77tmk and xbr8208

[mills0713]

New reloader here. I’ve seen a lot of folks loading 77tmk and xbr8208 at 23.5grns and above. The Sierra reloading manual states a max load of 22.0grns. Obviously, it’s working, but I’m curious as to why you’re “getting away” with being 1.5grns over recommended max load. Any thoughts? Again, new to all this. Thanks!

 

[swavescatter]

1) Lots of people load over book and over pressure. Tickling the dragon's tail..
2) Seating the bullets out longer than SAAMI spec allows you (requires you) to use more powder to achieve the same velocity.

FWIW I could never get XBR 8208 to shoot very well with 77 TMKs. H4895 was the magic dust...

 

[JF_Idaho]

Max load is always different between loading manuals. As always start low and work your way up checking for pressure signs. I know back when I started loading 8208 max was usually around 23.2 using different sources. I load at 23.4 for 77tmk in starline with no signs of over pressure.

 

[Chris in TN]

New reloader here. I’ve seen a lot of folks loading 77tmk and xbr8208 at 23.5grns and above. The Sierra reloading manual states a max load of 22.0grns. Obviously, it’s working, but I’m curious as to why you’re “getting away” with being 1.5grns over recommended max load. Any thoughts? Again, new to all this. Thanks!

Is the Sierra load for .223 or for 5.56 pressures? Load data will be different, though a lot of people seem to shoot 5.56 pressures in any .223 anyway.

What's the seating depth? I'm assuming Sierra is spec'ing 2.25 or 2.26 and a lot of people with bolt actions are loading 2.4" or more.

What brass are you using? Brass capacity for 5.56 will vary by 2+ grains from low to high between brands. That will account for over a grain of difference in the powder charge it takes to hit a certain speed/pressure.

This is why everyone has to work up their own loads.

 

[Matt5266]

Brass is a big factor. I load 23.5 in LC brass and it shoots great. I know it hot though, because I loaded a few up using random brass just for target purposes and I was blowing primers

 

[Fireflyfishing]

I’m running 23.5 gr of 8208 seated 2.340” in lapua brass.