I am shooting cast bullets from a lyman mold.
They are 40 cal 175 gr.
I size them to .401 after tumble lubing them and then lube again.
At 11 yds 8 out of 10 will key hole.
I am thinking either they are sized to small or to big,dont know. Thats why I am asking!
Or do they need lubed better?
Or what would cause this?
Thanks!!!!!!

I would guess not big enough or maybe two heavy of a bullet to stabilize. Or not enough powder to stabilize? You shooting these in a pistol or a rifle? You need to add more info. Jim

The boolit is not spinning correctly. Barrel too small up front, or boolit too small towards end of barrel. Clean the barrel excessively, getting rid of all copper/lube/lead. Shoot 5 or a clip full. If keyholing still exists, then the boolits are too small in diameter. Keep in mind the boolits can be knocked out of kilter by their slamming into battery not straight on. A longer boolit will prove this problem. Have several 200 grainers on hand for a check out. ... felix

Try not sizing them. Shoot them as cast.

try the green hill formula, given me by mr brooks a mold maker in butte montana.. maximum lenght= 150 x diameter x diameter/divided by the twist rate.. this will give you the maximum length of bullet for the twist your using before it will start keyholing.. i have a drilling and the bullets that i used at first were sized down from .366 to .361.. the lube was sparse, the sized down off center, the leading was severe, accuracy was good, no key holeing.. the bullet weight is 200 grains for the .360 caliber... your 174 grain bullet doesnt seem too long but you didnt give the twist rate.. put a very tight patch in the gun push it down until it makes one revolution (or half rev X 2) and measure how far it went down. if it is not the twist rate there has to be other clues to the problem, excess pressure, leading, etc?? a bad base or nick in the crown will cause a off course push also..
dave

I am geussing that you are loading them in a 38/40 Winchester. If an old M92 the bore may be very worn and oversized. Try lubing and shooting as cast. My rifle is made in 1896 with a excellent bore but prefers that Lyman bullet unsized .4032. Sized to 401 some show slight tipping on paper targets.

I am shooting a 40 caliber glock.

Load and alloy hardness? 40 S&W or 10 mm?

Could be polygonal rifling.

z1r, took the words right outa my mouth. Also, is not the 175 on the light end for a .40? I'd try a cast friendly after market barrel and same or a little bit larger boolit. sundog

Mrngunslinger,

Check the crimp diameter. An exccesive crimping sizes the bullet. I saw this effect in a 1911 .40S&W Caliber with cooper plated bullets.
Effect must be worst with plain cast bullets because sliding surface is softer than cooper plated.

Hope this helps

BA Shooter

If you are shooting cast bullets from your Glock w/ poly. rifling, they need to be very hard. The dia. of .401 should work. I shoot the same bullet from an H&K & S&W 40s & accuracy is almost as good as jacketed. Again the bullet needs to be very hard alloy, push them to at least 900fps & they should shoot.

Don't mess with cast bullets in a Glock. It won't work right. They do tell you that in the instructions. They are not kidding! If you must play, get a conventionally rifled barrel.