Re: Drop tests and some groups with 169.5 wildcats. ( with pics )
7RUMloader,
Since your rifle is shooting as well as it is I hate to even bring this up but I have found out through extensive testing with my Allen Mags that using a slow ball powder produces dramatically less barrel heat then the high energy stick powders do.
This became dramatically clear when I rechambered my 257 STW to to test my 257 Allen Mag.
I started out using Retumbo which was the powder of choice for my STW in the 30" barrel with 100 to 130 gr bullets. In the Allen Mag with its +20 gr case capacity increase I was getting severe pressure variations with any stick powder so I was forced to search for a ball powder that would work.
I quickly realized that AA8700 was perfect for 100 to 130 gr bullets and that WC872 worked best with 130 to 156 gr pills in my 257 Allen Mag.
In comparision, using the 100 gr Wildcat BCFBHP loaded to 3950 fps in the STW and 4080 fps in my Allen Mag the barrel temp difference was dramatic comparing Retumbo with AA8700.
In my notes I have written, "after 5 shots, barrel to hot to hold". This was for the STW when I was developing loads in late September last fall, temps were in the 50 degree range.
With the 257 Allen Mag loaded with 8700 I could shoot an 8 shot string and easily hold the barrel with no discomfort from barrel heat. The barrel is certainly warm but not hot and thats with +100 fps more velocity and nearly 20 grains more powder burnt. Admittedly not a good trade off as the STW is a better design with 100 gr bullets but from there up it does not even compare to the AM with heavier bullet weights.
Anyway, the point is that you may want to play with some ball powder and see what kind of results you can get. Since your using H-50BMG I would recommend getting ahold of Jeff at
www.gibrass.com and order in some WC872. You can use the same starting loads as with H-870 or 8700 with this powder but it is a bit slower. Even a bit slower then H-50BMG from what I have seen in my 270 Allen Mag where it performs extremely well with the 270 169.5 gr ULD easily topping 3300 fps. I am sure it would perform just as well in your big 7mm.
Advantages to ball powder:
1. Easy metering
2. Cooler burning temps
3. Less throat erosion
4. Cost
WC872 runs $40 per 8 lb keg from Jeff. I ordered in 32 lbs and with that large of an order you get a break on Haz shipping charges so the total for 32 lbs of 872 including shipping charges came to $188 and some change. Thats $5.88 per pound!!! A bit cheaper then H-50BMG.
There are a few disadvantages as well:
1. Does not burn clean except at good upper working pressure loads. Do not down load or it will look like a coal factory in your barrel!
2. Can be a bit more temp sensitive. Most run a winter and summer load with Ball powders. Ramshots new Magnum powder is said to be as temp resistant as Hodgdon stuff but I have not tested it enough to tell you 100% if this is true.
3. Lots can very from one to another but this is why you order 8 lbs of the stuff at a time or more. generally there are not alot of lots out there to get mixed up. The 32 lbs I ordered from Jeff is all same lot powder.
Just something to think about. In a round like the RUMS where you have 100 gr capacity, bore heat will always be an issue no matter what powder you use, but using a ball powder may get you 4 or 5 shots before fliers set in instead of 3.
Just an idea, like I said, as well as your rifle is shooting with the load you are using now I would think twice before considering a load change, there is really no real need as long as you keep your barrel cool.
Good Shooting!!
Kirby Allen(50)
