Is Lee compatible with all other manufacturers?

[tobnpr]

^^^
Thanks for the link. Didn't turn up on the search I did.

IMO, there's types of "slop" that shouldn't affect this, and those that would.

The turret deflecting (moving up) as that thread was about, shouldn't be an issue when it comes to sizing. It just means the ram stroke is infinitesimally longer to get it to bottom out with full force of the ram.

Simplifying what's happening, all we're trying to do is to bring the shellplate and the sizing die together. Once the two machined surfaces (top of the shellholder, bottom of the die) make firm contact, that's it. Can't go any further, that's all we're trying to accomplish.

Now, if the shellplate is not brought to bear with the base perfectly parallel to the bottom of the die, if the bottom isn't precisely machined and it "wobbles", then there's an issue. Contact won't be consistent and neither will be the results. I explained to my son that in the case of precision machined parts, they need to make full and even contact. Some "play" in the right places that allows this alignment to take place would be desired, just as I use a floating reamer holder when reaming chambers. It allows minute misalignments to self-correct.

With my LNL AP, the shellplate can rotate, and the case is lightly held by a spring- so it is free to self-align with the dies without "binding".

Next time I head over to his place, I'm going to bring some contact dye to see what the relationship is between the shellplate and die base. Now that I'm curious about this, I'll check my LNL AP as well to see if there's full/even contact with the shellplate.

 

[Unclenick]

Precision, repeatable sizing requires rigidity same as machining requires rigidity IMO.

Actually, it just requires repeatability. If you have an aluminum frame press, the modulus of elasticity of cast aluminum is greater than for cast iron so, for equal thickness, it will stretch more. However, as long as it is not stretched beyond its true elastic limit, that greater stretch will be more consistent than you can measure without a laser micrometer. Load cells for laboratory scales reading out past six digits work on the principle that the stress (stretching force) vs. strain (stretching resulting from that force) is virtually perfectly linear per Hooke's Law. No hysteresis or plastic distortion occurs with steel or aluminum within their true elastic limits and the time frame of the measurements. Indeed, that is how those limits are defined.

I believe there have been a number of comparisons of the shooting precision of ammo off different presses, but none by benchrest shooters, and that's pretty much what it would take to resolve the finest differences. This testing has to be done with rifle cartridges as quite good pistol and revolver precision typically groups about 4 times greater moa than quite good rifles do (2 moa vs. ½ moa — I am not including single-shot silhouette type handguns or benchrest rifles here). From ammo tests done with the Dillon 550B, it appears to produce good match ammunition for service rifle match shooting, where the hardest target is the 600 yard prone slow-fire target which has a 1.9 moa 10-ring and an X-ring that is half that diameter.

In the mid-1980's, when I first got into High Power match shooting I bought a Garand for that through the now-defunct DCM. In the 80's I didn't have an O-press because bull's eye pistol matches were the only volume shooting I had done since the '70's and I had bought a Lyman Spar-T turret press for loading for that. So, I started reloading .30-06 on that Spar-T press. After match accurizing my Garand, I did a prone slow-fire 100 yard test group with the ammo it assemble that was 10 shots at 0.7" C-T-C. Unexpectedly good for both rifle and ammo. The main trick back then was that even though I had a press not considered beefy enough for what I was doing, I had good dies. There was enough slop to let cases follow the die centers and thereby self-align some. Ultimately, though, it was too much work on that simple, non-compound press mechanism, and I got a Forster Co-ax press to take over the rifle loading work.

Where you want vertical consistency for matching sizing and seating, having lateral freedom of movement is actually better than total rigidity because your press doesn't have a Tool Room Lathe level of alignment perfection of the ram and die axes. Allowing self-alignment motion actually makes better ammo for that reason.

About the only thing I don't trust most presses to do perfectly is priming. If you want really consistent primer seating, you have either to do it by hand or with a fixed depth priming tool like the one on the Forster Co-ax press or one of the click adjustable bench or hand tools, or you can use shims to set up the Sinclair hand priming tool for fixed depth. The K&M Primer/Gauge tool lets you measure exact anvil compression of the individual primer into the individual case by zeroing the height of each unseated primer against the depth of the particular primer pocket it will go into, and I use this tool for test loads, but it it very slow going for anything but test or benchrest work.