IMO, the concentricity gage to buy is the NECO.  Be sure to get the Gem dial indicator.  If you don't get a NECO, get the Sinclair.  I actually dislike the Hornady gage.  I have one of each of these three.

I also have a Wilson trimmer and a Giraud.  The Wilson provides the most accurate (repeatable) trim length but the tiny variation from the Giraud has no affect on accuracy.

+1, I also have tried all three and don't touch the Hornady any more.

Love all the Wilson tools, but I still like the Giraud and the Forster stuff too. I also agree, the trim length doesn't have any strong affects on this topic. Where crimping comes up, I don't think there is anything wrong with the dispersion from a Giraud.

If your base to shoulder is the same from case to case the Giraud will trim them to the same length unless there is inconsistency in your method....in my experience with my Giraud it trims cases within a thou.

And to add, if you are taking about +/- a couple thou in length variance then that wont make any difference; I would bet .010" would show no difference.


I would want an indicating stand that would allow me to check the inside diameter and outside diameter of the neck, the OD of the shoulder and of course the projectile. I don't like the design of the ones that hold at the meplat of the bullet (cannot check IDs)unless you plan on straightening ammo. I shoot way too much to straighten every round.



I really like this one but it costs too much IMO considering I made mine for free and about a 45minutes time. I have their bullet pointing die and it is nice work.





BTW, if anyone were to buy the one in the video don't get the indicator. You can buy a Shars indicator from discount_machine on ebay for about $22 shipped. I use these everyday at work, there is no benefit to an expensive one. The one in my Forster die thread I bought in 1994 it still works perfect.

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I know that virtually everything and anything can affect accuracy, but I'm in the camp that bullet seating and powder weight management (repeated accuracy) has more impact on accuracy than does exact case length trimming and some other peripheral issues.

To those ends, I go with the Forster Micro Seater for bullet seating .223, and a decent powder scale, the AND FX-200i. I say "decent" about the powder scale because it costs half of an Entris 64-1s which is the almost perfect scale for the 1000 yard shooter (which I am not), but the AND scale is dead nuts as far as I need to be.

There are ways of doing it, I have not bothered. I would rather make it straight when I load it and leave the bad ones that slip through for foulers/warmup/larger tagets etc..If you only shoot 10-20 rounds at a time I suppose it would be worth while for that type of shooter. The reason I suggested an indicator that can check neck ID is so you can weed out the bad cases before even loading them. If the neck ID isn't true with the case OD it will be more likely that the projectile wont be concentric.


The case length will make a difference as a longer neck will have more of a hold on the projectile... theoretically. I trim my .308 cases to 2.038 quickload tells me if I trim to the "trim to" length of 2.005" I will decrease pressure by about 2.5%. Going from 2.015" to 2.005" will decrease pressure by about 0.5%. A variance between 2.008" and 2.012" (+/-.002") is range of 0.3% difference in pressure and 1fps. (these numbers are for the load I had up in QL different loads will be different so don't quote the number as fact).

In my testing, as I have grown my brass, I noticed no difference in pressure, velocity or groups size with minor differences in length. I ran some of my LC11 12x brass grown to 2.038" against some LC11 1x brass at 2.008" ;same load. If there was a chamber pressure or velocity difference it was lost in the standard deviation. The groups for the 1x were slightly worse but it was culled runout brass and was not fire formed to my gun. I was just testing pressure difference for when I start back on 1x brass again.

Point is +/- .010 might be a problem but +/-.003" I doubt would hurt.

Check these guys out.  21st century Reloading

My knowledge of the history of neck turning says it got started in benchrest shooting.  Benchresters wanted custom, tight necked chambers (smaller than SAAMI spec neck diameter).  They found the neck thickness variability meant an interference fit in these tight chambers, so they began turning necks to ensure the cartridges fit their chambers.

Also, if you are re-forming brass, you may end up with case necks that are too thick.  Neck turning is one way to reduce that wall thickness.

I have never seen any data saying trim length affects accuracy in any way.  I would suspect it does not but have no data.  Remember, upon firing the case is going to swell up like a balloon, get plastered against the chamber walls, and release the bullet.