37XC

[hypertex]

Needed a thread for the data as we play around with this new offering.

SO... still breaking everything in. Had to make some guesses as to where to start with IMR-8133(or any other powder for that matter) I used Retumbo in Quickload for predictions but the velocities and pressure were low.


108 deg 30% humidity today All loads 4.610" COAL IMR-8133 215M primer

375MTH fps 402MTAC fps
117.1 2820 113.1 2779
117.3 2891 113.3 2787
117.5 2850 113.5 2715
117.7 2855 113.7 2808
117.9 2903 113.9 2794
118.0 2912 114.1 2793
118.1 2920 114.3 2773
118.2 2868 114.5 2776
118.3 2935 114.7 2807 <<<very slight crater/swipe
118.4 2885 very slight crater

Shot 5 rounds, waited 10 minutes; shot 5 rounds, etc. It was hot. The hottest of the 402 loads was the last shot of the day.
YMMV, still don't have 50 rounds down the barrel yet

 

[jasent]

Tagging for later

 

[hypertex]

Vestal's site quoting a Tubb document with some development data. The Vestal's link will let you view, the Tubb link is a download

 

[jasent]

All loads are max

Results of testing from 4 different Schneider barrels – use caution when reloading by starting with a 4-grain reduced charge.
37XC 33-inch barrel. Warner 361 gr Flatline 7 twist 5P rifling 120 gr H1000. 3055 fps
122 gr RETUMBO 3080 fps
120 gr IMR 8133 3060 fps



33XC with 28-inch Schneider 5 P rifling barrel - 9 twist – medium contour
119.5gr Reloader 50 124 gr H50 BMG 128 gr H50 BMG 128 gr H50 BMG 121 gr Reloader 33 125 gr Reloader 33 128 gr Reloader 33
3200fps with Warner flatline 285gr turned solid bullet 3160 fps with Berger 300 gr
3380 fps with a 250 Solid Badlands bullet
3320 fps with a 250 Sierra
3120 fps with a Berger 300 gr
3425 fps with a 250 gr Badlands solid 3460 fps with a 250 gr Sierra

 

[jasent]

Hypertex how long is your barrel and what twist?

 

[hypertex]

Hypertex how long is your barrel and what twist?

My bad...
Tubb ATR 37xc 33" 1:8 twist
Going to load by tenths for another grain to see where primers are flattening.

 

[hypertex]

Went back to the range with more 8133 loads. Temps hovering at 100 degrees. incremental 375 to 119.0 and 402 to 115.3 yielded no real increase in velocity. Is the powder not all being consumed before the bullet leaves the barrel? (does that even make sense?)

 

[jasent]

Most likely the case. Or your in an upper node. Could try a slightly faster powder like retumbo or h1000. Might get a bit more speed. How’s the case fill??

 

[hypertex]

Virtually to the top of the shoulder. Here are the numbers for todays 8133 loads of the 375MTH. Noticeably slower than the first trip.

100* 35% 28.53 DA 4430

118.5 2857
118.6 2895
118.7 2824
118.8 2815
118.9 2824
119.0 2900

 

[hypertex]

Switching from 375MTH to 377MTAC bullets. So far performance is a direct 1:1; DOPE is lining up all the way out to 3185y. The less expensive bullet is flying just the same.

 

[hypertex]

I ended up trying some N570 for the 377 grain CEB MTAC's. My magnetospeed is acting up so I had to "do the math" to figure the MV otherwise I would post the ladder test info. The best looking load yielded 3025fps i.e. 118.4 grains in my 33" barrel . Next up are 402MTAC's and Retumbo.

 

[hypertex]

M/S is still on the fritz... same caveat as previous:
28.62" Hg 113.9 grains Retumbo w/ CEB 402 MTAC (460 yd. Zero)

Distance.....temp........Dial
1890 yds.......65............15.7
2169...............57.............20.8
2625...............65............31.1

Calculates out to 2851 fps using POI method

 

[jasent]

I’m still working on load development and getting the barrel all broke in. Currently shooting 350gr smk’s at 2945 with 118gr h1000. Had to remove the brake to get speed with the ms.
32” 1:10. When I finish off this box of smk’s I’ll start playing with the flatlines

 

[pinhead]

Does anyone have any more updates to their 37xc loads with powders other than H1000, Retumbo, or 8133?