Bullet Runout and Seating Dies

[hotrodlouie]

Reading the reloading forum articles about bullet run out seems to be a problem for
everyone and myself so I decided to make a bullet seating die with a different approach for repeatability.
Before I get started the seating dies the manufacture states there dies hold run out to close tolerance,
well I like to find one. I have a RCBS die the bullet hole bore is .005” loose and the center seating screw
is ¼”sae and loose, I have Redding die the bullet hole bore is .027” loose and the seating screw loose,
I don’t understand the thinking on the design ideas for what they call close tolerance run out.
The loose tolerance on these dies for repeatability even the O ring trick is tuff, and when changing bullet
length you have to start over again checking run out.

This die is for .223 rem. cartridge using .224” bullet diameter.
Starting with the bottom end of the die the bore is machined the same angle as the cartridge body.
The bullet bore is .225” or .001” loose The ram on the loading press is set all the way up,
screw the die down with a light touch on the cartridge so the when the correct bullet seating depth
is set with the top seating screw the cartridge is straight inline with the bullet bore. The cartridge neck
stops 1/16” below the bullet bore so the small amount of bullet diameter sticking out is still in the bullet bore
to help alignment.
Working on the top end of the die the threads is ½” sae did not use a tap, chased the threads to make sure
no misalignment. At the bottom of the threads in the die bored a .375” dia. hole 7/8” long to the top of the
bullet bore. The seating screw below the threads is machine .374” dia..001” loose and 7/8” long to fit the die
bore .375” the threads now are not used for centering for bullet alignment. The end of the seating screw shaft
is machine to the bullet ogive radius for more contact and alignment, a straight angle cut will have a small edge
contact.
Now the results,
New Lapua brass neck run out .000” / 25 rounds .000” bullet run out.
PMC brass 1x fired and re-sized, neck run out .000”-.001" / 40 rounds .000”-.001” bullet run out.
Tried some .002”-.003” neck run out / .002”-.004” bullet run out.
My theory on this die design is what you put in is what you get out and repeats.
I think the die bottom end angle might not be that critical, but bullet bore size and the top end of the die
bore for the seating screw machine fit is the answer for repeating.
This was not a 5 minute job if you know somebody with a lathe you can drill the top of a seating die out
with carbide drill and press in an insert and machine to what I did to the top end and make a seating screw
to match not as much time consuming if you have to pay for it. Machine work is not cheap.
Myself I don’t work for $1.00 day and 2 fish heads like China pays.
No expert on this stuff just something I wanted to tried, don’t shoot competition, don’t know a competition shooter
maybe this is how they make custom seating dies. This could be old news but it’s working for me.

 

[wapiti25]

Look at how the Redding competition seating die is made or the Wilson. Good brass is the first issue as far as neck runout and wall thickness. The tolerance or clearence in the die is a problem as one size does not fit all, so off the shelf dies are a compromise.
The next issue that I have is how people measure the run out. the question that I have is what is the datum on the round that the bullet is compared to. The Hornady bullet comparitor uses the rim of the case which I think is garbage. I think the body of the case should be the datum. Some use "V's or balls and this is close but you only have points to measure from. The case may not be perfectly round. The next is how true is the chamber to the bore.

 

[fdshuster]

hotrodlouie: I've never been able to straighten a round (case neck) that has runout by seating the bullet, and I'm talking about using both the Forster Benchrest Micrometer seaters, and the Wilson chamber type seating dies, with my arbor press.

The Wilsons are such a tight fit, ( they were modified by Wilson after I sent 3 sized cases to them/ can't get a tighter fit than that), that I must pull the loaded round out of the die by hooking a small screwdriver blade over the rim.

I'm talking about all Lapua brass here, 220 Russian to 6ppc, 22BR, 6BR, 6BRX, and now 30BR. All case necks have been outside neck turned, to zero variance in neck wall thickness.

It's always been my belief that runout is primarily caused by a defective piece of brass, beginning at the time it was formed. How else to explain 2 out of 20 that have excess R/O, when the other 18 are near perfect?

As you said, in effect: "Runout in, runout out".

 

[hotrodlouie]

You guys are right about starting with good brass with no run out.
The problem I was having even with good brass these two dies the bullet
run out was still .002"- .004" with no repeatability that's why I try something
different. To check neck run out I made a bushing sleeve bored the full length of the
cartridge body with just the neck sticking out using a V block. After reloading
and the neck shows run out I can lock down the bushing in the V block with the full body
length supported in the bushing and tap on the neck to 0 run out, the indicator reads
under the neck so I can see how much the neck moves. You guys are into this heavy an
experienced, I'm new and just like to make parts try things myself. I just want to show
that off the shelf dies with good brass has problems due to loose tolerances for us low
budget re loaders.
.

 

[fdshuster]

hotrodlouie: I really am not concerned about brass R/O 'til after it's been fireformed in my chamber(s) one or two times. If it has not straightened out by the second firing, then I write it off as defective from the time it was made, and mark it with a small jewelers file by cutting a very small "V" on the edge of the rim.

From that day on, that piece of brass is used for secondary purposes only. Basic scope sight-in, first round foulers, and a maximum of 100 yard distance only, where I find it to not make any difference in group size. In fact, at 100 yards, with 5 shot groups, using R/O's of as much as .005", I've often had groups that would be winners in our BR for score match's.

I'm using the Sinclair Concentricity gauge to determine R/O, and take the readings on the bullets ogive where it will contact the lands. Works for me.

Many times I have found that seating the bullets in 120 degree increments can help. Seat approx. 1/3, lower ram, rotate case, seat 1/3, lower, rotate, final seat.

 

[necchi]

Yup, your on too it louie.

Same trouble with the sizing die stem too, but your right, unless someone hase a lathe we're kinda in trouble paying for labor vrs buying the high end dies to begin with.

 

[bozo699]

hotrodlouie: I really am not concerned about brass R/O 'til after it's been fireformed in my chamber(s) one or two times. If it has not straightened out by the second firing, then I write it off as defective from the time it was made, and mark it with a small jewelers file by cutting a very small "V" on the edge of the rim.

From that day on, that piece of brass is used for secondary purposes only. Basic scope sight-in, first round foulers, and a maximum of 100 yard distance only, where I find it to not make any difference in group size. In fact, at 100 yards, with 5 shot groups, using R/O's of as much as .005", I've often had groups that would be winners in our BR for score match's.

I'm using the Sinclair Concentricity gauge to determine R/O, and take the readings on the bullets ogive where it will contact the lands. Works for me.

Many times I have found that seating the bullets in 120 degree increments can help. Seat approx. 1/3, lower ram, rotate case, seat 1/3, lower, rotate, final seat.

100% spot on Frank, at least it's my thoughts and process as well and seems to work pretty well, I size the same way, and it has been proven to me that it works! If I am getting .0000-.0002 or so runout from the chamber and .002 after I size it I can usually reduce that # to .001 or less by rotating 1/3 way through the stroke then another 1/3 then final sizing.
Wayne.

 

[amlevin]

I know that "Lee" is not often a name associated with precision but I've been using their Collet Die for neck sizing for a couple years now. Starting with a quality case that's been neck turned and fired a couple times finished rounds that were sized with the collet die and with bullets seated by a Redding die with a micrometer adjustable seating plug, I get runouts of less than .001, some as low as .0003". Only change I made to the Lee die was to completely clean the collet, removing some chips left from manufacture, and polished down the mandrel so neck tension was increased by .001". Having the mandrel in the center of the case, indexed on one end by the primer flash hole kind of makes it tough to reform the neck "crooked". Quality cases sure help too.