Using the .308 die has two limitations. One was mentioned earlier. Neck-sized cases grow tighter with each successive loading and firing cycle, and eventually need either to be full-length resized or to be run into a Redding Body Die or a Forster Bump die to set the shoulder back a little and/or narrow the case a little, so a .30-06-specific die of some kind will eventually be needed.
Ed beat me to the other limitation, which is that because the .308 case has a more gradual taper and a sharper shoulder than the .30-06, it leaves extra room for the neck expander to pull the neck off-axis with the rest of the .30-06 case as the case is withdrawn from the die. That increases runout in the cartridge because the bullet doesn't go in aligned straight with the rest of the case. That means that when the cartridge is chamber and fired, the bullet is at a slight angle entering the bore. That has been show to open groups as little as under 0.2 moa (tight benchrest chamber and extra tight bore) to as much as 2.0 moa (military barrel and chamber), depending on the chamber and bore dimensions.
That tendency to pull the neck off-axis is a problem to some extent with all neck sizing where an expander is needed. This includes your .308 die. The problem is that case neck wall thickness has a 0.004" tolerance in most chamberings. That adds up to 0.008" diameter tolerance because both sides of the neck are included in the diameter. The die has to be able to size the thinnest possible neck. Because it sizes from the outside with no internal limit, it has to make the neck 0.008" narrower than the thickest neck requires, or about 0.004" to 0.006" smaller than the typical neck is usually made. The expander then has to stretch it back out again on the inside to be 0.001" to 0.002" smaller than the bullet. That creates correct neck tension. This process also means the neck actually is sized twice.
Only the RCBS X-die for full length resizing, and the Lee Collet Die for neck sizing avoid the above problem. Both have mandrels that set the inside diameter of the case mouth correctly at sizing, and that also avoids the second sizing. It works the neck brass less so it needs annealing less frequently. I've misplaced the reference, but one British target shooting magazine compared all neck sizing dies about five years ago and found they all pulled necks off-axis by 0.002" or more except the Lee Collet die. It was always under 0.001". Same as is demonstrated in Ed's video link. So, you can see the reasons the die design has fans. It is just better in principle.
I read the Midway reviews, five in all in that link. Since each chambering or set has its own reviews, I also looked at some others. Many have only positive reviews. Here's
the one for .308. It is four five star happy reviews, then one more where a fellow blew the aluminum cap off. Of the reviews for the .30-06 version, two were very positive. Of the three that were not five stars, including the one with the cap blown off, they either didn't read the instructions (free download online) or could have been instructed how to use the die correctly. This die does require some thinking and learning, but once you understand the limitations it works better than any other neck sizing die made at any price.
How to use it correctly:
First, understand how people can blow the cap off so you won't. The people who did this had cases with thick heads (that varies by brand). They needed to loosen the cap enough to let the case push the mandrel up high enough to let the collet close before the top of the mandrel jammed against that cap. They jammed it. The collet wasn't closing completely because of the jam, so they laid a muscle on the press handle and pushed the rod up hard into it and blew the threads off the soft aluminum. One guy wrote that his wouldn't work even though he lubricated the cases (not needed with this die). Clearly he was jamming the mandrel with his particular case and misunderstood what was happening and thought lubrication would fix it.
Other reviews on other dies describe having to put washers between that aluminum cap and the die to get it to work. That means the same thing was happening to them. The mandrel bottoming out on their cases. The washers let them tighten the cap at a higher position to remedy that. If you feel the need to tighten it, that's fine. I just lightly flatten the edges of the aluminum cap thread on one side with a light hammer tap and let the friction from the lightly boogered thread keep it from moving.
To get the cap position right, just turn the die in, per the instructions, and push a case in just far enough to deprime it. Then remove the cap and run the die all the way up, closing the collet. With it in that position, turn the cap back in. If it goes all the way, fine, you are done. If it runs into the top of the mandrel, back it out a half turn and leave it there until you change case lots.
To address other complaints, no, this die is not suitable for use in a progressive press. That's just the way it is. The guy who found it too hard to be consistent with it and switched to a Redding neck die forgot to shoot groups with brass sized in both and compare the results. That is the objective in the end, right? Best groups.
Lee's 25 lb handle force recommendation is a ballpark number. If you adjust the handle of your press out far enough, or if you don't turn the die into the press far enough so that the press compound leverage is high or near overcamming, you can put too much force on it with 25 lbs on the handle. You don't need to use super force to size the neck. Size, lower the ram far enough to turn the case 180° and squeeze it again. I get very consistent results that way.
Alternative die: the
Classic Lee Loader is a neck sizer that will fit your case snuggly enough so you can usually keep on shooting without other sizing. A group shot using ammo loaded in one held top place in the Guinness Book of World Records for several years. The loading process with one is slow, but you can prime separately on your press or even seat bullets on your press, as you prefer. Unless you have a competition seater, the Lee Loader may seat your bullets straighter than your press does, though.