Guys,
I very well might be having a "blonde" moment but here goes.
Started reloading for the 8mmRemMag again yesterday after a long absence from belted/shouldered cases. I took once-fired brass and set up my Hornady FL sizing die as per instructions then backed it off a turn. Running a case in showed that the neck was being sized to with-in around a quarter of a millimetre from the neck/shoulder junction. The case body to shoulder juntion also showed it had been touched by the die. Placed it into the rifle's chamber and the bolt closed with a firm amount of resistance, but it closed. Length of most of these cases is around 2.843 - 2.846". Extracted it with some resistance to bolt lift, and put it back in, still firm resistance. Might need to size some more I thought. Now ... just for fun I pretended to shoot the shed cat with this unprimed, partially resized and tight case. Well ... now the case (and some others I tried) go in with considerably LESS resistance and the bolt opens with less resistance, and I mean ALOT less resistance. Why????
Cheers...
Con

I would say by you forcing the bolt closed on the tight case you have essentially "sized" it with the chamber. In fact, repeating this several times in essence is much like sizing the case. I doubt dry firing with the case had anything to do with it.

Clean the chamber, wipe the cases off before trying them. If they're to tight, then they're to tight. I neck size for my 7mm RM so if you can see the contact is to the base of the neck, and you've carefully measured the length, the shoulder may need to be bumped back. It sounds to me like the length may be something to carefully consider. My '06 has to have shorter brass than the one my Dad uses. In fact, when I load for my rifle specifically, mine won't even shoot in his rifle. My rifle will shoot his though. I'm sure there is a slight headspace difference as well. These slight variations can cause little problems to turn into bigger ones.

Cerrosafe a chamber casting if you want to know for sure. Nate

"Touched by the die" doesn't necessarily mean the shoulder's been pushed back. Something similar happened to me, once - the shoulder moved forward, not back, after sizing.

It took awhile for me to figure out what made the shoulder go the wrong direction, but it was pretty simple, once I figured it out. With the die not touching the shoulder, but squeezing the case body, the released material moved forward, shoulder and all.

I had to return the die to Forster twice to have 0.006" removed from the bottom. I was using an RCBS PrecisionMic headspace tool, so I was pretty certain Forster had a manufacturing error. They were much less certain it was them, but they did remove the steel I requested, and the die then worked.

Perhaps you should try your die with less than a turn backed off.

Jaywalker

Another thing that can happen;The inside expander button can pull the shoulder ahead a bit. Put a little Imperial die wax at the inside shoulder/ neck junction with a q-tip.
Good luck!

Or use Imperial neck sizing lube. Made especially for this very application. It's similar to graphite so will not need to be removed after sizing and won't affect the gunpowder.

Are you trying to partially size them or full length resize? Reason I'm asking is because with most dies you have to raise the shellholder to the top then screw the die in till it touches the holder then screw in another 1/8 - 1/4 turn, not back out like you said you did.

I think SuperMagnum has hit it. Sounds like you're trying to partial resize which I like to do also. But you need to size them just enough so you bump the shoulder just a bit. The Imperial die sizing wax is also a good practice.

Alliant Powders are awesome 8MM Magnum propellants. The RL25 with 220 Gr. bullets on their website is for real.

True 24" barrel velocities.

Thanks guys,
Yes I am trying to partially size these cases. They were originally fired in a "short" 8mmRemMag chamber, the rifle's original barrel had had a quarter turn taken off or something. Chamber was short enough for new reloaded cases to fit but not factory ammunition. Rather then push the shoulders even further back I figured to partially resize and achive a crush fit, which I obviously seem to have achieved. I think what Jaywalker mentions must have happened, its a first for me to have shoulders pushed forward.

Jay Johnson,
Yes those Alliant velocities do look good, and I will indeed be chasing 3000fps or close to it in my 26" barrel with a 220gr. Any experience with H1000, Retumbo or H870 in the 8mmRemMag? Also looking for a load for the 250gr Woodleigh.
Cheers...
Con

I'm haveing a blond day to. I don't think anyone addressed the dry fireing bit.

So the case was a bit tight, which may not be much of the case, and some rifles have a heavy clunk when dryfired, so maybe the case was "impacted" in a whisker??
If it happened to the other cases without dryfireing, I guess some crud was shifted in/from the chamber. So watch what you do to cats.

were the once fired cases out of the same rifle you reload for now? I use a sizing die that resizes the case from the belt up and that resizing makes the cases fit the chamber very well. I can't give the name of it as I am at my sisters house for dinner, if you are interested let me know.