Since Hodgdon took over marketing the Winchester powders, they have said W296/H110 are the same and W231/HP38 are the same powders.
They have always been made by the same powder manufacturing plant, St. Marks, FL, if I remember correctly.
I suspect that have always been the same but not necessary blended to be the exact same performance characteristic. Before Hodgdon had the marketing rights for Winchester powders, Winchester and Hodgdon may have had an agreement to say the two pairs of powders were not the same.
Supposition on my part. So, take it as you want. After all, this is the internet.
But, it is known that when Hodgdon took over marketing Winchester powders, Hodgdon announced that W231 is the same as HP38 and W296 is the same as H110.
Now, as an aside, IMR4895 is not exactly the same as H4895. I use them in my 30-06 Garands and to get the same bullet performance, the powder charges between the two powders is different. The published load data is different between the two powders.
If you look at the load data for a Western powder and a Ramshot powder, the data is the same. This would indicate the two powders are the same but the manufacturer/distributer has not officially announced they are the same. I do not remember which powders they are off hand, I'd have to look up the data for the two and I do not wish to give some false or inaccurate information here.
It is best to assume no two powders are the same unless you have official information from the manufacturer/distributer.
