Sierra Heavy TMK 6MM Testing

[Jordan Smith]

Continuing with the “painless method” with my 20” 243. The 116s don’t like my gun. I give up on those. Had previously shot the 107s with 42 of staball 6.5 into a nice group. Was about 20 fps under my desired 2775 fps. So I figured I’d bump it up by .1 and see if I could hit it and had hopes of being done. Both 42 and 42.1 grouped fine. Virgin lapua brass

Problem is my ES. Using garmin chrono
42 avg = 2759 es = 81
42.1 avg = 2762 es = 117

Any suggestions? I’m using an fx120i so don’t think it’s the amount of powder I put in being inconsistent

Yeah, that’s crazy ES, which will give you significant vertical at distance.

Brass consistency (what brand of brass?)
Neck tension consistency (annealing? Trimming? Neck thickness variation?)
Sufficient ignition (what primers?)

 

[Nine Banger]

This rifle is a 16" 6 creed with 1:7.5" twist. I'm at sea level.



I ordered this barrel originally as a 1:7" and it was a shotgun. It was replaced but I was given a 1:7.5" the second time around.

I had no anxiety about stabilization of the 116gr TMK because I've shot a few hundred Nosler factory 115gr RDF in this barrel in the last 2 months or so. I did wonder if I could get the speed on the 116gr TMK up to Quick Drop at sea level though. The Nosler 115gr RDF is loaded to 2.750"...it travels 2685fps in my 16" barrel which will line up with Quick Drop around 3500DA but not here at home.



The 116gr TMK load I posted in this thread prior (46gr 2.800" N565 2700fps) with N565 in my 18" barrel didn't have any room in the case left to push it faster in a shorter barrel to make up the 50fps needed for the 16" barrel to make Quick Drop, so with this rifle I went direct to H4350 and loaded 40gr to get started.

It groups well and is 2740fps average. I'm not going to find pressure; if anything I'll load it down to 39.5 or so to get the drops to line up but the load sounds like a salt shaker so I have some H4381SC coming to try to get the same speed without the air gap in the case. I'll probably cut my other barrel down to 16" too.

6 Creed
16" PBB 1:7.5" bbl
2.800" OAL
2740 fps
zero is for the Nosler factory load

 

[ckt3]

Any suggestions?

I’d say shoot a group of 20 with 42 grains and see how you like it.

One could argue you have a 10 shot group there if you make it a composite since a 0.1 grain difference is hard to resolve.

 

[huntsd]

Yeah, that’s crazy ES, which will give you significant vertical at distance.

Brass consistency (what brand of brass?)
Neck tension consistency (annealing? Trimming? Neck thickness variation?)
Sufficient ignition (what primers?)

I’m using quality components
Lapua
It’s virgin so not annealed or trimmed
I would think since it’s Lapua neck thickness shouldn’t vary too much?
Gm 205 lrp

Suggestions, ya just go shoot. You’re not shooting F class. Just go Hammer away and have fun

I’ll never shoot this gun past 700. you guys don’t think that es spread will show up at that distance?

 

[Nine Banger]

I’m using quality components
Lapua
It’s virgin so not annealed or trimmed
I would think since it’s Lapua neck thickness shouldn’t vary too much?
Gm 205 lrp

I’ll never shoot this gun past 700. you guys don’t think that es spread will show up at that distance?

Your ES seems normal to me. I've used balance beam, auto dispenser and a precision powder drop here and the ES ebbs and flows based on the dispersion of your data points.

 

[Matt5266]

I’m using quality components
Lapua
It’s virgin so not annealed or trimmed
I would think since it’s Lapua neck thickness shouldn’t vary too much?
Gm 205 lrp

I’ll never shoot this gun past 700. you guys don’t think that es spread will show up at that distance?

How many shots did you shoot to get those ES numbers? I just shot 2 days ago. Over 30 rounds my ES was almost 80. All 30 rounds were shot at 610 yards. Very few misses , and the ones that did were bad wind calls from me with the variable winds. Vertical they were all where they should be. For reference this was shooting a 12 inch plate.

 

[mtnbound]

I’m using quality components
Lapua
It’s virgin so not annealed or trimmed
I would think since it’s Lapua neck thickness shouldn’t vary too much?
Gm 205 lrp

I’ll never shoot this gun past 700. you guys don’t think that es spread will show up at that distance?

Plug your data into your ballistic solver to confirm but probably .2-.3Mils.

 

[43.6N]

I’m using quality components
Lapua
It’s virgin so not annealed or trimmed
I would think since it’s Lapua neck thickness shouldn’t vary too much?
Gm 205 lrp

I’ll never shoot this gun past 700. you guys don’t think that es spread will show up at that distance?

A) probably doesn’t matter. Most of the popular hype around low es/sd comes from insufficient sample size and the rise of cheap Doppler consumer grade chronographs. We’ve never been able to sample so much data so easily before.
B) 2nd firing on the brass will be more consistent. I’d suspend any ES concerns or testing until you’re on the second firing.
C) When you do test, do a water line test on a 10” plate at 500. See what your actual vertical dispersion is. I bet for you, me, and anybody else, the vertical dispersion with a 100es is less than the horizontal dispersion. Then step out to 700 and repeat the water line test.

 

[huntsd]

How many shots did you shoot to get those ES numbers? I just shot 2 days ago. Over 30 rounds my ES was almost 80. All 30 rounds were shot at 610 yards. Very few misses , and the ones that did were bad wind calls from me with the variable winds. Vertical they were all where they should be. For reference this was shooting a 12 inch plate.

10 shots

 

[Matt5266]

10 shots

Im with 43.6N load them again and give it a go. You have good components. If its still high maybe try just a primer change moving forward.

 

[pods8 (Rugged Stitching)]

Gm 205 lrp

If it’s bothering you, got anything hotter to try? WLR or magnums?