Controlling Runnout?

J

JDBraddy

New member
I'll shoot .2 groups with my 6ppc, but my .223 and .338LM are doing .75 to 1.25 consistently. I do the exact same thing with my .223 and .338LM that I do with my 6ppc , I start with new Lapua brass, turn necks, Debur flash holes, uniform primer pockets, resize using an RCBS Pardner press, Redding full-Length S-type bushing die, seat bullets with a Wilson micro-top bullet seater. I pulled out a Sinclair Concentricity guage. My 6ppc has less than a thousandth runnout on any round. The .223 and .338LM have as much as eight thousanths runout on some rounds, and average about three to four thousanths runout with a few under two thousanths. I don't understand how come I'm doing all the same things with the .223 and .338 as with the 6ppc, but not getting the same results. What else can I do to control runnout?
 
Do they all have different runout as in checking 10 of the 338 in a row? Those bullets are not known toy be of the best quality
 
I'm with Dusty,
Change your bullets and see.
what have you checked before you load them?
Jim
 
The straightest bullet in the world [everything is in axis / on the centerline, bullet, case, primer], regardless of caliber, will have its bullet deformed as it attempts to move up from sitting low in a factory chamber. The axis of the bullet sits lower than the axis of the barrel. When the bullet deforms, its balance is affected [assuming it was balanced to begin with], and all bets are off as to where it ends up.

If and when you can produce straight line axis cartridges, opt for the tightest chambered barrel you can find to line up both axis, the cartridge's and the barrel's. Neck turning comes to mind as one aid. Shilen [ http://www.shilen.com/ ] produces factory-neck, minimum-neck, and tight-neck chambered barrels. Take your pick depending on how much accuracy you want.

Note: Harold R. Vaughn's book Rifle Accuracy Facts will shine a lot of light on all the variables most of us overlook when trying to figure out why things seem to be out of whack.
 
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The late Ferris Pindell told me that most of the runout of a loaded round is caused by the sizing die. One should check his necks for runout before seating a bullet. Good shooting...James
 
I looked on line for "Harold R. Vaughn's book Rifle Accuracy Facts" online and its $550.00 on amazon.com.
It there a cheaper source for the same info?

Bill Hodkinson
 
Check the concentricity of your sizing bushings. Sometimes the holes aren't as concentric to the OD as you may think. If they aren't, and there isn't enough clearance between the inside of the die & the bushing OD to allow for the eccentricity, it will cause problems.
 
Hman1956 said:
I looked on line for "Harold R. Vaughn's book Rifle Accuracy Facts" online and its $550.00 on amazon.com.
It there a cheaper source for the same info?

Bill Hodkinson
Click to expand...

I didn't know I was sitting on a gold mine. Seriously, the Vaughn book is interesting reading, but much more practical real world information can be found in the benchrest books from Tony Boyer or Mike Ratigan.
 
r44astro said:
I relieved my shell holder so it floats, and made sure the ram was true, made a huge difference.
Click to expand...

Really???

I mean REALLY?

I'm serious here. I've done a lot of testing and IMO "trueness" and "squareness" and "alignment" are immaterial in mfgr of straight ammo.

You can't bend a case straight

or crooked

THE LESS YOU MOVE THE BRASS, ie the less you size, the better the fit of the die to the chamber...... the straighter the ammo

regardless of your choice of press.

IME

al
 
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