Eccentric Cartridge Adjustment

[ggibson511960]

There's a lot of ink in the gun press these days about concentricity of loaded ammunition, and which tool is best for measurement. What I have not seen yet is a reasonable fix for cartridges found too far out of concentricity except to cull them out for practice. Has anybody tried "bending" crooked ammo? Could a purposely mis-aligned sizing die work without too much tedium? Seems the next logical step after going to all the trouble of measuring runout.

[H Richard]

I believe the result is culling for shooting requirements that are not as critical. What these articles seldom mention is that it usually only pays off when you are a bench rest shooter looking for that .0001" group at 300 yards. The majority of rounds that may "fail" a concentric test will still shoot better than most factory rounds.

[Twoboxer]

Just an opinion . . .

The Hornady tool allows adjusting for one concentricity issue that appears "easy" to fix. Whether nudging the bullet actually fixes the issue or whether it exchanges it for another is pretty hard to prove one way or the other.

That same tool can be used to detect other concentricity issues, and my own approach is to simply discard the outliers. But IME there are very few when you start with quality, new cases. OTOH, I personally wouldn't waste my time testing concentricity if starting with range or unknown "once-fired" brass.

While I like to load precision ammo precisely, neck turning and mandrel neck sizing are just too exotic and have proven by omission to be unnecessary to meet my goals. I just use Lapua brass and quality bullets for precision loads, and that seems to work for me.

YMMV.

[Ivan the Butcher]

I have found the biggest fail comes from loading cases in a hurry and not getting the base of the bullet started into the case square and perpendicular. Decades ago Forrester invented the Co-ax press and co-ax dies to combat this problem. Redding uses a similar (or same) system in their Competition seating dies, and a micrometer (invented by Lyman or Wilson) in the sizing and seating dies to help combat the issues. If your chamber is a standard SAMMI spec chamber, it is loose enough for perfect ammo to lay on the bottom of the chamber and undo all the effort!

I have a Cooper 21 marked 223 Remington, it is actually a 5.56 NATO chamber in length and very tight! By only sizing half the length of the neck of cases already fired in that rifle and seating bullets to just touch the lands, I get groups that are in the 2/10's inch range at 200 meters (using good scope and a rest). Using a completely sized neck and SAMMI C.O.A.L., the same load and equipment do about 3/4" @ 200M. Both loadings will kill ground hogs as far a you can stand to use 223 (about 500 yards). Neither will get you in the money at a Bench Rest Match!

Ivan

[rockquarry]

Loaded round concentricity has become a fad topic, sort of like annealing case necks. I'm not implying that either procedure is nonessential. Both have a degree of usefulness, but often that degree is small.

Concentricity is easy to measure, at least with a Sinclair tool, the only one I'm familiar with. However, I seldom have a need to use mine. If a rifle is shooting beneath it's potential, concentricity is one thing I'll check, but it's pretty far down on the troubleshooting list. I've used the Sinclair tool less than ten years. In that time, I've found extremely few loaded cartridges that were more than just very slightly out of round and probably not enough to hurt anything.

I use regular Winchester, Remington, and Federal brass for about 95% of my handloading. I haven't found them to be the junk brass that some claim they are. I've used a Co-Ax press for the last thirty years or so for all rifle cartridges. Some say this contributes to concentric necks which seems to make sense, but I can't say for sure.

If you're satisfied with your level of accuracy, there's little point in worrying about or even checking for eccentric cases. There's even less point in buying a tool for the purpose.

[DWalt]

The two most important features in achieving the best ammunition grouping performance in a given gun are uniformity of case length and finding the optimum COAL for your specific gun, given that you have uniformity of bullet weight and propellant charge. Factors such as neck wall thickness uniformity, case weight uniformity, primer pocket/flash hole uniformity, concentricity (and a few other exotic considerations regarding bullet design) are more valuable to the bench rest shooter and ballistic experimenter than anyone else. Those guys are always looking for 0.0000" extreme spreads at 200 yards.

One factor which was formerly very important was the balance of the bullet, and many precision shooters used to spin bullets to see how true they were. But most of the "Name" makers now mass-produce highly uniform and well-balanced bullets, so that's not much of a consideration today.