I'm trying to work up some subsonic loads for my Ruger 77/44. How much danger is there with compressing loads of trail boss? 9gr under a 240gr XTP hit my target velocity almost exactly with 1042 fps, but I know that it is a somewhat compressed load. 9 gr under a 300 gr Nosler HP is definitely compressed and only yielded 919 fps. Zero pressure signs with either load. I don't know how much it would take to push the Nosler to 1040 fps but I don't think I can do it with TB because a full case is only 12 gr. Just wondering if there is any real safety concerns with compressing these light loads?
Feel free to make powder recommendations for a 300 gr jacketed bullet as well, can't shoot cast bullets in my Hybrid.

Thanks

Regardless of "compressed" or not, Trail Boss maximum load is defined by the imaginary line drawn around inside of case just below bullet. That is based on IMR Trail Boss info. A compressed load by definition would be above this line. Agreed?

http://www.imrpowder.com/PDF/Trail-Boss-data.pdf

Yep I would agree with that. As close as I could estimate with my calipers, that guideline put a max load under a 240 XTP at about 8.3 gr of TB which only clocked 935 fps. So I'm sure 9 gr was slightly compressed but gave me the velocity I wanted, couldn't get there with a 300 gr though. I've also found several guys having good luck with 9 gr and 250's. My point though, lawyer recommendations aside, these are still light loads for a modern bolt action 44 magnum rifle. I don't normally screw around above max loads but TB is not a normal powder and I'm wondering if anyone has experience with what happens when you push it. Judging by recoil and noise it is hard to imagine that even the compressed 9 gr / 300 load was anywhere near the pressure of 24.5 gr H110 under a 240, but I'm new to trail boss. My understanding is that TB was made to fill the case on low pressure cowboy action loads in primarily older and weaker guns.
From what I've seen so far I'm very comfortable with the 9 gr/240 load, but what happens with a 10 gr/ 300 load that is considerably more compressed? 11 gr?  I'm open to other powder suggestions for the 300's but mostly what I find for sub loads is guys shooting cast bullets, not jacketed.

I recall researching Trail Boss years ago. Lots of web lore about breaking donuts when you compress which changes burn rate. Essentially, if you change burnrate of a powder, you might as well throw the data out the window. Problem is no one has done enough scientific research to know what happens so anyone that gives you advice to go above max load is guessing.

Maybe try a different powder? Look for another fast powder like tighgroup or bullseye?

Trail Boss is designed specifically for low velocity Cowboy Action Shooting loads. It's designed to launch a bullet safely at low velocity with minimal recoil for easy follow-up shots.

Use as intended and it will serve you well. It was never meant to be loaded hot or even warm.

I would love to try it with my .41 Magnums and lead bullets. I have yet to find any data whatsoever in this caliber. The search continues.

Data for essentially any caliber is in my link. Folow the 70% capacity rule for starting load.

djryan13 Thanks! I've never seen that reduced rifle data before. I'll try the fill to the bottom of the bullets trick for .41 Magnum and multiply it by .70 as suggested for my start load in .41 Magnum.

It would be interesting to see what the pressures would be on a compressed load of trailboss.
The trouble is powders like tightgroup, according to Hodgdon, push a 300 gr XTP at 1079 for a starting load even out of a 8" barrel and I'm assuming it would be even faster out of a 16". Most of their powders are listed at a minimum of 975+fps in a pistol which wouldn't leave much room to work with in a rifle. CFE Pistol might be worth a try.

Just saw on another forum.. one guy that says he started experimenting with subsonic loads in 1957 says he prefers 700x for all his subsonic loads, not a fan of TB.  That may be worth a try..