I recently bought a concentricity gauge, happened to check my reloaded 376 H&H ammo and found it had a pretty large value. Experimentation showed that the runout mostly occurs during the sizing step. Cases all have less than 0.002" runout AFTER full length sizing with the expander but after seating the bullet the bullet runout is 0.005 to 0.015" measured on the bullet close to the case mouth. I tried a Forester Benchrest seating die and the bullet runout was the same. I have tried Winchester and Remington cases, and Barnes and Nosler bullets and I don't see any difference. Gun accuracy is about 1.5 to 2.5" for a 3 shot group at 100 yds. I measured bullet runout on some factory Remington rounds I have and they are 0.001" or less. Has anyone else noticed relatively large amounts of runout on "big" bore cartridges?

I played with runout this past summer. I started checking runout in some 7 mag. loads because I had a new rifle that wouldn't shoot good.

Some loads were out .015 and some ran zero. I did find that the ones that ran closer to zero outshot those that ran out alot.

I checked quite a view factory loads and found some that ran .002/.004 range these were Winchester power points. The one batch that threw me was a box of Hornady 7-08 Light Mag .139 SST lowest runout was .006 and four rounds were past .015.

Trial and error was how I managed to get most of my loads under .006 but I have found that short range accuracy ((100 YRDS)) this runout has litle to no effect.

Long rang however runout affects performance....think about a supertight spiral thrown from your favorite football quaterback and a flayling duck type of pass. The later doesn't go nearly as far even though it is thrown with the same effort.

Excessive runout is usually caused when the expander ball is pulled out of the neck during sizing operation. The case is held (sometimes loosely) by the shell holder only half way around the case which allows the case to tip somewhat as the ball is extracted, allowing ball to stretch neck to one side.

Some things that you can do to minimize this is to polish the expander by chucking in electric drill and spinning it in crocus cloth and use a dry lube inside your case necks. Next, set your expander ball as high as possible in the die (be sure it is clear of neck sizing portion of die) so that the case neck is still supported and centered by the die as it (the case neck) is pulled over expander. I have had some positive improvement in runout by putting a small o-ring under the de-capping rod lock nut and tightening just enough to secure stem but not enough to lock the stem 100%. In other words, allowing the stem (and expander) to "float" slightly in the threads and seek it's own center.

The good news is that, as TT stated above, runout doesn't affect short range accuracy nearly as much as long range and the larger calibers are usually shorter range rounds and the targets are usually substantially larger.

Regards,
hm

I have checked hundreds of cases that ran zero....then after I installed the bullet there was runout....If the bullet is not 100% inline with the case mouth it will have runout even with DEAD NUTS brass.

Bullet seating is the hardest thing to get right when you are talking runout of less than .003 TIR.

I Don't worry about it to much though anymore but I do still check every single round I load and mark the runout on the brass and sort them in the box.....best to worst. I then use the worst for fouling shots and warm up shots and the best for grouping and killing.

There are a few things that I have found that make all the difference in the world.

1) Pick a brand of brass. Load a bullet into it. Make sure you plan on continuing using this brand. Measure the OD of the case neck. Subtract .002. Send the die back to manufacturer and have them hone the die to where it will size that brand of brass to that diameter. Most sizer dies constrict the neck way too much and that simply work hardens the brass, especially when you couple that with dragging it over an expander.

2) Polish the expander as mentioned above.

3) Position the expander as mentioned above.

4) Make sure seater die is CLEAN. Many times after seating only a few bullets you will get bullet jacket shavings in there which can upset the alignment of the bullet as it goes into the case mouth for seating.

Having all of my sizer dies honed to a larger diameter has made an incredible difference.

When seating a bullet, do it in 3 steps: Seat it about what feels to be 1/3 of the way into the case mouth, back out of the die, spin the case about 60 degrees, seat another 1/3, spin the case, and finally fully seat the bullet.

I loaded up 75 rounds of 308, 100 rounds of 270, and 50 rounds of 270 AM last night. Not one loaded round exceeded .001 runout and most all barely made the indicator needle move more than .0005.

I used to not use the expander for a long time due to runout issues, until I got my dies honed. I would simply size them down, then use a graphite suspended in alcohol to lube the neck prior to seating a bullet. This method worked great too, and I still do it now and then to compare.

I believe you've determined that the sizing process is not the culprit. I've never satisfied myself why it works, but rotating the case during seating, as recommended by Doc, should help. Another issue is the alignment of the bullet in the case, but apparently the Forster die isn't resolving that condition if it exists. One other thing you can try if you are not already doing so, is to bevel the inside of the case neck with a VLD chamfer tool. It will help with the initial alignment of the bullet in the brass. Glen Zediker believes that a bullet started crooked will not straighten itself.

Be sure that the tip of the bullet is not contacting the seating plug.

quote:

Originally posted by JC454:
Gun accuracy is about 1.5 to 2.5" for a 3 shot group at 100 yds. I measured bullet runout on some factory Remington rounds I have and they are 0.001" or less.

You neglected to post the accuracy of the factory ammo. Because the runout was less, were the groups smaller?