77 TMK 8208 XBR load dev

[SouthPaw]

You’re getting 125fps more … with just 2” more barrel. Lower load, only diff is brass … hmm. What is you CBTO?

CBTO is 1.880. How many rounds on your barrel? This one has several thousand.

The 79g DRT does ~2800fps in this gun with the same components but 23.0g xbr. The 80g eldm is 2780fps with 23.0g.

The wife's 20" tikka 223 shoots the 79g DRT at 2800ish with the same 23.0g load and Starline brass, and that barrel is only a couple hundred rounds in.

 

[philcox]

CBTO is 1.880. How many rounds on your barrel? This one has several thousand.

The 79g DRT does ~2800fps in this gun with the same components but 23.0g xbr. The 80g eldm is 2780fps with 23.0g.

The wife's 20" tikka 223 shoots the 79g DRT at 2800ish with the same 23.0g load and Starline brass, and that barrel is only a couple hundred rounds in.

Been through the S2H class, so I'd sat north of 1200 down the barrel. The 79 DRT with 23.0 XBR was right at 2635, with 22.0 2553 ...

 

[Schmo]

Don’t overlook N150 and N540. I haven’t got to test the N540 in mine yet, but in Starline 5.56 brass, the N150 was giving me 2750-ish with the 77 TMK, and 2800-ish with the 75 ELD out of an 18” barrel. It has some additional freebore, but not a ton. I won’t be surprised if N540 gives more speed

 

[sveltri]

N540 will give great velocity, i almost got 3000 fps with the 77 TMK at VV's book max. However, I believe that N540 is THE hottest burning powder on the market, it will erode the throat pretty quickly.

 

[Schmo]

it will erode the throat pretty quickly.

Sure, but probably still have a barrel life of 4,000-6,000 rounds

 

[sveltri]

Sure, but probably still have a barrel life of 4,000-6,000 rounds

Sure, depending on your application, use, and accuracy expectations.

 

[swavescatter]

Speed was awesome with N540 but accuracy was awful in my tikka.

 

[Matt5266]

18”

Cool asking for reference to my load. I'm using the same COAL and load data as you except once fired LC brass .18 inch tikka. average was 2765 FPS

 

[Schmo]

Speed was awesome with N540 but accuracy was awful in my tikka.

I’ll see how it does in mine. N150 powder ladder spreading 2 grains in charge was still .75” for 5 shots.

 

[philcox]

I just realized that I have yet to shoot the 77TMK with the CCI450. I have been using the CCI400 as I had "pre loaded" a bunch of the 400 in the new SL brass I had. I need to give the same load a test with 1X and CCI450. I'll report back.

 

[Shortschaf]

I just realized that I have yet to shoot the 77TMK with the CCI450. I have been using the CCI400 as I had "pre loaded" a bunch of the 400 in the new SL brass I had. I need to give the same load a test with 1X and CCI450. I'll report back.

Please do
I have only 400's and wonder if 450's would be more juice. I get flat primers before any heavy bolt lift

 

[swavescatter]

Please do
I have only 400's and wonder if 450's would be more juice. I get flat primers before any heavy bolt lift

Look up my post on velocities with different primers. I got more speed out of 205’s than 450’s or 400’s.

 

[philcox]

My "next try" is loaded now: 77 TMK, 23.5 XBR, CCI 450, Starline 1X. I loaded to max Tikka mag length, turned out to be 1.815 CBTO (way shorter than @SouthPaw 1.880). Will update on FPS and how load performs.

 

[SouthPaw]

My "next try" is loaded now: 77 TMK, 23.5 XBR, CCI 450, Starline 1X. I loaded to max Tikka mag length, turned out to be 1.815 CBTO (way shorter than @SouthPaw 1.880). Will update on FPS and how load performs.

Not necessary for the 77tmk, but the Waters mag opens up the seating depth flexibility.

10x 77tmks at .7moa today:

 

[philcox]

Not necessary for the 77tmk, but the Waters mag opens up the seating depth flexibility.

10x 77tmks at .7moa today:

View attachment 908037

10-4 on the mag. As for the groups, .98 probability that it is the shooter opening the groups.