RPD DSA receiver /Vector Arms FCG build how to
Since there is a dearth (hey 4thIDvet this word was for you) of information on this build and I have gotten numerous e mails from folk expressing the same concerns, I will attempt to document my build. I do not know if I am doing this right but between all of us I think we can figure it out.
This build will be on a Polish nonreciprocating kit sold by SARCO, a DSA receiver, and the FCG sold by Military Gun Supply (MGS) which comes with a set of extremely vague instructions that has Vectors name on them.
I chose to remove the gas block and sight from my kit as i will be using a borrowed lathe (his is nicer then mine) and the owner would probably not want me (a novice) in his shop swinging the eccentric and entanglement hazard mass. You dont have too and the instructions indicate leaving them on.
I used a chop saw to remove the bulk of material from the front stub to free the barrel. Then I used an air powered hand cut off saw (3" disk size) to cut the last little bit so I would not hack into the barrel by accident. I then used a hammer to knock the two halves apart. This took all of 5 minutes.
(pic of barrel)
Next I moved to the lower receiver. I removed the sear, safety, trigger and leaf spring per the included instructions. To remove the stock, remove the little cross bolt and then GENTLY tap out the stock with a soft covered mallet. The recoil spring that has been captive will no longer be restrained.
Place the lower in a vise and mill the 2 rear areas shown.
(pic of milling)
you want to leave the "middle finger" sticking up as it appears a FCG spring pushes against it.
(pic of sear in place)
Then using a 1/8" end mill clean out the front pocket in the trigger area. this is indicated on the plans.
If you try to put the lower on the upper receiver you will not there is about a .5" gap. This is one of those BATFE things so be sure to mill the LOWER to fit.
You will need to take about .080" off the right side and .241" off the left, unfortunately i lost one of my matching numbers on the lower to this operation. I also had to radius the back lower edge of the DSA receiver to get a tight fit.
(pic of gap)
(pic of lower rails notched)
Then flip the lower up on its left side (right side is up) and clamp. Locate the scenter of the safety hole and then using the 1/8" CENTERCUTTING end mill relieve the areas for the FCG pins. Then drill each hole .118" all the way through both sides.
(Pic of clamped lower)
BOLT CARRIER: After studying the drawings, stubs and receiver it appears the TOP of the carrier rail needs to be shaved. I know several people have commented the lower does but I just cant see it ass being correct with this particular set up.
RECEIVER BARREL WELL PREP:
I used an OLD smooth flappy to remove the heat treat scale. I would NOT use a new one as they can eat away metal pretty fast. Just go light here and it only takes a few seconds (literally) to clean the barrel pocket
Ok I chucked it up with the muzzle end through the jaws and used an old go-no go gauge to center the live end. I expected some damage to the go gauge but there was none. Perhaps this is a way for you guys to turn the barrel with out having to make an insert. Ok I spun the threads off then measured the smooth barrel where it will mate into the receiver. .9435" OD The receiver measures .9410 to .9420" depending on where it is measured. I LIGHTLY touched it with the lathe. Then chamfered (spelling?) the leading edge to a 45 degree bevel and eased the first 1/8" or so to .941" to help get me going. I also made sure I used a file to smooth where the old pin went so I would not have an issue there during pressing. I was concerned with how thin the receiver is where the carrier slides underneath so I took the barrel to .9425 to .9230"
Lubed it and the receiver with black oil and pressed it home with a 40 ton jack. Went smooth as silk.
I did not drill my barrel pin for 2 reasons:
1. I have miss placed my bolt
2. I want to be sure all is well and straight before installing.
Lay down a TIG bead as shown in the instructions
I will grind this down tomorrow to fit the lower
Weld in the Carrier cross pin:
Put it in the mill and remove .018" from the TOP of the rails.
Then remove ALL material 3.7" from the piston side down .018" ***this is NOT the dimension on the plans, this is what fit my rails****
Heres a better idea of what to shoot for.
all the shiny was removed.