Muzzle Break causing feeing issues? Update

[Bocephus123]

@JEVapa

Do you know the specs of this data by chance? Twist, Barrel Length, Temp?

These were my findings:
21.5
View attachment 321139
21.7
View attachment 321140
22.0
View attachment 321141
22.3
View attachment 321142
View attachment 321145
This was the best group and just over an inch for 5 shots. I was impressed with it, but no clue what happened to my chrono. Same location of chrono, same location of rifle, no wind, chrono light on the entire time, but I'd assume this is 2458 FPS.

No pressure signs on the brass at all. I think I will work up a tad more and see what kind of velocity I can get and groups. I just wish that last SD was better. 25 isn't the end of the world, but I can do better.

I left the ammo in the bed of my truck over night and went from the bed to the rifle, so it was cold. Great thing about shooting in 31 degree weather, barrel stays pretty good.

nice groups

 

[rockchalk06]

Are you talking about the pdf I attached? If so, no, other than the info they give at the top.

Notes: Case trim length: 1.750; COAL: 2.260"; barrel length: 24"; NOTE: An 80.5 grain Berger Match Fullbore Target bullet can also be used for the 80 grain data. WARNING - Approach maximum loads with caution. (Berger Bullets Reloading Manual 1st Edition)

This is probably a 1-9 or 1-8 max.

Looking at your groups...it looks like you are using an electronic scale that's cold...or you're using a throw bar, or both. Just an assumption because your SD and ES should be way smaller...those are Lake City kind of spreads.
My scale will get all squirrely like that so I have to cal it often or bring it in the house.

Another thing is that your chrono looks like it's about to S**t the bed, or it doesn't like the cold. See if you can get a hold of a labadar, magnetospeed, or an Oehler to confirm. None of those speeds match up with the charges you have listed.
Don't forget a crimp

This is off Hodgdon for 77 gr SMK:

Ramshot TAC 0.224" 2.260" 21.1 2,483 49,100 PSI 23.4 2,759 54,500 PSI

I'm running an 18". Do you think with the 6 inches of barrel length difference, velocity will be that reduced?

Twist is 1-7. Scale is an electronic scale and it's always kept indoors. I loaded these indoors and it gets zero'd out between a set of loads. Each charge was dropped around 20-21 then hand trickled to the end.

I've never had my chrono do that, but I've never shot in this cold of weather. It was the last load of the day too.

Crimp was applied. Lee Crimp Die.

Something to note, if you skip forward to 19 minutes into the video, he doesn't reach 2700 until 24.5 grains of Tac. He's using a white oak 18" barrel suppressed.

 

[Norman]

I'm running an 18". Do you think with the 6 inches of barrel length difference, velocity will be that reduced?

Twist is 1-7. Scale is an electronic scale and it's always kept indoors. I loaded these indoors and it gets zero'd out between a set of loads. Each charge was dropped around 20-21 then hand trickled to the end.

I've never had my chrono do that, but I've never shot in this cold of weather. It was the last load of the day too.

Crimp was applied. Lee Crimp Die.

Something to note, if you skip forward to 19 minutes into the video, he doesn't reach 2700 until 24.5 grains of Tac. He's using a white oak 18" barrel suppressed.

24.5 is pretty hot, but Ramshot shot max load for 5.56 and 77 grain SMK as 24.8. I’d shoot for 2600 FPS+, which should be very doable while under sub MOA ( or .28 mils/whatever tickles your fancy). I’d also verify charge weight with a beam scale. Sometimes a draft, static, ‘dirty’ electricity, powder under the platen or not being turned in a while to “warm” them up can mess with chargemasters and electronic scales.

 

[JEVapa]

I pulled down two different LC MK262...they have about 25.7 of whatever in them. It looks just like H110; not saying it is, it looks just like it.
I have a couple others I'll take a look at.

 

[rockchalk06]

I pulled down two different LC MK262...they have about 25.7 of whatever in them. It looks just like H110; not saying it is, it looks just like it.
I have a couple others I'll take a look at.

I appreciate it. I borrowed a beam scale from a buddy at work and matched it with mine. Everything looks good on that front.

I also worked up 25 more test loads which should end me about 2600 FPS.