Hopefully somebody can help me with this. The rifle is one of the Japanese made Mark XXII (??) semi autos(it's at the shop now and I forget the actual model name/number) that is box magazine fed. Sometimes, I can get at least 9 of the 10 rounds in a full magazine to fire, other times less with just a click when the trigger is pulled. Ejected rounds show a very shallow mark in the rim from the firing pin. When it fails to fire, I can withdraw the bolt just enough to cock the hammer without ejecting the unfired round and it will work on the second strike. I have tried a variety of ammunition with the same results. So far I have;
1. Put a new hammer spring in
2. Clipped a few coils from the firing pin spring and thoroughly cleaned out the bore in the bolt where firing pin is.
3. Set the shoulder in the firing pin back a few thousands of an inch to allow a bit more forward travel of the firing pin and polished the firing pin.
4. Removed some material from the hammer as I wondered if the hammer was striking the bottom of the bolt before hitting the firing pin. No material was removed from the hammer where it contacts the firing pin.
5. Added a slight radius to the rear of the bolt where it contacts the hammer to cock it when the rifle is cycling.
6. More thorough cleaning and have tried both wet lubes and dry moly lube.
None of these has changed the problem! One thing I do wonder about is a roll pin immediately in front of the hammer that restricts forward movement of the hammer when the hammer, trigger sear assembly is removed from the firearm. The hammer or pin show no indication that the hammer is hitting the pin during normal operation when everything is assembled but at this point, I am suspect of just about everything involved in the way this thing cycles.
This is the third time I have run across a problem like this - the other two times it was with two different High Standard semi auto rifles. I was unable to get them to work and told the customers the cost of repair would be more than the rifle was worth.
Anybody have any ideas on how this might be fixed?
1. Put a new hammer spring in
2. Clipped a few coils from the firing pin spring and thoroughly cleaned out the bore in the bolt where firing pin is.
3. Set the shoulder in the firing pin back a few thousands of an inch to allow a bit more forward travel of the firing pin and polished the firing pin.
4. Removed some material from the hammer as I wondered if the hammer was striking the bottom of the bolt before hitting the firing pin. No material was removed from the hammer where it contacts the firing pin.
5. Added a slight radius to the rear of the bolt where it contacts the hammer to cock it when the rifle is cycling.
6. More thorough cleaning and have tried both wet lubes and dry moly lube.
None of these has changed the problem! One thing I do wonder about is a roll pin immediately in front of the hammer that restricts forward movement of the hammer when the hammer, trigger sear assembly is removed from the firearm. The hammer or pin show no indication that the hammer is hitting the pin during normal operation when everything is assembled but at this point, I am suspect of just about everything involved in the way this thing cycles.
This is the third time I have run across a problem like this - the other two times it was with two different High Standard semi auto rifles. I was unable to get them to work and told the customers the cost of repair would be more than the rifle was worth.
Anybody have any ideas on how this might be fixed?