Sierra Heavy TMK 6MM Testing

[Q_Sertorius]

Awesome and what are you using to set neck tension?

I’m seating the bullet using the die.

 

[blacktailcentral]

I’m seating the bullet using the die.

So no neck bushing die or mandrel?? And with the new brass are you sizing it first or just loading it?

 

[pods8 (Rugged Stitching)]

I didn’t see any sign of hitting the lands at 2.9” either. I cannot load them out further than 2.8”, or they won’t load in the magazine.

Is this a tikka? If so this is a silly stance to take when loading LONG bullets since M+ length mags (~2.97") work just fine in the same gun (same bolt stop). If you have interest in loading LONG bullets try loading them closer to the lands (single load them) and see if they improve, then you know if its worth pursuing the easy route of a longer M+ mag or not without having to buy anything initially. If they don't improve then different powder, etc. or move on from the bullet.

 

[huntsd]

Lapua is some of the best brass there is, but it’s not immune to the odd poor lot. I would measure neck thickness variation on that lot. I also agree with the others that said your consistency should improve on the second firing, as long as your brass processing method is consistent. I would also consider a hotter primer to ensure good ignition with ball powders (probably not the issue, but worth trying).

An ES of over 100 fps is enough to cause misses at distance.

For reference, I chrono’d two loads yesterday, a 20-round group with an ES of 45 fps and an SD of 13, and an 8-shot group with an ES of 37 and SD of 12. Both were with thrown powder charges, this first with Superformance and the second with H4350.

In general, I wouldn’t put too much faith in any statistical analysis your chrono provides of groups less than 10 shots, and 20 is much better, while 30 shots starts to inspire some statistical confidence.

If it’s bothering you, got anything hotter to try? WLR or magnums?

This is going to be my primary hunting gun for the year. Happy to do bit more work to improve it. Would 215m be your first pick? I have those on hand. I assume I’d have to back down few gr.

One thing to note is I am using a mandrel. I dip the inside of my case neck in carbon media before running the mandrel. I don’t wipe the carbon residue out before seating. Could this be a possible issue or not? First time using a mandrel

I’ll try one more “trick” if not may just need to move on from tmk

 

[pods8 (Rugged Stitching)]

This is going to be my primary hunting gun for the year. Happy to do bit more work to improve it. Would 215m be your first pick? I have those on hand. I assume I’d have to back down few gr.

I don't have a specific pick, just something hot (magnum or WLR which are pretty hot) to determine if the ES is from an inconsistent ignition issue. If your load is up there in pressure (I didn't look back) then backing off a little isn't a bad idea for this mental exercise. If those loads have more consistent ES then work back up in pressure and see if it holds.

 

[Q_Sertorius]

Is this a tikka? If so this is a silly stance to take when loading LONG bullets since M+ length mags (~2.97") work just fine in the same gun (same bolt stop). If you have interest in loading LONG bullets try loading them closer to the lands and see if they improve, then you know if its worth pursuing the easy route of a longer M+ mag or not. If they don't improve then different powder, etc. or move on from the bullet.

I’m using M+ magazines and Waters magazines (2.8”).

The first group I shot above was at 2.9”. It shot worse than the second group, which was at 2.8”.

I can try them again at a longer length. But I really don’t think that’s the difference maker.

2.8” next to factory

2.9” - definitely looks like it should be better.

Edit - I’ll try again at 2.95”.

 

[Q_Sertorius]

So no neck bushing die or mandrel?? And with the new brass are you sizing it first or just loading it?

It’s resized once-fired brass.

 

[blacktailcentral]

It’s resized once-fired brass.

Perfect, looking at the 2.8 vs 2.9 coal the 2.9 looks better for the neck shoulder junction. As i mentioned find the lands first, you may not need to seat at the full 2.9”. but if yiu aren’t finding the lands you are kindof just throwing paint at the wall and hoping it sticks.

 

[Q_Sertorius]

Perfect, looking at the 2.8 vs 2.9 coal the 2.9 looks better for the neck shoulder junction. As i mentioned find the lands first, you may not need to seat at the full 2.9”.

I definitely agree that the 2.9” looks far better for the neck shoulder junction. But after it shot like crap at 2.9” (the horrendous 10-shot group above with the three “flyers” marked with pink lines), I went down to 2.8”. That took the 116’s group down to about 2”, but I never saw much improvement from there.

At 2.8”, the 107s shoot about like the 100-grain Hornady factory load (around 1.6”).

This rifle just came back from getting its new stock (I never shot it before sending it off to Mike), so it’s still an unknown quantity to me.

 

[Q_Sertorius]

Appreciate the tips and advice here. This is RokSlide at its best.

 

[43.6N]

Appreciate the tips and advice here. This is RokSlide at its best.

Q im not sure, but I don’t think your reloads are the problem.
Have you put any factory ammo through it yet since getting back?

I’d love to know how a box of federal premium patterns before wasting more of your TMK/H4350 components.

Edit, never mind I went back and saw you shot 100gr factory loads for a 1.6” group.

I’d check action torque, and swap to a different scope.

 

[Q_Sertorius]

Q im not sure, but I don’t think your reloads are the problem.
Have you put any factory ammo through it yet since getting back?

I’d love to know how a box of federal premium patterns before wasting more of your TMK/H4350 components.

I agree. That’s why I tightened the bottom metal from 45 to 60 this morning. As soon as they cancel my 1:00 meeting, I am going back to the range. I’ll see if that makes a difference. The ammo I have is left over from my old Sako, which put it into 0.8” groups. But it was too pretty, so I sold it.

 

[43.6N]

I agree. That’s why I tightened the bottom metal from 45 to 60 this morning. As soon as they cancel my 1:00 meeting, I am going back to the range. I’ll see if that makes a difference. The ammo I have is left over from my old Sako, which put it into 0.8” groups. But it was too pretty, so I sold it.

Good luck man.