Without getting into all of this, there is a bunch of misinformation here. I'll provide the history and then the procedures.
You never want to use pliers, the butt end of dykes or a small crimp on the end. That folds the teeth over, and while not critical on a stripped splice, it does away with many benefits of the engineering behind the connector.
First, B-connectors are a Bell system item. They date back to the 50's and 60's. They are designed for 3-4 solid conductors, unstripped, up to 22 AWG. That's the engineering on them, period. No mismatched conductor sizes otherwise the crimp is uneven. Will they work on a pair of 18 AWG solid, sure, but if you "stack" the conductors in them, that's a sure way to get into trouble, as the conductors are supposed to lay side by side on the "long" side. They only fell out of favor because the telco guys' bad habits are hard to break in the field and UR/UY connectors were introduced by 3M at an attractive price (subsidized) so the Telco's did what any business would do.... It's no different than why cable lacing fell out of vogue compared to ty-raps, yet lacing are still prevalent in the industry on many projects.
They are designed to be parallel flattened/compressed to a known dimension using a tool like this:
http://www.gmptools.com/nf/85330.htm
I own 3 of these tools (all ex-Bell system tools, 1959, 1963 and 1974 as stamped on them). They work beautifully on the caps if you need to get it done right and "to spec".
This forces the teeth inside to cut through the insulation and into the copper making a gas tight connection when done properly (no sealant needed). If you over crimp, you flatten the teeth and they are worthless. When crimped correctly the splice is just as good or better than a soldered connection (Bell system docs) same as a wire wrap vs. physical connection to a terminal. The sealant filled ones are just an "extra insurance" policy and usually not necessary anywhere but outside or areas subject to moisture....think outside pedestals or similar.
That said, in the alarm industry, techs usually only use them as crimp connection insulators, stripping and twisting the pairs and then crimping over them. You should still use an "insulated" die to crimp as to not completely flatten the teeth and take advantage of the design of the cap, not mentioning you can remove the cap easily if needed. The uninsulated die has great potential to damage the conductors and usually pierces the insulating covering of the B-connector and shows inexperience.....I've had more issues with those connections in the field, typically done by those that twist wire nuts for a living.
While I own the real tools, I also use a T&B 112M for quick field work, and have been using the same tool since '99 with very little rework in the field to connections.
