Bullet runout problem with Dillon 308 dies

[Three57]

I am currently getting bullet runout in the .006” range. I am resizing my brass to .005” shorter headspace than the chamber. I measured fired brass to determine the size of the chamber and then adjusted the size die to headspace .005” shorter. I am wondering about taking this to .003", maybe I am sizing too small?

I am using new winchester brass and hornady 178 BTHP, and doing a slight inside chamfer with a wilson deburring tool. The rifle is a Knight SR25 ER.
I have ordered a forster ultra seating die, and waiting for it to arrive. Looking at different sizing dies as well. I am not sure this will solve the problem.

Any thoughts, ideas, suggestions are greatly appreciated.

 

[JGorski]

I am currently getting bullet runout in the .006” range. I am resizing my brass to .005” shorter headspace than the chamber. I measured fired brass to determine the size of the chamber and then adjusted the size die to headspace .005” shorter. I am wondering about taking this to .003", maybe I am sizing too small?

I am using new winchester brass and hornady 178 BTHP, and doing a slight inside chamfer with a wilson deburring tool. The rifle is a Knight SR25 ER.


I have ordered a forster ultra seating die, and waiting for it to arrive. Looking at different sizing dies as well. I am not sure this will solve the problem.

Any thoughts, ideas, suggestions are greatly appreciated.

Ive got some 178s that have mostly less than .002" runout, some were corrected I believe with my Hornady concentricity gauge, but only a couple from the box of 20 I have, but they were only out maybe .004" runout, I use Hornady custom FL bushing sizing dies and Hornady New Dimension seater. Are you using a expander in your resizing, that might be where your issue arise. Im not using the expander my Hornady custom bushing dies.

 

[Three57]

I am using the expander.
Will adjusting it's position help?
Possibly put the ball closer to the top of the stroke so the neck is still supported by the die?
I have not adjusted the position of the expander, I could take it out and see what the results are.

 

[jwp6114]

If you take it out your neck tention will be quite high... not sure how that will affect your accuracy but you can try, also keep in mind initial pressure will go up as so will velocity. bullet run out you say? how is the run out on the case neck? there are a couple trade secrets you can try. PM me if you want the skinny.

measure the run out on the neck and then on the bullet, let us know what the two different values are. the more tun out closer to the base the worse it will be at the bullet ogive.

we can easily get this solved for ya.

 

[jwp6114]

also measure one fired from your chamber at the neck then a resized one, I could talk you through this on the phone real quick if you want. PM me your number.

 

[former naval person]

While you are getting the Forster die go ahead and order a Lee Collet neck die. Use it to neck size and decap. Get a body die to use when the shoulder needs bumping. Sell the FL die with the expander ball. JMHO

 

[jwp6114]

I use redding S type full size neck bushing die, fo sure get away from the expander ball

 

[JGorski]

Spend 42 bucks I think they are and get yourself the Hornady custom FL bushing dies, youll need a 331 bushing for Win brass, 334 for rem & lapua brass. Yeah, and dont use the expander, just the straight piece that comes with the die. Itll look like this.

 

[turbo54]

I don't want to get too far off in the weeds with a tangential leap to a new topic, but gotta say my piece on neck tension as it relates to FLSing without the expander...

The maximum amount of neck tension achievable from most brass cases is ~.003", because brass is soft and malleable.

Force a .308" bullet into a 7mm-08 case and then measure the (loaded) neck OD. Now pull the bullet and measure the (unloaded) neck OD. The difference is your "neck tension".

Hint: You won't find that you had .027" neck tension.

Edit to add: I am a big advocate of removing the expander ball. This technique works well to keep good concentricty. I do, however, run a Sinclair "neck turning" mandrel into the caseneck to final size it. It's not a neck tension thing though, it keeps the bullet jackets from getting scratched up while seating.

 

[mk12bill]

As you're shooting an AR platform you'll need to keep the expander ball in place as the case mouths will take a beating and be deformed. That's my experiance shooting AR's, especialy my LR308. I'm also using the Forster Ultra Micrometer Top seater for my .223 handloading and most loaded cases have .001-.0015 bullet runout, with the max I've ever seen .003.

 

[Three57]

Resized loaded run out is .003" on the neck and .006" at the ogive.
Once fired is less than .002" run out on the neck.
New resized is .004" run out on the neck.

The case mouths are pretty beat up after firing.

It seems like everyone is suggesting new dies. I had placed an order for the forster ultra seater and the redding s type bushing sizer die. I cancelled the order hoping we could get the dillon dies to work. If the new dies are necessary to fix this issue. I will order them again. I do believe the expander ball or bushing are going to be necessary for the case mouths.

The Forster seating die and redding sizer die are on their way.

 

[chefcam864]

You could try polishing the expander. I do this on all of my dies and it does help. As MK12bill mentioned, you won't be able to remove the expander when loading for a gas gun. You might also try a new shell holder too, as that could also be the source of your problem.

 

[bas402]

I am currently getting bullet runout in the .006” range. I am resizing my brass to .005” shorter headspace than the chamber. I measured fired brass to determine the size of the chamber and then adjusted the size die to headspace .005” shorter. I am wondering about taking this to .003", maybe I am sizing too small?

I am using new winchester brass and hornady 178 BTHP, and doing a slight inside chamfer with a wilson deburring tool. The rifle is a Knight SR25 ER.
I have ordered a forster ultra seating die, and waiting for it to arrive. Looking at different sizing dies as well. I am not sure this will solve the problem.

Any thoughts, ideas, suggestions are greatly appreciated.

Am I reading this correct? Are you bumping the shoulders back .005"!!! You should only be .001" to .002" max. If your talking neck tension bolt guns .002" and semi's .003"
Sully

 

[Three57]

I am bumping the shoulder back .005".
I believe .001" to .002" is recommended for bolt guns, and .003" to .005" for gas guns.

 

[bas402]

I am bumping the shoulder back .005".
I believe .001" to .002" is recommended for bolt guns, and .003" to .005" for gas guns.

You need to go back and read some more. Bumping the shoulder whether it' a semi or bolt is... 001-.002" max. If you continue down this avenue and thought process you will have bigger problems than runout like case head separation! I'm sorry but get back to the basic's first and get your dies set up correctly. Don't mean to sound harsh but I don't want to see someone get hurt here.

 

[ZiaHunter]

You are correct and it is generally recommended to set the shoulder back .003-.005 with gas guns. I reload .308 on a 550B and have runout issues as well which is more pronounced with certain brands of brass. Typically it is with cases with a neck wall thickness greater than .0135. I have sized cases without the expander and they have neck runout of .001 or less which indicates that the expander is the culprit. Lubing the case necks is problematic since powder will still to it while charging so that is not a practical option. I am currently using Dillon dies and may try a bushing die with he expander removed and run a mandrel through the neck before sizing. These rounds are run through a gas gun and frankly haven't seen a material difference out to 300 yards between ammo loaded on the 550B v a single stage press. For my bolt and single shot rifles I only load on a single stage press.

 

[chefcam864]

You need to go back and read some more. Bumping the shoulder whether it' a semi or bolt is... 001-.002" max. If you continue down this avenue and thought process you will have bigger problems than runout like case head separation! I'm sorry but get back to the basic's first and get your dies set up correctly. Don't mean to sound harsh but I don't want to see someone get hurt here.

.005" is not gonna hurt a thing but your brass life, which on a gas gun aint long anyway. I routinely set my shoulders back .003"-.005" when loading for my M1A because it helps to reduce the chances of a slam fire or the dreaded out of battery detonation. I never get more than 5 firings on M1A brass, and it's not because of split necks or head separations. The bodies are scratched to hell, extractor grooves and rims chewed up etc.

 

[Three57]

I resized 100 pieces of brass at .005", I have been using these for load testing. So far they have all functioned great so the next time I resize them, I am going to move up to .004" and make sure that they all function correctly. I started small just to make sure everything was going to work correctly. After .004" I will try .003". I understand the less you resize the brass, the longer it will last and you should also gain accuracy. But with Semis, functionality is most important and sizing them small, will make them more reliable, at the cost of shorter brass life. Which like chefcam said, isn't long anyway.

 

[Ballistic308]

Are you sure you don't have a piece of debris, powder kernel or tumbling media in the shell holder where the case rim goes?

 

[427Cobra]

Never check run out with new brass, wait until its fire formed, also don't bump the shoulder back on new brass.

 

[jwp6114]

Also, try this, measure runout on a fired case then resize and measure again. If the run out gets worse try this. Sounds crazy but works. Get an o-ring the size that u can fit in the die threads and float the die atop the o-ring. This will allow the shell to align the die to it (as the fired case is more concentric than your previously resized brass. Pm me your number if u want a verbal explanation. It works.

 

[JGorski]

357, When you seat the bullets do you seat them partially, like half way then turn the shell 180 and seat it the rest of the way? I always do that. Oh, and I tested some 30-06 shells on my Hornady gauge and was amazed how low the runout was, less than .001", used Rem brass & 180 SBTs and a LEE seater, and those shells were sized by LEE dies with their new expander, cant recall what they call it. Maybe I got lucky.

 

[Three57]

I think I am getting closer to figuring it out.
Ballistic308, after seeing your message this morning, I looked at my shell plate and it has loosened up since I last adjusted it. There was a little bit of play in it. I could definitely see how this could cause this kind of problem.
jwp6114, thanks for all your ideas, I am getting a lot better understanding of all of this. If the shell plate holder doesn't solve the problem, I am going to try the O-ring. I do now have a good idea of how to test these and what to look for.
I will also try turning the shell 180 after seating half way.

Thanks guys.
I will work on it some more after work today, and let you know what I find.

 

[Deadshot2]

Two changes have brought finished cartridge run-out to near zero for my .308 rounds. I now necks size and bump the shoulder using a Forster Shoulder Bump/ Neck Size bushing die. By keeping neck wall thicknesses even I don't need to use an expander ball at all when sizing. I also leave the bushing slightly loose in the die. About 1/8th turn and tighten the lock screw. This lets the bushing float a little and yields a nice straight case.

I then seat using a Forster Bench Rest Seater Die. When seating the bullet, even though the BR seater uses a sliding sleeve to hold the case nice and straight, I still seat in about 3 moves. One to get the bullet just started into the case. Then loser the ram enough so I can rotate the case about a third and seat some more. Repeat, rotate, and finish seating. All I can say is that for me, this yields total indicated run-out in the .0015" or less range. Some won't even move the needle on the dial indicator.