Rebarreling a Yugoslav M48A Mauser in .308

hi guys thanks for tuning in to gun lab today we have a cool project lined up what we're going to go ahead and do is reburial a Mauser we're starting with a rifle like this this is a Eunice love in 48 a Mauser it's in pretty nice condition overall but the bore is trashed it's totally shot out so what we're going to do is strip the rifle down we're going to take the barrel off and we're going to go ahead and replace it with a really nice new 308 stainless steel barrel so follow along and let's get started we'll go through the whole process with you so the first step of course is to take the barrel action out of the stock we've done that and about half an hour ago I sprayed some spray lubricant some wd-40 onto the intersection of the receiver in the barrel and just let that sit standing up and now I think we're ready to give the try what I'm going to do is use these two aluminum blocks along with along with some abrasive grit abrasive mesh this is the sort of thing that you use when you're soldering for example to clean up a copper pipe and I just took one strip ripped it in half and I'm going to put one piece in each of these blocks and then drop this over my barrel that gives me a nice square surface to hold on to the round bar alright as you can see we have the the barrel set here in our hydraulic press I'm going go ahead and tighten that down it's important to note that we are clamping on the barrel not on the action these things can be a real pain to get off some put a lot of pressure on that now we have a two-part action wrench here this u-shaped piece slips over the ring of the rifle and then our crossbar goes through like that then I'm going to hit it with hammer generally a good whack on the hammer will break this loose just like that all right I hope you'll excuse the crashing noise as the receiver wrench fell off but that impact broke it free and now we can just unthread it the rest of the way and that is how you take the receiver and the barrel part on an old rifle all right now that we have our Mauser assembled and we have just a strip better receiver to work with we need to trim up the front of the receiver to make sure everything is nice and square and flush basically when we torque the barrel in we want to make sure that all the surfaces are mating on even parallel flat surfaces so that when we torque the barrel down to its final position we're not pushing it off in any direction so there are two specific surfaces of the receiver that we need to look at we need to look at the very front shoulder here and then we need to look at the inner shoulder back in here because those are the two surfaces that the barrel is going to meet with so we have a couple of tools that we put together specifically to do this our first tool is this it's a profile rod and it threads into the receiver we have the threading on here set so that it matches the barrel thread so we can run this all the way in until it stops there we go now this can be turned on centers in our lathe and that will allow us to turn the receiver nice and concentric without having to deal with lining it up in the four jaw Chuck so we're going to mount this in the lathe and then we're going to turn down just the very front face here until it's nice and flat all right you can see we have the tool mounted on the center's and faceplate of our late we have a dog on there to make sure that it turns appropriately when we come in and take a closer look at the face of the receiver we're going to be turning down this surface we have our tool set up here and we're going to do this in a couple of short passes to make sure that that we take nice thin cuts and only only take off what we need to alright so the next service we need to deal with is this inside surface where the face of the barrel is going to line up onto the receiver so what we're going to do for that is use another tool we put together here this is a two-part tool this is threaded to run into the barrel threads and then we have a brass removable brass plate there on shank so we're going to put a little bit of lapping compound on the face here we're then going to thread this into the barrel and then that allows us to spin that brass disc in the lapping compound on the inside face as you could see I've got some blue in there some marking blue and we're going to go ahead and polish it down until that's all nice and evenly disappeared alright there's a little bit of our lapping compound it doesn't take much go ahead not putting all that much pressure on this just enough to push it into contact with the back of the receiver in there a little bit more than will pull it out and take a look we still have a little bit more of the take out and again we're not really trying to remove material we just want to take out any high spots so that that inside face is nice and smooth and flat that's going to ensure that when we torque the barrel down we're not twisting it off in one direction all right guys we now have a nice uh that's polished inner surface there move on to our next step alright guys so we've got our receiver all prepped up and we're ready for the next step which is going to be cutting the barrel we have gotten our hands on this ar-10 barrel it was chambered incorrectly and so it's kind of useless as an arrow ten barrel so what we're going to go ahead and do is cut the threads off the end here we're going to rethread it up on this shoulder to fit our Mauser receiver and then we're going to reach hammer it so absolutely the most important thing involved in properly chambering and threading a barrel is getting it exactly concentric we want to make sure that the the threads that we're cutting are exactly parallel to the bore of the barrel and we want to make sure that the chamber we're cutting is exactly parallel to the bore of the barrel now on any pretty much any barrel there is going to be a little bit of Bend the bore is not going to be drilled perfectly straight so we can't just line it up based on the ends of the barrel because we know that barrel is doing this in the middle so what we've done instead is we've set it up in a four jaw Chuck take a closer look so this four jaw Chuck allows me to perfectly Center the barrel here and then on the backside of the lathe we have a spider and I put I made a little plug that sits over the end of the barrel because the barrel is not quite long enough to reach this end by itself and those brass screws allow me to hold the back end of the barrel right where I need it so at this end what I've done is set my dial indicator just inside the chamber and as you can see I have just a couple tenths of movement now that's a good start but what I need to make sure is that when I move the indicator into the barrel farther like so let's move this as far in as I can get it and we'll bring it back down now we want this to also be perfectly concentric you can see I've got right about the same amount to play there what that tells me is that this chamber end of the barrel is lined up back here it may be going up or down or somewhere else but the most important thing is to have the chamber where I'm cutting the chamber and the threads to be perfectly concentric which it is so I can go ahead with the next step now which is going to be cutting off the existing threads and then cutting a thread relief groove up here so that I can cut my own new threads it's important to lock down the carriage when I'm doing this now this barrel is made of stainless steel so in order to cut properly I need to make sure that my cut off tool which in this case is just high speed steel need to make sure this is very nice and sharp and I need to have it perfectly level so that it doesn't try to climb over dig into the part and turn on the coolant and get going at the slowest spindle speed that I can manage there we go alright so the next thing I need to do is cut the threads to fit my receiver I can take a depth micrometer here and measure down to see exactly how deep my threads need to go threads and relief groove and on this particular receiver that is 0.618 inches so I need that much space combined between my threads and my relief group so go ahead and move my parting tool over to the correct spot and go ahead and cut that relief group so I can cut the threads there we go there we go perfect now before we move on I do want to point something out here I indicated my barrel concentric to the inside of the bore which is what matters what doesn't matter is the outside of the board because it will probably always be a little bit different the outside of the barrel won't be perfectly concentric to the inside as you can see we have almost mm run out here just on the outside where we're pretty much perfect or within a few tenths on the inside now the reason that I'm pointing this out is because when I cut the threads I want them to be concentric to the inside so that when I thread the barrel in I'm threading the bore directly into the center of the receiver all right we're assuming you know how to cut threads here so what I'm going to go ahead and do is thread this section I'm using a carbide threading tool it's nice and sharp it'll do a real nice job on this stainless steel and I have a 1 in 12 pitch so I've got that set up on the lathe and we're ready to go all right so we're done with our threading this is now threaded all the way until it stops on the barrel this black line here that you can see you can see this black line indicates the top of the barrel so I need to rotate this thread the receiver on an additional one and 1/4 revolutions so first I have to trim up the end of the threads so that it will come forward that much then I will also need to trim this shoulder right here back to allow it because we want let me take this off we need this surface and this surface to lock up at the exact same time against the the two matching areas on the receiver so we're going to start by cutting back our thread face here and then we'll cut this back to match alright let's test fit our receiver again cut about sixty five thousandths off so this should go just about up to the shoulder on the barrel we're close we go ahead and use a set of feeler gauges to see exactly how much we have left it's like we have about 29 28 thousandth left there and as you can see we've done about a half a rotation so our receiver is now quarter turn past the top of the receiver so we have about 3/4 of a turn left to go we can do a little bit of math there we have a 1 and 12 pitch which means that one full revolution is 83 thousandths of an inch I need 3/4 of that tells me I have about sixty three thousandths still to go to take off of the inside threads and then this amount 63 minus the space I have here to take off this shoulder all right guys our threading is all done when I tighten this up just do a hand snug you can see I'm very close to having my top dead center mark meet the very top of my receiver this is going to require you know just a slight turn more that's probably between one and two thousandths of travel forward for the receiver on the threads and we'll do that with a big wrench to torque the barrel down once everything else is done there are a couple things that we need to pay attention to when we're chambering all right so this is my reamer holder and you can see there's a gap in there and this reamer will move I don't know if you can quite see that but this reamer has some play in the holder that's very important because what we want the reamer to do is Center itself in the bore as it travels that will ensure that it cuts nice and straight and to size as a matter of fact the reason that we have these AR ten barrels in the first place is because when they were originally chambered the the guy running the machine used a rigid holder for the the reamer and as a result the back end of the chambers was way too it was egged out it was too large and cartridges kind of wobbled around in there I have this setup in and my remark holder I have a four flute roughing reamer this is 308 caliber it's a 308 barrel of course and we're going to go ahead and run this in it's a very slow process we don't want to rush this we don't want to break the reamer we don't want to dull the reamer so I'm going to go ahead and use my same very low speed setting we will be running coolant on the reamer and let's get started I'm advancing this reamer really slowly and we're backing it out a lot to clear chips I don't want the chip to get stuck one of the cutting edges and start to score the inside of the chamber or start to make the whole thing we'll be following this with the finishing remark but I still want to be real careful with the roughing reamer all right we're just about done with the roughing reamer here I have one or two more passes through they did was use a live cartridge just lined up on top of the reamer and made a little felt tip pen mark on the body of the reamer itself so that I know roughly how deep to go I don't have to be very precise because like I said this is just the rapping manner all right we're going to call that good bringing that in here and now I need to change out to a finished room all right so I've got my finishing grammar in there this is a six flute where the roughing was a for flute and you can see right here I've made myself a similar mark just with a felt-tip marker and that I'm not using that for any sort of final measurement that's just the point where I'm going in before I start measuring so once I get there then we'll we'll start being real careful in measuring back and forth between passes so for now same process as the roughing reamer just going to take it real nice and slow and easy run coolant and pull it out to flush the chips very very often it takes very little pressure on the tailstock dial to and here I want to be really careful about not catching any chips under there cutting edges this is my final pass final tool all right so I've run our finishing reamer all the way into my stopping point so now I have to do my first test-fitting of the barrel I'm going to blow this out get all the chips and coolant out so in order to test fit our receiver we're going to go ahead and thread it on here now I pretty well know that the headspace is not nearly deep enough yet but we'll go ahead and put that there then I'm going to take my go headspace gage put that into my chamber and then I have my bolt body now I've taken out taken off the extractor and I have taken out the firing pin mechanism because what I want to be measuring is the distance I'm measuring the the lockup of the bolt face against the gage when the bolt lugs are fully engaged so I don't want a firing pin getting in the way I don't want the extractor getting in the way anything like that there we go now because the barrel isn't threaded all the way on the bolt will lock down nice and easily what we'd normally do is we'll leave the bowl unlock we'll thread the receiver all the way on and then what we want to do is check to see if the bolt flows and as you can see it will not it'll get to that point and stop so that tells me that my headspace isn't deep enough yet I need the bolt to just close on the go gage so in order to measure how far I need to go I'm going to unscrew this about a Turner to lock that down and now I'm going to thread it in again until I feel it stop and that's right there now I can measure with a feeler gauge the gap that I have left between the barrel and the receiver face and that will tell me how much more headspace and to cut the answer is right about 57 thousandths of an inch so I'm going to go ahead and cut 40 with my finishing reamer and then come back and make another measurement this will probably take me two or three passes is pulling the chips out so now I should have right about 17,000 left and I'm going to test fit the receiver again and see what it really is and now you can see that the bolt is moving farther forward but still not closing which is good it shouldn't yeah we'll go ahead and open unthread the receiver close the bolt and then tighten it down again that's right about snug now once again I'm going to use a feeler gauge to measure this space right here I do want to leave that with about one or maybe two thousandths so that when I torque down the barrel that presses right up nicely against the face of the receiver so we should be at seventeen let's start with a 17 gauge and that fits 1819 I may have missed measured the first time 20 all right a 20,000th fit some 21 does not so we have 20,000th here - the one or two that we want to leave so I need to cut another 18 I'm gonna do another incremental step this time I'll take 10 and that will leave me with just a couple left now up to this point I'm using the standard tail stock we have our dial indicator right here and this is what I'm using to to count how far I'm going to measure how how much headspace I'm cutting I'm going to do that again for this next 10,000 then after that we'll transfer over to a more precise measurement and I'll show you that in a moment all right you can see here we've got a little more travel but we're still not quite there again as expected so let's unthread this a bit close the bolt down and run it home that snug now start with 11 Levin just barely fits and 12 does not so I have 11 thousandths now I should say there is one other consideration we need to take into account and that is that when I torque the barrel down for a final assembly on the receiver I am going to move it 1/2 mm in which is going to tighten up the headspace so if I have the headspace just just perfectly on the edge of acceptable as tight as possible when I've got it hand fitted like this it will in fact be too tight once it's finally torqued in place so I'm going to go ahead and cut the full 11,000 and that should set me up properly for my final assembly all right I mentioned I was going to use a slightly different type of measurement for my very final cut which is where we are right now so what we have here is a plunger dial indicator I have a metal plate that's a torqued down on to my tail stop and then I have this plunger running up against it so it's got a magnetic base and it's not moving off this and what this does is as I as I run the tailstock and reamer in this gives me a very accurate reading of exactly how far I'm going so that's not necessarily important when I've still got ten or fifteen or twenty thousand the very last pass I'm gonna go ahead and use this right both is hand or the receivers hand tightened headspace gauge now this time I can predict that this will close with absolutely no resistance which it does affect if I lift the bolt handle up and drop it it just closes now as an experiment I'm going to go ahead and take a piece of paper which is about mm thick 3000 on my piece of paper wet it just a hair stick it to the bolt face that will increase now I have resistance which is perfect I can no longer drop the bolt and have it closed I have to push it home which tells me that with this hand fitted and my little piece of paper my head space is just perfect which means when I torque this down and get rid of the paper it will again be just about perfect so let's go ahead and do that I'm going to go ahead and use the lathe in its low gear setting as a resistance so I can torque this down and again I want to line up the little star on my receiver here with that line that I have marked so that the top of the receiver is lined up with the muzzle brake that's been cut in the barrel turning my barrel just slightly in the check so tighten it up that is just about perfect so let's try our headspace again brilliant now that this is torqued in place I have just a little bit of pressure when I close my bolt on the headspace gauge so that's it for the chambering we can go ahead and take this out of the truck now alright and here we go there's our finished product at this point we have our nice stainless 308 aar barrel mounted it on our m48 a receiver so we still obviously have to put together a stock or a chassis for this and a good trigger for it but we'll cover that in a separate set of videos so if you have an old shot out Mauser or other rifle that you've been wanting to read barrel hopefully now you have a good idea how to do it thanks for watching

Channel: GunLabDotNet

Views: 1,280,007

Rating: 4.8344889 out of 5

Keywords: barrel, change, Mauser, 308, threading, lathe, timing, receiver wrench, headspace, gunsmithing

Id: 1Ufes_zrZmg

Length: 33min 10sec (1990 seconds)

Published: Thu Jan 03 2013