Run out

[340PR]

Lots of good info above. I too had the Hornady tool, and experienced several issues with it. After spending an inordinate amount of time trying to attain consistency, I realized that I needed to find the source of the runout.
I bought the Sinclair tool, and started checking case necks after firing (baseline) and after sizing. After fixing all the issues with runout to that point, I went to checking the cartridge after seating. There can be "stack-up" in the process, and if you don't know where it is coming from, it is hard to correct. Today, I rarely check more than 5 cartridges/100 in a run, and find runout to be less than .002", and consistent to each other in that run. FYI: Forrester Co-ax, Whidden FL bushing and micrometer seating (with projectile specific seating cone).

 

[JohnT]

As Savage has noted I have found that sizing in 2 steps does have a very favourable effect on runout. I remove the sizing stem & FLS (easier to do with Redding than Hornady style dies ) then as a seperate step run the cases again with the stem in place to uniform the inside case neck diameters. I short stroke the press and lube the inside necks. It's still pretty quick. I have found that the runout with this method typically is less than 0.002. Doing the FLS in one step the runout is typically up to 0.005. Now in hunting rifles I'm not sure it makes any difference at all, just nice to know you've done the best you can with your equipment. You may see a difference on the bench and if so it would be a confidence booster and that's important!

 

[nksmfamjp]

My results are everything maintains sub MOA. I've never seen groups open up as a result of using the gauge. Truth be told however, I don't have any empirical data to back it up but I figure whatever I can do to keep things concentric is contributing to accuracy. It feels good, so I do it.

Now, with regard to dies - with RCBS I average .003-.004 runout and I correct them. With my Redding dies, I don't even bother to check anymore.

I'm just interested....how do you measure your runout?

 

[JohnT]

I'm just interested....how do you measure your runout?

You buy a concentricity tool. We reloaders love gadgets right! There are quite a few manufacturers such as RCBS and Hornady and some more custom suppliers and a wide range of prices too. Mine is the RCBS one - will do but I cant recall the supplier but there is one with a wheel to spin the cases thats nice but also pricey.

 

[DUSTY NOGGIN]

one of the causes of runout is the seating dies do not support the case body at the same time of seating .. too much neck tension results in pushing down on the case mouth on one side first .

lessening the initial seating pressure via graphite , mica or pre-expanding with mandrels or neck turing to lessen the neck wall thickness.. Or combining more that one of these

standardized FL sizing dies will oversize up to .008 too small on the down stroke and then pull the button through that on the upstroke (which in its self can bend the mouth axis off the case body axis ) seating into an already out of round case , doesnt give alot of chance to your end result

pulling your stem out of your full length sizer to measure how much it is sizing your necks down will give alot of insight on where any runout you have is coming from

 

[YZ-80]

I'm just interested....how do you measure your runout?

Oh, sorry. I just measure it on the gauge and correct it at the same time.

 

[nksmfamjp]

You buy a concentricity tool. We reloaders love gadgets right! There are quite a few manufacturers such as RCBS and Hornady and some more custom suppliers and a wide range of prices too. Mine is the RCBS one - will do but I cant recall the supplier but there is one with a wheel to spin the cases thats nice but also pricey.

I have the RCBS Casemaster, but I was wondering what points he spun it on and what point he measured at. By his answer, I'm guessing Hornady.

 

[YZ-80]

I have the RCBS Casemaster, but I was wondering what points he spun it on and what point he measured at. By his answer, I'm guessing Hornady.

With the Hornady gauge you put the round into the recesses of the cylindrical shafts and it self-centers on the case head with the tip of the bullet in a recess on the opposing shaft. The gauge has a plunger that rides along the ogive of the bullet a 16th of an inch or so ahead of the neck junction and you spin that bad-boy and watch for deflection on the gauge. You find the low point and then use the thumb screw to gently push the bullet back into true. It's easy to overcorrect if you got marginal neck tension and you end up chasing it all over the place. This only happens once in a while, however.

 

[RYEWSKY25284]

Where are you measuring a load round for OAL? What bullet is being used? If it's an open tip/hollow point bullet like a matchking, the tips (meplat) are not going to be consistent. If measuring base to tip of the loaded round it will throw you off.

That's a very important point....(no pun intended). Ogive length is most important measurement for length.