As no one had any suggestions for using SRB-118 powder in the 7mm Int-R, I did what pretty much all us gun loonies do....I tried it anyway.

Did some interpolation with known SRB loads in the .223 Rem, .30-30, and a couple of other cartridges, and started with 27.5 grs. behind the 130 gr. Sierra Pro-Hunter handgun bullet. Also loaded a few rounds of same bullet with 28.0 grains of same powder. Used F-210 caps.

At the range last Sunday, tried both loads. Pressures, by all normal signs, are extremely low. No visible change in primers after firing except for firing pin mark. Cases literally fall out of chamber, etc.

The interesting thing, which raises some questions, was the chronograph results. Using the 28.0 grain load, one round chrono'd at 1,868 fps. The next round, which was considerably louder but showed no more pressures signs on the case or primer, chrono'd 2,479 fps! Both of course from the same 10" Wichita pistol barrel.

So, either the second round was an incorrect reading by the chrono, or the pressures are right on the lower cusp of being able to burn the full charge completely.

My previous experience over the years tells me it may well be a chrono error. But, the pressure signs tell me maybe I should step up to a magnum primer and a little heavier charge for this ball powder...especially as it regularly moves its previous load with heavier (160 gr), Speer bullets and IMR 4320 at well over 2,000 fps.

Think I am going to go down to the shop this afternoon and load 5 each of the same 130 gr. Sierra bullets, with 28.5, 29.0, 29.5, and 30.0 grs of that SRB-118 and Federal 215's.

Any comments, suggestions, whatever?

AC, Conclusions of one single round can be misleading. Sometimes I found a considerable difference in velocity with or without a blink of sunlight, coming through an overcast weather condition. This reflection could possibly cause a wrong reading. The varying heights of the bullets above your chrono can also be of influence. For statistical results, measure at least 10 rounds.
J.

quote:

Originally posted by Jan:
AC, Conclusions of one single round can be misleading. Sometimes I found a considerable difference in velocity with or without a blink of sunlight, coming through an overcast weather condition. This reflection could possibly cause a wrong reading. The varying heights of the bullets above your chrono can also be of influence. For statistical results, measure at least 10 rounds.
J.

Jan -

I uderstand statistics and chronographing pretty well after years of experience with both, but thanks for the thoughts anyway. The chrono was not mine (I hadn't intended to do any chrono work Sunday & didn't set mine up). It was in use by an anesthesiologist shooting pal of mine who was testing loads for his .338 WinMag rifle. (Elk season starts here SOON.) As I had only taken a few rounds of each load to the range, there was also no opportunity to chrono 10 rounds of anything.

As noted, it could have been chrono error, or it could have been too light a load to burn correctly. We will find out more definitively once pressures appear up to the level at which I want to shoot.

Those two shots were mentioned just as a curious variance, and were fired just out of interest to see about what speed those very light loads were producing.

Of course, what we actually found out was that neither shot could be trusted as being clocked correctly. (Either might be correct, but then only more chrono work could tell us which.....or they might both be incorrect for a variety of reasons. Again only more chrono data would tell us that.)

Anyway, once we have tested some more vigorous loads for pressure signs, then I will start testing for accuracy and will do chrono work of a statistically sound confidence level as part of defining the rounds I find to be accurate.

Thanks again for your comments.

As a general observation, so far this lot of SRB-118 appears to be somewhere slower burning than H-4895, more on a par with a fast lot of IMR4064...so maybe is an odd lot of WC-846 or the equivalent?