Sierra Heavy TMK 6MM Testing

[walkingduckwaterfowl]

How much powder did they put behind the tmks? Seems like those are cooking out of a 20”.

This was my thoughts, but I don't reload so I can't speak to it. I realize that this is a blunt tool, but maybe we can do some back engineering math if anyone knows what norma brass and primer weigh. I weighed several and they were all within half a grain of each other, so whatever they did it appears to be consistent.

For further context on the rifle, it has about 120 rounds through it now and has been very accurate with just about everything I have shot through it with the notable exceptions being 95gr berger classic hunter factory loads and the TMKs. I am wanting that TMK terminal performance so it'd be great if I could get it to run in either of my 8 twist Tikkas. Also potentially of note, I was shooting at about 1k elevation 70 degrees ambient temp.

 

[huntnful]

This was my thoughts, but I don't reload so I can't speak to it. I realize that this is a blunt tool, but maybe we can do some back engineering math if anyone knows what norma brass and primer weigh. I weighed several and they were all within half a grain of each other, so whatever they did it appears to be consistent.

For further context on the rifle, it has about 120 rounds through it now and has been very accurate with just about everything I have shot through it with the notable exceptions being 95gr berger classic hunter factory loads and the TMKs. I am wanting that TMK terminal performance so it'd be great if I could get it to run in either of my 8 twist Tikkas. Also potentially of note, I was shooting at about 1k elevation 70 degrees ambient temp.

Can you pull a bullet out and just weigh the powder?

Depending on neck tension you can grab on with a stout pair of pliers and rock it back and forth to loosen the neck and then twist it and pull it out.

 

[walkingduckwaterfowl]

That's a great idea I'm trying to leave a much of it intact as I can in case UM wants it back but will do when I find out

 

[huntnful]

Like so. I do it all the time instead of setting up the bullet puller.

 

[huntnful]

I’m getting a .135 freebore 6 creed barrel next. None of the good bullets needs .183 freebore.

 

[Treelineasassin]

I’m getting a .135 freebore 6 creed barrel next. None of the good bullets needs .183 freebore.

These heavy tmk like to jump thus far in my testing, 60-70k jump has been very forgiving with the 107s in a couple different cartridges I've tried them in. Still waiting for my 116s, should be here tomorrow!

 

[huntnful]

These heavy tmk like to jump thus far in my testing, 60-70k jump has been very forgiving with the 107s in a couple different cartridges I've tried them in. Still waiting for my 116s, should be here tomorrow!

Dang. They didn’t do anything special for me unfortunately. I really like the numbers on those suckers. If they hammer in your barrel, they’d be a great option!

Let us know how the 116’s do . My barrel stacks them pretty tight in a central cluster and then spits one out every so often. I think it’s just the reality of a tipped bullet. At least one going fast.

 

[sierracharlie338]

These heavy tmk like to jump thus far in my testing, 60-70k jump has been very forgiving with the 107s in a couple different cartridges I've tried them in. Still waiting for my 116s, should be here tomorrow!

Interesting, I find that 40-60k-ish window to be a common denominator in good groups for most bullets I’ve tried over the years. Seen as far as 120 with some Berger hvlds but 40-60 seems to be a good place to start.

 

[Treelineasassin]

Interesting, I find that 40-60k-ish window to be a common denominator in good groups for most bullets I’ve tried over the years. Seen as far as 120 with some Berger hvlds but 40-60 seems to be a good place to start.

Yeah I agree, that realm of jump works. I typically use Bergers 25/35 off, the again 60-75 off. Sierras are usually the similar. Eldm I find usually shoot well around 45-60 off. Tested a lot of these in various 6mm and 65s. Primarily run Bergers in 7mm and 30 cals.

 

[Castle Rock]

Rifle took it like a champ without heavy bolt lift. It hammers with almost every factory offering I have shot with it including cheap fiocchi 95gr sst that I used to get on paper today. Here is a photo of the load cards from UM. It doesn't show grains of powder or anything so probably not that helpful.

Norma brass is junk, probably the softest out there

 

[TradLife406]

How are 7.5 twists doing for the 6 UM with the 116's?

On the last podcast Avery mentioned that Sierra says the 116's need a 7 twist.

Just ordered two barrels on the LS wild group buy in December.

Will they work? Or sell them and buy an Ace?

 

[huntnful]

How are 7.5 twists doing for the 6 UM with the 116's?

On the last podcast Avery mentioned that Sierra says the 116's need a 7 twist.

Just ordered two barrels on the LS wild group buy in December.

Will they work? Or sell them and buy an Ace?

It’ll be fine. I shot them at 1000 yards at sea level in a 7.5 twist and factory BC was good.

 

[TradLife406]

It’ll be fine. I shot them at 1000 yards at sea level in a 7.5 twist and factory BC was good.

Perfect.

I'm at about 3500-6000 elevation.

$500 was too good of a price for barrels that'll only last 750 rounds.

 

[Lawnboi]

I’m getting a .135 freebore 6 creed barrel next. None of the good bullets needs .183 freebore.

I shot a short throat 6 creed barrel for a season of PRS. It was the most accurate 6 creed out of a few barrels I had by a long shot.

 

[wind gypsy]

I shot the 107 TMK loaded from UM in my 20" 8 twist black/blued tikka .243 with omega 300 suppressor today. I didn't get the results I was hoping for. They were going faster than I expected at an average of 2985 FPS. Accuracy was 1.96" for 10 shots the way that I measured it...either way not what I was looking to do. Rooke mistake, I was not inspecting any of the brass for pressure signs and it is now mixed together with other brass that I shot today.
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I then shot a 7 shot group with the 103 eld-x ammo from UM for 0.92". The average speed was screaming fast at 3055 FPS and I was happy with the accuracy I was getting. I noticed that recoil felt like it was more and started looking at some of the brass and there appeared to be ejector marks?
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The ammo is expensive, so I switched to the 108 eld-m ammo from UM and shot 5 shots at 1.55". This group had two flyers that were likely me as well as two ejected primers and an average speed of 3040 FPS which to me seems like its absolutely cooking for a 20" 243 with 108gr bullets.


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Based on the collective experience here, would it be worth asking UM to take it down a notch powder-wise on the TMK's, or is it more that the barrel just doesn't prefer the TMK? Also, I just brought home a brand new tikka specter 8 twist .243 today. Is it worth trying this ammo to see if it works in that individual rifle?

Also, on the pressure stuff in general, I have full confidence UM will work with me to find out the right answers. This was the "factory load" so I am surpised it was so spicy.

You're not the only one that has excessive pressure signs with UM 243 ammo in a tikka. I PMd with a guy who had similar issues. Either the factory tikkas build pressure early or UM is loading them way the fug too hot. Possibly a little of both but id say unacceptably hot loads from UM and I'd be looking for a refund/replacement. Stop shooting them if you care about the condition of your firing pin and bolt face, amongst other things.

 

[walkingduckwaterfowl]

I have had really good customer service from UM in the past and I don't have any doubts that will be the case here. I did some more hillbilly math with my grain scale and I am finding that there appears to be about 43-44 grains of h4350 in these loads. Those figures are not accounting for any powder residue still attached to the brass, so it could be higher than that.

In terms of getting the TMK to shoot, would dialing back the velocity a bit potentially help? Or is it more likely that the rifle doesn't like that bullet?

 

[ID_Matt]

I have had really good customer service from UM in the past and I don't have any doubts that will be the case here. I did some more hillbilly math with my grain scale and I am finding that there appears to be about 43-44 grains of h4350 in these loads. Those figures are not accounting for any powder residue still attached to the brass, so it could be higher than that.

In terms of getting the TMK to shoot, would dialing back the velocity a bit potentially help? Or is it more likely that the rifle doesn't like that bullet?

That would be hot for a 6 creed, let alone 243 win.

 

[walkingduckwaterfowl]

I also shot my 6cm yesterday for the first time, I was getting 2769 average from a 20" barrel with 108eld-m factory ammo.

 

[WyldGoose]

The latest S2H podcast Jake said they’ve got a lot of returns on the ammo. He said it’s for shooting in hunting weather, not in the summer.

 

[mlevimadden]

116 TMK
6 creed SAMMI
26” CF Benchmark 1-7.5 twist
2.920” COAL. Lands are at 2.940”
42.5gr. N555

I had to get a new mag to accommodate the longer COAL. My other mags had binder plates in them. Just went out to function test the new mag.

Two 5 round groups fired consecutively just loading the mag in between.

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Are you having any issues with bullets staying seated being fed from a mag at 2.92" COAL? Not that 6CM is a heavy hitter, but my 116 TMKs showed up yesterday, and I'm getting very similar measurements to yours for jam in a SAAMI chamber. Looks like you're loading roughly 0.13" of bearing surface into the neck with a 0.020" jump. I was planning to start at 2.90" COAL, but it's definitely less bearing surface/case neck engagement than I have done in the past.