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270 SS (Sherman Shortmag) Load Data

Idaho Trecker

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Apr 19, 2013
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Figured it was time to start its own dedicated thread since my build thread is getting a little old and alot to wade through if starting from the beginning and only looking for load data. ( and it sounds like Rich will be adding to it soon gun))

All of my data is for my rifle which has a 24" 1:8 twist Brux and using Norma 300 Saum brass. Bore was HBN treated along with all bullets.

All loads are using Fed 210 GM primers.
My rifle also has a longer throat than what Rich's reamer will have.

Getting right to it I started off with seating depth tests with 170 Bergers and 165 Matrix at .007, .060, and .110 off. Interestingly enough both bullets really shined at the .060 off.

A pressure test with the 170's and RL 26 showed that 64 grains was max in my rifle as the bolt barely opened. This max gave me 3013 fps over my Magnetospeed. I have not had time to retest my 62.2 grain load since I took care of the carbon ring that had built up in the throat and was playing hell with me but when I do I'll post the results.

Just for fun a case full of RL 33 was also tried to see if enough could be stuffed in this case to pressure up but it did not. One shot was fired with 67.4 grains and the 170 Berger which only yielded 2838 fps.

The 165 Matrix seating depth test was done with a 60 grain charge of RL 26.

.007 .060 .110

2918 2838 2871
2870 2844 2853
2881 2838 2866

A quick pressure test with one shot each fired at 1 grain apart showed 64 grains of RL 26 was also max with the 165 Matrix.
62 3049
63 3101
64 3167

This max with the same charge of RL 26 and the 165 Matrix vs the 170 Berger has had the same speed differences in my 270 Sherman also. I believe this is attributed to the longer bearing surface of the Matrix more so than the 5 grains weight difference.
I settled on 62 grains of RL 26 with the 165 Matrix shooting at 3017 which is very easy on brass. There is room to push it a faster.
Again I tried to pressure out with some RL 33 at 67.6 grains but no luck. It pushed the 165 at 2827 fps.

Yesterday I played with some 150 Nosler Long Range Accubonds since I had them. The hope was to get some lighter bullets screaming along but didnt work out with this bullet. This round I was just going for pressure max and seated the bullets at .020 off. A load of 66.3 and 67.3 grains of RL 33 was shot and gave a dismal 2738 and 2787 fps respectively.
Next powder up was RL 26.
63 3117
64 3161
65 3209
66 3264
At 66 grains the bolt barely opened and had a very deep plunger mark on the case head. I would say 64.5 would be my max in this rifle to work around and probably be about 3180 fps. That still isnt a slouch and comes in at 20.1 moa at 1000 yards with 1108 ftlbs at my elevation of 3000'.

Sorry if I babbled on. I'll post as I do some more shooting and it wont be so jumbled.
 
Good work Ryan. Rhian got mine chambered today so it won't be too long now. He will shoot it enough to break it in and send it off to nitride......Rich
 
Just got back from running 3 shots over the magneto with my 62 grain load and the 165 Matrix to see what it is doing at a temperature closer to what my hunting temperatures will be. These shots were done at 46 degrees F and 26.9 inHg.

This is what I came up with 2974, 2990, and 2974. This average is 2979 and sd of 9. Not to bad for a 24" barrel.

Seems like there is more room for a little more speed but this load is just starting to get a shiny mark on the case head from the plunger. I just keep hoping that Alliant will come out with a powder or two between RL 26 and 33 in burn rate.
 
Ran 64, 65, and 66 grains of Retumbo and 66 was max at 3041 fps. 65 was 2987 and 64 at 2916. Looks like RL 26 is still at top velocity and accuracy for me.
 
A pressure test with the 170's and RL 26 showed that 64 grains was max in my rifle as the bolt barely opened. This max gave me 3013 fps over my Magnetospeed. I have not had time to retest my 62.2 grain load since I took care of the carbon ring that had built up in the throat and was playing hell with me but when I do I'll post the results.

Just noticed this from my first post in this thread that I got my numbers jumbled on my max with the 170 Berger and RL 26. The actual number is 3103 fps.
 
After Rich's success recently with H1000 in his 6.5 SS and 143 ELD-X I decided to give it a go and load a quick pressure test. I only loaded 1 each and shot over Magneto at 100 yards.
53 degrees 26.78 inHg
165 Matrix Fed 210 GM Norma brass neck sized only without expander
61 grains 2787
62 grains 2847
63 grains 2883
64 grains 2943

To start with the first shot ended up being 2" higher than the next 3 shots which I'm going to write off to being the first shot with this powder and having not cleaned between using RL 26. The next 3 shots were all basically on the same vertical plane with some horizontal spread. This is very promising since there was 3 grains powder difference between them and nearly 100 fps difference. Some of the horizontal can be attributed to not having the exact same cheek weld every shot and my scope is only a Zeiss HD5 3-15x50 with rapid z 800. The crosshair is pretty thick at .350.

The bolt lift on all shots was easier than my RL 26 loads with the primers still being rounded and just starting to get a hint of a crater at 64 grains. I didnt load high enough to max out but i'm going to try and get 65 and 66 shot today to see where i max out then start some groups. I'd expect somewhere around 3050 fps with 66 grains but need to see where the pressure is.... This would be comparable to my RL 26 load with 62.4 grains which I shot over the magneto yesterday with 64 degrees and 26.9 inHg. This load yielded 3043 and 3045 fps.
 
I made it back out and luckily the conditions were the same as yesterday. I shot 65 2965
66 3001
66.7 3036
of H1000 just a single shot and found my max pressure and physical capacity at 66.7. The 66 and 66.7 load both had a very shiny extractor mark and heavier bolt lift so I'll try some groups from 64 to 65 in .3 or .4 grain increments next time out.
 
I made it back out and luckily the conditions were the same as yesterday. I shot 65 2965
66 3001
66.7 3036
of H1000 just a single shot and found my max pressure and physical capacity at 66.7. The 66 and 66.7 load both had a very shiny extractor mark and heavier bolt lift so I'll try some groups from 64 to 65 in .3 or .4 grain increments next time out.

Any more data on loading?
 
I've done some shooting on and off. I'll have to look at notes as I have played with rl 23 and n565 some. Later in the week I'll get time to check. I'll actually be shooting it Wednesday or Thursday. I have some 165 long range accubond on backorder for when they are released to try out also.
 
Sent Rich and email about where to post load data and he provided me with this site. Have attached a file for the load data developed for my 7mm Sherman ss and 180 grain Lapua Scenar L bullet.
 

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  • 7mm ss load data.txt
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