I don't have an issue with more extensive background checks in principle, but serious reservations in practice. For starters, these aren't background checks for "sales" ... it's for "transfers". A very big distinction. One of the earlier versions of the bill would have made someone an "oops ... instant felon!" for handing a firearm to a buddy on their friend's private property during a round of plinking. They had exemptions for shooting ranges incorporated for the purposes of conservation or marksmanship (you did read your shooting range's incorporation documents, didn't you?), and for handing a firearm to someone in your own residence, but not fo shooting on private land or another residence, or an automobile, etc etc. Also, it was considered a "transfer" if the firearm were kept at home with other residents, and the owner was gone for more than 7 days. Doesn't matter if it's locked in a safe. Gone for more than 7 days means you've illegally "transferred" the firearm, instant felon. So, aside from a made-up term to scare peope, what is an "assault weapon" really? Same deal here - what constitutes a "transfer" really? It's easy cheezy to shout bumper sticker slogans such as "universal background checks", have everyone nod in agreement that we're going to save lives, only to cart thousands of people off to prison because they and their buddies shot one another's firearms while enjoying a day of steel target shooting in Joe's 40 acres. Or at least putting them at risk of being carted off - there is the issue of being caught, but I'm not willing to lean on that. Meanwhile, criminals will continue to trade guns in dark corners, all without filling out 4473s. Just like most of them do now. The implementation isn't as easy as a bumper sticker. "Transfer": I do not think it means what you think it means.
Then there is the issue of "mental health" disqualifications. Sure we all agree the raging maniac shouldn't own a firearm, but there are proposals kicking around to disqualify anybody who has ever taken or been presribed anti-depressants or psychoactive drugs - including drugs that may not have been prescribed for their psychoactive qualities but may be prescribed for that reason. Example would be Benadryl (Diphenhydramine). Considering they hand psyche pills out like candy on Easter, this could be a problem, further compounded by the fact many over-the-counter drugs are also psychoactive in nature and very similar to SSRIs even if their intended purpose is to fight allergies, for example. Ever been diagnosed with depression, even if you're "supposed" to be depressed (such as the death of a loved one)? Turn 'em in. PTSD, another "handded out like candy" diagnosis? Turn 'em in. The politicization of mental health by mental health professionals is also an issue. Google "liberal mental illness" ... then repeat but replace "liberal" with "conservative" ... once more with "libertarian" ... and you'll see my point. Depending on who you ask, the mental health community will tell you we're all insane. "Mentally ill": I do not think it means what you think it means.
Essentially, in my opinion anything that makes someone an instant, accidental felon is bad law, hands down. Further, any law that allows someone to use their title, combined with their inherent political bias, to deny a person their rights with the stroke of a pen, is bad law. The original proposal for extended background checks didn't (because it couldn't) cover so many normal contingencies and mundane firearms-related activity that it was full of "GATCHA!"s that would have made people unwitting felons by not reading the fine print of the law or their shooting ranges' incorporating documents to make sure they're exempt, or by going on a vacation for 8 days. Or by going on a 6 day vacation but their flight home gets delayed due to unforseen circumstances. In order to address this, the bill presented was pretty lukewarm. And leaves me scratching my head as to why the anti-2A'ers are upset it was defeated. Conversely, one might ask why pro-2A'ers were upset it was presented. My answer is that it was a half-assed attempt to "DO SOMETHING!" when in fact it doesn't do much of anything. While not as bad as the original proposal, it still had instant-felon "GATCHAS!" in it. Ostensibly passed to "do something" about mass shootings like Sandy Hook, it did nothing of the sort. Those firearms were legally purchased and (in CT) legally registered to her. About the only thing it had in it of any consequence was to require 4473s for any transfer at a gun show, FFL or not. But were two people to walk outside the show and make the sale in the parking lot, no 4473 required. Which highlights the problem: it's not easy to come up with a practical, workable compromise between an iron fist and freedom. It kinda has to be one or the other.