are y'all sick of hearing about glue guns yet? 'cuz I learned a thing...

 I was reading patents on glue guns (the way you do) and between the patents and the advertising, it seems most hot glue guns have had some kind of anti-drip gimmick for a long time.  Apparently, most of them have a check valve assembly in the nozzle - just a ball and spring, keeping the nozzle closed until a bit of pressure is applied to the glue to force the valve open.

 It was easy enough to look for this feature on the 3M, I just unscrewed the nozzle. Lo, there it was... brass 3M nozzle on the right (with ball visible at bottom of hole) and silver Arrow nozzle on left.

 I hadn't taken one apart before that I could remember, so I took the junked one apart, revealing its failure mode in all its splendor: 

(uh, look ↓ down ↓ there ↓ sorry I suck at page-setting...)

Somehow*, the glue had flowed back out of the heater and gummed up the works.  Oh well, so what, I have a new one.  I was more interested in the nozzle on the far right which, it turned out, could be unscrewed just like the intentionally replaceable ones on the fancy 3M unit, once the anti-unscrewing plastic collar was removed during disassembly.  I feel it was put there to discourage this. The nozzle assembly with its anti-drip valve need to be fabricated separately, then assembled to the heater body, which necessitates the threads, but the consumer isn't intended to take it apart, and they will, if they can... which means more returns...

And lo, once I dug the solidified glue out of the inside of that nozzle, I could see that the cheap nozzle has the same anti-drip ball valve feature!

 I didn't think about how I was going to write this when I took the photos, sorry.

Anyway, check valves in glue guns, who knew?

 During all this disassembly I spotted another interesting feature at the bottom of the hole in the heater of the 3M unit, where its nozzle screws in:

 I have expended a bit of skull-sweat analyzing this feature, and I have absolutely no clue what it does.  Do glue sticks need to be mixed after melting?  This is right before going into the nozzle.

EDIT, later: this might be intended to remove bubbles from sticks as they melt.  Bubbles could be bad, because air expands a lot more than glue when it get hot; bubbles in glue sticks could cause little pops and bursts of hot glue emission from the nozzle, something we all would like assiduously to avoid!

 Incidentally, the nozzle on the 3M unit is sealed with a conventional looking black O-ring, probably viton, maybe silicone.  The service temperature for Viton O-rings (200ºC) is sketchy-close to the melting temperature of low-melt-point dispensers, so maybe silicone.

That's all for today unless I think of something new, I just thought these were interesting fine points. 

Tool nerd, sue me.

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*read as: "operator error" - I probably pushed too hard before it was fully
warmed up