IMR 8208 XBR - Burn Rate Issues?

[rcw3]

I know there have been a lot of threads on the IMR 8208 XBR since it came out but I guess I wonder where people are placing it in terms of burn rate. I have an 8lb jug that seems to be right around a burn rate of VV N133, but then I look at loading data and some of the applications people are shooting it in and think either I have a fast lot of that powder or something else is going on.

To me it seems the burn rate on it is on the fast side of medium burn rate powders but then it also seems like some are using it almost like a compact substitute for H4895.

Any thought by users of it on these issues?

Robert

 

[thefitter]

How do you judge the burn rate of a powder? Thanks

 

[rcw3]

All I can say is based on results from loadings with various powders you get an idea of where things are relative to each other.
Robert

 

[Steve Blair]

Robert,[br]
FWIW, the attached results were obtained in my Viper SS 6BR on 2011-11-11 in 65° temps. At least my lots are pretty similar in 6BR. Loaded with a .030 jump and all five shot groups.[br]
The lots are:
H4895 - 80605094722
8208 XBR - 81021094773

 

[82boy]

If you look at Hodgdons web site the place the powder at #85 spot in between AA 2460 and Ramshot with H4895 sitting at the #87 and N133 sitting at the #79 spot.
http://hodgdon.com/burn-rate.html

I can say from my experience the XBR powder is closer to burn rate to 4895 than it is to N133 or the old IMR 8208. I found that it is impossible to get enough XBR into a PPC case to cause pressure problems, not so with the old IMR 8208. I have shot both, and the loading data is not even close, in some guns I could get a sticky bolt with a load of old 8208 part way up the neck. The sad thing is it is impossible to find a burn rate chart anymore that shows the old 8208. I remember seeing it listed on a chart right at the same time as XBR and they was far apart. If I remember right the old 8208 was listed around 4198, and the XBR was rated right under 4895.