I have a vintage 03A3 Springfield 30-06 that I recently replaced the entire bolt in. The headspace was too tight so I had it headspaced properly by Derrick at Horizon.
I had two different loads I had worked up prior so decided to check to make sure all was good. It wasn't as both loads were way too hot it seemed with both very flattened primers and a sticky both. Both according to QuickLoad are moderate loads and I checked and I am seated .100 off the lands.
Not sure what the change is that could cause these loads to be that high of pressures??

This isn't one of the Mann Accuracy versions it is? Do you have a stainless barrel?

No it's a Smith Corona with a 2 groove barrel.

D, did you verify that the load is truly still .100" off the lands? Can you describe exactly what was done to change the head spacing?

Yes I measured first because I assumed since Derrick said they took a reamer and bumped the shoulder about .004/.005 that I might be close to lands but I still have plenty of jump it seems.
I also thought maybe there was some cutting oil or some type lube in the chamber that caused the primers to be so flattened so I cleaned the barrel and chamber good.
The sticky bolt makes me think that is not the issue though.
Going to pull some bullets and reload try again at lower charge.

I would bring this to the attention of the folks at Horizon, and see what they say.

They may have a suggestion for you, or may want to take another look at the firearm.

Note that fired cases from a rifle that had too-tight headspace would be on the short side after the headspace was adjusted, creating a headspace condition. If you are using the same brass this may be the problem, or at least part of it.

The way to test this would be to re-load a few of the brass that you have fired with the new bolt, using the same load. The shoulder should now be blown out to the new dimension, eliminating any headspace condition. If they behave OK, then you have identified the problem.

If this fixes it, then I'd toss all of the old brass and start off with a new batch. Firing all of the old brass to stretch it out could be dangerous. Remember that the nut behind the trigger is the only irreplaceable part.

I measured a case fired with my old bolt with the Hornady headspace gauge. It measured 1.983 and my ammo that is reloaded is running 1.981-1.982.
I am glad Charles brought this up as now my brass fired with new bolt is measuring 2.003 which means my shoulder is being stretched .020 upon firing.
So I will need to fire all this brass then adjust my dies accordingly to prevent case head separation of course. BUT that still leaves the question of why the extremely flattened primers.
This is what I am thinking now. My brass is loose in chamber now since its undersized and upon firing pin hitting the primer it's pushed forward then the ignition of the powder is slamming it back against bolt face thus flattening the primer to the extreme.

If I was going to attempt to save all this brass which is now headspaced short, I would consider loading light charges with "junk" bullets seated out to jam the lands firmly. That way you stand a chance of blowing the shoulder back out where it needs to be without stretching the brass.

I happen to have a supply of pull down 172gr that should work fine.

Good call charlesb.