Thread: Trailboss, 151gr cast hollow points and 300blk

I can comfortably fit about 5.5gr of trailboss into a 300blk case, under a 151gr cast lead projectile of roberts

Im guessing it will be around 800ish fps which would be fine with me

I have tons of both and would love to bang up a cheap load for banging things over.
I cant seem to find any load data to help me out

Is anyone used Trailboss and learned anything useful?

Pretty much the same story with any case and TB, work out what 70% capacity is and start from there. With TB sunsonic loads you work down, not up. My 7.62x39 and 151gr cast required 6.7gr TB to be reliably subsonic (ie not the odd transonic one), but completely different case capacity/shape.

I thought the go was as long as its not compressed its good to go with this bulky stuff?
I am concerned that if i start with less ill get a bullet stuck, even at 5.5gr im getting a bit uncomfortable

id rather work down if poss

For the 300 blackout, if you want 1050 fps:

6.3/950 = X/1050 solve for X
X= 6.9 gr of Trailboss for ~1050 fps

For my 308 subsonic for 175gr/178gr bullets: at ~1050 fps it is 10.8gr of Trailboss

10.8/175 = X/150 solve for X, the load using 150 grain bullets
X= 9.3 gr of Trailboss for 150gr bullet at ~1050 fps

The above calculation method will get you very close to your desired load, with slight variation in loads needed to account for barrel friction differences and barrel lengths (maybe off by 0.1-0.2 gr at most). Try it and let us know. I can't help you with Trailboss subsonic loads for 5.56/.223.


Does this make any sense to anyone else? seems like there is a way to calculate before pulling the trigger

I copied it from a Usa forum

Work out case capacity with bullet seated (mark depth of projectile). Fill with TB to mark, multiply by 0.7. Load this calculated charge, and work out whether it's sub or supersonic (either with chrony, or I assume you have a suppressor to go by ear). Drop in say 0.2gr increments, until it's just going subsonic, then drop 0.1-0.2gr below that to allow for temp/pressure/altitude differences. Trying to work out what makes the same projectile go a certain speed in a different cartridge and replicating that isn't the way to go about it..

I think I have been as low as 6 grains of TB in my 30-30 with the 151gr casts, so you should be fine.
I’ll check how low I got later.
Subsonic in the 30-30 and one of the 308s is 7.5gr, the other 308 is 8gr, so a long way different to what has been quoted for other projectiles.

As long as it's not compressed it's happy. Compressed it's highly erratic and potentially dangerous. It was designed for cowboy loads and sub or transsonic loads trying to get speed out of it is definitely not recommended.

Originally Posted by Marty Henry

As long as it's not compressed it's happy. Compressed it's highly erratic and potentially dangerous. It was designed for cowboy loads and sub or transsonic loads trying to get speed out of it is definitely not recommended.

Could still use a drop tube. From the above it sounds like the Blackout case cannot hold sufficient TB to make a 151 grain boolit go supersonic.

The compression issue is if you compress it enough to break the TB donut flakes, just shoving the bullet against the top of the powder won't get you into trouble that way, but proper compression as with black powder tamping is inadvisable. The donut holes give enough case "air space" even with a filled case.

I've found a federal large rifle primer alone is enough to put a 210 grain cast lead bullet a few inches up a (worn) barrel so the stuck bullet risk is overrated. The bullet in the barrel problem is a problem of 'no powder' rather than 'too little' powder.

Probably better to swap tb for 2205 as it works real well on subs and supers with lots of data around . Also the 300 was designed from scratch to be a super/sub cartridge with a fast twist barrel for the heavier bullets .

The Hodgdon website doesn't have a starting load for 140-150 grain bullets but has 6gr as the max load.

Originally Posted by Cordite

Could still use a drop tube. From the above it sounds like the Blackout case cannot hold sufficient TB to make a 151 grain boolit go supersonic.

The compression issue is if you compress it enough to break the TB donut flakes, just shoving the bullet against the top of the powder won't get you into trouble that way, but proper compression as with black powder tamping is inadvisable. The donut holes give enough case "air space" even with a filled case.

I've found a federal large rifle primer alone is enough to put a 210 grain cast lead bullet a few inches up a (worn) barrel so the stuck bullet risk is overrated. The bullet in the barrel problem is a problem of 'no powder' rather than 'too little' powder.

I have managed to stick a jacketed bullet in my 450bush master with trailboss in the past but at least with that i can gently tap it out with an ali rod
good luck in a 30cal

doesnt ANYBODY else use lee dipper spoons???? they might well have been made for trailboss loading.....as you start by VOLUME NOT WEIGHT they just make life easy.
50 quid to knob of goat shit using one of Roberts awesome 151s your data will be close enough,use std primer as magnum has enough/too much oomph and gets you down to silly small amounts of powder to stay subsonic.......which MAY actually help you out here if the 5.5 is all you can fit and is too far below the magic 1000fps mark.
in bolt or break open tapping a stuck projectile of cast construction out if it got stuck isnt going to be such a major hassle but I cant see that happening as I got down to the volumn you going to use when I was playing with 7.62x39mm and same projectiles.

Originally Posted by m101a1

Probably better to swap tb for 2205 as it works real well on subs and supers with lots of data around . Also the 300 was designed from scratch to be a super/sub cartridge with a fast twist barrel for the heavier bullets .

If I have to buy ill look into that or lil gun if I cant get away with using what I have
at the moment i have 2208 and 2209 on hand
as well as trail boss
I also live in bumfuck nowhere and getting powder is a long slow process

I use my 308 dipper to fill my powder scales mostly just as a spoon

I weight measure each powder load, no matter what its going into

AP70. 2205 won't create enough chamber pressure to obturate.