Sierra Heavy TMK 6MM Testing

[Formidilosus]

Stop with the nonsense.

1:7.5” twist is just fine for the 116’s. So is a 1:8” so far. You guys chicken little’ing are not helping anyone.

 

[huntnful]

tip melting?

Shit I’m not sure on that one lol. Never crossed my mind.

Playing with the Berger stability calculator, the 116 moving at 3100 fps at 1,000 DA in a 1/7.5 shows “Marginally Stable” (1.49 SG)

The same bullet at the same atmospherics going only 2700 from a 1/7 barrel shows “Stable” (1.64 SG)

Right, but I’ve shot a lot of bullets in the 1.4-1.49 SG range with zero issues at distance.

I don’t think it’s a stability thing. But not sure what it can be lol.

I just know for a fact that if I true at 1000 yards I’m high as shit at 600, and if I true at 600 I’m way low at 1000 lol.

And the other gun didn’t have that issue, and I’ve never really had that issue before, except with some hammer bullets, but those things are wack lol

 

[coya]

My ace 6cm 1:7.5 shoots the 116 very well from 100 to 1000.
With that said, I'd be interested in the @Lawnboi group buy

 

[Carl Ross]

Stop with the nonsense.

1:7.5” twist is just fine for the 116’s. So is a 1:8” so far. You guys chicken little’ing are not helping anyone.

Seriously. I used them with two 1-8’s when testing, at 2840 and 2960 fps if I recall. Took the slower one hunting in the winter.

Shot a match with my 1-7.5 twist Dasher at 2735, used a .300 G7 to have drops line up, zero weirdness.

Sierra is going to be extra conservative with their recommendations. If I was building a hot rod 6mm for the 116’s for my use I’d probably spec a 1-7.5” on purpose to keep rpm’s a little lower.

 

[Lawnboi]

Seriously. I used them with two 1-8’s when testing, at 2840 and 2960 fps if I recall. Took the slower one hunting in the winter.

Shot a match with my 1-7.5 twist Dasher at 2735, used a .300 G7 to have drops line up, zero weirdness.

Sierra is going to be extra conservative with their recommendations. If I was building a hot rod 6mm for the 116’s for my use I’d probably spec a 1-7.5” on purpose to keep rpm’s a little lower.

I’m sure 7.5 is fine, Iv shot a lot of bullets that don’t have a 1.5 SG.

I need to be stable in a dasher at -2000ft DA, only reason for wanting 7 twist for them.

 

[Formidilosus]

Shit I’m not sure on that one lol. Never crossed my mind.


Right, but I’ve shot a lot of bullets in the 1.4-1.49 SG range with zero issues at distance.

I don’t think it’s a stability thing. But not sure what it can be lol.

I just know for a fact that if I true at 1000 yards I’m high as shit at 600, and if I true at 600 I’m way low at 1000 lol.

And the other gun didn’t have that issue, and I’ve never really had that issue before, except with some hammer bullets, but those things are wack lol

If you are positive of all the things- zero, inputs in the calculator, environmentals, etc…. It sounds like a scope swap is in order.

 

[huntnful]

If you are positive of all the things- zero, inputs in the calculator, environmentals, etc…. It sounds like a scope swap is in order.

Will do. It’s the only logical next step

 

[Carl Ross]

I’m sure 7.5 is fine, Iv shot a lot of bullets that don’t have a 1.5 SG.

I need to be stable in a dasher at -2000ft DA, only reason for wanting 7 twist for them.

In that application with the variables all stacked against you I get it. Same for a short barreled 6x45 or 6 ARC.

 

[Sako300]

Will do. It’s the only logical next step

Only the Shoot2Hunt scope of course!

 

[huntnful]

Only the Shoot2Hunt scope of course!

Hahaha I’ve never had an issue with these scopes, but there’s a first time for everything.

If it’s a scope issue, it’s sure consistently inconsistent lol.

Already swapped them so we’ll see next weekend!

 

[Lawnboi]

Hahaha I’ve never had an issue with these scopes, but there’s a first time for everything.

If it’s a scope issue, it’s sure consistently inconsistent lol.

Already swapped them so we’ll see next weekend!

Probably an moa problem

 

[Lawnboi]

@Carl Ross

Are you shooting these for PRS?

 

[Carl Ross]

@Carl Ross

Are you shooting these for PRS?

I shot one match with them, but I only have the prototypes they sent me, not a large stash. Just got 1,000 105 SMK’s for that purpose, but I’d be fine shooting the TMK’s too.

 

[huntnful]

Probably an moa problem

that’s the mostly likely scenario TBH

 

[KingOfTagSoup]

What’s the details on the gun and load?

I’ve been trying to get them to shoot good. Best I can do so far is about 1.5 moa.


Sent from my iPhone using Tapatalk

Factory Howa mini action. 31.0 grains Leverevolution, OAL 2.310, Federal 205M primers

 

[huntnful]

I've shot the 116's twice now at distance to confirm what puzzled me on my first trip out.

The trued data I need to hit center at 1020 yards puts me 1 MOA (.3 mils) high at 700 yards.

I can't really make sense of that large of a discrepancy, but I've shot it twice now, once in the morning and once in the evening. Both times with good environmentals. Both times, same exact results.

That correction would put me at .31 G7 at 600-700 yards, and somewhere between there and 1020 yards it drops to a .28 G7. Just seems like a large drop. Not quite sure what to make of it, wondering if anyone else has any similar info?


The bullets also shot well on the last trip out. 5 shots into a .5 moa group at 622 yards and 4 shots into a .5 moa group at 1027 yards.

Update to this post. I swapped the scope and ran back out this evening.

Conditions were perfect. 5-7 mph right wind. Bullets trued perfectly to the advertised .609 G1 BC out to 1000 yards in a 7.5 twist.

New scope. Re-zeroed at 100 yards.



3 at 600 yards


3 at 1000 for a 2 3/8” group. Upper group was my 6.5-7. I missed off the left edge with my first shot and the dust “looked” high. I dialed down .5 MOA and held more wind and shot the 3 shots on the plate. Had I just left the turret where it was, elevation would have been spot on with the data.

 

[Sako300]

Update to this post. I swapped the scope and ran back out this evening.

Conditions were perfect. 5-7 mph right wind. Bullets trued perfectly to the advertised .609 G1 BC out to 1000 yards in a 7.5 twist.

New scope. Re-zeroed at 100 yards.
View attachment 1048240


3 at 600 yards
View attachment 1048242

3 at 1000 for a 2 3/8” group. Upper group was my 6.5-7. I missed off the left edge with my first shot and the dust “looked” high. I dialed down .5 MOA and held more wind and shot the 3 shots on the plate. Had I just left the turret where it was, elevation would have been spot on with the data.
View attachment 1048244

View attachment 1048246

I think you made Forms blood pressure go down!

 

[huntnful]

I think you made Forms blood pressure go down!

Haha I was pretty clear that 7.5 twist didn’t scare me, and that a BC drop/correction of that magnitude didn’t make sense. Also that a SLIGHTLY low SG was likely not an issue. I’ve shot lots of bullets in “marginal stability” per Berger’s calculator with zero issues.

I was just trying to make sense of what I was seeing on target after two consecutive range trips of weird shit. It’s nice to be able to just ask a group of knowledgeable people instead of make numerous range trips trying only my ideas. Even if people panic…. That’s on them lol

 

[BBB]

thanks for sharing huntnful. This is something many, I’m sure, have experienced. Always great to watch a problem be corrected and we all learn from it. Can I ask, what is your thoughts on the initial scope error? Tracking error? Do you mind sharing which scope it is, out of curiosity?

 

[huntnful]

thanks for sharing huntnful. This is something many, I’m sure, have experienced. Always great to watch a problem be corrected and we all learn from it. Can I ask, what is your thoughts on the initial scope error? Tracking error? Do you mind sharing which scope it is, out of curiosity?

To be totally honest, I’m still on the fence about it truly being a scope issue. It definitely could solely be the scope, but maybe I was also underestimating how bad the mirage really was, because tonight was crystal clear and it was apparent. Mirage can be terrible where I shoot and absolutely causes impact shifts. But these were pretty drastic given how good the data was. 6” high at 600 yards is a lot, even with bad mirage in the air.

The scope was a trijicon tenmile 5-25X50 FFP.

I have three of them, and they have been zero issues for me. It just seems a bit odd for the one on a little 6 creed to randomly take a shit between range trips, but still holding a rock solid zero and RTZ.