FWIW:
If anyone thinks their Lock, or Trigger, never gets dirt, dust, grime on them, I would suggest taking another look, especially if you use WD-40, as most of us do.
If someone has used a lot of WD-40 over the years....and didn't wipe it off as we should have, it builds-up over time as a "clear, varnish" looking substance.
Something I was personally very guilty of doing for years on end.
From the time I discovered the wonders of WD-40 I used it on everything, lots of it, not wiping, but just "slinging", or "shaking" the excess off.
It has kept many a 1911 shooting and ejecting for years on end, and will likely continue to do so.
It has, in all probability, been used on every muzzleloader ever made, or at least some part of that muzzleloader,
In the 1990's I attended CST (Colorado School of Trades / Gunsmithing) and the very first day of introduction to the Class, we were all told...."You can't use WD-40 in this School, if you are caught with a can on your bench, or in your locker, it is an automatic 3 day suspension that must be made up before Graduation, 2 years from this date. If you are caught a second time, you are gone!"
Needless to say, that caught my attention.
So, I made it a point to find out why that rule was so tough....and, it didn't take me very long, likely the very first month I was in Basic to see why that rule was so stringently enforced.
CST is billed as the largest Gunsmithing Shop in the Free World....each day they process dozens and dozens of gun through that shop, with all monies going back to the School....they are also the least expensive of all gun repair shops because all the work is done by the students under supervision of the Instructors...after Basic Shop, D&F (Design & Function) and 3 months in Stock Work, each student is then State Certified on the Mill, Lathe, and the 3 Welding types, and then every graduating student must repair 100 guns in order to graduate....Afterall, they are going to train you in 2 years to walk right into your own shop, or, maybe, if you are real lucky, work for one of the larger Gun Companies.
That process of assigning guns for repair is much like taking a ticket at the DMV to get your Drivers License...you never know what's coming next.
You pull a ticket and take it to the Supply Room Counter and you receive the next available Firearm.
A Firearm that you become totally responsible for, the student has no choice insofar as if it's a Rifle, or a Handgun, he simply picks up the NEXT firearm, no matter why it was brought in or what it was brought in for, but whatever it is, that is the student's next assigned project, which will be repaired, go through 3 safety checks, test fired, graded, and cleaned again before that Gun is released back to the Customer.
Due to the close tolerances of all guns, the number one cause of malfunction and a trip to the repair shop, is simply a dirty gun.
The best method for cleaning a gun or gun parts is the use of a Sonic Cleaner, and the School owned a lot of those, they were located two, sometimes three, in ever shop section, with some as large as 30"L by 12'W by 10"D.
If you take a trigger, or a lock, and run it through a Sonic cleaner you will see a lot of small "Crystals" in the bottom of the pan....it's hard to describe this without a picture, but it's tiny, tiny, little pieces of varnish that closely resembles glass particles....that is WD-40 you see!
If the weapon or part is really dirty, there will be other colors but mostly black, and that makes those little "crystals" stand out like a sore thumb.
BTW: CST recommends a very light coat of plain ol' 3-N-1 oil above all other products for lubing a firearm.
I feel confident that in the last 20 plus years, with all the major new products on the market, they may have changed...but from their establishment in 1947 until the 1990's their preferred lube never changed, maybe it has by now, I don't know.
Such buildup, when allowed to continue, can simply "freeze" a gun up.
In our field of interest, ie, muzzleloaders we don't see this as much because we are always cleaning and wiping due to our propellant being Black Powder....but Black Powder brings with it the responsibility of more cleanings, more wiping, more pampering, than our Smokeless counterparts.
Morale of this long and boring story;
WD-40 is a Water Displacement tool, and a very good one at that.
If you use it, be sure to wipe the part good, and never fail to use a good Lubricant AFTER you use WD-40.
Uncle Russ...