Gentlemen,
In working up a load for my 40XB-KS in .22-250 I decided to give thrown powder charges a shot. Using a Harrell's Premium Culver Powder Measure with VARGET. When I found the ideal seating depth the groups turned into bugholes with a single high flier. I would have four in a bughole and one shot 1/2-3/4" high above it. I could either have flinched or more likely I could have thrown a heavier charge. Am I missing another culprit? I can't really see flinching as the rifle weighs 13lbs on the bench and it's the lightest recoiler I own(aside from the Kimber Hornet).

Cases are fire formed and neck sized with a Lee collet die. The Sierra Blitzkings are seated with a Forster Ultra Seater in a Co-Ax. Runout is less than .001" via my sinclair concentricity fixture that uses a Starrett .001" Dial Indicator. Primers are CCI BR-2 seated with a Sinclair Benchrest Handtool in Primer Pockets that are uniformed by Sinclair Primer Pocket Uniformers. Seating depth is .003" off the lands via a Sinclair OAL tool and Starrett Dial Caliper. (Yes, Sinclair has done their very best to bankrupt me;-).

Sincerely thinking of going to weighing powder charges on my RCBS 10-10, however, there is always a difference between the balance scale and my Pact Precision Unit. Makes me think I need the check weights to set the 10-10 properly. That and John Barsness's article a few months back. Any ideas?

Regards, Matt.

Are you using windflags? Conditions, (even when it "seems" calm), can be a big variable....ol blue

Also, the way you are backing up the rifle from shot to shot can have dramatic effect. More or less sholder pressure on the butt of the rifle can throw shots up or down...ol blue

Matt, if that flier were only a bit high, say .2 or .3, I might be inclined to suspect a slightly high powder charge, as you have suggested. But assuming these are 100 yard tests, I just don't believe that high quality Harrell measure is "burping" enough to raise a bullet .5 to .75.

You hint that perhaps before the Harrell you weighed every charge. If you were using exactly the same brass and other components, did you get fliers with weighed powder charges?

As you've noted, the most likely cause is a flinch. Or perhaps you're letting the gun shift so it isn't riding the bags in precisely the same position each time.

Could it be the brass? Maybe do some slow-fire tests and each time you throw a flier, eliminate that piece of brass. Next, using only the "proven good" brass, does the flier pattern re-appear? If not, or if it lessens, you may simply have some inconsistent brass.

Another possibility is that some of your brass has thicker necks, leading to increased tension on the bullet, higher pressure, and, thus, higher velocity. I doubt that variance would be near enough to cause a .75 flier, but I guess it's possible.

Try culling out the brass from the fliers and then let us know what happens.

[This message has been edited by Kentucky Fisherman (edited 04-17-2002).]

Matt,
Most powder scales sold these days are magnetically dampened. This is done to keep the powder scale from endlessly swinging back and fourth. However it also has the capability of introducing some error into the measurement.

This is one of two main reasons most bench rest folks have gone to using thrown charges. The other being that environmental conditions (Temp / humidity) can influence how much a given volume of powder weighs. (i.e. You load 46gr on Monday and 46gr on Friday, you may not get exactly the same charge.

Of course, this topic is the source of endless debate and in my experience, power charges have had the least influence on my group size. On a 35gr charge +/-.1 is less than .3% deviation in charge weight. (This will not generate enough deviation in velocity to be noticeable at 100 -200 yards.)

I would stick with your Harrell measure and eliminate everything else first.

------------------
J.W.
Hero of the Hapless
Master of the Obvious

[This message has been edited by J.W. Blute (edited 04-17-2002).]