Keyholing at 200 yards?

[richbug]

I just attempted to use my #4mk1 at our local high power match over the weekend.

13.0 grains of Winchester Super handicap. 178 gr Fat Loverine as cast with a check installed, .317" diameter. At home, at 50 yards they shot into a 2" group, no idea on velocity as the weather has not cooperated. At 200 yards about 1/2 the holes were showing some keyholing (the other half shot a reasonable group, though it tended to move around). What does this indicate? Need a little more velocity?

[Larry Gibson]

Need a little more velocity?

That would seem to be the case.

Larry Gibson

[JeffinNZ]

I'm with Larry. You seem to have all else in order. Got a velocity for us?

[Spudgunr]

How long ago did you test them at home? Cold air is denser and needs a faster twist for a given bullet to stabilize. If it was the same temp at the match as at home then ignore this, but if you tested in the summer and now are in the winter they may have just been on the verge of stability.

Cold weather I believe is why AK's have a twist rate of something like 1:9.5" or so even though the bullets are only 123 grain. This is about what garands have (1-10").

[GrizzLeeBear]

I agree with Larry also. You need a little more velocity for that length of boolit. The wandering group and keyholes are telling you the bullet has slowed down to where it is unstable. Just guessing, but I bet that load just stays supersonic to about 100 yds. As it slows to below the speed of sound it gets unstable. For Highpower work up a load that stays supersonic all the way to the target, say 1600 - 1800 fps muzzle velocity.

[richbug]

Any thoughts on a suitable load using 2400, or XMP5744?

[45 2.1]

Velocity can be a big factor, BUT powder selection is another factor not looked at much. I do know very low charges of WW231 will shoot very nice groups at 200 yards. Try another powder...................

[Spudgunr]

Powder shouldn't have anything to do with keyholing though. Group size yes, but a bullet flying sideways, probably not.

[leadman]

With 2400 in my 1903a3 (30-06) 18 grs is pretty good. Might want to start just a little lower and work up. Found a load in the Lyman Cast Bullet Handbook 3rd Edition for a 30-40 Krag with 2400 that starts at 17grs for 1547 fps with 173gr Loverin 311407.
The Accurate Manual #2 shows 25 grains with a 180gr. RNGC for a start load, 28 grs max. 1983fps and 2159fps.

As always, use this info at your own risk.

[bkbville]

A fast powder and a soft boolit combination can effect instability even to the point of keyholing.

[1Shirt]

Spudgunr on temp is IMNTBHO probably right on track. Loads that I have loaded and shot in the winter at temps below freezing often have (most usually have) a different point of impact at temps say above 80 degrees in the summer. Keyhole at that range, due to temp, don't know, but think is reasonable.
1Shirt!