Neck Bushing Causing .002 additional Run-Out

[foxguy]

The comp


I thought the price on the comp sizers was outrageous too - I mean who needs a flippin' micrometer adjustment on a neck sizer. But when I got my 6mmBR bench rest riffle, I bought the full set of Redding Comp dies, which was a comp neck sizer, body die, and comp seater... because that was what they had in stock at the time, and like a little kid at Christmas, I didn't want to wait for the separate dies to come in (who knows when).

When I looked at the comp neck sizer, it all made sense.

The bushing neck sizer is like the comp seater - the case is in a floating sleeve and locked in place. I do not know how much play the bushing has in it's own chamber. The bushing is 0.500", I do not know if the bushing chambers are 0.501, 0.503... or whatever - I do know that they work very well, and I am replacing my Bushing "S" dies with comps, as the money becomes available.

I will confess that I modify all of my bushings when I get them.

As to the wifie... back some time ago, she said, "If you buy one more gun, I am leaving you."

It was fully 7 or 8 weeks before I realized that she meant it. It is so peaceful now. I get to have bacon cheeseburgers for breakfast on the weekends, and I don't have to have a mother-in-law telling me that I should stop killing poor widdle woodchucks.

John,

What do you modify on them, How do you do it?, What is it correcting?

 

[ptf18]

Fellows: Have a "similar" situation as the OP does. I've got a 6mm250. I have measured several fired case necks (WW brass)and found that they are less than .001 out of round. I deprime the fired cases in a separate step then clean the cases.

I use a Co-Ax press. Hornady New Dimensional FL 22-250 resizing die that I use with a RCBS .268 neck bushing which "floats" when I have it installed.

The neck OD of my fired cases measure (on Average) .273

Using a RCBS Precision Mic I find that I'm setting the shoulder back, IF ANY, less than .001 from the case fired condition.

The resized cases easily chamber in the rifle.

The issue Im having is this.

After running a fired case thru the sizing die SOMETIMES I get near 0 runout yet the next case I will get up to .003 R.O.

Then I started checking R.O. on all the fired cases before sizing them and found less than .001.

I tried sizing cases in 2 or 3 steps by rotating the die 1/3 way around until the case was fully sized. That didnt help.

My dies are clean.

Any idea why the inconsistency in R.O.? I could understand if ALL the resized cases were the same amount (or close) of R.O. but why do some cases have near 0 and the next case have .003ish?

Im starting to think its the press. Maybe the floating neck bushing is "floating" to much and is actually getting "cocked"?

Thoughts?

ptf18

 

[DOGCAPPER]

Some testing has been done on various sizing dies and finding some straighten runout while others do not and others cause more problems. Names escape me. Before buying other gear try sizing the case then rotating the case 180 and sizing again. Works some time.

 

[ireload2]

Redding bushings don't have much lead in chamfer. I would use a steel bushing and polish a little bit of lead in on it.
Using a 10 to 1 angle will open the bushing about .003 per side (.006 on the diameter) if your chamfer is .030 long.
This will prevent a sharper corner on the bushing from making the neck creep off center when it is sized. Be sure to put a uniform chamfer on the case neck too.
I have a lot of bushings made by Neil Jones and they have a very generous lead in radius on the edge that contacts the case mouth when sizing. Wilson bushings also have a bigger radius than the near non existent chamfer on Redding bushings. I would avoid the Redding titanium nitride bushings since they would be more difficult to modify the lead in edge.

 

[jepp2]

My experience is similar to yours. Neck runout with a Lee Collet die or FL sizing dies I had honed the neck on - less than 0.001" TIR. Neck runout on Redding S Bushing dies with Titanium coated bushings - about 0.003" TIR and can range from 0.002" - 0.005" in any given test lot.

Folks tried to help. Said my setup was wrong and I wasn't floating the bushing, my die was bad, my technique bad, my press not aligned, etc. Someone did suggest I try the CRT bushing from Whidden. I did and it helped. I already knew everything else was Ok as I have been working on this issue for years.

Then I found this bulletin: http://bulletin.accurateshooter.com...ading-checking-the-geometry-of-neck-bushings/

Now I just accept for the lowest TIR (and I don't know what the magic number is) can't be achieved with a bushing die (Redding S). And it seems the Titanium coated bushings are worse, either for the entrance or the coating. I'm not a Redding basher, they are my preferred die.

 

[John Russell]

John,

What do you modify on them, How do you do it?, What is it correcting?

I change the throat angle to 15°. I don't use the Titanium Nitride bushings - I get the steel ones - they are more better. The TiN bushings suck.

 

[RonAKA]

I am using laupa 6MM BR Brass, Barnes 68 gr bullets and I am 80% sure the fired neck size is .270 OD (loaded rounds are measuring .268-.2685).

Off the runout topic, but a "Barnes" bullet? I have found in my Savage 6BR that the bullet is the most significant component in determining accuracy. If you haven't tried them yet, I would suggest a Berger 68 grain Target bullet, or a Bart's Ultra 68, or the Berger 69 grain High BC bullet in that order. They are all flat base bullets which are better for the 100 yard game. In the Savage barrel I find they do best at 3420 fps with a 0.010" jam. May give you more of a chance of shooting with the 6PPC guys than improving your runout by 0.001". Just my thoughts, and it sounds like you are getting close to solving your runout problem.

 

[dedogs]

I change the throat angle to 15°.

John, could you please explain how you go about doing this? Thanks, dedogs

 

[John Russell]

John, could you please explain how you go about doing this? Thanks, dedogs

I have a long tapered "pointy thing" that is pointed like a dart and fits in a 1/4" hand drill. I put double sticky tape on the pointed end, and then use #2000 grit silicone carbide paper on the double sticky tape.
I oil it and put it in the throat of the bushing - when the drill is running, I roll the drill and bushing around to soften the edges of the taper. I make sure that the entrance to the throat is a few (like 5) thousandths larger than any fired case mouth would be. This allows the case mouth/neck to enter without an abrupt change, which in my thoughts, is what causes necks to run off axis in off the shelf bushings.

 

[ptf18]

[QUOTE Maybe the floating neck bushing is "floating" to much and is actually getting "cocked"?

Thoughts?

ptf18[/QUOTE]

Found the source of the R.O. The neck bushing is/was too loose. I tightened the retaining "nut" to the point I just barely heard the bushing rattled.

Resized cases now have .001 or less runout

 

[pete1955]

[QUOTE Maybe the floating neck bushing is "floating" to much and is actually getting "cocked"?

Thoughts?

ptf18

Found the source of the R.O. The neck bushing is/was too loose. I tightened the retaining "nut" to the point I just barely heard the bushing rattled.

Resized cases now have .001 or less runout[/QUOTE]

So your telling me I have to wear my hearing aids when I adjust my bushing dies. Next it will be braille dies in the aging process, the "Golden Years" are so much fun.

 

[ptf18]

Found the source of the R.O. The neck bushing is/was too loose. I tightened the retaining "nut" to the point I just barely heard the bushing rattled.

Resized cases now have .001 or less runout

So your telling me I have to wear my hearing aids when I adjust my bushing dies. Next it will be braille dies in the aging process, the "Golden Years" are so much fun. [/QUOTE]


Ah to be 30 again..... or 40..... heck I'll take 50....

 

[mikecr]

Mikecr,
So if I understand this correctly, As I continue resizing my Fired Brass even with the .267 neck bushing which was giving me .001 run-out variance, the more times I fired and then resized, the run-out would progressively get worse? This makes me have to ask........ How do you correct it? Would the Redding Competition Neck Sizing Die help to correct this?

Most reloading issues are better solved with understanding than a credit card.

I don't know for sure why your runout is growing the relatively small amount it is(nothing extreme). Could be multiple reasons.
But we could at least begin at the root cause of runout; sizing of thickness variance.
-Thickness variance is inherent to brass manufacture and exists from webs all the way to case mouths. If you mark a case and measure a thicker portion at x-degrees around the case, this circumferential attribute will usually trend as you measure up & down the case. That is, separate from thickness generally decreasing from webs to mouths.
-Sizing is changing relaxed dimensions from one to another, and there is both yielding and spring back in this action. So supporting or even squeezing brass is not sizing, until done so to cause yielding, and this changes spring back.
-Given same ductility, thin brass springs back a bit less than thick brass.
-Ductility changes with each yielding of brass, and it's changing differently with sizing of thin brass -vs- thick (different yielding).
-Spring back variance, from thickness variance, can and will grow by amount of sizing. If more energy is repeatedly added(more sizing), runout will grow greater and faster. Is that what you're doing?

A benefit of neck turning is that you remove thickness variance in necks, which allows for partial length sizing of necks without causing runout -from sizing of thickness variance in necks otherwise (that much of it anyway).
This can still be screwed up by any other sizing(esp FL).. It can also be screwed up by equipment problems, but I've yet to see my bushings contributing(not really). There are a few tricks to reduce runout contributors.
If you want to mitigate most runout, you can cull out cases with thickness variance right from the git go. You can pre-seat necks using expander mandrels. You can adopt a plan that includes minimal sizing. You can smartly measure runout with each stage & cycle of sizing, fixing any method/equipment issues.

Does runout matter? I think it's a local matter, and not so easy to answer otherwise. The cartridge & chamber would have to be considered into it. It could be no more isolated in testing than ballistic coefficient from field drops (filtering through noise).
Opinions:
I doubt it matters in sloppy chambers, and think it would in low clearance chambers. But on the flip side, sloppy chambers lead to greater sizing leading to higher runout, and opposite of tighter chambers. A wash there. I think fast powder cartridges remove runout before it matters. I believe the notions of ammo centering with chambering is hogwash, and that the affects of runout(where seen) has nothing to do with where bullets are pointed w/resp to bore centerline. Here, I believe it's a matter of chambered tension points, varying barrel vibrations as an abstract.

 

[Cool Tool]

Most reloading issues are better solved with understanding than a credit card.

I don't know for sure why your runout is growing the relatively small amount it is(nothing extreme). Could be multiple reasons.
But we could at least begin at the root cause of runout; sizing of thickness variance.
-Thickness variance is inherent to brass manufacture and exists from webs all the way to case mouths. If you mark a case and measure a thicker portion at x-degrees around the case, this circumferential attribute will usually trend as you measure up & down the case. That is, separate from thickness generally decreasing from webs to mouths.
-Sizing is changing relaxed dimensions from one to another, and there is both yielding and spring back in this action. So supporting or even squeezing brass is not sizing, until done so to cause yielding, and this changes spring back.
-Given same ductility, thin brass springs back a bit less than thick brass.
-Ductility changes with each yielding of brass, and it's changing differently with sizing of thin brass -vs- thick (different yielding).
-Spring back variance, from thickness variance, can and will grow by amount of sizing. If more energy is repeatedly added(more sizing), runout will grow greater and faster. Is that what you're doing?

A benefit of neck turning is that you remove thickness variance in necks, which allows for partial length sizing of necks without causing runout -from sizing of thickness variance in necks otherwise (that much of it anyway).
This can still be screwed up by any other sizing(esp FL).. It can also be screwed up by equipment problems, but I've yet to see my bushings contributing(not really). There are a few tricks to reduce runout contributors.
If you want to mitigate most runout, you can cull out cases with thickness variance right from the git go. You can pre-seat necks using expander mandrels. You can adopt a plan that includes minimal sizing. You can smartly measure runout with each stage & cycle of sizing, fixing any method/equipment issues.

Does runout matter? I think it's a local matter, and not so easy to answer otherwise. The cartridge & chamber would have to be considered into it. It could be no more isolated in testing than ballistic coefficient from field drops (filtering through noise).
Opinions:
I doubt it matters in sloppy chambers, and think it would in low clearance chambers. But on the flip side, sloppy chambers lead to greater sizing leading to higher runout, and opposite of tighter chambers. A wash there. I think fast powder cartridges remove runout before it matters. I believe the notions of ammo centering with chambering is hogwash, and that the affects of runout(where seen) has nothing to do with where bullets are pointed w/resp to bore centerline. Here, I believe it's a matter of chambered tension points, varying barrel vibrations as an abstract.

Mike from North Carolina that is a first base hit good job.

 

[dmoran]

Mike from Colorado that is a first base hit good job.

George -
mikecr is from NC and is an engineer.
mike from CO is Mike Nagengast from Aurora, CO
Two different people.
Donovan

 

[pete1955]

The late Jim Hull of the Sierra ballistic test lab and competitive shooter full length resized all his ammunition. And Mr. Hull had a very humorous saying about full length resizing.......

"The cartridge should fit the chamber like a rat turd in a violin case"

The full length resized case is supported in the rear by the bolt face and in the front by the bullet in the throat. A resized case is normally .003 to .005 smaller in diameter than its fired size and the body and neck of the case never touches the chamber walls. Meaning the case has wiggle room to allow the bullet to be self aligning with the bore.

So if you full length resize the case, neck runout can be more forgiving.The Hornady concentricity gauge holds the case the same way as described above. And the Sinclair concentricity gauge rotates the case on the body and if the case is egg shapped the Sinclair gauge will read twice as much bullet runout.

 

[dmoran]

Looking like we have "bigedp51" back in the form of "pete1955"

 

[pete1955]

Looking like we have "bigedp51" back in the form of "pete1955"

When I get up in the morning and look in the mirror to shave I see "me" and not a imaginary screen name.

And a big problem in forums is the person looking at his computer screen thinks what he is looking at belongs to him.

But the biggest problem in forums are the midgets sitting at their computers pretending to be giants.

 

[Cool Tool]

George -
mikecr is from NC and is an engineer.
mike from CO is Mike Nagengast from Aurora, CO
Two different people.
Donovan

My bad he is the only one I put a name to.

 

[dmoran]

When I get up in the morning.....

Your just a huckleberry above a persimmon in your "pete1955" first week here.... wow