I don’t recommend using 8208XBR for 129gr class of bullets as it’s fast for that weight, but can be done safely if you follow standard procedures and published data.
I’ve mainly used ball powders like CFE223 and LVR under the 129gr ABLR.
Using a calibrated pressure test breech cut with a mid-life spec SAAMI reamer built specifically for that purpose by Manson Reamers, 2410fps from an 18” was achieved using CFE223 without exceeding 50,000psi, 10-shot string average.
I ran some pressure ladders with it from an 18” Lilja several years ago as well that tracked right along with that. A 2.284” COL (won’t work from Elanders) allowed a 31fps increase over 2.271”, which doesn’t amount to a hill of beans difference other than on paper, but could help with finding a node.
I haven’t shot any 129gr from my 12” yet. Running that load through a Grendel-specific internal ballistics engine shows a 12” doing 2246fps with that.
Factory 90gr TNT does 2698fps avg from my 12”.
120gr Federal AE does 2418fps.
129gr ABLR doesn’t really care what speed you shoot it at since expansion floor is 1300fps, and BC is .553 G1/.283 G7 according to Bryan Litz analysis.
Even if we assume a
2200fps mv from a short barrel, it still retains over 900ft-lbs out to 300yds
100yds 2057fps 1211ft-lbs Zero
200yds 1919fps 1055ft-lbs -5.7”/ .8 mils
300yds 1787fps 915ft-lbs -20.9”/ 1.9 mils......8”/ 2.5 MOA/.7 mils drift for 10mph full value wind
The numbers are all really similar if you shoot it from 11.5” and 10.5”.
It gives you a lot of options for more compact, carry-easy hunting set-ups, especially with a suppressor.