030 to .045 is "nomial"
Beside "normal" some FP are of an inertia type. They are shorter and it is the energy imparted by hammer or sriker fall imparting energy that lets it drive forward enough to strike the case rim and then "bounce" back for clearence in the extract and feed cycle. Causes of light hits or failure to fire are more often traced to something hindering the FP travel...like dirt or burrs built up in the FP channel or...more commonly, damage from dry firing..with a .22 rimfire(actually any rimfire) the FP will strike the edge of the barrel and dent or peen a burr into the chmaber..this results in a couple of issues...first, the FP has nothing to whack against of a solid nature and the FP energy is absorbed as the FP drives the case rim into the dent..sometimes a burr formed into the chamber will keep the case from seating fully into the chamber and FP energy is absorbed trying to bottom out the case..most of the time both. Check the barrel face at the point where the FP strikes the case rim(clock position on the barrel face)..if there is a dent and burr...a repair is in order..DON" remove the burr, that metal has to be "ironed" back into place. You can get a tool for this task at www.brownells.com..it/ is a Menck/Brownells chamber iron...Brownells also has instructions on how to use it on their web site..next..This guns heyday was in the time of corrosive primed .22 ammo and if the gun was not cleaned properly(special technique for corrsive primer cleaning) then chamber and bore dame has happened and..if a goodly number of .22 short ammo was fired..then that damage occurred at mid chamber. This damage will often prevent a .22 LR round from seating fully and FP energy is used up seating the round in the chamber. If the damage is minor..no deep pitting...then a light cut with a 220 grit lap, folllowed by a 400 grit and a 600 grit lap(make a lap from a hardwood dowel by saw slitting the end about a 1:-1 1/2" and cutting automotive sand paper to size and using that..beware in that 220 will take metal the finer grits will polish...and..if the chamber and bore is damaged..the cheapest and easiest fix is to install a barrel liner. This is a kitchen table task and the instructions,parts and tool list are on the brownells website....
BTW..if the barrel liner is installed so the muzzle end is just shy of the end of the original bore..then at a casual glance it is invisable and the gun looks original..this fix will also deal with the dry fire damage and retain all the original markings on the gun...including those put there by Grandpa.....
I can't tell you how helpful your input on the Remington Model 12 firing pin is. I too have inherited a family heirloom with sporadic misfires. I am a complete neophyte but you have given me a very good place to start. I just joined the forum because of your input and can't wait to investigate a bit. Thanks Again!
I'm years late on this reply but I just fixed a misfiring Rem Model 12A and thought I'd pass on the knowledge. Light firing pin strikes were caused by excessive head space. Looking into the receiver where the bolt tips into a recess for lock up, I noticed the bolt had beat back the recess and bulged up some metal behind it. I clamped the receiver into a mill vice with some folded note paper beneath for padding and used a 3/8" diameter punch and a large hammer to peen the bulged metal back down. Although a "field" head space gauge still will still allow the action to be locked, the head space has been reduced enough so that the gun fires every time now.
In the past, Remington rifles have had a reputation for having a difficult bolt to operate. This was due to the bolt being made of steel and the firing pin being made of hardened steel. The firing pin would wear out over time, causing the bolt to become stuck in the back position. To fix this problem, Remington began producing their rifles with a softer firing pin, which could be easier for the user to operate.To further help ease this problem, some Remington owners started filing down the sharp edges of their firing pin. By doing so, they were able to get more “bite” on the firing pin and make it easier for them to fire their rifles.
Contact for work at Heardle - DCL Group