Sizing die causing brass runout

R

russell m

Guest
I use a Redding F/L sizing die. I measured 20 fired case & my runout is
.0005. after sized the runout is .0015 to .001. & a couple at .002. I have disassembled the die & cleaned,checked for any burs,& tried flipping the bushing over. NO change. will Redding work with me to get the perfect die? Any suggestions.
russell m
 
Sizing die runout

There are a couple of simple things you can do to ensure your die is as square as can be before you suspect the die is at fault. When setting up a new die for the first time I leave the lock ring loose and screw it all the way done until it touches the shell holder with the press arm in the down position with the ram cammed up. I advance the die about 1/8 to 1/4 turn further down until there is sufficient camming force to square the die relative to the shell holder. Then fasten the lock ring down tightly and secure the set screw to hold the lock ring in place. I usually take an extra piece of #8 lead shot to place in the set screw hole so that the lead gets squished out between the threads to maintain this position. When the press arm is raised and the cam force released, the die cannot be removed by hand and I use a pair of padded Channel Locks to remove it. Mike your shell holder to ensure it is dimensionally the same all around. I surface grind my locking rings on both sides to ensure they are flat and parallel. The other question I have is what type of brass are you using and where are you measuring the run out?
Chino69
 
Last edited:
Sizing die causing brass run out

I've seen this before. I bet your die isn't lined up properly with your press.
Of course Redding will check your die. One possibly slipped thru ,
I doubt it though their quality control is excellent.
The threads in the top of the press may be the problem. Or even a shell holder.
 
Brass runout

Russell,

Are you using any lube when resizing? If not lightly lube the entire case including the neck with Imperial Wax. Don't use so much that you cause a dimple on the sholder. I have found this to reduce the runout in my dies by at least 50%. If this doesn't help you may need to continue your quest for the perfect die.

Brian Moore;)
 
I am using Russian Lapua brass for 6ppc. Yes I use imperial die wax. The press is a Harrells.
Chino69. How do you set your headspace with your method.

I use the shimes for Siclairs. Once the lock ring is locked down if i need to make any changes I do it with the shims to get correct headspace.
 
Setting headspace

russell m said:
I am using Russian Lapua brass for 6ppc. Yes I use imperial die wax. The press is a Harrells.
Chino69. How do you set your headspace with your method.

I use the shimes for Siclairs. Once the lock ring is locked down if i need to make any changes I do it with the shims to get correct headspace.
Click to expand...

I usually take a .005 cut off the base of the die in the lathe. My smith uses Henricksen reamers that are usually min. spec. A normal die will not size the brass enough so by taking a little off the base of the die, I'm able to re-size brass exactly with the use of shims, as you do. I seriously doubt the problem is in your Harrells press as that is a pretty well made piece of equip't. from reliable people.
Chino69
 
Before you go too far check out your shell holder. I have had a couple that were improperly machined. The relief for the forward part of the extractor groove was not big enough and the shellholder bore against the beveled section of the extractor groove and not the base of the case.

I now check any new shellholder to make sure there is plenty of clearance in this area.
 
OK Russell

Asking a few questions for your consideration:

Does a basis exist for concern other than you have the tools to measure runout and assume that the tools exist for a purpose?

If you load, chamber and extract a dummy round what is the before and after runout? What is the runout as it lies in the chamber?

If runout is worth the concern, what will you do to correct the initial .0005? What is acceptable?

A loaded round of .0005 in a .0005 chamber could result in .001 effective runout.....or effectively zero.

What would be the difference in your five target agg - .002 runout versus zero runout?

Finally, are you working on a problem that is not worth working on?
 
Wilbur
You are right. My worst runout on a loaded round is .0025. The only way I will know if it makes a diff is by testing on a perfect day preferably with a rail gun. But my wife tells me I am a perfectionist. This has its draw backs. Thanks for the advise. Is it really worth the time & expense. I shot a 16X 250 at my first match with 6PPC at the Tomball club. The rounds cant be that bad as is.
Have to out for a while will ck back later.
russell m
 
one quick check you can do is the lock ring. I've had some (not Redding) where the threads were really bad. When you spun them onto the die they wobbled like a flat tire! Try another ring or better yet two rings jammed together so you're not using the set screw. That has helped me several times.
 
Russell

Your bushing could be at fault. Order another of the
same size and see if it fixes the problem....
 
Russell
I had the same problem and it was the bushings. I checked them for being square and they weren't. when they came up against the stop they cocked causing the neck to be off.
 
When

55,000 to 65,000 lbs of pressure hits that bullet in the butt does .002 really make a difference in the way the bullet exits the case?

Don,t know. Just wondering what every body thinks.
 
Wayne,

I think it way down the list of why I don't shoot so well. I've sorted loaded rounds into groups by runout -- these are 1,000 yard rounds, so they a looong -- and found no difference in group size testing at 100 yards.

The way to do one test would be to find 10 rounds with a fair bit of runout and 10 that were dead perfect. No identifying marks. Give them to a friend to hand to you, so you don't know which you are using, & fire a couple of groups. I'd bet there would be no significant difference in the size.

Moving to theory, runout might cause a bit more in-bore yaw. If so, there would be no difference in group size with no wind, or with constant wind, but a slight difference in variable wind. Of course, if there is variable wind, the guy who reads it better will come out ahead; far more important than the small amount of dispersion in-bore yaw variance causes.
 
Another deal is....

A fair percentage of us prepare our "stuff" to the nth degree and get beat by those that don't......and vice versa.

Must be something else at play.....
 
Russell,

I bet there is nothing wrong with your set up, that is just the nature of shoving a brass tube into a steel hole with only a very short radius to guide the brass tube in. You will induce runout in the brass tube (your case necks) and the more you size down the more runout you will induce.

If you were to use a series of say 4 bushes to size the case in small increments instead of doing it in one step I bet your runout would be less. If you could have a longer tapering lead in angle on the bushes (can't due to the neck length) I bet your runout would be less.

If you tried a one piece full length die with a fixed neck diameter and no bushes the hole the brass is pressed into is likely to be aligned better and forced to stay aligned, also the shoulder angle creates a better lead in area for the case. The end result is a good straight one piece full length die with the neck at the proper diameter for your use will almost certainly size the cases with less runout than even the best bushing dies.

Loose bushes so they can self centre, tight bushes so the don't, dead straight bush alignment, doesn't seem to make any real difference, the simple fact that you are jamming the thin wall brass tube into a hole that will constrict the brass and doing so with very little lead in to ease the process will induce small amount of misalignment.

Remember when you measure on a concentricity gauge you are measure the "total indicated runout" which is twice the actual misalignment from centre. The case or loaded round will move up at the point of misalignment lifting the dial gauge and when you spin the case 180 degrees the high spot will no be the low spot and the dial gauge will read the difference below centre as well. End result is that at a reading of 2 thou on the gauge the misalignment is actually only 1 thou off centre.

Bryce
 
Last edited by a moderator:
You must log in or register to reply here.
Back
Top