According to http://data.hodgdon.com the load is on the hot side. They call for max load of 16.7. I don't think 16.8 will cause you any serious problems.
I recently acquired my father's older .357 magnum security six along with all of his reloaded ammo. I noticed he has some stuff loaded up that I can only assume is fairly hot. Since he also had a Thompson Contender with a .357 magnum barrel, I'm not sure if the hot reloads were for it, or for the security six.
For example, one box I have sitting in front of me has written on it; 158 HP, 16.5 GR 296, 550 PP. I know they have a 158 gr Hollow Point, and how much powder, but I dont know how hot that powder is. And although I dont have it directly in front of me, I know I found a couple of boxes of reloads with 20 grains of powder in them.
I guess basically what I need to know is, how hot of a load will a well functioning security six handle?
I saved that site for future reference.
I forgot to add that my father just recently passed away so I cant ask him what they were loaded for, or how hot they actually are.
I would never shoot anyone else's reloads... even my dad's... unless I was there when they were loaded. The expense of replacing mystery reloads, is much lower than the expense of replacing a gun, or a hand, or an eye.
Just pull them and reload them yourself, or dispose of them.
I agree with Jeff. I found about 300 rounds of .45 that I reloaded 20 years ago that had been stored during a move. Its hard but I will break them down and reload them again later. Better safe than sorry.
If you are over MAX on the weight side your are way WAY over on the pressure side. It gets exponential really fast- really fast.
Wanna KB yer gun or at lest shoot it loose and shag the shells?
Otherwise, if the cases are pristene yank the bullets, dump the powder, go back to the START load or 3% under that and do 'em over with the propper min. COL.
I shot some 'safe' reloads once that were a gimme. Lit off one round and that was enough. Glad it was a Ruger.
I pulled them down, reloaded at a reduced charge and still split some cases in the first 6- who knows how many pressings these went through. I trashed the rest of the batch.
Free ammo is cool- expensive gun replacement aint. I won't shoot a load I didnt make.
And the TC is a bolt gun compared to your revolver.
Dont even think about over-MAX loads in that pretty lil' SS.
I'd consider some mellower loads for her for sure.