Hi all,
my favorite gun - the Otto Bock 1939 made Over/Under Combination gun with a .222Rem barrel insert in the 16bore shotgun barrel -
needs major firing pin rework.
Some time ago I noticed 'cratering'of the .222 primers which made it difficult to open the gun after firing.
On a closer look I noticed that the firing pin hole was worn out and there was quite a gap which produced the cratering.
a few months ago I made a bushing and a new firing pin
bushing: 5mm dia 5mm deep (on the deep side)
friction fit (freezer overnight)
the (top) firing pin on this over/under sits at an angle which makes things more complicated
approx 25-30 deg. up from horizontal
and approx 10-15 deg. from the side
machined at the correct angle, press fitted the bushing, filed the thing flush, new firing pin - went to the range: beautiful! no problems - firing pin in center and no cratering.
3 months and a 100 rounds later the bloody thing worked itself loose!
The hammering must have worked the metal and it nearly fell out.
The options - as I see it (and keep in mind that I am not a qualified gunsmith - just fairly handy with a lathe and milling machine) - are as follows:
a) use the existing bushing and secure it with a flat head screw on one side - or
b) make a proper, T-shaped bushing with a thread and two holes for a 'bushing tool'
solution 'b' is what appeals to me - one problem is that I need to watch the depth of this angled 'job'
as the workings of the 'Greener' crossbolt are very close behind a T-bushing (outside dia 8 or 9 mm) which at the deep end of the angle will be approx 6mm deep.
The other thing is that on a 6mm or 1/4" thread I will only have about 3mm or so of thread (provided I can find a proper bottoming tap -
the thread on the bushing I can do on my lathe
-needs to be a very fine thread
40 tpi on the 1/4"
or 0.5 on the 6mm I think ?
should I harden the bushing?
silver steel = harden/temper or
mild steel = case harden (with the powder)
I can do either
What say you?
I will post pictures as soon as my camera battery has recharged
best regards
Günter (England)
NRA Life 1974
Last edited by Gunter; 06/10/14 03:29 PM.
