Premium Dies: Are they worth it?

[Unclenick]

AllenJ,

If you read the Forster and Redding patents on their sliding sleeve seating dies, you’ll see the difference is that Redding went to a floating seater plug that the patent claims avoids one bullet tipping scenario than the die sold by Forster, which has a one-piece seating stem, can still have. I’ve never had the opportunity to do a side by side, so I have no clue how often that tilting mechanism might or might not appear. People using either brand like them.

I bought the Redding in .30-06 back around 1990, when they were new on the market (and half the current price, IIRC). Reloading LC brass, I found that seater kept the 168 grain MatchKing runout down to about 0.002” total indicated runout (TIR¹), even seating on an old Lyman Spar-T turret press. By comparison, the more rigid Redding standard seater die I had would leave the same bullets in the same lot of LC 72 cases at 0.008” total indicated runout. I found I could keep the runout under 0.001” using cases selected for neck wall thickness and concentricity runout that low.

Lee also floats its seater stem, though it contacts the bullet higher up on the ogive and Richard Lee says he doesn’t believe in the case alignment sleeve concept, anyway. I can only say it works well for me. I’ll also say the RCBS standard seater works very well. It’s seating stem seems to be flexible enough that it behaves somewhat like it’s floating.

Originally Posted by tobnpr

Exactly what the inexpensive LNL bullet comparator and modified cases tell you.

If you also buy the case comparator inserts it can do it with rimless bottleneck cases. You have to keep in mind the gauge case is a new case and that your own fired and resized cases may be a different length from breech to headspace datum diameter on the shoulder. That’s why they offer the service for taking one of your fired cases and drilling it out and threading it (which you can do yourself; 9/32” drill bit and 5/16-36 tap; though the tap with S&H will set you back the cost of three pre-fab gauges, so you need to want to do this).

If you have the case gauges, you can do a double-reading; one being the standard ogive contact measurement and the other being the shoulder position on the gauge case. Compare the gauge shoulder measurement to that of your resized cases. Seat the ogive a thousandth longer for each thousandth your case shoulders are longer than the case gauge’s is, and vice versa.

Originally Posted by Jimro

Are we talking firing pin movement or are we talking when the bullet is released from the brass? Because if we assume that the brass has swelled from internal pressure to fill the chamber then the jump to the lands doesn't matter. If the bullet leaves the case before the case fully expands to fill the chamber then it does matter.

As Bart says, the latter seems to be what happens. When the gun fires, the firing pin pushes the round forward, though I suppose it might rebound some if that were the only forward pressure it was under. But it’s not. The primer makes pressure faster than it can vent through the flash hole, so it backs out of the primer pocket like a little piston, assisting the inertia imparted by the firing pin in pushing the round forward in the chamber. It’s got some strength. J. C. Garand’s first semi-auto design was primer actuated, but had to be abandoned in the 1920’s when the army started crimping primers to keep them from popping out and jamming the works in machine guns.

At any rate, the little primer piston holds the case forward as the powder burn gets underway. As pressure builds, it expands the thinnest parts of the brass (neck and shoulder) first, releasing the bullet and sticking the case to the chamber (assuming adequate load pressure for that). H. P. White measured bullet movement at about 10,000 psi years ago, though QuickLOAD suggests it starts at about 1/3 of that, though only at microscopic level. At higher charges, the expansion also makes it to the thicker part of the case wall before stretching gets underway.

If you have a very low pressure load, like primer-only loads, the primer is never reseated. If you have a load at normal non-magnum revolver pressures, the whole case backs up in the chamber and reseats the primer. At full rifle pressures in roughly the 50 kpsi and up range, the brass sticks the case wall all the way from shoulder to near the head, and the head is then stretched back only at the pressure ring, which thins as a result. The tricky part is the medium pressure loads. If you get enough pressure to stick the shoulder of the case, but not the thicker sides lower down before stretching of the brass commences, the whole unstuck portion stretches and slips along the chamber wall. This allows much more brass spring back than stretching the pressure ring does. So, as the bullet clears the muzzle, the case starts to pull the head back toward the stuck shoulder before all residual pressure is gone, and that residual pressure starts to push the primer back out again before it drops completely. Thus you can get primers that protrude at very, very low pressures, that stop protruding at pistol pressures, go back to protruding a little at intermediate pressures, then stop protruding again as pressure gets still higher. It makes reading the primer a pain.


Bart,

That tool of mine has a removable shoulder at the bottom (knurled part). What I do is cut a length of ¾” drill rod and knurl and then thread to the left of the knurled portion. Behind that I turn it to ⅜” for an inch. I then bore and ream the whole length and run my own chamber reamer in far enough to get the case mouth just pas the end of the threads, then part it. That gives me the removable chamber and I then just turn the freebore off what’s still in the chuck. The remains becomes the plunger plug driven by the dial indicator spring, and it fits the bullets exactly like my chamber does. Extra bother, but it gave me just one tool that did all calibers when I had the adapters made. So, for me it’s the time invested in making the adapter vs. buying an extra seater die and setting it up to gauge. After adapting the die, I’m not sure I’d have saved time.

I don’t own one, but I understand the Redding Instant Indicator will make the same measurement, but using neck bushings in place of a throat. They have the same drawback for me that modifying


¹ TIR is twice the actual tilt of the bullet tip off the cartridge axis because the tilt adds to the reading on one side of the cartridge rotation and subtracts from it on the other. Thus, the needle swings by twice the tilt amount.

[Bart B.]

Unclenick, all my primer only rifle cases' primers stay flush or a bit below when fired in all rifles. Only with my pistols do primers back out of empty cases. I think the reason's the amount of force the firing pin puts on them. Bolt guns' firing pins have a lot more force behind them than pistol ones do.

With reduced loads more than about 12% in my .308 cases, primers are backed out past the case heads. At 15% or more reduction in otherwise empty cases, they stick out near .010" in virgin brass. And that with factory spec rifle firing pin ratings or 10% greater ones.