Personally, it isn't a whole lot of fun for me to take out a 500 dollar HD shotgun like my 590a1 with extension or a Sig Sauer pistol and beat it up, beyond the prescribed break in/evaluation period.
But, this is my point....No such "break in" period is generally necessary when dealing with todays weapons. Everything I mentioned I have done with my 590 (A1 convert), my Benelli SNT, my Sig P220, my Springfield, etc.,...all with no negative affects.
I will NOT clean the cosmoline and bore out before shooting.
This, from what I understand, is not a good idea. Ditto with the rest of the gun (particularly the receiver and all components within) as leaving this "gunk" in the weapon can, upon firing it, lead to malfunctions, minute damage to the bore (not such a big deal with a smoothbore shotgun, however) or other parts, and so forth. Besides, Im of the mind that leaving a bunch of gunk in the bore, just prior shooting it, is simply dangerous if nothing else. Bad things could happen....
From what I gather, "breaking in" a weapon mainly concerns the bore. Why? For possibly enhancing/maintaining accuracy and helping in the attainment of that much desired "mirror smooth" finish. I guess you call this "seasoning" the barrel. But, again, unless we are speaking of extremely long range weapons such a rifles, I just dont see the point. I mean most handguns and shotguns only have an effective range of less than 100 yards, give or take.
Now sure, my weapons may not have acheived that "mirror smooth" look as of yet, but then again, I havent blasted through 1000s of rounds. But, after a "deep" cleaning, they look pretty good to me. Sure, I may not win any awards, but all of my guns are meant to be used rather than simply being stored away for posterity. Plus, they are all more accurate than I am
To sum up...from what I have been told by various weapons manufacturers, most guns of today (mainly handguns and shotguns) simply do not require a "break in" period as they might have before. Better metals, better methods, better tolerances? I dont know. But, it does make sense.
Ive personally never heard of a (fairly current to current) handgun or shotgun going south due to the lack of any strict "break in" method. Most pump shotguns, by nature, are brutes and should be capable of withstanding much abuse. To me, a nice, thorough cleaning and 20 to 30 rounds of low to mid strength ammo (through a new gun) is far from abuse and is certainly all that is truly necessary to "break in" the thing. Frankly, Id be more concerned about the inherent reliability/durability of the weapon. If a weapon needed to be treated with "kid gloves" in order to remain reliable, well...I wouldnt own it.
Now, once again, for that $1500-$3000 rifle which is expected to remain accurate around 500-1000 yards or so....then yes, I would be much more concerned with the "break in" thing. All else falls within the category of clean, shoot, maintain and enjoy.