Sierra Heavy TMK 6MM Testing

[Schmo]

The sierra site says available mid-March and given their availability issues in the past I would assume even that date is optimistic.

I’m hopeful that the new leadership will be able to hold to that timeline

 

[KyleR1985]

Based on my correspondence with Sierra, I would expect staggered delivery of the new TMK’s, following which ones get design/testing done first.

While I can’t speak to when bullets actually get produced and shipped - 6mm 107’s and 6.5mm 153’s will get run first, with .25’s, 6mm 116’s, and .22 88’s to follow loosely in that order.

 

[wind gypsy]

131 TGK might be a nice bullet for fast quarterbores too.

 

[Schmo]

131 TGK might be a nice bullet for fast quarterbores too.

Gross

 

[dreamingWest]

Any chance a 10 twist 243 would stabilize the 107s?

 

[Carl Ross]

Any chance a 10 twist 243 would stabilize the 107s?

You’d have a decent chance…at 12,000 ft in July.

For general use, no.

 

[eric1115]

Any chance a 10 twist 243 would stabilize the 107s?

No, especially if they are as slippery as advertised. 95 TMK is your huckleberry.

 

[wind gypsy]

No, especially if they are as slippery as advertised. 95 TMK is your huckleberry.

Even that might be marginal. Sierra calls for 1:9 min twist.

 

[eric1115]

Even that might be marginal. Sierra calls for 1:9 min twist.

That's true, but it does seem like they set that twist spec to be able to shoot a 6x45 in Death Valley at -20°F.

Still, @dreamingWest you should probably buy 100, not 1k to start.

 

[dreamingWest]

If I end up with 10 twists 243s, I'll just stick with NBTs.

I'm shopping a lefty 6mm for my son and a righty for myself this year. I'm hoping for easy button no gunsmith necessary options from Tikka or Browning. Watching Shot Show releases this week.

 

[blacktailcentral]

131 TGK might be a nice bullet for fast quarterbores too.

How much of a difference in expansion between the tgk and tmk?

 

[24valve]

Even that might be marginal. Sierra calls for 1:9 min twist.

Sample size of 1, but we've shot 95 TMK's out of a 1-10 Tikka 243 with no stability issues in the mountain west.

 

[24valve]

How much of a difference in expansion between the tgk and tmk?

I'll preface this having only shot elk, deer, and antelope with TMK's but I understand that there is a very large difference. TGK's have a much tougher jacket, which means that they expand and fragment minimally, but penetrate deeper compared to TMK's.

Here is a link to the 6mm success thread to someone with firsthand TGK experience: "Entrance was caliber size and exit was probably a one inch hole." A friend of mine killed an elk with them this past fall and this was his experience as well.

Post in thread '6mm /.243 hunting success on Big Game'

Dec 4, 2025

I didn't take any more photos after I started processing it. Entrance was caliber size and exit was probably a one inch hole. There was a very good blood trail. We have 10-15 kills with the 90s and 6.5 130s with great results. Most of our shots are 200 yards and in though.

• Mrwoodard

 

[Jordan Smith]

I'll preface this having only shot elk, deer, and antelope with TMK's but I understand that there is a very large difference. TGK's have a much tougher jacket, which means that they expand and fragment minimally, but penetrate deeper compared to TMK's.

Here is a link to the 6mm success thread to someone with firsthand TGK experience: "Entrance was caliber size and exit was probably a one inch hole." A friend of mine killed an elk with them this past fall and this was his experience as well.

Tough to make an assessment based on a small sample size. I've seen similar performance (caliber entrance, 1-1.5" exit) from various models of the ELD-M in multiple instances, as well, but that doesn't mean that the ELD-M and TGK are terminally equivalent, broadly speaking.