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Concentricity gage?

 
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  #8  
Old 03-08-2008, 04:56 PM
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It could be your brass, and specifically the neck thickness and uniformity. I get a lot better results when not turning necks with quality brass like Lapua etc.

It could be your seating die. I prefer Redding comp seaters.

It could be your sizing die expander ball causing friction and pulling your necks uneven. A lot of people either don't use the ball or use collett dies. On my dies with balls, I use a floating carbide ball and it works great.

It could be out of square case mouths or uneven internal bevel/chamfer on the case mouth.

I know some people are anal about making sure the inside of the case necks are clean before seating. I run mine over a brush chucked up in a drill press just to be sure. It may not make a difference but if it makes you feel better then do it.

There's a lot of things to check but you may reach a point of diminishing returns if you are getting really picky and shooting a factory gun. But like I said, if it makes you feel better then do it. It's only time involved.;)
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  #9  
Old 03-08-2008, 05:16 PM
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Thanks for the info!

Quote:
Originally Posted by ss7mm View Post
It could be your brass, and specifically the neck thickness and uniformity. I get a lot better results when not turning necks with quality brass like Lapua etc.

It could be your seating die. I prefer Redding comp seaters.

It could be your sizing die expander ball causing friction and pulling your necks uneven. A lot of people either don't use the ball or use collett dies. On my dies with balls, I use a floating carbide ball and it works great.

It could be out of square case mouths or uneven internal bevel/chamfer on the case mouth.

I know some people are anal about making sure the inside of the case necks are clean before seating. I run mine over a brush chucked up in a drill press just to be sure. It may not make a difference but if it makes you feel better then do it.

There's a lot of things to check but you may reach a point of diminishing returns if you are getting really picky and shooting a factory gun. But like I said, if it makes you feel better then do it. It's only time involved.;)
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  #10  
Old 03-08-2008, 05:19 PM
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If you have a loaded round that has unacceptable runout,how do you fix it?Do you just push the high end down against something then recheck it?
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  #11  
Old 03-08-2008, 05:29 PM
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That hardly ever happens anymore but when and if I had one that wasn't what I wanted for long range, I'd set it aside and use it as a fouler or sighter or use it for playing.

I'd note what was out of specs, neck, bullet etc., and check and make sure I didn't have a problem with any equipment or components. If the neck was out I'd mark the case and track it through the next batch of processes and see how it turned out.;)

There are ways to "straighten" a loaded round that has a bullet seated out of line but I never use them. If you impose a force on something you are likely to get an opposite, and usually unwanted, action somewhere else.

I don't even want my loaded rounds to get bumped or expecially, the tips to get hit, bumped etc. I'd never just push on the tip of the bullet and try to straighten it. You couldn't control it and you'd only make it worse and more than likely even add more problems than you originally had.
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  #12  
Old 03-08-2008, 07:05 PM
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Quote:
Most of my long range rounds run .0015" or less runout.
I agree with that and I use the same RCBS runout gauge and I also shoot the same cartridge.

The best use of the runout gauge is to teach you where you are making mistakes in your loading process.

Finally, if you have a rifle whose chamber is out of alignment, then there is no hope of runout helping you. I have a factory Rem 700 in 17 Rem which has an out of alignment chamber and there is simply nothing you can do except give the rifle decent ammo and keep the barrel clean. No runout gauge in the world will help that factory barrel.

So if you are shooting a factory chamber that gives you high runouts on the fired cases before resizing then there is a limit to what you can coax out of the rifle as far as accuracy.

To answer the question as to accuracy of low runouts, to be honest, I personally am not good enough with a rifle to see it, but I do it anyway. There comes a point in distance that all of the little stuff starts adding up.
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  #13  
Old 03-08-2008, 08:30 PM
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'So if you've got alot of runout, what sort of stuff might one try to decrease runout?'

Trim your cases to the same length, load them with a full charge and shoot them. That will insure that your spent cases reflect your chamber. Then, for concentrict loading:

First, check your fired case necks for runout; they should be pretty straight. If not, you are whipped by a bad chamber before you start.

Second, size the case/necks and check again. If you have much run out in the sized cases it will insure that the bullets cannot be seated straight until you get it corrected. A conventonal button type expander is perhaps the most frequent producer of bent necks, lubing inside the necks helps.

I like Lee collet neck dies made without a conventional expander for best concentricity. I use Lyman "M" expander dies when I full length size; it expands by pushing in, not dragging out, of the necks and that makes for somewhat better necks.

Third, use a really good seater. If you get good concentricity from a conventional seating die, that's great but it's uncommon. If you get much bullet runout use a seater die from Forster or Redding which have a sliding sleeve which envelops the full case (not just the neck as the Hornady and a few other so-called "competion" dies do) for true straight-line seating.

Forth, if you crimp at all, use a Lee Factory Crimper, not the crimping ring built into most seating dies. The Lee dies are not overly length critical and won't tend to drive the neck down into the shoulder like the others.

Other that these few suggestions, I have no idea.
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  #14  
Old 03-09-2008, 04:54 AM
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If you use Reddings 'straight line' bullet seater,you won't need a concentricity gauge.
I have one,but rarely use it anymore,since I went with the Redding dies.
I only use it on my 300 Win Mag,270 Weatherby Mag and my 22-250 Rem/22-250 AI for setting up my dies,once they're set for that brass I don't need to alter them,and bullet run out stays constant @ .0005" in all cases.
I have found that unless a rifle is capable of less than 1/4 MOA,it is a waste of time fiddling with run out,because you can't tighten groups with changing run out alone.You need to tune the rifle first before worrying about bullet run out.
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