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Discussion Starter · #1 ·
So here is my question. I am building from a flat that has the center support hole drilled in it. THe rails have no holes in them. Do I weld the rails in then, drill through the rails to install the center support using the holes that are already in the receiver. Or do I install the center support then weld.
 

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Are you using an AK-Builder flat? If not, "Stop" and go get one... Slip in front trunnion and use old 5/32 drill bits to hold it in place while you figure out where your rails will be spot welded in. Make sure you heat treat the ejector tip prior to instalation. Spot weld the rails in, pull the front trunnion and drill your holes in the receiver through the now installed lower rails before you heat treat. After holes are drilled Heat Treat Axis Pin Holes with your MAAP, and then Install the Center Support Rivet. The rails installed during heat treat give the receiver strength, helps prevent "Hourglassing" of the receiver. The AK-Builder Center Supports are Pre-Heat Treatd, so this is why I install it post receiver being Heat Treated. Process after this is builders choice, but I pretty much build up the receiver from front to back after it is preparred. Front Trunnion, Triger Guard, Rear Trunnion, Press in & Headspace Barrel..... Good luck with your mission, if you should choose to accept it....
 

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Discussion Starter · #3 ·
They are ak builder. The holes have already been reamed and heat treated. The rails were also heat treated. Just wasnt sure what to do with the center support. Looks like i will weld the rails in then drill through the rails to install the center support. The center support is ak builder as well.
 

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speedracer211 said:
They are ak builder. The holes have already been reamed and heat treated. The rails were also heat treated. Just wasnt sure what to do with the center support. Looks like i will weld the rails in then drill through the rails to install the center support. The center support is ak builder as well.
Exactly right. The rails have to installed prior to the center support.
 

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speedracer211 said:
Rails should be slightly higher than the trunion and backed off from it 1mm?
On all of my builds, the rails are level with the trunnions. IIRC, I use a 5/32 drill bit as a spacer. Don't hold me
to that though, verify it for yourself to be safe...
 

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turbothis says 1/4th for lower rails. Read a post of his last night

Tx Dogblaster said:
speedracer211 said:
Rails should be slightly higher than the trunion and backed off from it 1mm?
On all of my builds, the rails are level with the trunnions. IIRC, I use a 5/32 drill bit as a spacer. Don't hold me
to that though, verify it for yourself to be safe...
 

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I do my rails based on the action of each rifle.
I use really strong magnets outside the reciever to hold the rails on.
The I put the BCG in and press the rails up as high as they will go at the back.
Then I slide the action forward until the bolt is just behind the front trunnion, and press the rails up as high as the will go there too.
I do this a couple of times to make sure nothing is diagonal, then I check for interference as the bolt enters and exits the front trunion.

Once all is well, I clamp with 1" c-clamps and start welding them in.

The reason I do this is simple: You want the rails as high in the receiver as they can be without binding the action, because then the magazines can go in as high as possible. This will go a long way toward preventing BOB (bolt over bullet) especially in the more finicky 5.45 builds.
 
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