I am going to start by making it absolutely clear.... if you do not have good eyesight, do not have a decent "eye" for things, are not decent at basic math with fractions, do not follow instructions well, have no attention to detail, have no patience, and do not have relatively good hand skills, do not attempt the following procedure.... any of it. If you do have all of the above, PROCEED AT YOUR OWN RISK This type of procedure is not for everyone. If you have any doubt.... send it out.
This stuff isn't "rocket science", but Saiga 12 barrels are not easily obtained if you screw it up, and the potential for infringing upon NFA laws does exist when chopping barrels. 10 years Fed time is not my idea of a good vacation. Be absolutely careful and please check your measurements many times before you press forward. You have been warned.
This is not meant to be the "end-all-be-all" resource for these procedures. It is merely one way of many to do this. I certainly could do this on a lathe, but that doesn't do the average Joe a bit of good when he doesn't have access to one. I will try my best to keep the reading short and make this easy to follow (key word "try"). You guys can thank King of the Hill for this as he gave me that nudge that I needed to get going on this. I hope this inspires some of you to tackle a chop, crown, and rethread and do it with some degree of precision and quality.
ETA: EPIC FAIL ON THE "SHORT READING" PART. SORRY GUYS....
Assuming that you have enough sense to not start working on a loaded weapon.... lets get started!
How long is your barrel?
You need to figure out exactly how long your barrel is before you cut anything. I use a coated steel rod that is about 1/4" in diameter, but a cleaning rod, dowel rod, or just about anything that is ridgid and of small enough diameter to fit in the bore will do, assuming that it is long enough to go from the breech face (the forward surface of the bolt head which contacts the shell when a round is chambered) to beyond the muzzle (the end of the barrel). Insert the measuring stick into the barrel all of the way to the breech face with the bolt closed. Make sure it is not in the barrel diagonally and it is best to have the measuring stick resting on one side of the bore. Evenly with the end of the barrel, wrap a piece of tape around the measuring stick to mark it. Cycle the bolt and recheck this measurement a few times. If the bolt is not all of the way forward, you will get an inaccurate length measurement. Measure from the end of the stick that rested on the bolt face. If you have done it correctly, this measurement will be exactly what your barrel measures from breech face to muzzle.
How short can you go?
If you have applied for a Form 1 to manufacture an SBS and you have met all engraving requirements on the receiver of the weapon, you need to go with a length that is, at least, reasonably close to what you applied to manufacture. If you have no approved Form 1 in hand, the weapon needs to end up being LONGER THAN 18".
What are the average longitudinal dimensions of the threading on a Saiga 12?
From my experience, the threads are 1/2", and the unthreaded portion of the barrel at the muzzle is usually 3/8". There is a combined length of 7/8".
diy chop1.jpg 97.64KB 54 downloads
Now we move on to the "basic math with fractions"....
You now know the exact length of your barrel and need to subtract the length that you want it to end up being from that barrel length. For instance, if you barrel measures 19 3/16" and you want to have a 18 1/8" barrel, you will need to remove 1 1/6" of barrel.
For someone that just wants to lose the extra length over the legal requirement for a non-NFA shotgun....
19 3/16" - 18 1/8" = 1 1/16" (to be removed)
For someone who wants to do an SBS without moving the gas block back....
19 3/16" - 12" = 7 3/16" (to be removed)
To do this project, you will need the following tools and materials or some reasonably similar substitute....
Ruler or quality tape measure
Well mounted vise
Masking tape (not the blue stuff)
Hacksaw, Chop saw, or Dremel with a cutting disc (EZ-Lock system is recommended if you use a Dremel)
Bench grinder or Dremel with grinding wheel
Files (Lowes has a great Kobalt set and will replace them if they wear out or get broken)
M22X.75 RH threading die http://store.carolin...E-BARREL/Detail
Threading die stock handle for 1 1/2" die http://store.carolin...LE-SAIGA/Detail
Thread alignment tool (TAT) http://store.carolin...T-THREAD/Detail
400 grit yields a very nice semi-polished result
Some of what I used....
diy chop4 2.jpg 98.36KB 61 downloads diy chop14.jpg 75.83KB 27 downloads
You should have the length that you want to chop to figured out by now and you have the ability to calculate what needs to be removed from the barrel to achieve that length. Onward we go....
Mark the barrel where you want the new crown to be (I use a sharp pencil, but it can be marked with the edge of a file or whatever is not easily smudged).
Cut a strip of the copy paper, the short way, and mark the factory edge so you don't get it confused with the non-factory edge. It should be around 3-4" x 8.5". Have the masking tape ready to use for the remainder of this step. Wrap the piece of paper tightly (factory edge toward the muzzle) around the barrel about 1/16" or more further toward the end of the barrel than the mark that you made in Step 1 if you are not confident that you can get the crown right on the first try. Make that factory edge end up exactly on your mark if you feel confident. Make sure that each wrap of the paper lines up with the previous wrap (be sure it doesn't "spiral" around the barrel, not even a little). Secure the paper by wrapping it with tape. You should be able to move the paper a little to adjust it if you need to. Once you have it exactly where you want it, wrap the tape around the paper once more, for the full length, and let the tape wrap around the barrel a few times to keep the paper from sliding. Now we have a visual guide for the next step.
Before proceeding, see Step 2 of the Threading process. Depending on how much barrel you want to cut off, you may want to 'set' the die before the barrel is cut.
With the barrel well supported and padded in the vise, cut the barrel (with the hacksaw, chop saw, or Dremel) about 1/4" from where you want the new crown to be and save the threaded portion that you cut off. You will need it later if you have not already chosen to "set" the die. Grind the barrel back to just shy of the paper. I usually go about 1/32" from the paper (I am very confident in my ability to remove exact amounts of metal with a grinder and file). Go slow and cool the barrel often in water so it doesn't change colors because of the heat. Cooling the barrel will also keep the paper from burning. Do your best to keep the paper from getting wet. I spin the barrel while grinding and it yields a fairly even starting point for the next step.
It should look something like this....
diy chop2.jpg 71.13KB 50 downloads diy chop3.jpg 71.96KB 32 downloads
Using the paper as a guide, use a file to "fine tune" the crown. Take your time and file the crown from different sides of the barrel while checking how far you are from the paper guide. You want to end up very close to the paper (equally from all sides) without filing into the paper. Reposition the barrel in the vise multiple times if you need to in order to file from different sides. When filing is done from one side only, you will likely angle the crown, which is an undesirable result and could make starting the threads difficult.
Here is the file that I used for this step....
diy chop4 2.jpg 98.36KB 61 downloads
It should look something like this....
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Cut a piece of sandpaper about 2" x 2" (enough to wrap around the file with a lap). With the sandpaper wrapped tightly around the file, with very little pressure, sand the crown to perfection in a circular motion while changing the position of the file about 1/4 turn often. You don't want to just do it from just one position or there will be a "valley" in the crown. The object is to get this thing flat and show up the original Russian crown job
The paper wrapped around the file should look something like this....
diy chop7.jpg 102.37KB 37 downloads
The result should look something like this....
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Ideally, there should be a slight angle on the inside and outside of the crown, but without a lathe it would be very hard to do. I usually take that square edge off on the inside and outside of the crown by using my thumb and another piece of the sandpaper in a rotational motion. As with the file and sandpaper, change positions about 1/4 turn often. I usually go until my thumb hurts. This will polish the crown to some degree as well.
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The difference is not extreme, but it is a nice touch if done correctly. It should look something like this. Note the inside of the crown. The result is subtle....
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Remove the tape that laps from the paper to the barrel.
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Work the paper back from the muzzle exactly 7/8".
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Now you have a guide for where to stop when cutting the threads.
Before you start cutting threads, get to know the equipment if you haven't used a threading die before.
Note the 'flat' surface on the interior of one side of the die. This is the side that will go toward the crown as you start cutting the threads. Do not cut the threads with the other side of the die. They will absolutely not be nice and could turn into a nightmare.
Setting the die....
* If the die is like mine, it is adjustable. Back the adjusting screw out of the die one full turn after it does not apply outward pressure. Secure the die in the 'Die stock handle' so the knurled screw will be positioned on the part of the die that allows it to be adjustable (see pic in Step 3). With the die in the handle, run it onto the original threads of the barrel or barrel stub. Is it tight, but not so tight that it starts to cut the threads deeper? If it isn't tight, tighten the knurled screw and recheck until it is tight. If it starts to cut the threads deeper when you try to run it onto the threads, back out the knurled screw on the die handle 1/2 turn. Repeat as necessary until it is correctly adjusted.
diy chop17.jpg 71.69KB 51 downloads
Apply cutting oil to the TAT shaft and threads. Thread the TAT into the die until it is recessed beyond the inside edge of the flat surface noted in Step 2. If you insert the TAT into the barrel, there should be a gap of about 4-6 threads from the barrel crown to the TAT and the flat interior cutting surface of the die should be resting on the crown. Adjust as necessary.
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I will say it many times.... FLUSH THE DIE WITH CUTTING OIL OFTEN. I try to flush the die with Cutting Oil generously for every full turn of new threads cut. For every 2 full turns of thread cutting, I like to blast the die with Brake Cleaner then flush it with Cutting Oil again before more threads are cut. The cleaner the die is, the nicer the threads will be, assuming you do everything else right.
Wrap a rag or cloth around the barrel a few times and tie it to catch the cutting oil that you are about to go crazy with. You should now be ready to cut some threads. With the barrel pointing vertical and well supported in the vise, lube the die generously lubed with Cutting Oil, apply even pressure to both handles of the die stock handle and rotate clockwise 1/2 turn, rotate counter clockwise 1/4 turn, and then rotate clockwise until you feel resistance again. Repeat once. Flush the die with Cutting Oil to remove chips from the die. You should be able to spin the die back and forth a little and feel that you are starting to cut threads. From here on out, you will be rotating clockwise 1/4 turn, rotating counter clockwise one full turn, rotating clockwise until you feel resistance, and then repeating this process until you feel the TAT bottom out on the crown. This should be after you have about 4-6 threads cut and you should be able to cut threads without the TAT now. If you like, you can back the TAT out a few turns and continue to use it until it has been backed out of the die enough to become loose. Flush the die with Cutting Oil often. Don't be stingy with the cutting oil as your use of it can make or break how nice the threads are and whether or not they are actually functional. A bottle of Cutting Oil is much cheaper than buying a Saiga 12 just to get the barrel or sending one out to have it re-chopped and permed because you botched the threads. Flush the die with Cutting Oil often. Repeat the thread cutting and die flushing process until the die is touching the paper that is wrapped around the barrel at 7/8" back from the newly crowned muzzle. Flush the the die with Cutting Oil often.
If you prefer, you should be able to leave the TAT in there until you have about this much die above the crown, but it can be removed after about 4-6 threads have been cut. If it feels like the die is binding, you probably have the TAT bottomed out on the crown. Back it out and carry on....
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Die is touching the paper....
diy chop21.jpg 79.3KB 33 downloads
At this point, you need to back the die off a few turns and inspect the threads to see if you have indeed threaded all of the way to the paper that is 7/8" back from the newly crowned muzzle. If it isn't, cut threads as previously instructed until there are threads all of the way to the paper. you will also need to check the threads on the end of the muzzle by spinning a muzzle device on there. A factory barrel nut will do fine, but bear in mind that they usually fit a little loose. If the muzzle device will not thread onto the barrel (as if the O.D. of the threads is too large), tighten the knurled screw on the die handle to compress it and repeat the thread cutting process. Flush the die with Cutting Oil often.
You should have something very similar to this, at this point....
diy chop23.jpg 91.22KB 38 downloads
Assuming you have functional threads now, onward we go to my favorite part....
Now to remove the threads 3/8" back from the crown. Remove the die from the handle, blast it with Brake Cleaner, blast the newly cut threads with Brake Cleaner, remove the rag or cloth that was wrapped around the barrel to catch the oil, and wipe any excess oil off of the barrel. You can put away the Cutting Oil now, lol!
Run the die back onto the barrel with the flat cutting surface toward the barrel as you thread it on, just like when you were cutting threads. Bottom it out. There should be roughly 3/8" of barrel protruding past the die. If there isn't adjust the die until there is 3/8" of threaded barrel protruding past the die.
diy chop25.jpg 73.41KB 31 downloads
Now comes the second part where good eyesight and a good "eye" for things is employed. Using a file like in Step 4 of the Crowing process. File the threads off of the barrel at even intervals around the barrel. You only want to just barely remove the threads from the barrel (when the lines are gone, the threads are off).
diy chop26.jpg 53.3KB 34 downloads diy chop27.jpg 52.09KB 28 downloads
Continue to use the file to remove the threads from the barrel until it looks something similar to this....
diy chop28.jpg 62.26KB 34 downloads
Cut a piece of sandpaper small enough to wrap around a small flat file like this....
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From here on out, it is all up to your desired final result and ability to achieve it with your "eye". Take your time and do not apply a lot of pressure when sanding the marks out of the barrel that were made during the last filing process. After you get the last filing marks out with the sandpaper wrapped file, cut a piece of sandpaper that is long enough to wrap the full curcumference of the barrel. Do the final polishing by spinning the barrel while applying pressure to the wrapped sandpaper by hand. You should end up with something like this....
diy chop31.jpg 75.55KB 54 downloads
In the near future....
I may get around to doing the AK100 install tutorial. Please understand that my businesses are blowing up right now and I have to chase the dollar while it is there.
Spare time is at a premium and some TAC47 M.A.G.12 action footage and a full review will be next. I will be using it at 3 Gun this Saturday and hope to kick some tube fed ass! I hope to get some decent footage with the GoPro mounted to the weapon as well.
After my Form 1 for SBS is approved (including the amendment to 8"), I may be doing a step by step DIY tutorial for how to build an 8" SBS). It will be my first time, but I am confident that I can pull it of. The only things that I do not have figured out is the number of .093" ports that will be needed to cycle bulk ammo. I'm ok with my hands and extremely stubborn (like a young mule)
Edited by evlblkwpnz, 25 March 2012 - 01:10 PM.