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Offf work early today so spent time working on my pistol build

2910 Views 60 Replies 10 Participants Last post by  flintoid
I have built quite a few AK's out from kits. Both bent flats, and milled re-welds. In the time I have been doing it I have gathered quite a few spare parts. I was looking for something i hadn't done before that would be a fun gun to shoot so I decided to build an AK pistol. Today's project was cutting down a FSB, and fitting it as well as welding it to the gas block to increase my options for barrel length (since I am re-profiling a Yugo barrel to go into a Egyptian front trunnion with Egyptian barrel parts, and haven't cut it to length yet). Some dremel work, and fit up to this:

Some welding, and clean up to this:

Still want to clean it up a tad more before I blue it but pretty happy with how it came out.:headbang:
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Good job there. they look like they were originally made that way :)
That looks nice, keep us updated
Good for you! Nice to have a day off - haven't had one in quite a while :(

I did my combo gas block a little differently:

What I did basically was use the flat pieces as straight edges for alignment. It worked surprisingly well and it is not canted :) Fresh paint makes it look so much better ;)
Looks nice hcpookie.
Alignment on mine was also easy. Left the bayo lug , and cleaning rod holder attached to pieces to line up, and put a wooden dowel (made snug by wrapping with tape) through the hole the barrel will normally go into. Line up the cleaning rod retainer with the hole for the cleaning rod in the GB while tight on the dowel, and BINGO a good alignment for welding.
After it's welded I cut off the bayo lug, and cleaning rod retainer flush with the back pop out for the GB retaining pin.


Continued on the work today. Removed old gas piston, and installed new one.

Looking at about a 9" barrel (give or take 1/4") for this build thanks to the combined gas block/ FSB.
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Great looking combo. I have a kit that I am doing the same thing with. I was thinking about 8 1/2" for the barrel and make the other parts fit. Have one other kit to finish before I start that one.
Did final clean up on the carrier, and GB/FSB combo, and blued this morning.

Mocked up front end, and I'm looking at a 9" barrel for this build. Only gained 3/4-1/2" by combining the FSB, and gas block but IMHO a fun project, and worth the time for a cleaner finished product.
Will be getting together with a friend of mine who has a lathe on Tuesday to re-profile the barrel (Yugo) to work with the Egyptian barrel parts.
OAL of the pistol will be 20 1/2" with Krink style cone or ~18" with slant muzzle break. Still unsure which I will use.
Which would you put on it, and why?

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looking good. is that a bulgy krink gas piston?
looking good. is that a bulgy krink gas piston?
It's an AK builder pistol length gas piston. I am unsure if it's the same length as the Bulgy Krink or not but it does work rather nicely for my build.
Found some more time after the kids baseball game this afternoon so took care of the gas tube, and welding shut the cleaning rod hole in the handguard retainer.
Still will need to file to fit once barrel parts are mounted so currently it's about 1/8" longer than what I believe to be the final length of it.

Wasn't happy with the silver solder idea so put a couple of tacks on the underside of the front retainer to hold it in place. Not concerned about them potentially being in the way of installing the wood as I am modifying a UTG quad rail to fit this build.

All patched up :)
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i never saw an builder gas piston except for image on the site. i noticed the short head. it put me in mind of the krink. i kind of worked backwards on mine i set the gasblock and had hotbarrel make my gas piston. on the upper hand guard i drilled the spot welds and moved the front retainer back to length needed . i didnt weld mine. the wood on one side and swedge on the other holds it in place. the crimps keeps it in time. works well enough for me. what size gasport are you going to use?
what size gasport are you going to use?
Good question.
Any input from those that have built an Ak pistol is greatly appreciated on that.

After some research into it I find for a 9 1/2" barreled Pistol build I'm looking at drilling the gas port at 3.5mm or 1.378".
Since mine should end up at 9"-9.25" this should work.
Nico, you mean .1378. The tutorials for a standard gas port say to drill it with a #30 drill bit, which is .1285. For a pistol do you need smaller or larger gas port?? I would think that less mass, would need a smaller gas port hole. My mechanical common sense (which is probably wrong) says to decrease hole diameter by the same percentage as the decreasing of mass in the piston. (20% less mass=20% smaller diameter hole.) I'm probably way off base, but I'm just sitting here postulating.
Good question.
Any input from those that have built an Ak pistol is greatly appreciated on that.

After some research into it I find for a 9 1/2" barreled Pistol build I'm looking at drilling the gas port at 3.5mm or 1.378".
Since mine should end up at 9"-9.25" this should work.
i drilled mine at 3mm and its runs great .some of it depends on how tight your rifling is. if you have compression loss you will have to increase gasport size to compensate, start small its much easier to increase then to decrease
Nico, you mean .1378. The tutorials for a standard gas port say to drill it with a #30 drill bit, which is .1285. For a pistol do you need smaller or larger gas port?? I would think that less mass, would need a smaller gas port hole. My mechanical common sense (which is probably wrong) says to decrease hole diameter by the same percentage as the decreasing of mass in the piston. (20% less mass=20% smaller diameter hole.) I'm probably way off base, but I'm just sitting here postulating.
lol that would be one big gasport. my logic is pressures are higher closer to chamber therefore gas port must be decreased to prevent over cycling.
my first attempt at a 5.45 pistol resulted poorly. gasport was too large and i thought the frigging carrier was going to blow out the rear trunnion it kicked like a 308. half way thru my first mag it stretched the rivets enough that the dustcover came unseated. i ended up with a 1.5mm gasport to get that under control. weld it over and redrilled. it took like 3 drill bits the weld was
like rockwell 50, it feltlike . long story short she's smooth now
Yes, sorry about that. I was meaning to say .1378 (darn tired fingers make mistakes sometimes).
I agree that starting small, and working up is the better method for sure than having to weld over, and re-drill (I'm gonna have to do that for the barrel pin hole already).
I think I will start at 3mm, and enlarge if need be for reliable function.
Thanks for the input guys. It's greatly appreciated.

In other news...........
Went to see my new friend Dan today to lathe the old Yugo barrel to the new profile needed for the pistol build.
The barrel wasn't the most concentric but Dan worked his magic on the lathe, and made it happen.

Next to the cut off portion I don't need:

I have also tapped all the holes in both the front, and rear trunnions. Mounted them in the receiver. Mig welded in the interior rails, mounted the center support, and fit the carrier, and bolt to the receiver.

Thanks Dan. I can only imagine what the barrel would have looked like if I attempted to turn in using my drill press.
Lady Luck is smiling on this build since I just met Dan at my local range last week.
Meeting a guy with a metal lathe, and the time (and willingness) to help me re-profile this old Yugo barrel for free couldn't have been better timed.
I'm gonna see what I can do to repay the favor.
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yea ak barrel's are not famous for their concentricity. one of my pistols was crazy looking when looking at muzzle leaned at least .0015 to to 7:00
position.. but i got it threaded good enough to keep bullet from hitting the
FH on the way out. your looking good . do you plan on riveting it after you get it running. i never heard of that receiver before.where did you pick it up at? you said you welded rails in. was it a 80% receiver? it is good to have friends. i would have wasted a lot of money learning on my own without the help of others. keep us informed
i'm anxious to see the completion and hear results of the test fire.
Coming along nicely Nico. Those old Yugo barrels are good for something, as long as you have access to a lathe and you know what specs you need. I think it's in someone's signature line here on Gunco: "It's metal, not magic". Great write-up too. Keep 'em coming!!
The receiver is a flat I bent.
Nico Armory is located in my garage :D
I learned to build out kits by reading tutorials on the web, and asking questions at forums like Gunco.
Couple things I had to learn by doing (like tuning a trigger, getting a magazine to sit properly without wobble, and high enough, truing up carrier impact to front trunnion, etc).
After doing 3-4 of them i had a pretty good idea of problem areas to look for, and how to set them up properly (basically tune the parts to your bent flat receiver, and check head space, repair FS, and GB cant, etc)before the first fire test.
The model designation 'FUCADOJ' I'll let you guess what the acronym stands for seeing as I'm in California.
Some funky laws here as well as the 'approved handgun list this state has but thankfully there are ways to still get what we want (with some minor concessions like a mag lock since the magazine is outside of the pistol grip, and for a pistol build I have to construct a magazine 'sled' to document it was built as a single shot pistol (to avoid needing to be on the list). No law that says I cannot convert it to holding more than 1 round after it's built though :) (max 10 rounds in this state). )
I have built every AK I own, and helped 4 friends to date do the same for their first builds.
This pistol is number 8 that I have had a hand in re-building.
Dan was just a guy I met at the range one day who was interested in my AKs. He mentioned he had a lathe, and I asked if I could rent it from him for this barrel.
He declined but offered to help me turn it down for free instead.
Cool guy, and like me into building things.
Gotten pretty good at bending flats, and fitting all the parts. I don't own any fancy tools or a 20 ton press so I do screw builds or re-weld milled receivers that have been cut up.
I haven't had any issues with any of them. A little JBWeld on the threads when you screw them in, and you're all good. If you ever want to remove them heat it up over 500 degrees with a torch, and the JBWeld softens up enough to unscrew them.
Don't own a spot welder but do have a 220 mig with shield gas, and over 20 years welding experience. Not that tough to stitch weld in the rails. Hard part is getting the torch head inside the receiver. Mag well is prime for this.

Found that the Egyptian front trunnion, and carrier did not meet up evenly on both sides when locked into battery. Spent a little time with a file, and a marking pen today to true it up.

A bit tired from work today so taking a break from the build but will be looking at pressing the barrel in, and setting headspace so I know about where to drill the barrel pin, and location for the RSB. Will press back out to either weld up the existing notch so I can re-drill it or (if it's close enough) I will drill for a larger pin. Also looking at threading the muzzle end for 14x1 LH (I have the die for it).
Also have to build the mag lock device for it (easy peasy with a piece of tube steel, and set screw).
I know the laws suck here, and that's one of the reasons I am an AK builder. I could just buy one, and have a middle man FFL add a maglock, and bullet sled to transfer it legally into my state. That lacks the fun of building it yourself as well as me exercising my legal rights to build one for my own use here while openly showing my disapproval to my incumbent elected officials for stupid laws, and piss off the liberals by staying within their rules but still getting what I want. :lildevil:

The last build I did was a re-welded milled receiver Yugo M-70 under folder (where i got this old barrel from as I replaced it with a new Green Mountain barrel).
That rifle shoots 10 shot groups at 100 yards with Wolf military classic, and me behind the sights that look like this:

I had most of the parts for this build just laying around after the amount I have constructed. Flat, and Egyptian parts kit + some other misc parts put the cost of this build at about $200. Far cheaper than I could buy a Draco, and for me tons more fun.
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Another short day of work for me today.
Rough on the paycheck but great for working on projects!

Pressed barrel back in, and found that the old barrel pin notch in the barrel was only off by about 1/100" for correct head space.
Soooooo close but no cigar.
Pressed RSB on while barrel was still installed, and drilled (left a tiny bit of margin for error since although head space was set the barrel pin was not in at the time.
Pressed barrel back out, and pressed RSB off barrel. Ran a weld bead on the one side that needed to be built up, and then file, and emery cloth back to smooth with the exterior of the barrel.
Re-pressed on RSB, and installed pin. There's a method to my madness as I used the RSB to index the barrel as I re-installed it seeing as now the old barrel pin hole could not be used.
Pressed barrel back in, and set head space. Then drilled new hole for barrel pin (actually only taking a bit off the muzzle side, and cutting through the weld bead on the other side), and installed.
I had already threaded the muzzle end of the barrel (last night) so next I modified the interior of the handguard retainer removing the pins that would normally slide into the notches in the barrel. Also modified the rear of the gas tube to clear the RSB (since now it's much shorter, and would wedge between the GB, and RSB if not modified).
Pressed on FSB/GB combo, and set distance off front of carrier piston when carrier was installed, and in forward position. Filed Gas tube to fit.
I had previously fit the carrier, and bolt to the receiver.
Now we tilt test it for cycle.
The new gas piston was a slightly larger diameter than the original one so I had to polish the interior of the GB until it cycled smooth. Also filed a bevel on the inside of the GB to assist in piston function.
Cycles smooth by tilting receiver 15 degrees both ways with very little side to side slop in the carrier to receiver. I had also fit the carrier to the front trunnion previously to ensure even impact. :)
Screwed on thread adapter, and filed a tad off the back side for a tight fit against FSB when locked into my custom FSB detent (retaining pin is on top not bottom since the port would have been too close IMHO to the hole that needed to be drilled for it had it been the other way around). Did the same for the Krink style cone I will use on this build.

Still need to drill gas port in barrel, and cut notch for handguard retainer as well as square up end of barrel, and cut a new crown. Also need to custom cut, and fit the UTG quad rail I will be using on this build.
After that I can focus on the receiver internals.

She's coming together nicely.

NOTE: For those that may be wondering the flat was marked 'Pistol', and has builder, city, and state, unique serial number, caliber, and model designation BEFORE it was bent into a receiver. It is on the opposite side from the side visible in the pictures.
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I had a bit of time after work today so drilled the gas port hole, cut, and trued the barrel end as well as cut a new crown on my barrel.

This weekend I will be very close to completion if not finished with this build.
Glad you guys are enjoying the ride like I am.
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