Sierra Heavy TMK 6MM Testing

[Formidilosus]

I really need to go to these classes sometime and show that I’m all talk, no skill…


Maybe it’s been posted a bunch in here but does anyone know the OAL of a 6UM with 116 TMK’s and how far from the lands that is with a UM reamer? Ryan is the expert but he’s a busy guy and I know a few of you prob know this.

2.920” is what I have used for a couple different ones. No idea how far it is away from the lands- it’s no where close. Ryan’s one rifle shot better when I loaded his ammo like mine, and not close to the lands.

 

[walkingduckwaterfowl]

I’ve shot 80 or 100 rounds of their 108 eld-m and x. Prone on pack groups were 1.5-2 in. No bad batches. For comparison, I get cheap stuff for volume shooting that groups around 3 in.
Never chronographed, but 2900-2925 is about what matches trajectory. 22 inch barrel 1/8 twist tikka.
Overall, very satisfied.

Was this with copper creek or choice? Thanks for the input

 

[5MilesBack]

Seems like UM is/was loading 243 with heavies in particular to retard hot levels, not just in your gun. I'd bet if you could get them to load it around 40.5 grains H4350 it would be a good place to source from still.

I pulled all my UM 108 eldm's (Norma brass) that I had and reloaded them with 41gr H4350 and to 2.80" COAL and they still shot 2960fps in a 22" Tikka 243. Loaded some virgin Lapua as well to the same spec and those shot 2856fps avg.

 

[walkingduckwaterfowl]

Seems like UM is/was loading 243 with heavies in particular to retard hot levels, not just in your gun. I'd bet if you could get them to load it around 40.5 grains H4350 it would be a good place to source from still.

Sierra has sold good factory 6 creed ammo with 107 SMKs, kind of doubt they'll do 107 TMKs in a 243.

I do have a 6cm seekins that is shooting really well with factory white box 108eld-m....but its not a tikka. I would definitely buy factory TMK in 6cm if that ever happens.

Initially UM was initially going to dial the loads back for me but they ended up getting me a refund minus the shipping costs. I think UM is a great company that brings great ideas to life and I am happy with the resolution. I knew there was risk when I made the purchases but I miscalculated the risk of pressure issues and more expected potential accuracy issues just like when buying any factory ammo (your rifle may or may not "like" it). I don't blame them for not wanting to enter a potentially endless loop of load development when thats a service they normally charge 1199$ for.

I do think there is a market for good killing bullets loaded to some sort of book or SAAMI standard with a disclaimer for accuracy issues absent load development. Something like "these are loaded per specs in X manual". That's more what I thought I was getting in a "factory load". In all other areas I commend UM for attempting to do cutting edge stuff that other companies aren't interested in bringing to market.

The recent podcast was interesting where they refer to rokslide as a wastebin for complaining. That's a strange thing to say about a good percentage of your customer base. That being said, the carbon ring comment is a bit tongue in cheek. I went waaay back and re-listened to one of the episodes of the early podcast I believe it was FF 15 in 2024 about barrel break in and cleaning. Form appears to express that only absurdly hot loads or bullets entering the lands will experience pressure issues in a rifle thats not been cleaned. I'm no expert at reloading or long range shooting, but do have experience shooting thousands of rounds from suppressed gas guns that run very dirty without issue. Considering the advantages in design of modern bullets, it seems that loading for reliability instead of speed would also likely achieve good enough accuracy and terminal distance for most real world use.

 

[atmat]

The recent podcast was interesting where they refer to rokslide as a wastebin for complaining. That's a strange thing to say about a good percentage of your customer base.

This is an opinion they’ve expressed in one way or the other multiple times here on the forum.

While I do see their point to some degree, I don’t fully agree with it.

That said, it doesn’t seem to be hurting their business so no reason for them to change.

 

[6creed]

Moved

 

[waspocrew]

Anybody have recent load data for the 107s in a 6ARC? I have a PBB 18" barrel and have been shooting 95 tmks but they seem pretty tough to tune. I am about 1.5 inch groups with varget and much worse with all other powders. I just ordered a box of 107 tmks hoping they tune better. My barrel shoots 103 eldx very well, but everything else just doesn't seem to group. I am not opposed to using the 103s but there seem to be mixed reviews in terminal performance. I will be shooting elk with this rifle and hopefully a moose in 2028. Please let me know what your experience has been.

I just started working with the 107 in my 18” 6 ARC. I’ll contribute more to the thread next week.

Thread 'Sierra 107 TMK Load Data'

Apr 14, 2026

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• Ryan Avery
• Replies: 97
• Forum: Reloading

• 

 

[Ryan Avery]

I really need to go to these classes sometime and show that I’m all talk, no skill…


Maybe it’s been posted a bunch in here but does anyone know the OAL of a 6UM with 116 TMK’s and how far from the lands that is with a UM reamer? Ryan is the expert but he’s a busy guy and I know a few of you prob know this.

They seem to like big Jumps. Nick and I loaded the Endex 6UM at .90 off and the Preferred barrel 6UM at .120 off.

 

[Odd1out]

They seem to like big Jumps. Nick and I loaded the Endex 6UM at .90 off and the Preferred barrel 6UM at .120 off.

I have seen the same situation with the 153s jumping .80, 107s jumping .95 and shooting awesome groups.

Sent from my SM-G986W using Tapatalk

 

[Luxin Tenebris]

Was this with copper creek or choice? Thanks for the input

Copper creek