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More work on .45ACP conversion.

8K views 34 replies 12 participants last post by  Rhino_66 
#1 · (Edited)
Well, since the Gunco WV shoot is next weekend, I figured I'd better get some more work done. This project has been simmering slowly for over a year and a half, so the heat is now being turned up! This project began in fall of 2003. A lot of early discussion with HCPookie, Vis, Geodykt, Daewoo, Golovko, U.S.M.C.Man, and a few others, helped me develop my initial design. A lot of that time was spent calculating the clearances and cut dimensions. A lot more time was spent using Photoshop and MSPaint to move portions of photos around to get an idea of what problems would evolve and what to do about them. Here's where I'm at, right now.

The gray paint makes it easier to see the areas that were machined. The raw machined surfaces wash out with the camera flash and are difficult to see.




This is the basic machining done to the bolt carrier. The cuts were made before any welding because I wanted to make sure all the interferences were accounted for. The cocking handle has been removed, the clearance slot for the bolt lug is cut, the ejection clearance cut is made, and the firing pin access hole is drilled. Portions of the cuts will be filled with weld once the primary machine work is completed. The rotation channel will be welded up and a notch for the cocking handle will be cut.




This shows the position of the bolt in the carrier. The bolt has been cut to the proper length. The triangular tab on the back of the carrier has been cut flush with the back surface. The bolt will eventually be welded into place.




This is a close up of the cut bolt and carrier. I considered filling the 2 upper bolt grooves with weld and reshaping the bolt, but I think I'll just silver-solder the back end and leave all the welding at the front...




This pic shows the clearance channel for the bolt lug. This is what allows the bolt to slide straight in before final welding. There are several large gaps that will be filled with weld and ground to shape before final assembly. This will allow for a more solid attachment, and prevent the possibility of cracking.

The angled cut for ejection clearance can be clearly seen in this pic. It's tough to see in this picture, but this is the bolt that I opened up to fit the .45ACP cartridge. The extractor only required minor grinding with a dremel stone to get the groove to match the cup diameter.

With the bolt in this position, the ejector lines up correctly with the slot in the bolt. The 7.62 ejector rail will work perfectly with the conversion.




This pic shows the hammer engagement with the modified bolt and carrier. The striking face of the hammer is perfectly flat against the back of the carrier. Because I designed this for blowback operation, the bolt cannot be positioned in the forward position. For proper operation, the bolt must be shortened, moved closer to the back of the carrier, and rotated. The bolt is shortened 0.800". Because of the bolt being shortened, the hammer will not make contact. My design calls for moving the trunnion back the same distance that the bolt was shortened. This will position the back of the carrier in line with the hammer face in the same place that the original bolt stem was positioned. Hammer function is smooth and the carrier easily pushes it back down to engage the trigger and disconnector.





I performed the alignment checks using a standard OOW receiver. This pic shows the carrier moved back exactly 0.800" from the postive stop of the trunnion. This lines the carrier up perfectly with the hammer. I will be using an IBE battle blank for the .45 receiver. The dimples in a standard receiver prevent the magazine from fitting into the receiver far enough. The thicker blank is a little easier to weld on, as well. By only shortening the receiver by 0.800", standard handguards can be used without modification.




This pic shows the carrier seated against the positive stop of the trunnion. When the barrel is installed, the breech face will be right up against the face of the bolt. This gap between the carrier and trunnion is unavoidable, because of the position of the bolt. The barrel will take up most of the gap, but I will add a small piece of sheet steel to the top cover to keep debris out of the receiver. It will also look a little cleaner. This gap is present on the Bizon, too. The Bizon top cover is stamped to cover the gap.




This is one modification that early on I realized was necessary after deciding to weld the bolt in the carrier. The firing pin retaining pin cannot be removed once installed, unless a clearance hole is drilled. Once the bolt location is determined, the clearance hole was marked and then milled. I used 1/8" carbide end mills for this step. I started with a ball end mill to make the hole in the underside of the carrier. Then I switched to a standard end mill to punch through the top of the carrier. The rounded surface inside the recoil spring tube prevents drilling through the material. The sharp corners of the mill bit easily cut into the curved surface and allowed the holes to line up without breaking a drill or screwing up the hole.



My next steps will be to fill in the carrier slots with weld, attach the cocking handle, and then permanently attach the bolt. After that is completed, I can work on the receiver and barrel. After that, I can work on the magwell and think about test firing. WHEW!!!!
 
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#2 ·
Thanks for the compliments, Cephus. I'm just a hack machinist. I have worked in various industries and my dad taught me more than enough to get by with the mill and lathe. There is still a LOT I need to learn, but I can muddle through for now...

I'm going to use M3 "Greasegun" mags for this. The Thompson stick mags have a couple issues that make their use a little difficult. The issues could be dealt with, but the M3 mags don't require any modification and are excellent feeding mags. They look like a Sten mag on steroids.

For a magwell, I'm using one of the magazine conversion kits for the MAC-10. There is a kit that has a magwell and catch that replaces the original one on the MAC. I'm just going to trim the height to get the feed lips lined up with the barrel and weld it to the receiver. There's a similar kit for the M11/9.

Winn hooked me up with some RPK barrel blocks, awhile back. Those will fit the .45 barrel easily. I have an RPK lower handguard for it. I'm thinking about having Z-Recto do a Polish laminated stock, pistol grip, and upper handguard to match it.

I'm going to sandblast all the parts and parkerize the whole thing. After that it's going to get GunKote, but I'm torn between satin black or the GunMetal blue.

There's a lot of work being done on pistol caliber conversions lately. Vis, jungp, jpglee1 (if he can get those welds cleaned up... :biggrin: ) and a few others have some irons in the fire. When I get this finished, I will put together a scrapbook of what went into my conversion. There are a few issues to deal with, but I think I have most of them ironed out.

I'm considering dropping the original recoil spring assembly and making a new one that uses 1911 recoil springs. That would allow me to tune the action by using different "weight" springs. 1911 springs range from 6 to 24+ pounds, so tuning the recoil should be feasible.

I won't get any more work done on it for a couple of weeks, but I am bringing the parts with me to the shoot.
 
#5 ·
Looks good! I wondered if you were going to put the firing pin hole into the carrier.

Question, since you milled off the rear spur, what are the chances of an out-of-battery discharge?
 
#6 ·
hcpookie said:
Looks good! I wondered if you were going to put the firing pin hole into the carrier.
Thanks! I had to put it there. With my luck I would have broken the firing pin on the first shot...

hcpookie said:
Question, since you milled off the rear spur, what are the chances of an out-of-battery discharge?
Only slightly more than the Bizon. The Bizon doesn't have the spur. Of course the Bizon does have the auto-sear to prevent hammer fall until the bolt is all the way forward...



I have to remove the spur. If it's left on, the hammer can't hit the firing pin.

Since I don't have an auto sear, there could be an out of battery discharge. But there would have to be a catostrophic failure of the trigger hook for that to happen. A double hook G2 trigger group will provide an extra level of redundency (also gives me 3 U.S. parts). If the hammer breaks, I'll just have to ride it out. The only way to ensure there would be no OOB, would be to install an auto... I mean safety sear. Kind of like what is on the Romak 3. Somehow, I don't think the Feds would accept that as a reasonable excuse.

That brings up another topic, the parts count...

These will be the U.S. made parts.

1. Trigger
2. Hammer
3. Disconnector
4. Receiver
5. Barrel
6. Magazine body
7. Magazine follower
8. Magazine floor plate
9. Muzzle device (if I make one...)

The bolt carrier and bolt have been substantially modified. Modified to the point that they will not function in the original firearm in their current state. The scuttlebutt is that if enough modification is done, imported parts magically become U.S. made parts. If so, I get 1 additional part for the bolt (bolt and carrier get welded into a single unit).
 
#7 ·
Cephus said:
I DON'T KNOW FOR SURE POOKIE BUT IT LOOKS LIKE THE CARRIER WILL STOP THAT ,
TAKE A LOOK AT THE 5TH PIC DOWN AND YOU CAN SEE THAT IT WOULD HIT THE BOTTOM OF THE CARRIER IF IT WASN'T CLOSED .
IT KIND REMINDS ME OF ONE OF THE OLD FALLING BLOCK .22'S IF IT'S NOT ALL THE WAY UP IN PLACE THE HAMMER WON'T HIT IT.

I COULD BE ALL WRONG BUT THAT'S WHAT I SEE THERE.
MAN I WISH I COULD HAVE BOTH OF YOU GUYS HERE FOR THE SHOOT
SEEING HOW I CAN'T SHOOT MUCH I'D LIKE TO PICK YOUR BRAINS
ALITTLE .
Ah you're right! OK that looks better now in my mind. I know this has been discussed before but safety always lurks in the back of my pea-brain mind.

Yeah I wish I could come too but I'm just not going to be able to do anything with this work project I'm on. With any luck it will finish up on or around May 15... BUT I'm hopeful that it could be even sooner. I want to have my Spring back.
 
#8 ·
Rhino_66 said:
That brings up another topic, the parts count...

These will be the U.S. made parts.

1. Trigger
2. Hammer
3. Disconnector
4. Receiver
5. Barrel
6. Magazine body
7. Magazine follower
8. Magazine floor plate
9. Muzzle device (if I make one...)

The bolt carrier and bolt have been substantially modified. Modified to the point that they will not function in the original firearm in their current state. The scuttlebutt is that if enough modification is done, imported parts magically become U.S. made parts. If so, I get 1 additional part for the bolt (bolt and carrier get welded into a single unit).
You know that's one of the great things about these conversions - you have so many US parts that you almost don't need additional US parts. I was doing the math on the Bizon and I think I'll have no problem with US parts, and will be able to use the original trigger group. That magazine really helps out.

What kind of muzzle device you looking at? I'm thinking that I can make that Dragunov-style flash hider with relative ease on the lathe & mill. I need to get one more cutter but everything else should be relatively easy to fab. Speaking of which, has anyone considered using a BFA as a starting piece for a muzzle device? It's already threaded & everything... if one put threads on the outside, presto there's an adapter. If you welded a pipe to it, presto there's a new muzzle device...
 
#11 ·
IF you are welding the bolt ot the carrier, HOW do you plan to remove the extractor/firing pin for maintenance??? I notice this is a common thread amongst pistol caliber conversions for AKs...I assure you THERE IS A WAY to NOT weld the bolt and carrier together with MINIMAL machnining...once fused you have NO way to maintain the parts. I know AKs are robust but still, it would royally suck to have to rebuild a bolt/carrier unit when all you need to do is replace an extractor or firing pin....

Your work looks very nice, I just am concerned with welding the bolt/carrier together... I didnt have to and it works very well. I have DSL now, PM me with your email addy and I will send some HI RES pics of my bolt/carrier so you can see the mods I made to allow them to float together as one unit but still be seperable. On my bolt you rotate it 30* to the right and pull it forward. The rails keep the bolt in position during operation. It is a very positive setup. IF you dont care and want it welded anyway, I understand. However, MY PERSONAL OPINION is that welding is a half ass way to do it. Just my .02 cents thats all...
 
#12 ·
jpglee1 said:
IF you are welding the bolt ot the carrier, HOW do you plan to remove the extractor/firing pin for maintenance???
Look VERY CLOSELY at that first pic...
 
#14 ·
hcpookie said:
Look VERY CLOSELY at that first pic...
AND the last pic.

The paragraph under the last pic clearly explains how I am dealing with the firing pin retainer pin. The extractor pin is not blocked in any way by the carrier.

Pantera, the machining looks nice because it removed all evidence of the butchery that took place earlier... I'm kidding (partly). I have spent a good portion of the last year and a half designing the conversion and then working out the machining cuts and setups.

I used carbide cutters for all the cuts. The carbide is perfect for working on the bolt. I didn't have to mess with the heat-treat/temper, so the bolt is still on spec for hardness.

After I finish this one, I'm going to make a bolt/carrier from a single piece of steel just like the Bizon carrier. I've got a majority of the cutters, so it's just a matter of laying it all out on paper and then writing job cards for the individual machining setups. I think I may use a 1911 firing pin for the next one to have the benefit of a spring-loaded firing pin.
 
#15 ·
Rhino_66 said:
I think I may use a 1911 firing pin for the next one to have the benefit of a spring-loaded firing pin.
http://www.tapco.com/product_information.asp?number=AK0616&back=yes&dept=192&last=



Note how the back is thicker - I think if we drilled out the firing pin hole about 1", you could insert a spring and be "done". You'd need something the size of a ballpoint pin, and about as stiff as a disconnector. We may be to find those from HD or Lowes... I know they some good compression spring assortments.
 
#16 ·
Ryan-- I'm impressed. You've come a long way with this!!

How did you figure sufficient mass for the blowback or is it a start with a heavy spring and work down?
 
#17 ·
Winn,

The bare AK carrier and bolt is approximately 16oz. I weighed a standard 7.62 carrier with the bolt and piston, but I cannot find the cheat sheet where the exact weight was written down.

When the grooves are all welded back up and the additional welds are made to the bolt lugs, there will be slightly more metal than was originally present. When I replace the piston with a solid rod, I will pick up about 3 more ounces. This will leave me with an assembly that is approximately 19.5 ounces.

Golovko posted these weights on that other board in the BIY I forum before it went to paid subscription access.

"A full-size open-bolt Uzi uses a 24.2oz bolt."
"A full-size closed-bolt Uzi uses a 22.8oz bolt."
"An open-bolt Mini Uzi uses a 19.2 oz bolt."
"A closed-bolt Uzi pistol uses a 14.4oz bolt."

My bolt will be a little lighter than the full-sized closed-bolt Uzi, but there are 2 springs to overcome. Those weights are for 9mm. An M1A1 Thompson bolt weighs right at 26 ounces, so it looks like the .45 needs a slightly heavier bolt.

I'm going to use a fishing scale to see how much weight it takes to overcome the hammer spring, the recoil spring, and then both springs together. This will be my baseline. If I need to go to 1911 springs, I'll just make up a guide rod and see what spring weight works the best.

The Bizon doesn't have anything screwed to the front of the carrier, so the bolt will be even lighter. There may be special recoil springs for the Bizon, but I don't have access to any replacements, and there's no way to know for sure what is used on it...
 
#18 ·
Rhino_66 said:
When I replace the piston with a solid rod, I will pick up about 3 more ounces.
Why not totally remove the piston, as with the Bizon? That will reduce parts count by 1 part...
 
#19 ·
Rhino_66 said:
Winn,

My bolt will be a little lighter than the full-sized closed-bolt Uzi, but there are 2 springs to overcome. Those weights are for 9mm. An M1A1 Thompson bolt weighs right at 26 ounces, so it looks like the .45 needs a slightly heavier bolt.

I'm going to use a fishing scale to see how much weight it takes to overcome the hammer spring, the recoil spring, and then both springs together. .
Ryan--I don't have a mac 10 but that should give an apples to apples comparison.
Wildman 43 on this board knows alot about those and may be a source.
Best regards and I'm happy those RPK parts found a good home.
 
#22 · (Edited)
Yeah, since there is no longer a separate bolt and carrier, the parts count drops by one. I think I'm going to buy that cheap TIG welder at Harbor Freight sometime in the next couple of weeks and get the pieces welded together. I just bought a 20-ton press and a set of taps, so my hobby budget is drained for a while

Every once in awhile, someone brings up the question about modifying a foreign part and magically turning it into a U.S. made part. Since I have made substantial mods to the things and it can no longer function as it originally did, I think I might have met this fabled condition. Parts count won't be an issue, as I already have 8 U.S. parts and my overall total is down to 14 without a muzzle device.

I am considering threading the barrel for a muzzle device. The muzzle end of the barrel will only be about as thick as a 1911 barrel once I turn it down to fit the Front Sight Block. I think I might make a threaded sleeve to slide over the end of the barrel once it's all assembled. That would allow me to have muzzle threads without weakening the barrel. For a muzzle brake, I'm thinking about a compensator like what was used on the Thompson SMG.

EDIT: Since there is no gas system, I drop the gas piston from the parts list too. That makes my overall total 13 without a muzzle brake. Can't believe I forgot about that...
 
#23 · (Edited)
Got a little work done on the barrel today. I turned the acme threads off the barrel and rethreaded it for 3/4-16.



After I got it rethreaded, I silver-soldered the sleeve on. Then I did some rough work on the lathe to check out the joint between the barrel and sleeve. I need to clean up the groove on the breech face. The groove is left over from the threads that I cut. It won't interfere with function, but it's ugly.



I still need to turn the barrel to the correct diameters for the RPK blocks, but I won't have time this weekend to get that done.
 
#25 ·
555th said:
Looking good Rhino. You think you'll have it finished by the time the August shoot comes around??
I'm hoping to. The barrel can easily be finished in a few hours now. The main thing will be getting the bolt finished. After that, I just need to shorten and assemble the receiver. Then I can install the barrel and then the barrel blocks. THEN I can do the magwell. After all that I can test fire it and tweak it. Actually there's only a few hours of work required to finish it.

Considering the amount of time I spent trimming the bolt and carrier, I could have cut a new one from a solid block (just like the Bizon). That is still an option, and I may do it just for practice. A new bolt would be easier since I wouldn't have to piece it together and weld up all the gaps.
 
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