Has anyone experienced an increase in c.o.l. when using the FCD? I was reloading some .223 today and noticed after using the FCD that c.o.l. increased between .oo2" and .003".
* how close the bullet is to the start of the rifling when full seated in the chamber may effect accuracy
We often "tune" the load to get max accuracy by adjusting the COL to determine what the gun likes for max accuracy. A 0.002 to 0.003 inch difference in insignificant as long as the cartridges reliably fit the magazine and the bullet is not jamming into the rifling in the chamber.
The reason for this growth (I believe it is not normal) is that you probably are over crimping. Disassemble one and observe the removed bullet. It it is deeply marked from the FCD action you are over crimping. If you continue to over crimp like that, such that the bullet is distorted, then accuracy may be effected. Bullet are precision devices. Distort them and they may not fly perfectly, wobble in flight, and who knows where they will hit the target.
For the ones already loaded you can shoot them if the max COL is not exceeded but don't expect stellar accuracy.
*** As an aside, measuring the COL is not a precision measurement because of the way most bullet are manufactured. Any excess of material flow from the process used to make most rifle bullets is left in the nose of the bullet and can vary from bullet to bullet. What is important is the distance from the reference point on the Ogive of the bullet to the end of the cartridge at the rim. You need a cartridge gage or comparator adapter for your calipers sized to that ogive reference point diameter to get accurate measurements of variation in the cartridges finished length. The COL listed in the manuals is not expected to be measured to 0.002 to 0.003 inch accuracy whereas using the bullet comparator on calipers can be accurate to much less than that.
Thanks LD. When I set up the FCD I did so per the instructions for a "light" crimp (1/2 turn after it made contact with the shell holder). I'm going to back this out to perhaps a 1/4 turn and see how that works.
For .223 do I need to be concerned with too light of a crimp? Or, alternatively, is neck tension sufficient given the recoil of a .223? Also, the measurements I referenced in my post were made using a comparator.
Interesting. My 223 fcd (opened 4 quadrant collet style) didn't do that with any of the grain weight bullets I used. I used a 1/2 turn. If you measure the bullet diameter before loading, it is correct? Was it just a couple rounds?
I didn't measure the diameter of any bullets before seating. It was more than just a couple of rounds. I loaded 20 rounds and they all increased in c.o.l. I plan on backing down the adjustment on the FCD to a 1/4 turn when I do some reloading this weekend. I'll report my results.
I didn't measure the diameter of any bullets before seating. It was more than just a couple of rounds. I loaded 20 rounds and they all increased in c.o.l. I plan on backing down the adjustment on the FCD to a 1/4 turn when I do some reloading this weekend. I'll report my results.
As to the degree of crimp, it depends on the gun. If the ammo is for a semi-auto like an AR them you need the crimp. It the ammo rides in a magazine in a bolt gun then you need a little less crimp. If you single feed a bolt gun you can probably get by with no crimp if your brass and bullets end up with enough neck tension.
I think you need to tear one down and see how badly the bullet is dented from the FCD action. Use that to determine if you need to reduce the crimp.
But regardless, a variation in comparator reading of 2 to 3 thousandths is nothing to worry about if you don't have the bullet sitting on the rifling lands in the chamber. There are many other variables that much more impact the accuracy than this tiny variation in comparator COL. I just worry that you may be crushing the bullet so check that out first.
For my "AR" food I use 1/4 turn crimp on the FCD with never a problem.
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