Sw1ngK1ng wrote:I made a nice jig for welding mine up. I used a block of steel that I machined to fit snug in the rails. Both ends of the block were bored to except a 1in rod on one end and the buffer spring in the other. The 1in rod extended to the front bushing and had a sleeve that fit snug between the rod and bushing. The back of the block being bored for the buffer spring helped a lot in keeping it strait with the rails. Im sure there are better ideas for jigs out there but the more ideas the better.
A few things I messed up or did differently:
I accidentally welded the barrel bushing is a half rotation out of place and had to cut it off and reeled it so triple check that before welding. The cutout one the inside dose on the side that the barrel comes out.
I cut my charging handle hole too far forward and had issues with it falling out when racking the bolt so only cut as far forward as needed. If you do cut too much I welded a short extension to the end of mine to make it stay in.
When welding in my grip mount I welded it to where the grip wanted to sit with the cuts in the receiver, not where it has to sit with the recuperator which was an issue. If I build another I would drill the hole for the front recuperator lug after welding the receiver together then installing it so I can weld the grip mount in the right place. My fix was grinding a small amount off the back of the recuperator with was kinda scary.
The BRP grip is tough to work with because the trigger group is mounted too high and I had to grind too much off the hammer so I made my own. I used the diagram on their site and lowered the trigger pin holes .07in lower. plus its steel not instead of aluminum so it can take the same finish as the receiver.
For the buffer tab rivets I headed them with a torch before setting them, otherwise they are pretty hard. The rail rivets are smaller and not so bad.
One of my biggest regrets is not learning to tig weld until after I did all the welding. I miged all the receiver parts and they are not very strong, luckily they have been strong enough so far. I strongly recommend tig welding your receiver parts even if you have to pay someone else to do it.
The first time I riveted my rails in I didn't realize a spacer was needed underneath the rails inside the receiver. I don't have the exact measurement on me but make sure your rails are spaced properly before riveting, don't just check the receiver. I used .03in washers to space mine.
That is all I remember doing differently or wrong on mine. I may also be offering a bolt carrier hardening service in the near future since the welding required to make them semi-auto takes all the heat treating out of them.
Last piece of advice, measure 10x before cutting, 2x is still too easy to mess up.
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