Run out ?'s

[steveinflag]

Lots of questions!

Although not new to reloading I might have to consider some more advanced reloading techniques.Therefor I need some more experienced bench rest reloading help.

I recently noticed a trend in my 30-375 Ruger Pearce.The load is 71.5 gr R-25,240SMK at 3.9 OAL,Win mag primers at 2775fps.500 rounds down the tube.I've checked all the screws for tightness in gun and scope.The rifle has a Krieger 9 twist 30 inch barrel,Surgeon XL action,bedded to an Anschutz composite stock.Customshop Hornady dies with bushings.

First off,I have benchrest prepped the brass and weight sorted.I have used the expanderon, turned the necks but have only used the carbide K&M mandrel for the inside neck reaming.Also I don't have access to a cement shooting bench so I am forced into shooting off the ground F-class style.

A typical group at 1oo yards will be 4 touching and 1 a 1/4 out of the group sometimes all touching and sometimes 3 touching then 2 touching a 1/4 inch away.I'm trying to eliminate these flyers.

With my 6x47L run out is only 1/2 a thou but the 30-375 is on average 3 thou measured .10 inch from the case mouth on the bullet.On a Sinclair run out tool.

Where do I look first to identify the problem?


Can you list all the reasons why there is so much run out and what I could do to correct this?

Also can custom inside neck reamers be ordered in 1/4 thou increments and if so from who?I don't want to take any more off the inside of the neck than i have to.

Thanks in advance

Steve

 

[chino69]

Runout

Steve,
What type of brass are you using? A tubing or neck micrometer will show how consistent your neck thickness is and is a good place to start. Measure neck thickness at 90 degrees to each other to determine how consistent your thickness is. My guess is you are using Lapua brass for your 6 X 47. Lapua tends to be very consistent brass. If all the above are performed and you are still having runout issues, you need to look to your dies. Did you square your die with the shell holder prior to re-sizing or seating?

When using threaded dies, I tighten the die down firmly into the shell holder with the locking ring loose. While the die is firmly locked in place with the shell holder and die threads, I tighten the locking ring firmly and screw in the locking ring set screw. I place a piece of #8 lead shot in the lock ring set screw prior to screwing the set screw in. The set screw will deform the lead shot and actually squish it into the threads of the locking ring and die. You will probably need a padded pair of Channel Loks to remove the die from the press. What has just been accomplished is squaring the die in the press. Mark your shell holder so that the same one is used with that set of dies. I mike my shell holders to ensure they are square and true but have never found one to be out. I have also gone the extra step of surface grinding my locking rings and using a hard Arkansas stone to lightly hone the mating surface of the press that contacts the die's locking ring. Everything at this point should be square, parallel, and true within the constraints of commercially available components. Hope this helps.

Lou Baccino
Chino69

 

[steveinflag]

My 6x47L is near a perfect round as I have found and the runout is acceptable at less than .001.

I'm talking about this 30-375R.I saw your post at SH and I am going to try it.I will also measure both sides of the brass at opposite sides and see.

This brass is necked down Hornady 375 Ruger cases.

Thanks Steve

 

[steveinflag]

Chino,
I measured a half a dozen cases and the neck thickness was .0002 variance between the thickest and thinest.

I checked the runout on the case neck compared to the body and most were less than .001 but did find one that was really bad at.003.

Might that be the way to sort them,checking runout of the case neck after it has been sized and before the bullet is seated.

Would some more of you top notch BR shooters chime in please.Show me the way Obeywon's.The force is not strong with me.

Steve