How long a waiting period would the Second Amendment allow? A week? A month? A decade? Do please bear in mind that one of the design goals of waiting periods is to increase the hassle of purchasing a firearm. Someone who does not live conveniently close to the point of purchase must make two trips. If the gun store is 45 minutes away, that's 90 minutes of the purchaser's life wasted. Any reason that much hassle is okay, but requiring the person to show up ten times, on separate days, to buy a gun wouldn't be?
Also, while states have the authority to brand convicted felons as slaves who are forbidden from owning firearms, and while the Second Amendment and the "full faith and credit clause" would probably allow for some federal statutes that would make such prohibitions issued in one state applicable in others, explain how the federal government has the authority to declare that anyone convicted in any state court of any crime whose sentence could be more than 366 days in prison (regardless of the actual amount of time to be served). Shouldn't the question of firearm prohibiton be a matter for the sentencing state's government to determine?
A short waiting period, which is what we have.
I don't know if I favor the Brady Law or not.
But gun-rights advocates don't help themselves
with the public when they whine about "90 minutes" of trouble for the purchaser.
The waiting period part of the Brady Law has sunset. All that remains is the "instant" background check. However that can, in theory, result in up to a 3 day wait, IIRC. However it hasn't for me and I've bought 4 firearms since then, (plus one right before Brady went into effect (1911A1) and one (serious social purposes shotgun) right before it began to apply to long arms. Only bought two subject to the check though, the others were from private sellers, not subject to the law. The two checks took less than an hour each, how much less I'm not sure, since I wandered off to look at more guns. :) (both at gun shows).
Of course YMMV depending on your state. Some states do have waiting periods. And bans on things the federales do not.