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Presses and runout

Tikkamike

Tikkamike

Well-Known Member
Joined
Dec 26, 2009
Messages
5,505
Location
Big Horn Basin, Wyoming
I have been thinking about cartridge concentricity lately. A lot goes into making a straight cartridge, Quality brass, good dies, and a square press among other details that you could probably chase for an eternity. I have been asking some of who I consider to be industry experts about equipment and techniques. David Tubb told me he uses a Dillon 550 for all of his reloading and has excellent results, Jim See uses the same press that I do.. an old RCBS Rockchucker... So how do we make straighter cartridges? I saw the new Frankfort Arsenal press which looks a lot like a Forster at SHOT this year and while I consider FA to be low end they did build what looks to be a solid press. but is a floating shell holder that moved perpindicular to a floating die the best method? I dont know the answer to that, I have read both good and Bad. Dillon and Redding both make high quality stuff, I think their presses are probably great, but without setting up a bunch of dials and guages there is really no way to know if your current press is the reason for any runout that you may have. Now I realize most of us have no issues getting a rifle to shoot a large percentage of the time BUT what if it could be better just by spending a few hundred bucks on a press? or some other piece of cool equiment? most of us would probably do it. What do you all do to ensure as little runout as possible? how much runout is acceptable to you? and what is the average amount of runout that you typically see on a given cartridge?
 
The idea of a floating die and shell holder is not new. Many years ago Bonanza made one and now forester has bought them out.

The concept is to allow the die to center over the case to allow the case to be sized without any misalignment that could cause concentricity issues. All presses are machined to a tolerance and a slight misalignment is/may be present. The press is strong enough to alter the case if alignment is not perfect, so the concept of a floating die and shell holder "Should" solve this. (At least in theory).

I have done some extensive testing as to how much concentricity is necessary for best accuracy and my findings were fairly consistent and linear. I used one of my most accurate rifles for the test and the results were predictable.

.000 run out produced 3 different groups of .054, .053 and .057 (3 shots @ 100 yards.

.001 run out cartridges produced 3 groups ranging from .069 to.076.

Cartridges with .002 run out produced 3 groups ranging from .091 to .123.
The first group I shot with .003 run out jumped to over .200 so the test was discontinued.

In an attempt to save the loads with over .003 run out I tried to straighten the loads and found that even the ones that i was able to get below .001 did not shoot as well as the ones loaded to .002.

It did help, and straightening these rounds could save them for hunting at closer distances, but for pure accuracy they must be loaded straight to perform their best.

Accuracy is relative to the shooters needs and these differences may not be important to some. but it shows me that concentric ammo does make a difference.

J E CUSTOM
 
J E Custom said:
The idea of a floating die and shell holder is not new. Many years ago Bonanza made one and now forester has bought them out.

The concept is to allow the die to center over the case to allow the case to be sized without any misalignment that could cause concentricity issues. All presses are machined to a tolerance and a slight misalignment is/may be present. The press is strong enough to alter the case if alignment is not perfect, so the concept of a floating die and shell holder "Should" solve this. (At least in theory).

I have done some extensive testing as to how much concentricity is necessary for best accuracy and my findings were fairly consistent and linear. I used one of my most accurate rifles for the test and the results were predictable.

.000 run out produced 3 different groups of .054, .053 and .057 (3 shots @ 100 yards.

.001 run out cartridges produced 3 groups ranging from .069 to.076.

Cartridges with .002 run out produced 3 groups ranging from .091 to .123.
The first group I shot with .003 run out jumped to over .200 so the test was discontinued.

In an attempt to save the loads with over .003 run out I tried to straighten the loads and found that even the ones that i was able to get below .001 did not shoot as well as the ones loaded to .002.

It did help, and straightening these rounds could save them for hunting at closer distances, but for pure accuracy they must be loaded straight to perform their best.

Accuracy is relative to the shooters needs and these differences may not be important to some. but it shows me that concentric ammo does make a difference.

J E CUSTOM
Click to expand...
Thanks for that piece of info. Along the same Line of "floating" dies, have you tried the o-ring method where the o-ring is place between the lock nut and press? Appears to be the same concept in theory anyway and much cheaper to do with standard presses. Thanks in advance for your reply.
 
To this day I have reloaded for several, several high end rifles in an assortment of calibers. I am the type of person who does not quit until I get little bug holes and super low Chrono numbers. But one thing I have never done is measure run out. I mean with the groups I lay down and the distance I shoot most of my rifles I would assume my run out is very low or I would think I would see it on paper, I dunno. However, I have never been shy about spending money on my reloading gear. Always best brass that is available for that caliber, high end dies, been running co ax for years, normally neck turn all my stuff, mandrel size, I mean I do a lot of extra steps usually but I have always seen my efforts in the groups I shoot. I guess to really find out the culprit one could measure run out after each of the various reloading steps to identify whether its a die problem, press problem or both. Thanks Mike now I got to go buy me a **** run out measuring tool thingy!
 
Well, why spend hundreds more on a press. I am still using the Lee Classic that was in the kit my son bought for me over ten years ago. My runout is less than .002" and that is using my Harrell's bushing die for my 6.5x47 and a set of Lee dies for my 7mm RM.

The old standard test for runout was to roll the loaded rounds on a mirror. If you could not see movement at the bullet tip the runout was not an issue. I got the tool to measure runout due to my curiosity, but once I saw what my runout actually was over quite a few loading, I just don't take the time to measure much anymore. When I do measure, it is a sample from the batch i loaded.
 
Ever notice how much play is in a shell holder seated on any press? Ever notice how much play there is with any cartridge set in any shell holder? There is more than enough slop there to allow the cartridge to self align as it is pressed into the die. Just set a cartridge in the shell holder a little offset from the die, slowly raise it and watch it self align. IMO a press would have to be way out of square to make much of a difference.
 
I use Lee lock rings on my dies that allow the die to float and self center in the press threads.
I use Forster full length dies with their high mounted floating expander that greatly reduces case neck runout.
And I still use the Rockchucker press I bought in 1973 using Redding competition shell holders.
A full length die with the expander removed will make the case as concentric as it ever will be.
And a off center expander and neck thickness variations are the biggest cause of neck runout.

In another forum a poster reducing his neck diameter .011 with a bushing die is wondering why his neck runout is so high. In the Redding bushing die FAQ they tell you if you reduce the neck diameter .004 or more the bushing will induce neck runout. In the same FAQ they tell you to reduce the neck diameter in several steps to reduce the neck runout. They also tell you if the cases have .002 or more neck thickness variations to use the expander included with the Redding bushing die. At the Whidden website they tell you they get more concentric cases using non-bushing full length dies.

 
J E Customs post drives home the points that concentricity does make a difference in a benchrest setting and that most folks don't have the equipment to bother worrying about it at all.
 
I use a Lee classic cast, Redding body die, Lee collet die and a forster seating die. With this set up my case neck run-out( with preped cases) is 0 to .0015, and bullet run-out from 0 to .002, with most at ..001-.0015.
 
I was setting up one of my presses years ago, and I noticed when I tighten the bolts down, the press would bind slightly. You could feel it when running the press. The bench top must have been warped and it cause the mounting plate of the press to distort enough to bind the press. I thought that would be terrible for runout so I did steps to fix the binding. I never tested it, but figured it was a problem.
 
Last edited:
Rick Richard said:
Thanks for that piece of info. Along the same Line of "floating" dies, have you tried the o-ring method where the o-ring is place between the lock nut and press? Appears to be the same concept in theory anyway and much cheaper to do with standard presses. Thanks in advance for your reply.
Click to expand...


I have not. but I still use my RCBS press for some duties and will have to try it.

I did try using an O Ring to hold the shell holder in place instead of the spring clip that locks it in place and found that the O Ring was an improvement and allowed the shell holder to self align better.

I also tried locking the ring on the die in place with a full sized case still inside the die to force the threads to self align (All threads have some clearance and the theory is that they will self align if not restrained) Locking the ring with a load on the threads and dies seamed to improve the concentricity.

Some of these experiments to improve concentricity showed no improvement, but other test show improvements and are worth the time, (At least to gain knowledge).

Thanks

J E CUSTOM
 
I use the MEC Marksman single stage press and it is the best press I have owned (4 th press). You do need a priming tool though since you cant prime with the press (RCBS BENCH PRIMING TOOL) but run out is a not an issue. I installed the Hornady lock n load bushing so I dont have to re-set my dies and its fit and function are excellent. I wish they made this press a decade ago.
https://www.midwayusa.com/product/1018146888/mec-marksman-single-stage-press

Here is a review located on LRH.
https://www.longrangehunting.com/articles/mec-marksman-reloading-press-review.1202/
 
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