As you guys asked here is the details on making a semi auto 740/42 series a manual or straight pull action. I will try to describe it in detail guys.
OK the picture is not mine it came from the internet as did the exploded drawing from Numerich Gun Parts Corp. Look at the barrel after you take the forearm off you will see that block hanging from the barrel with the gas port faceing the receiver after you block the action open or use the clip to do so. See number 50 that is a set screw and number 49 is a small ball bearing used as a gas check. You do not have to take anything off the gun except for the forearm. Then you take out that set screw and hang on to it and take out that small ball bearing which may be stuck mine was a gentle nudge with a pick or small screwdriver will un-seat it. OK on that set screw you took out if you know the threads by having thread gauge or just know by looking great I forgot what the thread pitch was but it is a common one you can get at a hardware store and it is a common set screw with a Allen wrench head. OK after you take out the set screw and the ball bearing use a piece of wire or thin rod ect to put in the hole you took the set screw out of. Measure how far you have to go up into that hole to block the gas port and not go into the barrel. I put the wire on the outside of the block to see where it met the bottom of the barrel I then made allowances from the bottom knowing the set screw would screw into the block. Go to the hardware store and buy several longer set screws that you will figure will work. The ones I bought measure .379 on my Caliper and looks like 3/8ths long on a tape measure. I then took my dremel tool and with a stone or you can use a sanding drum work down 3/4ths of the longer set screw so it would fit into the hole. Roughly think of a golf tee with the wide part being the threads. If I remember right I had like three threads left after I ground down the set screw. This I screwed into the hole as far as it would go I then took the short set screw that was the original one and screwed that behind the altered set screw for more strength. Or you could just buy longer set screws than I did if they make them and have more threads on the bottom of the altered set screw. This stops enough gas from hitting the gas port that it does not cycle the action. I suspect if you wanted to you could also plug the gas port facing towards the receiver but I felt I did not need to since the action does not cycle this way. Put on the forearm and shoot it to see if your successfull. I was the first time around.
Milanodan after he read my first post on this wanted to try it with his 7400 so it would not extract as hard so he could find his brass easier for a softer gentler extraction. Last I heard he was inbetween where he wanted from full ejection to no ejection so he is making some set screws in between to get where he wants to be.
Leave the rest of the action alone all you have to do is block that gas port and then use the bolt handle to eject the shells. IF you wanted you could make a new forarm to fit the action block and work the gun as a spring controlled pump action. I thought about that but then found that the bolt lever on the bolt extracts the shells just fine. Either way would work and back in the early days one of the First Semi autos had a cut off valve on the gas port so you could use the gun semi auto or pump. I forget the name of the rifle but it was made in the early part of the century and had a fancy pump grip on it made of metal.
|
   
   
|
|
Reply With Quote
