Concentricity Minimum

[RustyRick]

Just got a new toy. Shocked at the out of round my H dies seat my bullets.

Hoping to eliminate some flyers.

How small a wobble is being acceptable by you long range guys.

 

[dieseldoc]

Rick:
less than .002 better yet get it down lower the better.

Also watch your ES and Ed

 

[Unofficial Gun Addict (UGA)]

Heya Rick...

I got a Hornady concentricity gage and found that by using it, there was no appreciable difference in those bullets that were concentric, vs those that I used the tool to make concentric. After several tests all confirming the above statement... I took it back for a refund at sportsmans warehouse, which I almost never do.

What I found was that by switching my seating dies to forster ultras, and my neck dies to lee collet, accuracy improved dramatically across the board, so much so that I am shooting out to 600 yards and consistently getting 5 round groups in a 2.5x3.5" rectangle.

Now I'm pretty sure that concentricity matters, but I believe that your dies and setup need to be responsible for it, as opposed to something like the Hornady tool which forces the round after it's been created, into concentricity. I was pretty sold on the idea until I put it into action. To say the results were disappointing would be an understatement.

Now I don't worry about concentricity so much, as to what kind of groups my ammo gives me at the ranges I'm shooting. That's all that really matters to me, and so I haven't bothered with concentricity since.

Good luck!

 

[RustyRick]

What's "your ES and Ed"?

 

[Bill Johnson]

Dieseldoc uses the same numbers most do, .002 or less. I can understand jboscobuys' disappointment. He got sold a bill of goods.

The Sinclair gage or something like it gives you a true reading. At that point, you can determine what the problem is. Sometimes it's as simple as how you set up your dies. For instance, locking down the decapping pin/neck expander per manufacturers instructions can force necks out of alignment! Leaving the locknut loose until you have a case inserted and the expander in the neck, then locking it down, leads to decreased run out on the finished cartridge.

You have to take the right readings then fix the tooling issue. This is my little home made rig:



I read case-to-neck, case-to-bullet and neck-to-bullet runout. This helps to run down the issues.

 

[Unofficial Gun Addict (UGA)]

What's "your ES and Ed"?

I don't worry about it so much... As at 600 yards... If my shots stay in a 2.5" high x 3.5" wide rectangle, then I'm well within moa and confident of my shots on big game out to 600. As it's a 308.., that's about where I consider my effective max range anyways.

When I get to shooting the 300wm out to a grand this next spring, if my groups are widening vertically, then I stop and consider ed & sd.

 

[RustyRick]

What is "ED" and what is "SD"?

 

[RustyRick]

I'm shooting a X-Bollt 243 with an 18 or 24 power scope. And I can load numerous loads and threaten the 1/2 MOA at 100 yards with 3 shot groups.

However at 5 shot groups and sometimes with 3 shot groups I'll get 2 touching and one an inch away or more.

So when I saw the concentricity toy it makes sense. I've seen some rounds at .005 so I think it makes perfect sense to straighten. I've see factory loads even worse.

I don't thing a quarterback throwing wobbly footballs in the NFL would get hired. At least not by Denver.

 

[Unofficial Gun Addict (UGA)]

I'm shooting a X-Bollt 243 with an 18 or 24 power scope. And I can load numerous loads and threaten the 1/2 MOA at 100 yards with 3 shot groups.

However at 5 shot groups and sometimes with 3 shot groups I'll get 2 touching and one an inch away or more.

So when I saw the concentricity toy it makes sense. I've seen some rounds at .005 so I think it makes perfect sense to straighten. I've see factory loads even worse.

I don't thing a quarterback throwing wobbly footballs in the NFL would get hired. At least not by Denver.

Yeah... I hear what you are saying and I do believe that concentricity matters... I just discovered that the Hornady concentricity gage, at least for me, didn't do what it was intended to do.

As for Ed & Sd, that was a typo... Should have been es & sd... Extreme spread and standard deviation. I do think both matter and especially as distance you're shooting increases. If the extreme spread of our reloaded ammo widens, so will vertical groups.... And sd is just a another way I'd indicating that bullets are consistent or inconsistent with respect to velocity. Sorry for the typo.

 

[barefooter56]

RustyRick,
Couple things. A concentricity gauge is really a diagnostic tool to help you find where and what is causing the run out issue. Basic rule of thumb we use is .000 to .005 run out usually will not affect accuracy. Always use a fired ( once is ok) case. Think of your rifles chamber as the last step in the forming process of that cartridge case. Pre-load the the dial indicator on the neck of the cartridge case you are checking at least .010 to .015 so the probe will not lose contact with the neck as you rotate the cartridge case. Re-zero the face of the indicator. With the first step you are checking the cartridge case about in the middle of the neck right out of the chamber. If the rifles chamber was reamed correctly the run-out should be right about zero. Step two, run the cartridge case through the neck or full-length die you are using and check on the neck at the same point of the neck as step one. Note the amount of run-out. Step three is to seat a bullet in the cartridge case. Here you want to place the probe of the dial indicator as close to the casemouth /bullet junction as you can get it without the probe contacting the neck. Note the run-out. Some times you will find that seating the bullet can actually decrease the run-out measurement from the neck or full-length sizing check! Following these steps you will find where the problem is and can concentrate on that point to fix the problem. Can save you a lot of money on dies ! I have fixed a problem with something as simple as backing the lock screw in the lock ring back away from the threads on the die body and letting the die "float" in the threads. Glen Zedikers book "Handloading for Competition" has many more easy hardware store fixes for die issues and is a good reference book to have in your reloading library. If you have the Hornady tool pay close attention to the instructions. They do list a run-out range where you can use the "bullet pusher" to straighten a round. Using the bullet pusher on rounds with more run-out can result in just loosening the bullet in the neck. I use the Sinclair tool because of the ease of rolling the case on the fixed ball bearings and the fact that you can check the cartridge case by itself and/or with a bullet seated.
The reason you don't check the bullet out farther is that the bearing surface of the bullet is what contacts the lands. The Hornady tool is really made to be used on a loaded round only. Factory or reloaded.
Take care,
Phil Hoham
Berger Bullet Tech

 

[RustyRick]

Thank you Phil for your lengthy explanation. I copied it into my word doc for future reference.

I'll also tell you that I have 2 boxes of Berger bullets in my drawer ready to try out in my new 7mmRM. I'm really anxious to see where I can get with these.

Thanks again!!!

 

[barefooter56]

RustyRick,
You are welcome sir. If you need any more help please feel free to contact us here or at [email protected].
Take care and have a Merry Christmas!
Phil Hoham
Berger Bullet Tech