On the ones that did not fire,what did the firing pin strike look like?A good dent,or wimpy?
And,as Uncle Nick mentioned.off center is significant,too.
My early handgun reloading adventures included not belling,or not sufficiently belling some 38 Super brass I fed to a 1911.It had a Clark bbl,headspaced on the case mouth.I used copper plated lead bullets.The case mouth shaved a little bullet metal forward.That shaving messed with the functional headspace,and so at times the slide was almost fully locked,but not quite.There is a little wiggle room in the disconnect,so the hammer would drop.
Unfortunately,at that point I also went down the velocity column,and picked a hot rod load of Blue Dot.
And,once I got to the range,I wanted to come home with empty brass.
I still have that Clark bbl in my junk drawer.The lugs set back on the half locked bbl.
I'd say,generally,if something about your handloads does not work,stop.
Ignition problems are also a fine way to lodge a bullet in the bore.Its a bummer to drive the bullet out sometimes.It is possible to batter the bullet so it gets tighter.
A squib doesn't make much noise,you might not notice it with ear protection.Then,you might react by racking the slide and shooting the next round.Two bullets in the barrel does not end well.
So,back from the side story:
You can look through the handgun,firing pin tunnel clean?
Dry snap much? Firing pin head can mushroom,then drag on the firing pin retainer plate.
Old gun? Get a spring and pin rebuild kit.You might have a limp hammer fall.Strut pin may be walking and dragging.
For about $20 you can get a box of 50 hardball factory loads.Try a couple mags.Zero problems? Maybe the gun is fine,but clean and lube it.Also,inspect the locking lug surfaces.
With your barrel out of the gun,drop several of your loads in the chamber.Do they fully chamber?Or do they stop short?
See,bullet dia a little too big(is it .451?) or the crimp bulging the case,etc can cause the round to stop short of headspacing on the case mouth.There is not an "anvil" so the strike energy goes into pushing the cartridge forward.
Did you use rifle primers by mistake?Cups are harder.
Are you handling the primers one at a time?Oily fingers are not good.
And,its been mentioned,high primers are just something to not do!
Clean,lube,inspect the gun.
Reloading,use universal decap die on the dirty brass,tumble till its clean.
Make sure the flash hole is clear and the primer pockets do not have crud in them.
Seat and crimp as two operations.Use a taper crimp or factory crimp collet die.There is often a crimp dia specified in the load book.
verify the rounds will drop full depth into your chamber.
No high primers.
Stop if it does not work.