Concentricity

[joelkdouglas]

Gents

I've heard measuring concentricity isn't important for a hunting rifle. Can someone explain to me why that is?

v/r
Joel

 

[rick smith]

For short range, 100yds or less it probably won't have much effect unless the rounds are past 5 or more. But will have more effect the farther out you shoot. Strive for zero but 3 or less won't hurt your shooting.Rick.

 

[Mountain Goat]

Gents

I've heard measuring concentricity isn't important for a hunting rifle. Can someone explain to me why that is?


Joel

My take is this: the small difference in runout between "target grade" and "hunting grade" handloads will not make the difference between a kill shot or not at common reasonable hunting distances. Two guns with consistent points of impact, one shooting 1" groups, the other shooting 1.25" groups are equally effective in hunting situations.

Now, if you want to make more precise handloads, then by all means gear up for better concentricity. For many, it's all about additional confidence instilled by knowing your loads have very little runout.

If you are shooting small animals like squirrels and such at long distances, then runout is a factor in a dedicated varminter. Target applications would also apply the same needs for precision handloads.

For me, I'm not good enough from the bench on a consitent basis to know if runout is even a factor or not in my group results. And since I've never had much problem with getting rifles to shoot around an inch or better at 100yds with my current handloading methods, so measuring concentricity just seems to be more of an obstacle and hinderance then beneficial.

I'm sure others will have different opinions and results.

 

[ElmerThud]

If you're reloading for hunting rather than target shooting, my guess would be you'd be prepping your brass to a reasonable standard of uniformity. Whether full length or neck sizing, apart from ensuring cases are of the same length & in good condition, the only other thing you might do is de-burr the flash hole.
It's all about consistency. Provided the brass is prepared correctly & the load works in your firearm, for hunting, there's little or no percentage in doing more.
Cheers, ET

 

[velvetant]

I use a Concentricity Gage to make sure I don't induce run-out when I full length size my brass.
It really surprised me how a little change in setting the die can have a drastic effect in run-out.
I found the biggest problems are caused by the expander ball.

 

[atmoshpere]

I found the biggest problems are caused by the expander ball

Any tips you'd like to share on setting up the die to minimize expander ball induced runout would be greatly appreciated!

I tried leaving the die and decapping rod loose at the height I wanted in the press, then I raised a case into the die until it just engaged the outer neck sizing portion. You could see the die move a little to center on the case body. At this point I tightened the die body lock ring. Next I continued the stroke until the arm cammed (full length sizing new brass). Then I pulled the case back down until the case neck engaged the still loosely held decapping rod which held the expander ball. Again, you could see the top end of the decapping rod move slightly as the expander ball centered in the case neck. Now I tightened the decapping rod lock nut, and pulled the case the rest of the way through the motion.

Is this anything like how you set your die up to reduce runnout? I haven't measured anything yet, so I don't actually know if I accomplished what I hoped to.

Thanks,

atm

 

[rick smith]

Use a dry lube inside the case neck. I now use a Redding body die, type "S" neck bushing die without an expander ball and a Forster or Redding competition seater. Very little or no runout, also use a Forster Co-Ax press.Rick.

 

[Oldtrader3]

I have changed over to Forster Benchrest neck sizing buttons stems for most of my calibers and in fact, Forster Benchrest dies for several rifles (the more accurate ones). I will not produce loads that are .004 or more TIR, as indicated by my RCBS Univeral Gauge block. I hand prime, weigh each load, weigh each bullet and check runout. I also Dremel (cratex) to inside chamfer each case on the first loading.

Since I started doing these things, I have quit worrying about the rest and get MOA loads or better. This is plenty good enough for my uses and I quit worrying.

 

[velvetant]

I found the biggest problems are caused by the expander ball

Any tips you'd like to share on setting up the die to minimize expander ball induced runout would be greatly appreciated!

I tried leaving the die and decapping rod loose at the height I wanted in the press, then I raised a case into the die until it just engaged the outer neck sizing portion. You could see the die move a little to center on the case body. At this point I tightened the die body lock ring. Next I continued the stroke until the arm cammed (full length sizing new brass). Then I pulled the case back down until the case neck engaged the still loosely held decapping rod which held the expander ball. Again, you could see the top end of the decapping rod move slightly as the expander ball centered in the case neck. Now I tightened the decapping rod lock nut, and pulled the case the rest of the way through the motion.

Is this anything like how you set your die up to reduce runnout? I haven't measured anything yet, so I don't actually know if I accomplished what I hoped to.

Thanks,

atm

Without a Concentricity Gage all you are doing is guessing.
I've done exactly what you described and had good accuracy but after I got the gage I seen .005-007 run out on a couple dies when checking. Other dies showed only .001-.002 run out
I've also tried leaving the nut loose and letting the expander ball float, was not much better
If you don't plan on getting a gage Ricks method works very good, although bushing dies work best with neck turned brass.
Polishing the expander ball or use a carbide ball works well, make sure to use some sort of neck lube.
Dry lube like Rick suggest is great stuff, I personally use Imperial sizing lube applied with a q-tip.
I shot for 20 years without using a Concentricity Gage and got some great groups, It's just another tool to help keep everything as consistent as possible.

 

[atmoshpere]

Thanks all.

atm

 

[bullet]

I use a Concentricity Gage to make sure I don't induce run-out when I full length size my brass.
It really surprised me how a little change in setting the die can have a drastic effect in run-out.
I found the biggest problems are caused by the expander ball.

Yes, setting the die can have drastic effects on run-out. If you are not as anal as some of us when it comes to reloading a simple trick will greatly improve your groups when reloading. Take dime and lay it between the die and the shell holder and set that as you distance between the two when you are resizing fired brass. Also, get a flash hole tool and make sure you do each peace of brass, trim to same length, clean primer pocket and square it "WAIT I AM GETTING ANAL AGAIN". :mrgreen: :roll: Try the dime trick, it might save you a lot of time and headaches and you won't end up as anal as some of us. But what ever you do remember be consistent. :mrgreen: :mrgreen: :mrgreen: Oh yeah, did I mention weighing brass and when you have a flyer mark that piece and get rid of it "HERE I GO AGAIN!!" OH YEAH ONE MORE THING, GET A CONCENTRICITY GAGE :shock: :shock: :mrgreen:

 

[Oldtrader3]

That is why I have switched several older die set FL sizer dies to Forster. Since they have a shorter stem length to the sizer button, there is less TIR.

 

[boomer68]

What concentricity gauge do you recommend? I am looking to pick one up, but not sure which one to go with.

 

[bullet]

What concentricity gauge do you recommend? I am looking to pick one up, but not sure which one to go with.

Here are two good tools for case necks
http://www.google.com/products/catalog? ... CEMQ8wIwAQ

http://www.sinclairintl.com/.aspx/pid=3 ... rning_Tool

 

[Oldtrader3]

I use the RCBS Universal Gauge with a dial indicator. They sell for about $100. and are useful for other gauging tasks as well.