Investarm O/U FTF

[red95gtcoupe]

I have an Investarm 20g O/U shotgun that I picked up not too long ago (cheap impulse buy). So far, the majority of the time I pull the trigger, it does not go boom. One barrel occasionally fires, but the other fails to probably 99% of the time. Below I included pics of the shotgun and a fired and unfired/dented primer. Does anyone have any clues on how to fix this problem? Would getting a stronger hammer spring, or shimming the current spring help? I figure I will never be able to find replacement parts so I would just have to search for a longer similar spring, or just shim it. The firing pins both stick out even amounts and what appears to be far enough, however, on the barrel that usually does not fire, the firing pin is able to be pressed back in a little with not too much pressure. Would that indicate a weak or short hammer spring that causes the light strike on the primer? I believe it is the top barrel that FTF most. Also, that firing pin is struck towards the top of the hammer, while the spring is low on the hammer, much closer to the hammer pin. Would this allow the firing pin for that barrel to be pressed back in easier due to the leverage it has (thus making it weaker). Hopefully the pics below will help explain what I am talking about.

Thanks
Brian

 

[navyretired 1]

Is it hard to open? The action of moving opening lever moves barrel locking block back which cocks the hammers and then placing safety in fire position places kickoff block under sears. The barrel of the opening lever uses mechanical advantage to move locking block back. You must remove this lever out of it's hole in breach, the lever is also a safety through which the firing pins move unles they have interference which is where I think your problem is with the light hit's on primers because of pins hitting the locking cylinder. Then when you pull trigger each sear should release a hammer one after the other. You should be able to see these actions with the locks exposed like they are. pull trigger while watching sear and hammer action. identify problem area and fix it.
I recently had one of these and every single function didn't do it's job. You couldn't open it which was caused by the opening and cocking block had no polish or taper at all for inclined surface on barrel block to push back to cock hammers as well as little silver pin that you can see on topleft of brach face was smashed and had to have a replacement spring and make a new plunger.Thats what made it so hard to open. When that was fixed I discovered that sear block wouln't go under hammer sears at all which prevented the firing at all. After that I had to time sear block so it set of one hammer before other and then on second pull second hammer fell. Hammer springs looked like yours and were plenty strong. I don't know how that gun had got out the door of a factory. The gentleman who owned it said he'd never even managed to open the gun let alone fire it. there were several other problems but they were easy to find and repair. Just function test and watch you'll figure it out. BTW those pictures are awesome I couldn't find any guidence at all in all my shotgun books.
I hope this makes some since as this was the first shot gun I ever had to redo the actioneer job over start to finish. The gentleman sure likes the shotgun now because for some reason he likes that you can fold it in half?