Sierra Heavy TMK 6MM Testing

[wind gypsy]

They shoot very well, but there's just some sticker shock for a pimped remmy 700 in a McMillan.

That's badass @Carl Ross, tmk did some work!

Yeah but it sure seems Mike is way more detail oriented than the average gun plumber. I’d love to own one. Can’t logically justify it but they are sweet.

 

[Southernfried]

Just for reference, a 77gr. I had cut open a few months ago for some government work.

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That is an awesome job, I cant even slice a tomato that fine.

 

[CBB1]

DA was around 4500 ft.

View attachment 986393

Is that a 117gr in a .243!?


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[ID-Muley]

Yeah but it sure seems Mike is way more detail oriented than the average gun plumber. I’d love to own one. Can’t logically justify it but they are sweet.

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

 

[Rockpicker]

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

Beverly Hills Mike at TacOps. His attention to detail is on another level.

If I won the powerball lottery he’d be the second phone call made after a lawyer.

 

[Carl Ross]

Is that a 117gr in a .243!?


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Yes

 

[Dude270]

Appreciate the report Carl.

I had pretty much dismissed the 115-ish grain offering due to the only 6mm I have twisted faster than 1 in 8 is a 6 ARC.

Looks like they will work in a 1 in 8 at my elevation, if not optimized. I may get in line for a box. I can't see the added mass being a bad thing for a killing bullet.

 

[DangerRanger]

They shoot very well, but there's just some sticker shock for a pimped remmy 700 in a McMillan.

That's badass @Carl Ross, tmk did some work!

FWIW it’s pretty heavily pimped, call him and talk to him, he does a lot more to those than screw a new barrel on it and put it in a stock.

 

[DangerRanger]

Since I’m at sea level I’m skeptical of an 8 twist 243 but that 117 is very attractive

 

[Carl Ross]

Since I’m at sea level I’m skeptical of an 8 twist 243 but that 117 is very attractive

The calculator I used suggested SG ~ 1.2 at sea level, 1.4 at my elevation. I'd be skeptical about it too.

 

[solarshooter]

I added these bullets to my spreadsheet, backed out a g7 BC from Form's trued numbers, and ranked by g7 form factor i7.


I tend to look more at form factor than outright BC when I'm choosing a bullet, since it's a measure of "BC per bullet weight" (you'll see it tracks the BC/gr ranking) and should give you the bullet with the best overall trajectory, factoring in recoil, MV, and wind.

These new prototypes are definitely on the upper end of performance in this regard, which is nice to see from Sierra since some of their bullets are absolute duds.

If you rank by i1, they look even more competitive:

But, I try to focus more on g7/i7 since it's a better drag model for the modern bullets we use.

 

[khuber84]

My common thoughts was a lighter than lead plastic tip would aid in stability from a lil slower twist, but my understanding may be backwards. The longer the bullet, and further rearward the center of gravity(due to plastic tip), the faster twist it needs, so sources have said.

 

[pathnz]

The Miller stability calc doesn't do well with plastic tipped bullets. The Berger stability calc, for example, suggests that an 80gr .224" ELDM is unstable at 2700fps and 1:8" (SG 1.15). In reality an 80 ELDM is perfectly stable at this speed and there is no BC decay at distance.

The JBM stability calc uses a modified miller that accounts for tip length/density and gives answers that align much better with observed reality for tipped bullets (SG 1.47 for the above example)

 

[ACHILLES]

My common thoughts was a lighter than lead plastic tip would aid in stability from a lil slower twist, but my understanding may be backwards. The longer the bullet, and further rearward the center of gravity(due to plastic tip), the faster twist it needs, so sources have said.

If you want an accurate stability rating with tipped bullets use the Jbm stability calculator that accounts for tip length of bullets and you can find the plastic tip lengths in jbm’s bullet library. I believe your line of thinking is correct. Because if you run the stability rate in a standard calculator with a tipped bullet it will give you a lower SGR than if you run it in jbm’s calculator that accounts for tip length.

 

[pathnz]

light reading on the matter if you're interested

https://arxiv.org/pdf/1410.5340

 

[pathnz]

That doesn’t line up with my experience with that bullet out of a factory 8 twist Tikka in cold temps at a 2800 fps MV. The BC definitely dropped off at distance. I had to have two different profiles in order to get hits past 600 yards. The 1/7 barrel I replaced it with allowed me to keep the same BC out to 1,000+ without the drop off that the 1/8 had.

Factory tikka .223 barrels don't seem to like the 80 ELDM for some reason. Multiple rifles don't seem to shoot it well (or the 75). I've always wondered if perhaps they're not quite a true 1:8

 

[B_Reynolds_AK]

Factory tikka .223 barrels don't seem to like the 80 ELDM for some reason. Multiple rifles don't seem to shoot it well (or the 75). I've always wondered if perhaps they're not quite a true 1:8

Perhaps that could be the case.