Sierra Heavy TMK 6MM Testing

[BCsteve]

Tgk is a much thicker jacket than the tmk. It will have a much longer neck length than the comparable tmk.

I did my best and sectioned a 145gr TGK and a 143gr ELDX. The TGK is thinner than the ELDX and probably closer to an ELDM or TMK, maybe in between. I wouldn't call it "much thicker". The copper alloy might make it tougher though. The lead is definitely harder i could easily scratch the ELDX not so much with the TGK.

 

[Jud96]

I’m looking forward to these and happy to see Sierra stepping it up. Hoping they are as consistent and shoot as well as Berger’s.

 

[Formidilosus]

6x45mm. 117gr TMK. 23gr Leverevolution. 2.615” coal. 2,207fps MV average.




The “bad” group-





@Ryan Avery 6UM 30, 115gr TMK



116gr TMK-



117gr-

 

[Brandon.miller.4]

6x45mm. 117gr TMK. 23gr Leverevolution. 2.615” coal.

View attachment 993026


The “bad” group-
View attachment 993027




@Ryan Avery 6UM 30, 115gr TMK
View attachment 993028


116gr TMK-
View attachment 993034


117gr-
View attachment 993035

Is there a quick reference to how these rifles shoot with other bullets?

 

[Formidilosus]

Is there a quick reference to how these rifles shoot with other bullets?

Ryan’s is “ok”. He says it is about a 1.5 MOA rifle with 115gr DTAC’s- so the 115gr TMK and 117gr TMK are right there with it. The 6x45 is @longrangelead rifle, and I do not know how it shoots normally as these are just first rounds with it. It also is just for low velocity impact testing, 1.2 MOA is just fine.

 

[Moose83]

6x45mm. 117gr TMK. 23gr Leverevolution. 2.615” coal.

View attachment 993026


The “bad” group-
View attachment 993027




@Ryan Avery 6UM 30, 115gr TMK
View attachment 993028


116gr TMK-
View attachment 993034


117gr-
View attachment 993035

Curious why the 6x45? Wouldn't the usable velocity window be rather small?

 

[Formidilosus]

Curious why the 6x45? Wouldn't the usable velocity window be rather small?

Read my last post- low impact velocity testing.

And no, with 26gr lever it got 2,440fps MV- it hits 1,800fps impact at 5,000ft DA at 570 yards.

 

[Kaleb]

That's interesting. A little 6x45 would be pretty cool. What magazines are you using or what modifications did you have to do to the magazine to get the length? My longest 223 loads are 2.515 with 88's so I've not thought much about going over 2.6 Thanks.

 

[nm.otter]

The 6x45 is @longrangelead rifle, and I do not know how it shoots normally as these are just first rounds with it. It also is just for low velocity impact testing, 1.2 MOA is just fine.

I'll take 0.36" MR and say, "Thank you."

 

[43.6N]

Thank you guys for taking the time to keep us updated! I’m sure you have a lot of irons in the fire

 

[Formidilosus]

That's interesting. A little 6x45 would be pretty cool. What magazines are you using or what modifications did you have to do to the magazine to get the length? My longest 223 loads are 2.515 with 88's so I've not thought much about going over 2.6 Thanks.

This was an NDR mag, but I had to single feed it. I will make the next ones 2.6” to fit.

 

[Moose83]

We must've posted at the same time... I didn't see your post yet. Those are decent numbers for only 2440fps. I doubt I'd get that where I'm at tho.

 

[PathFinder]

243 Improved testing. Started at 2.945, which is about .020 off. They seemed to shoot a bit better at 2.910. All loads are 48 grains of H1000 in a factory Tikka 20" 1:8 twist barrel.
One of the three seems prone to leave one a bit out of the group. The other two shoot about identical to every other bullet this barrel has been fed, which is good. MV is just over 2900.

 

[rharbaugh]

6x45mm. 117gr TMK. 23gr Leverevolution. 2.615” coal. 2,207fps MV average.

View attachment 993026


The “bad” group-
View attachment 993027




@Ryan Avery 6UM 30, 115gr TMK
View attachment 993028


116gr TMK-
View attachment 993034


117gr-
View attachment 993035

Do you have a barrel length and muzzle velocities for Ryan’s UM?

Since the 6x45 was used for low impact velocity testing, does that mean the UM was used for high impact velocity testing?

Edit to add: are you seeing any differences with impact testing vs other TMK performance?

 

[rousseb]

@Procision Arms just finished up my 22 Creed. Could not be happier. 20" 1:7 Proof Research and Trigger Tech trigger. MDT LSS XL Chassis. I put about 40 rounds through it yesterday and it a shooter. Not my first rifle by @Procision Arms . These guys are meticulous when it comes to sub tensions and QC.

Who are we talking about that works magic on rem 700 builds?

The men over at @Procision Arms

 

[7SAUM-J]

I appreciate all of the info on these. The 6mm hunting thread sucked me into a 20” Ruger American II in 6 creed a month ago and I’ve got all of the current heavier offerings to do load development with. It’s been quite fun so far.

 

[Formidilosus]

Do you have a barrel length and muzzle velocities for Ryan’s UM?

18”. 3125fps MV

Since the 6x45 was used for low impact velocity testing, does that mean the UM was used for high impact velocity testing?

Edit to add: are you seeing any differences with impact testing vs other TMK performance?

Yes the UM will be used for high impact velocity testing. When completed we will share what we can about the results.

 

[khuber84]

Who's been shooting these in a low to mid mileage barrel 6creed?

What's oal touching the lands?

What's the bearing position in the case neck when touching?

Some pics would be greatly appreciated!

 

[Grumpystilskin]

Very interested in this thread, as I just bought a Weatherby Live Wild in 243 Win. It has a 1-7.5 twist barrel. Thanks to all the testing y’all are doing!!

 

[B_Reynolds_AK]

Who's been shooting these in a low to mid mileage barrel 6creed?

What's oal touching the lands?

What's the bearing position in the case neck when touching?

Some pics would be greatly appreciated!

Did you see this post?

C

Post in thread 'Sierra Heavy TMK 6MM Testing'

Dec 21, 2025

This is in your Seekins 6 CM correct? If so, SAAMI freebore of .183.

Seated at .080 off, where does this put the boat tail to shoulder junction in the case?
Wondering if a longer fb, such as the PVA Standard (.210) might optimize these even more.

Any chance you could take a photo of a loaded round with a bullet lined up next to it?

@khuber84 I think a short 6 CM slinging these 117’s at 2800-2850 would be absolutely phenomenal.

Apologies for the terrible lighting. This is seated at a .085" jump, but this barrel also has over 1400 rounds on it. My typical...

• Carl Ross

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