Sierra Heavy TMK 6MM Testing

[coya]

Is your 107 load with imr4350 also? Do you mind sharing what it was?

107 tmk/108 eldm
Imr4350 41.9gr
2.800
107 tmk 2982fps
108 eldm 2983fps

Both shoot a 1.5 inch group

 

[brucemt]

107 tmk/108 eldm
Imr4350 41.9gr
2.800
107 tmk 2982fps
108 eldm 2983fps

Both shoot a 1.5 inch group

Thanks coya, appreciate it

 

[coya]

Tried the 116's a touch hotter at 41.0 grains of imr4350 and the gun didn’t like it. Gonna keep the 40.6 load and just let her be a "good gun"

 

[Hurley88]

Ok, rooouuugh mock-up (time constraints & not using this gun with the 116 TMK), but here goes.

I didn’t disassemble the bolt for a real Wheeler test, didn’t use bullet seater with microneter adjustment, just did it by feel and measured as I went. So don’t trust my numbers, I just didn’t want the bullet rammed into the lands.

Looks like when seated to mag length in M+ mags, the neck grabs the whole bearing surface of the bullet and the jump distance is somewhere around 0.088–0.116” (like I said, rough).

I’ll be out in the morning hopefully to shoot some and post velocities. Will do as I usually do, just a half grain difference per round and record the velocity. First sign of any pressure, I subtract a grain and call that max. I’ll post up here if I can get ‘em done.

 

[coya]

Tried the 116's a touch hotter at 41.0 grains of imr4350 and the gun didn’t like it. Gonna keep the 40.6 load and just let her be a "good gun"

Forgot to mention, this load shot 2910fps

 

[Hurley88]

Tikka 243, 16” McGowan barrel, Starline Brass, 116 TMK. Seated to mag length in M+ magazines.

H4831SC
42.5: 2542
43.0: 2599
43.5: 2611
44.0: 2639
44.5: 2689

H4350
39.0: 2608
39.5: 2630
40.0: 2665
40.5: 2696
41.0: 2726

No stiff bolt lift or discernible differences in primers or case head. But this was shaded, breezy, and 66 *F so not a scorcher. 740ft elevation. I would caution anyone at around 40.5 H4350 or 44.5 H4831; the best determiner of pressure we currently have is velocity, and the 2650-2690fps range seems to be the red zone for this barrel length from all the similar reloading data I could find. Those numbers would be 2770-2790 for 20” barrels and 2890fps for 24” barrels.
I’m not the type to push the envelope, I’d just build a PRC or put a longer barrel on if I wanted more.

But, there’s some data for everyone. Good luck guys! Ima get back to what I came here for haha