bullet and case concentricity

[Killswitch Engage]

not sure how many thousands of times this has been discussed but i couldn't find it in the piece of shit search feature. how many of you guys check concentricity of your case and the runout of your loaded round? what effects and at what run out do you see the effects or does it really matter.

 

[The Mechanic]

Re: bullet and case concentricity

Here is a great article on it.
http://www.6mmbr.com/jgcaseprep.html

 

[Fuzzball]

Re: bullet and case concentricity

Most don't. It matters. Better concentricity = better accuracy, but how much better depends on a lot of other variables, including shooter ability.

 

[Lumpy Grits]

Re: bullet and case concentricity

Try to keep all of "match" loads at a T.I.R. of .002" or less.
Anything with a T.I.R. over .005" will show at distance.
(T.I.R. = total indicator reading)
Respectfully,
LG

 

[Killswitch Engage]

Re: bullet and case concentricity

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lumpy grits</div><div class="ubbcode-body">Try to keep all of "match" loads at a T.I.R. of .002" or less.
Anything with a T.I.R. over .005" will show at distance.
(T.I.R. = total indicator reading)
Respectfully,
LG </div></div>

thanks...i was wondering what the majic number was for run out with no noticable effect on accuracy. i do shoot for as close to.001 as possible but it is damn tough to do.

 

[Victor N TN]

Re: bullet and case concentricity

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: lumpy grits</div><div class="ubbcode-body">Try to keep all of "match" loads at a T.I.R. of .002" or less.
Anything with a T.I.R. over .005" will show at distance.
(T.I.R. = total indicator reading)
Respectfully,
LG </div></div>

+1...

Banging steel at 100 yards...? Don't mess with it. Going for accurate loads... <span style="text-decoration: underline"><</span>.002" TIR

 

[Killswitch Engage]

Re: bullet and case concentricity

i have come to the conclusion that the run out i do get is in my seating die/process. it is generally around .004. what seating die do any of you use to get more precise. i hand staighten my loads after the fact down to .001-.002

 

[Winchester 69]

Re: bullet and case concentricity

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: dgunn</div><div class="ubbcode-body">i have come to the conclusion that the run out i do get is in my seating die/process.</div></div>
Forster and Redding Competition seaters are designed to guide the bullet during seating. If you rotate the case and seat in steps you may have better results than what you're getting.

 

[kombayotch]

Re: bullet and case concentricity

I check each an every round after seating the bullet, while waiting for the Chargemaster to finish. Bullet runout <= 0.0015 for long range or anything precision. Most are 0.001 or less...

A fully supported seating die like the Redding or Forster match/benchrest types are the best (regular presses, not counting arbor setups). It isn't necessarily the seating die though. If your necks are uniform and concentric, there are other culprits for higher runout. It can show up even when using the supported dies. Other things that can help get it down:

*Clean the insides of the necks. Dirty necks can affect bullet runouts even if your necks are straight. They can affect neck runout when sizing in a collet die too. If I dry tumble the brass (as opposed to US or ceramic), I clean the necks with a bore brush with some 0000 steel wool around it or with a bore swab and a bit of Flitz. Not looking for a shine, just don't want to see any grit.

*Make sure that you're trimming your brass square and that the chamfer is also square. Many people obsess over trimming and then ruin their "perfect" trim job with a sloppy hand chambering. The edge of that chamfer is the first and last point to contact your bullet, it needs to be square.

*Anneal your brass. Stresses in the brass caused by work hardening are not necessarily uniform. They may create more tension on one side of the case than the other. When brass starts to get hard, runouts creep up.

Also, check that your press isn't the problem. A buddy of mine could never reduce of his runouts. He eventually realized that his new Rockchucker had extremely poor tolerances and that the ram was "kicking out". Here are some vids of a display model at Cabelas that did the same thing:
http://s23.photobucket.com/albums/b356/k...nt=P1040808.flv
http://s23.photobucket.com/albums/b356/k...nt=P1040807.flv
http://s23.photobucket.com/albums/b356/k...nt=P1040805.flv
There is an option to watch them in full size.

 

[Lumpy Grits]

Re: bullet and case concentricity

I use Redding dies in a Dillon 550
LG