concentricity

[murf]

just finished loading a batch of 357 magnum rounds with 140 grain xtp bullets. just for fun, i decided to check bullet runout on my concentricity gauge.

out of a sample of ten:

three had .003"
one had .002"
one had .001" and
five had .000" runout.

i am not going to worry about runout with xtp bullets anymore.

i'll check the 180 grain lfngc bullets later, but i expect similar results.

will let you know.

thought this might be important to some of you.

murf

update:

the 180s came out better.

three had .002"
four had .001"
three had .000" runout.

won't worry about these either!

 

[10 Spot Terminator]

Are you using a progressive press or a single stage ? If using a progressive this can be expected and .003 isnt all that bad unless you are a benchrest competition shooter or something . Most of the runout comes from how squarely the bullet is in conjunction with the brass when the bullet is started into the case when seating . With a single stage press you can reduce the runout by by just raising the ram until the bullet just touches the seating die then back the ram off just enough to allow you to rotate the case in the shell holder 180 degrees then raise the ram again to touch the bullet , rotate again and seat the bullet . This allows the bullet to true up against the top of the seating die somewhat better than just setting them in there and driving them home . By the way the same thing applies to seating rifle bullets where runout is more critical to performance than handguns .

10 Spot

 

[murf]

single stage.

i don't agree with your advise on bullet seating, or your last statement about performance.

the correct seating stem is most important.

a crooked bullet is detrimental to performance whether in a rifle or pistol.

but, i thank you for your advise.

murf

 

[788Ham]

Seating the bullet, between turning the case 180 degrees, before final seating? I've done this since starting reloading 30 years ago, make perfect sense to me. I've not been asked to do any shooting at those fancy shoots in Ohio, but its worked for me. Spot on 10 Spot !

 

[gamestalker]

I started rotating 180 right from the get go more than 30 yrs. ago as well. No one suggested it, it just made sense to me.

GS

 

[aklaunch]

The Rotate Trick

I was taught to rotate the brass on both bullets and while priming.

Only a guy with the gauge and good documentation will know for sure though.

 

[murf]

yes, i rotated the bullets 180 before fully seating. i also rotated the case 120 when hand priming. and rotated the the case 120 when crimping (always in a separate step).

my point is that the correct seating stem is more important than rotating the bullet 180. for instance, a flat stem is going to push a pointed bullet sideways no matter how the bullet is started, imop.

again, thanks for the feedback.

murf

 

[10 Spot Terminator]

Murf ,

You were quite right about the seating stem and is why I use RCBS dies as some others only come with a universal seating stem . As for the runout in how it relates between handgun and rifle round performance I should have stated " As with all things there can be excess". As you were talking about a maximum runout of .005 in my expierience I have seen very few pistoleros who shoot well enough to discern target grouping between ammo with .003 vs. .005 runout on the bullets shooting at 20 yards or less . I have however ran into numerous rifle shooters who would know something was not right with the grouping of the .005 runout ammo at ranges of 100 yards and definitely at farther ranges . My personal runout limit for hunting ammo for rifle is .003 . My limit for target loads are .001 . You get out of your handloads the performance based on the effort you put into them . I tend to have a touch of OCD when it comes to loading and perform those extra steps that many shooting editors have concluded have little if any effect on accuracy . They make me feel better . Of note on my target rifle loads I use Redding competition seating dies to help address the best bullet seating that I can to reduce runout from the start . I also have the C&H cocentricity tool which later was bought out and remarketed by Hornady . I am one of those who am more proficient with a rifle than a handgun but still strive to be able to say if I pull off a not so perfect shot that it wasnt the fault of my ammo .

10 Spot

 

[brutus51]

Just out of curiosity was the bras used all the same brand?

 

[Rangemaster]

Before you seat any bullet check the concentricity of the brass first, then proceed to seat the bullet. Then check again, this will tell you if there is a problem with the seating die.

 

[Offfhand]

Excuse me, but I'm a bit curious, when the experts measure concentricity, or bullet runout, or whatever it's called, with their fancy measuring gadgets, where is the measurement taken? Like at the neck or at bullet tip, or somewhere in between? Seems like there could be a difference depending on were the indicator is located. Or is there?

 

[savanahsdad]

Excuse me, but I'm a bit curious, when the experts measure concentricity, or bullet runout, or whatever it's called, with their fancy measuring gadgets, where is the measurement taken? Like at the neck or at bullet tip, or somewhere in between? Seems like there could be a difference depending on were the indicator is located. Or is there?

about half way between the case mouth and the ogive , or 1/8" in front of the case mouth

 

[Swampman]

I feel that I have been remiss in my reloading practices and quality control.

It has honestly never even occurred to me to check runout on straight wall revolver cartridges.

I guess life's too short and I'm too bad a handgun shot!

 

[Offfhand]

"about half way between the case mouth and the ogive , or 1/8" in front of the case mouth"

Thanks for reply, but would it not be more logical and informative to measure runout of a rifle cartridge near the tip of the bullet? Are there opinions about this?

 

[murf]

been busy and my smart phone is too small for my aging eyes.

anyway, 10 spot, my rcbs casemaster also measures case wall thickness quite accurately. what i have found is the variation in case wall thickness around the circumference of the case is the culprit regarding cartridge runout (at least in pistols). i have a 45 colt case sitting on my reloading bench that varies from .009" on one side to .013" on the other. the case won't even fit all the way into the sizing die without getting stuck.

brutus51,

all cases are winchester from the same lot (bag of 100).

offhand,

one v-block is about a quarter inch in front of the case rim, the other block is at the very front of the case (mouth).

 

[murf]

offhand,

i usually measure rifle cartridges about half way along the ogive. measuring at the tip is not practical because the tip doesn't contact the rifling.


swampman,

took care of that for you. no worries!

rangemaster,

have already checked the rifle brass and it almost always comes out .000", or .001". that changes when you seat the bullet. the case runout can get bigger after seating the bullet.

 

[murf]

no rhyme or reason. the next time that same brass gets reloaded, the runout can increase, decrease, or stay the same. don't have a clue why.

thanks for the input.

murf