more room for powder if the throat was set up for them....

Food for thought i guess

 

[Idaho Trecker]

Shawnb... thats some good speed with the 208. What barrel length do you have? Talking with Rich last night the n560 came up. I may have to get some and try if some of my other options I already have dont work.

 

[Idaho Trecker]

Made it out to finish up my barrel break in (at least cleaning wise) last night. The 2 loads of rl23 with 56 grains ran 2511 and 2527. 2 more with 56 grains of rl26 got 2456 and 2467. The one load of 59 grains of rl 23 netted 2651.

This leads me to believe rl 23 will also be a no go with this cartridge/bullet combo. I'll be concentrating on rl 17 and Hybrid 100v this weekend. I also may try some h 4831, imr 4451, and/or imr 4831.

I should have my rings to mount the scope up Saturday and be able to shoot some paper finally!!!

 

[shawnb]

Its a 26.5in barrel with 9.5tw

I have 150 round down the barrel and it did pick up a bit of speed once broke in. Maybe 30fps.

I can shoot my 4350 load over the chrono some time and see what it tells me exactly.

 

[Idaho Trecker]

Finally got the right rings and mounted the scope up. Came together nicely! Made it out to rub pressure test with rl 17 and didn't go high enough. Started at 53 in 1 grain increments to 57. 53 came in at 2575 and 57 at 2808. I think my load with 57 grains was a poorly prepped piece of brass (my bad) since it didn't hit the target at 100 yards and bolt lift was stiff but primer looked perfectly round and not catered at all.
Not up to the speeds we were expecting yet but very pleased with the accuracy... lots more powders to test still.

 

[Pdvdh]

As I recall, the 300 WSSM couldn't keep up with a 300 Win Mag with the heavier bullets. Does equally well with the lighter weight bullets. I also seem to recall that Winchester couldn't get the performance they wanted out of a 338 WSSM, so they never brought that caliber WSSM to market. No benefit over the .338 Win Mag.

So it seemed as though the out-performance of the short mags diminished as the caliber/bore increased. Will be awaiting additional reports from your load and MV testing.

 

[tbrice23]

I'm going to have to agree. Diminishing returns with increased bore diameter.
Every 300wm barrel I've had stomps my 300wsm in heavy weights.
However I'm astounded in the performance im getting from my 270wsm with 150s at 3280 fps in a 24" barrel. I never thought it would amount to as much.

 

[Barrelnut]

I think the RL17 and a longer throat will help it. I have a long throated 300 WSM and get 2850 FPS with 210 VLD and 59.7 Gr RL17 out of a 26" barrel. It's not at the top either... Think I could get the 215 to go faster because of the shorter bearing surface. RL17 has a loong power curve that really helps the speed.

 

[Barrelnut]

Looked at my notes for the 300 WSM, 215 Berger RL17 63.5 Gr. = 2975 FPS
My notes say it was a wee bit hot with some slight ejector marks. I settled on 62.5 Gr. at 2915 FPS.
These loads were .40 off the lands

300 WSM
26" barrel
215 Berger
RL17 63.5 Gr.
Norma Brass
Fed215M
2975

 

[elkaholic]

I think when Ryan gets the right powder in it (maybe N560) you will see velocities in the 2900's. After he runs through the first tests , and it gets some additional throat work, I still believe 3000 is possible. We will see..................................Rich

 

[Idaho Trecker]

As I recall, the 300 WSSM couldn't keep up with a 300 Win Mag with the heavier bullets. Does equally well with the lighter weight bullets. I also seem to recall that Winchester couldn't get the performance they wanted out of a 338 WSSM, so they never brought that caliber WSSM to market. No benefit over the .338 Win Mag.

So it seemed as though the out-performance of the short mags diminished as the caliber/bore increased. Will be awaiting additional reports from your load and MV testing.

It certainly seems like the speeds are not there yet but this cartridge is not as small as a WSSM. The case length is 1.960 and the neck/shoulder junction is around 1.610. I agree with you so far on bore vs. diminishing returns when I look at the speeds produced with those of smaller bores in this case design.

I'm hoping the right powder will put this right back up there with good speeds.

 

[Idaho Trecker]

Ran 57, 58, and 59 of RL 17 this morning to get my max. 57 gave me 2821 (same load gave me 2808 yesterday) 58 2834 with extractor mark and 59 at 2896 with more pronounced extractor mark but still had to look for it so not terrible.

Also did quick pressure test with Hybrid 100v which came up almost exactly the same speeds as RL 17.
55 2658
56 2699
57 2754
58 2826
Going by bolt lift and case head it looks like I could maybe run 1 to 2 grains more 100v than RL 17 but still not where I want to be for speed.
I think my next pressure tests will be in the 4831 and RL 22 burn rates. I filled a case to the base of the neck with RL 22 and was able to put 65 grains in it. Hopefully I can find some N560 in my travels up to CDA today.

 

[Pdvdh]

It certainly seems like the speeds are not there yet but this cartridge is not as small as a WSSM. The case length is 1.960 and the neck/shoulder junction is around 1.610. I agree with you so far on bore vs. diminishing returns when I look at the speeds produced with those of smaller bores in this case design.

I'm hoping the right powder will put this right back up there with good speeds.

I meant WSM, not WSSM. My recollection was that Winchester never offered a 338 WSM, because there were no bragging rights in muzzle velocity gains.

I think you'll end up with an acceptable MV. It may or may not shine as much in MV, as the case does in the smaller calibers, was my only observation. I'll be following your thread. Thanks for sharing.

 

[Capt RB]

Try the short cut 7828. I think you can get enough in there to get where you want to be.