Sierra Heavy TMK 6MM Testing

[ckt3]

haha end of discussion

 

[Liberty Risk]

lol the answer I was looking for and more

 

[blacktailcentral]

Any more terminal reports with the new tmk bullets?

 

[The Guide]

.223 88 TMK at 3400fps
6mm 107 TMK at 3100fps

Which one would would you choose to hunt with. Disregard other factors like barrel life ext.. More of a fun question. Or maybe it's a dumb question..either way I'm here for it.

What cartridge are you going to use to get the 88's up to 3400 FPS? Just curious as I don't know of any that will push an 88 that fast.

Jay

 

[Liberty Risk]

22 prc with a 20in shilen barrel. You can get there with alpha brass and a long barrel in 22 creed but for hunting I like shorter barrels. Wouldn't deter anyone from having fun but as far as juice worth the squeeze to me it wasn't enough to walk away from the 22 creed. Hoping to see someone get the 223 NAS3 case working with an 88 at 100K psi.

 

[TURNER208]

Decided to order 100 to make a dummy round for some 6mm-284 instead of doing a PRC.

Let me know how that works out! Been thinking this will be my next build, the 284 case is one I’ve always been fascinated with even if brass isn’t the most available

 

[IrkedCitizen]

Doesn't Lapua make 6.5-284 brass?

 

[806guns]

They did, believe it was one they quit making a few years ago. I will be using Peterson brass.

 

[SeanM243]

Any more terminal reports with the new tmk bullets?

I've shot a few hogs up to 150 lbs with the 88 TMK and have been happy with their performance. Or are you meaning the 6mm TMKs?

 

[WoolyBugger]

First rounds out the barrel, figuring out where I stand for velocities. 116tmk, Alpha lrp brass, h4350. 6cm 7twist 19” barrel

 

[Orchemo]

I bribed @Tanner with some TMKs and he was kind enough to load some up 6cm for both of us.

He can add in his rifle info, I just know it was a re-barrelled Tikka.

His 107 loading was some tired Starline brass (I believe), 40.5 gr H4350, 10.5 fps SD, 2875 fps avg.

For the 116s, same brass, 39.5 gr H4350, 21 fps SD, 2811 fps avg.

For my MRC, 107s in once-fired Lapua over 40.5 gr H4350, 9.6 fps SD, 2870 fps avg.

For the 116s, same brass, 39.5 gr H4350, 9.6 fps SD, 2800 fps avg - these 5 shots had stiff bolt lift but no other pressure signs. I had 4 more and shot them 10 minutes later with no stiff bolt lift (2805 fps avg, 6.2 fps SD), not sure what was going on there.

Both loads out of both guns were about 1MOA with a stiff breeze and some mirage. Time to load 50 and go kill some bears. I don't know if we will chase a different load for more accuracy; I want to shoot 10 on a calm day, I think .7ish MOA is very realistic.

 

[FrankieP1988]

Freebore?

I finally reached out to GA precision, looks like they used a .120" FB

 

[Redbaron307]

I’m sure it’s been mentioned somewhere in the 85 pages on this thread but in hopes of not having to scroll through all of them…

I just got a 6 creed 20” 1:8 twist. I wanted to run the 108eldm, but the 107 and 116 tmk have my attention after the latest exo podcast with Form. I’ll be going anywhere from 9,000+ elevation down to sea level on Kodiak and I’m on the fence if my 1:8 twist will stabilize the 116 at the lower elevations effectively?

I want to go with the 116 if it’s possible for an across the board bullet in my setup. Does anyone want to point me in the direction of one bullet in particular? Any experience with this same setup at these elevations?

Thank you!

 

[Chris in TN]

I’m sure it’s been mentioned somewhere in the 85 pages on this thread but in hopes of not having to scroll through all of them…

I just got a 6 creed 20” 1:8 twist. I wanted to run the 108eldm, but the 107 and 116 tmk have my attention after the latest exo podcast with Form. I’ll be going anywhere from 9,000+ elevation down to sea level on Kodiak and I’m on the fence if my 1:8 twist will stabilize the 116 at the lower elevations effectively?

I want to go with the 116 if it’s possible for an across the board bullet in my setup. Does anyone want to point me in the direction of one bullet in particular? Any experience with this same setup at these elevations?

Thank you!

No experience, but how cold is the weather when you're near sea level? I live in the SE USA. I'm assuming Kodiak Island gets a bit colder, I just don't know what sort of weather you hunt in, but I'd think that at some temperature an 8 twist is going to start getting shaky. It might well be fine on a 90 degree summer day but less so at -10F.

 

[Redbaron307]

No experience, but how cold is the weather when you're near sea level? I live in the SE USA. I'm assuming Kodiak Island gets a bit colder, I just don't know what sort of weather you hunt in, but I'd think that at some temperature an 8 twist is going to start getting shaky. It might well be fine on a 90 degree summer day but less so at -10F.

I’m assuming the temps will be around freezing, I’m going for a blacktail hunt next November up there. I don’t have any experience with shooting at low elevations in different conditions, everything I have done is in Wyoming at 7,000’+ during all times of the year.

 

[Chris in TN]

I’m assuming the temps will be around freezing, I’m going for a blacktail hunt next November up there. I don’t have any experience with shooting at low elevations in different conditions, everything I have done is in Wyoming at 7,000’+ during all times of the year.

32F is certainly better than -10 but.....ehhh, I simply don't have enough experience at the edge of theoretical stability like that.

I'd go to the 107 and never look back. But that's just me.

 

[Jimbee]

I’m sure it’s been mentioned somewhere in the 85 pages on this thread but in hopes of not having to scroll through all of them…

I just got a 6 creed 20” 1:8 twist. I wanted to run the 108eldm, but the 107 and 116 tmk have my attention after the latest exo podcast with Form. I’ll be going anywhere from 9,000+ elevation down to sea level on Kodiak and I’m on the fence if my 1:8 twist will stabilize the 116 at the lower elevations effectively?

I want to go with the 116 if it’s possible for an across the board bullet in my setup. Does anyone want to point me in the direction of one bullet in particular? Any experience with this same setup at these elevations?

Thank you!

This was near sea level on a chilly day. No bueno.

 

[Jordan Smith]

Here you go: https://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

And for bullet lengths: https://www.jbmballistics.com/ballistics/lengths/lengths.shtml

An SG value below 1 is unstable, and over 1.5 is super-stable. Between 1 and 1.5 is moderately stable. Why should you care about how stable the bullet is, instead of just whether it is stable or not? Because the BC value depends on the degree of stability. For anything less than an SG value of 1.5, the bullet's BC decreases at a rate of approximately 3% per 0.1 in SG value. So a bullet with an SG value of 1.5 may have the advertised BC value, but with an SG value of 1.0 the bullet sees an effective decrease in BC value of ~15%.

The decrease in BC itself is not the biggest issue, but the variability in the BC as a function of atmospheric conditions can be a bit of a problem, depending on how precise you need your shooting solution to be (shooting out to 400 yards isn't far enough to resolve these issues, generally).

With a 6mm barrel and 1:8" twist, I default to the 108 gr ELD-M class over bullets instead of the 115 DTAC/116 TMK class of bullets, due to the fact that while the BC value may be lower, at least it is constant across atmospheric conditions.

 

[SouthPaw]

I’m sure it’s been mentioned somewhere in the 85 pages on this thread but in hopes of not having to scroll through all of them…

I just got a 6 creed 20” 1:8 twist. I wanted to run the 108eldm, but the 107 and 116 tmk have my attention after the latest exo podcast with Form. I’ll be going anywhere from 9,000+ elevation down to sea level on Kodiak and I’m on the fence if my 1:8 twist will stabilize the 116 at the lower elevations effectively?

I want to go with the 116 if it’s possible for an across the board bullet in my setup. Does anyone want to point me in the direction of one bullet in particular? Any experience with this same setup at these elevations?

Thank you!

Kodiak can have negative DAs in November. If I'm in your shoes, I'm loading the ~108 class bullets.

 

[mlevimadden]

Here you go: https://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

And for bullet lengths: https://www.jbmballistics.com/ballistics/lengths/lengths.shtml

An SG value below 1 is unstable, and over 1.5 is super-stable. Between 1 and 1.5 is moderately stable. Why should you care about how stable the bullet is, instead of just whether it is stable or not? Because the BC value depends on the degree of stability. For anything less than an SG value of 1.5, the bullet's BC decreases at a rate of approximately 3% per 0.1 in SG value. So a bullet with an SG value of 1.5 may have the advertised BC value, but with an SG value of 1.0 the bullet sees an effective decrease in BC value of ~15%.

The decrease in BC itself is not the biggest issue, but the variability in the BC as a function of atmospheric conditions can be a bit of a problem, depending on how precise you need your shooting solution to be (shooting out to 400 yards isn't far enough to resolve these issues, generally).

With a 6mm barrel and 1:8" twist, I default to the 108 gr ELD-M class over bullets instead of the 115 DTAC/116 TMK class of bullets, due to the fact that while the BC value may be lower, at least it is constant across atmospheric conditions.

Those twist rate calculators are best-estimates off very basic formulas. They're great to get you in the ballpark or let you know if you might have a problem. I definitely wouldn't take it as gospel and build a rifle/bullet system based off the calculator saying your SG is 1.05 and you're good-to-go and "moderately stable" with just lowering BC.

There are plenty of variables not captured in those basic formulas that affect stability (center of gravity, center of pressure, moment of inertia) as well as environmental factors like a stiff cross wind that can push a "moderately stable" bullet over to "unstable". I'm personally less concerned with the BC reduction, but the increased dispersion and erratic flight of "unstable" bullets are the deal-breaker for me.

If I have am shooting a rifle/bullet with a calculator output under 1.3, I'm definitely going to investigate stability with fired data.

Agreed on the sentiment that the 108 class bullets are the safer bet for an 8 twist at zero or negative density altitudes.