Hi Roscoe,
I have been using BH209 in 45-70 and 38-55. I have been pleased with the results.
Most of the shooting has been with a Sharps Creedmoor repro using 490gr bullets. It requires magnum primers (I use Fed 215). Velocities seem to be most consistent with a bit of compression on the powder. I use a 0.60 veg wad under the bullet and a newspaper disc over the primer hole.
I was using conventional SP, I didn't like the fact the powder occupied so little of the case volume. I was told the recoil is mitigated a bit with the slow burn, and it does seem a bit softer on the shoulder than my SP loads at the same velocities.
I shot the 45-70 and 38-55 out to 500 yds at hanging silhouettes with very good results. Clean up is easy and it is not corrosive. No extra case cleaning.
I even got it to work in a TC Hawkins, but it requires a very tight patch.
Down side; it's very expensive.
If you can handle the price, I would recommend it very highly.
Mike.

I've shot 30 gr 4895 in my 458 W under a 540 grain bullet. Heavy recoil.  50 Grains? 

Not a trapdoor load I assume. 

There was a thread about Blackhorn 209 here recently. 

       Joe. 

No, it is H4895, check the Hodgon data! 50 grains of H4895 is UNDER 20,000 CUP in a 45 70 case and a nice comfortable load to shoot with the 405 grain jacketed Remington bullets I use. 

From the Hodgdon web site,

Hodgdon
H4895
.458"
2.540"
50.0
1,614
19,200 CUP 

I dont know what the deal in 458 is but I shoot H4895 in my 45 90 all the time and its essentially a beltless 458 case, I deffinetly use way more than 30 grains!

Hodgdons STARTING load for the 458 with a 500 grain bullet is 70 grains! 

re
Grs.
Vel. (ft/s)
Pressure
Hodgdon
H4895
.458"
3.310"
70.0
2,068
42,000 CUP 

Trapdoor loads using H4895 and 405 grain bullet,

Hodgdon
H4895
.458"
2.540"
40.0
1,424
14,900 CUP

Thats Black powder pressures! 


The max for the trapdoor is 48 grains of H4895 and it yields a bit under 19,000 CUP.


H4895 fills a 45 70 case nicely and is an excellent powder for that round even in the BP firearms.  In fact H4895 is Hodgdons choice for their reduced rifle loadings,

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According to that Formula from Hodgdons own web site the suggested reduced, or very light load, for that 458 Winchester should be 44 grains! 

The max H4895 load with a 500 grain bullet for the 458 is a compressed load of 74 grains.