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Hey Pirate nice work...I'm not sure if I can get theese mods right with a drill and a dremmel,,I know, I know..very primitive But should I do these now or wait for weekend??

Now it is time to install the bolt block stud that prevents a FA bolt from being put into the
receiver. I measured from outside the receiver to the flat on the bolt carrier. the
measurement was .680", I ground down a 5/16" dowel pin to .580" for clearance and
radiused the top to clear the recoil spring. I tacked the pin in place to check the clearance
before welding it fully.

Now the receiver is ready to weld. I installed the feed cover to set the length of the receiver.
I also checked the length against the drawing. not all dimentions match, but the cover fits,
So I will work from that. The sttel plates align the sections and also hold in place copper plate
to back up the weld. This prevents weld filler from protruding inside the receiver.
In order to reduce warping and shrinkage I welded a pass on each side of the torch cut to close
the gap, then did another pass to weld the sections together. This gives good penetration and
eliminates undercutting at the edge of the welds.
I tacked one side, checked the alignment and tacked the other side. Then tacked the top
and bottom. As you can see in the photos there are some areas that will require a lot of
filler.
After the sections are tacked together and you are satisfied it is straight, make some formed
copper plates to fit in the bottom to back up the weld. This area can't have weld protruding
inside the receiver.

Superb pics Pirate !! What model/type welder did you get? Also, after the tack up, how are you getting the
copper in without removing the alignment bars? Are you sliding small peices in from the back?

THat camera really does the job !! Great pictorial !

Karb

The welder is a Harbor Freight TIG, I got it on sale for $199.00. In addition you need a regulator, $39.00, tungstens and collets, and a plug. It cost me about $400.00 for everything including gloves, rod and a shield. I am renting an argon bottle.

The copper plates are sandwiched between the receiver and alignment bars.

I have my receiver almost done, about 3 hours more to go. I will be finishing it on saturday. I built a simple fixture from unistrut and some nuts and bolts to align and hold the front and rear halves. I am waiting to hear from salt6 to see why I am unable to post more photos. as soon as I am able I will post the rest.

I suggest as an alternative to tacking it together and THEN filling the large gaps , try building up the individual sections while they are apart .
This method ...
1) gives you the ability to manipulate the torch into positions that are very awkward or impossible when its together.
2) lets you use a thicker backer bar early in the process so you can use a little more heat where the old meets new for good fusion.
3) makes it easier to grind and clean the prep welds , especially inside.
4) makes filling the small gaps still left almost fun .
After the large gaps have been filled then line the parts up and tack into one piece.
I've had good luck lining the pieces up with just a stupid string line and some patience.

Pirate,


Gave you more room.


Also posting this to the FAQ.


Steve

drooling idiot wrote:I suggest as an alternative to tacking it together and THEN filling the large gaps , try building up the individual sections while they are apart .
This method ...
1) gives you the ability to manipulate the torch into positions that are very awkward or impossible when its together.
2) lets you use a thicker backer bar early in the process so you can use a little more heat where the old meets new for good fusion.
3) makes it easier to grind and clean the prep welds , especially inside.
4) makes filling the small gaps still left almost fun .
After the large gaps have been filled then line the parts up and tack into one piece.
I've had good luck lining the pieces up with just a stupid string line and some patience.

I see what you're getting at Drool--Preliminary fill could help on spots that were severely torched out (being able to stick fingers through). Perhaps set up the reciever first...scribe original positions...undo and fill...return to scribed lines. This way, one would not loose the length setting if they built up so much the parts were pushing away. Lines for position.

Pirates brace bars not only line pieces up, but do alot of position holding when the connection welds are being made. Strings are good for checking... you can even lay a straight edge ontop the ratchet plate for the front and back alignment, but you really have to have that sucker Stable for the potential heat twisting that's about to occur.

Man, this looks like quite a process..........

I hope I can do it.. Though I'm not sure about the welding part, I think I can.. I only have (very little) experience with cheap arc welders. Gonna need to find someone to do the welding I guess.

Looking good Pirate!! Can't wait to see pics of her all finished up along with a range report!!! Wish I had my kit to look over while you're doing this too.. Do you have a model/part number for that TIG welder you got from Harbor Freight? I wonder if I could have it welded into a 100% receiver cheaper than spending the $400 you did on your welder..... I guess I'm just thinking out loud...

drooling idiot wrote:I suggest as an alternative to tacking it together and THEN filling the large gaps , try building up the individual sections while they are apart .
This method ...
1) gives you the ability to manipulate the torch into positions that are very awkward or impossible when its together.
2) lets you use a thicker backer bar early in the process so you can use a little more heat where the old meets new for good fusion.
3) makes it easier to grind and clean the prep welds , especially inside.
4) makes filling the small gaps still left almost fun .
After the large gaps have been filled then line the parts up and tack into one piece.
I've had good luck lining the pieces up with just a stupid string line and some patience.

1. if you build up the edges it is a lot more work, and you introduce the potential for more error.
2. the purpose of the backer is to prevent oxygen from reaching the back of the weld and to support the weld.
It doesn't have to be thick copper, the thinner the better as it is easier to bent to fit corners.
There are no Awkward positions, just rotate the receiver.
3. doing it this way lessens the amount of grinding.
4. by laying indivdual passes it gives 100% penetration with less heat..
I made a simple jig for alignment, will post pic's

Karbinator wrote:

drooling idiot wrote:I suggest as an alternative to tacking it together and THEN filling the large gaps , try building up the individual sections while they are apart .
This method ...
1) gives you the ability to manipulate the torch into positions that are very awkward or impossible when its together.
2) lets you use a thicker backer bar early in the process so you can use a little more heat where the old meets new for good fusion.
3) makes it easier to grind and clean the prep welds , especially inside.
4) makes filling the small gaps still left almost fun .
After the large gaps have been filled then line the parts up and tack into one piece.
I've had good luck lining the pieces up with just a stupid string line and some patience.

I see what you're getting at Drool--Preliminary fill could help on spots that were severely torched out (being able to stick fingers through). Perhaps set up the reciever first...scribe original positions...undo and fill...return to scribed lines. This way, one would not loose the length setting if they built up so much the parts were pushing away. Lines for position.

Pirates brace bars not only line pieces up, but do alot of position holding when the connection welds are being made. Strings are good for checking... you can even lay a straight edge ontop the ratchet plate for the front and back alignment, but you really have to have that sucker Stable for the potential heat twisting that's about to occur.

By doing small areas at a time and connecting the parts it makes it ridgid. then by filling small areas it minimizes the heat and shrinkage of the weld as it cools and potential warping.

Here are photos of the rear section welded and rough ground with the feed cover installed
to check fit. The 2 holed in the bottom will need some extra attention and will be finished later.
It is a good Idea to test fit the parts as you go.

MauserMatt wrote:Man, this looks like quite a process..........

I hope I can do it.. Though I'm not sure about the welding part, I think I can.. I only have (very little) experience with cheap arc welders. Gonna need to find someone to do the welding I guess.

Looking good Pirate!! Can't wait to see pics of her all finished up along with a range report!!! Wish I had my kit to look over while you're doing this too.. Do you have a model/part number for that TIG welder you got from Harbor Freight? I wonder if I could have it welded into a 100% receiver cheaper than spending the $400 you did on your welder..... I guess I'm just thinking out loud...

If you buy the welder you can learn to TIG a usefull skill, and have the welder for other projects. Considering you are building a $4.500.00 gun it is not bad.
It is doable for some one with patience and some ability. It is a time consuming process but the reward is awesome!!

When I got ready to attech the front section I found that using the rails I made
wouldn't work, so I cobbled together a jig to align and hold both halves. All it is is a peice
of unistrut and 4 3/8" x 3" bolts some nuts and flat washers. I bolted the rear secton on and
then aligned the front and bolted that tight. It made the job a piece of cake.

With the sections aligned and bolted to the jig, I removed the trunnion and welded the halves
together. After welding, I rough ground the welds and fitted the trunnion.

With the trunnion installed I installed the barrel to align the front section. It didn't seem to
align properly so I tacked it in place and tested the barrel for free movement and checked
the over all length, it measured 37 11/16 which is supposed to be correct., so I finished
welding the front section.

Now the receiver is all welded, it is time to reconstruct the ratchet plate. I have opted to
do this rather than replace the whole plate as I don't have a spot welder and seems like
less work. I will clean up the area , grind the welds and put in a small section from a scrap
plate. This is where the brp cut pieces are usefull!

be sure and set the rec on the ground tripod this will show if you are correct length at the trunion are and to show if you are twisted or bowed

How about cutting a piece out of some scrap ratchet plate to replace the missing area? Just weld it in and clean up.


Steve