View Full Version : How to fill in holes on a receiver
02-29-2004, 11:59 AM
In putting together my screw build I find that te holes in the Vulcan receiver are off enough to really mess the the proper function of the bolt carrier group. The rear of the trunion is about 1/8th of an inch too high. Unscrewed the trunion will fit and the rails are inline with the trunion. The receiver is a Vulcan.
The question is do I have to use a mig welder or can I braze the holes closed and then redrill the holes.
Any other options?
02-29-2004, 12:58 PM
I tig welded the holes on mine, then ground flush.
02-29-2004, 04:50 PM
braze the trunnion in place, or mig weld it after drilling the holes out to .250
grind and polish flush, and you have a unique gun. i have stick welded the lower rails into a few receivers, but will be silver soldering them in from now on. will be silver soldering, brazing, or welding the next gun together, as the mood strikes me.
02-29-2004, 04:58 PM
braze the trunnion in place, or mig weld it after drilling the holes out or welding the next gun together, as the mood strikes me.
I assume you have had good luck with silver soldering rails? I have seen the question raised but never completely discussed. Do you do anything out of the routine to get a better solder? Perhaps you could run some of us through what you do. Thanks!! :small_gri
03-01-2004, 12:51 PM
get good quality eutectic cadium free silver solder (what is used on comercial kitchen stainless) coated rods in 1/16" diameter at your welding supply house, and brighten your surfaces with sandpaper before assembly. the flux on the eutectic rods are so strong that a preclean is not so important, but a good idea. maap gas will make this 1150* solder go fluid. get your parts up to a dull red temp and touch the rod to the base metal, brightening your color till it flows. this is just like brasing with a coated rod and oxy/acetylene.
when soldering sheet metal have the parts clamped in place to prevent them from warping under uneven heat. the capillary action will draw the solder in between the closely held surfaces, and has a bonding strength equal to 20KSI. much stronger than screws or rivets, and no need to grind plug welds. the flux is very acidic, so a clean up with warm water after air cooling is important.
Not to rain on your parade, but heating up the receiver enough to melt silver solder should also dramatically effect the hardness of the steel. Silver solder melts around 1250 to 1370 deg F. The temper (hardness) of the steel around the pivot pins is important becuase these will tend to "wallow out" over time if the steel is not hardened. Also, you'll tend to get less support from the rails. After silver soldering and air cooling, the steel should return to the annealed state. Unless you reharden the holes and rails, you may experience that excessive wear.
There are some low temperature brazing filler metals which may work, but I know nothing about them, or how strong they are.
All that said, we probably don't subject the reciever to enough stress to cause any real problems in the short run. But I'd keep a close check on the pin holes to make sure that they remain close to their intended sizes.
03-02-2004, 07:38 AM
When I assembled my screw build I was able to use the holes as-is, and egg-shaped them to draw them into the right spot. Clamp together, tap them, and you should be set. Most all people that use these usually end up having to dremel down part of the magazine retaining lever, otherwise the mags won't fit into the mag well. A small issue that is easily resolved. That topic's been touched many times on the other forums...
Pics of the finished deal on my site here:
I can't in good conscience recommend silver solder in place of rivets or screws... Good Luck on that endeavor.
03-02-2004, 11:33 AM
clamp a copper block against the insde of the receiver, right behind the hole.
tig or mig weld the hole closed with mild steel rod.
grind puddle weld flush with outside wall of receiver.
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