Effect of Concentricity

[Allen Humphrey]

I've just got my first Redding S type bushing sizer to go along with my Forster Micrometer seater die. I made up a few of my favorite 200yd match loads with the new stuff. The new rounds generally were better with run out averaging about .003 with a max of .006. My old loads averaged about .004 with a max of .010.

Just for fun I grabbed some of the worst old loads...most being .006 to .009 and some of my best new loads and shot a 10 rd string of each on the same day from 200. Single fire from a sling. Used my RRA NM service rifle. I was surprised at the difference.

[Johnny P]

I use Wilson hand dies in an arbor press for .308 for my Mike Lau copy of the M40A1, and at 200 yards there is a difference in those and rounds loaded with conventional dies and reloading press.

[Hefights]

I always try to ensure mine are .005 and below. The guys at Sinclair Intl told me that they try to maintain less than .004 runout. For me doing that is what you found. It means using decent quality brass, and a competition sizing die, or a neck bushing sizing die, and a competition seating die that supports the bullet through the process. I also measure case neck runout prior to seating the bullets and measuring bullet runout.

If I get cases that are way out of tolerance like .01, I will toss them. For any between .005 and .01 I mark them and set them aside for fouling shots or plinking the gong. Some think its a little obsessive, but I can't stand wobbly bullets as a matter of principle. I recall getting cheap remanufactured ammo and seeing as much as .01 and stopped buying it.

[Matt Anthony]

If your bullets are not straight in the case, your accuracy is going to suffer. I stopped using conventional seating dies years ago and switched to the straight line seating dies Wilson manufactures. There is no question in my mind that the Wilson die is superior in all respects to any RCBS, REDDING or other standard dies. Also, I have the competition seating dies from Redding and RCBS and it was a waste of money to buy them when comparing the end product to the Wilson.
I bought the Hornady Concentricy Tool which has a dial indicator and a screw which will straighten an out of plane bullet in a case. You can straighten a bullet, no doubt, but there is another factor that they don't tell you. Once you move a bullet in a case after it's been seated, that bullet is now loose so to speak. You just cocked it! The idea is sound to straighten it, but that's not right either. A bullet needs to be inserted once and not disturbed in the case and it needs to be straight to begin with.
The other factor is the brass. You must have good brass to have great results. Lapua and Norma are probably the most consistant, and they are expensive. Remember, if you are hell bent on producing world class competition ammo, you must spend the money on good brass. Buy 100 rounds of Lapua, do the normal prepping and load them up being ever so careful on your powder charge. Shoot three shot groups letting the barrel cool at least 10 minutes between strings. Watch for any fliers, if you experience a flier, put that case aside to use as a barrel fowler. Do that with the entire batch of brass. This may take a couple of trips to the range and many cleaning cycles after shooting 20 rounds. Culling your brass will give you better results and is just another step to increase your accuracy. I am sold on the Wilson seating dies because the die will produce cartridges that are under .001 on concentricy when using culled brass. And of course you must buy good bullets!!!! Just my experience for the last 50 years of reloading.
Matt

[Hefights]

"The other factor is the brass. You must have good brass to have great results. Lapua and Norma are probably the most consistant, and they are expensive. Remember, if you are hell bent on producing world class competition ammo, you must spend the money on good brass."

Ditto to what Matt is saying, my experience exactly, a point I neglected to make in my response. I also bought some Norma and Lapua brass in the 2 calibers that I want to make precision ammunition for, and there is a distinct difference. Brass concentricity is markedly better and results in a lower "failure rate" in cartridge concentricity.

[Allen Humphrey]

Good points guys. I never get straight loads on brass that is crooked. In my NM AR I find that I get noticeable accuracy difference at about .006 for magazine length 55gr ammo. I suspect that the jump is so far on those rounds that only the really crooked rounds show up. Good 55 grain bullets shoot so well for me that I use them in matches for the 200 yard stages. However, on my single load rounds (75gr a-max) which I seat very much closer to the lands seem (to me at least) to shoot differently after about .004". I nearly gave up on the A-max load until I figured out what was going on.

[Matt Anthony]

Good points guys. I never get straight loads on brass that is crooked. In my NM AR I find that I get noticeable accuracy difference at about .006 for magazine length 55gr ammo. I suspect that the jump is so far on those rounds that only the really crooked rounds show up. Good 55 grain bullets shoot so well for me that I use them in matches for the 200 yard stages. However, on my single load rounds (75gr a-max) which I seat very much closer to the lands seem (to me at least) to shoot differently after about .004". I nearly gave up on the A-max load until I figured out what was going on.

Allen, I bought the Hornady Concentricity tool just to see how far off my cast bullets were in the beginning. I was going to quit casting after tens of years of frustration. Stopping and starting loading cast bullets for years with poor results.
Wilson straight line seating dies are not for cast bullets, only jacketed, so one is at the mercy of the competition/standard seating dies when using cast. I was absolutely surprised how far off my cast bullets were when seated. Up to like you said, .010, which is not tolerable. That's when I said, hell or high water I will find out what my problem is. It turned out to be a couple of problems that could of been fixed years and years ago, but when one gets frustrated, one loses his common sense on that matter. And sometimes, work, family and other obstacles stop you from going as far as you can, as we all can say, there just isn't enough time! I now use only Lapua brass on every caliber I reload. This change makes reloading alot easier.
First of all, the base of the bullet must be flat, initial bullet alignment in the case and your powder charge. How did I do this, well I researched moulds, Hoch 185 gr. 30 cal. nose pour bullet. This mould insures the base of the bullet is perfect when poured. Hoch makes bullet moulds that in my opinion is like a fine wine! Next, I bought the Lyman M dies for all my rifle calibers. These open up the mouth of the case to accept the bullet and makes sure when the bullet is started it's centered in the case. The M dies can be used for jacketed bullets also! The last thing was speed of the bullet, cast bullets have better accuracy when slowed down. Velocity is not your friend and the sooner you realize this the better. The old Lyman 1970 manual had accuracy load data and factory load data on most of their listings. What I have found is that they are almost dead on! 14 gr's of Green dot under a 193 gr. cast bullet in a standard out of the box 30/06 Rem. 700 BDL will print 3 shot groups at 3/8th of an inch at 100 yards. Just as good as my jacketed loads but at 1559 fps instead of 2660 fps. After many, many years of experimenting, month's of frustration, hundreds of dollars and billions of hours in time developing loads when honestly the few small steps I took fixed all my frustrations.
I take alot of time prepping my brass, culling, casting bullets and checking everything twice. When I throw powder, every charge is weighed, and every charge is thrown short and then the powder dribbler takes over and as soon as the scale shows my charge, I stop. I use the Accu-lab scale I bought from Sinclair. It's extremely accurate. All of these plus the other things I do, make my range trips a vacation and a happy experience, every time! People look at my groups and can't believe they are looking at cast bullet performance. The same is true when dealing with jacketed, the more time you take insuring everything is right will give you the best results.
Matt