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Thread: 8mm m70/76

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    Gunco Veteran jreifsch80's Avatar
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    Default 8mm m70/76

    hello everyon, I decided to start my own thread for my questions concerning my build.

    I decided I would try building an 8mm rifle with an M70 as my base, bought one of the underfolder frontend, bolt and carrer kits from cf, a few other needed parts, mags i hope to use and a new m76 barrel from orf. it's exciting when waiting for parts but i also knew the m70 barrel parts wont fit my m76 barrel without mods to either them or the barrel.

    first question, what seems to be the best option? moding my barrel parts for my thicker barrel or turning down my barrel for my parts? personally i would rather do a little of both but i am not sure i want to remove too much material from my barrel. what prodlems could i run into if i turn my barrel down for my reamed out m70 parts?

    second question, I have been deciding between a psl length receiver with a lengthened bolt and carrier or massaging my front trunnion and moving my mag forward and massaging my FCG a little if needed but that path i would want to use a standard length bolt and carrier. are there any safety issues with moving a mag farther into the front trunnion and how far forward could a mag move forward and still be safe and functional? also if i go the stretched route, is there a need to stretch my carrier as well as my bolt? or do i just need to lengthen my bolt and the piece on the end of the carrier that protects the bolt from early hammer strike (can't think of the name)

    finally, if anyone has any other issues i haven't addressed please let me know. as for 922 stuff I was thinking my us barrel, receiver, fcg and some type of us muzzle break or a us piston. i like making my own things and adding a little custom flair but safety, legality and reliability are all the first considerations.

  2. #2
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    Gunco Irregular TRX's Avatar
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    You'll find a lot of help in the 8mm, .308, and .30-06 threads linked from here:

    http://www.gunco.net/forums/f244/cal...ce-page-51901/

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    Gunco Veteran jreifsch80's Avatar
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    Default mags

    the mags i decided to try are going to work perfect. I decided to try out those 7.5mm french LMG mags that are dirt cheap from IMA (i bought the package of 4 for 20$ but now i'm tempted to do the 25 for 100$) after researching that french gun i read that the 7.5x54 was originally a 7.5x57mm round but the french shortened the case 3mm as it was so much like the german 8x57 that they would have misshaps with people loading german ammo into french rifles with horrible results. anyway if anyone is wondering about these they took only a little bit of massaging in fact the claw on the front was almost just right but a little thick also i needed to trim a tiny bit of the front top where the mag goes between the extentions of the trunnion on my m70 trunnion but that was easy and only took about 10 minutes with a dremel a little grinding, checking, cutting.... now that i fit the first it would take just a minute or two to mod the rest likewise. also if anyone is wondering the length inside the mag is 3.06 inches roughly and the outside length is right about 3.68 inches including the nice thick bolt catch. width is right about 1.01 inches so a perfect fit with the front of the mag well widened out the same as the main part of a normal mag well. depth being just about 7.35 inches. 25 8x57 rounds loaded without any problem the 26th wouldn't load (i wasn't sure how many would fit but i assumed 25) though with 25 in the mag the spring was pretty tight but i doubt an ak system would care.

    anyway by mocking things up for some rough measurements i looks like i will only have to lengthen my bolt by .75 inches also i appears i will be able to lightly shorten my trigger gaurd and change the pin location for my mag release and i think i might be able to use a standard length receiver and topn cover. that's without even moving the mag forward in the trunnion. I'll keep my fingers crossed also i might shave down the bolt catch on my test mag if i need a little more room as it's .5 inches shaving it in half would get the overall mag length to just under 3.5 inches. anyways things are going a little better than planned so i'm sure to have a misshap soon haha. if my camera hadn't been destroyed by my chocolate lab i'd show some pictures, mocking up is fun when things go right. though i still need to find a gas block around .75 inches and a romy rpk hand gaurd retainer otherwise i might just have to float the lower hg

  4. #4
    Gunco Regular Shadow Walker's Avatar
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    I believe the Saiga .308 has the magazine pushed about 3/4 of an inch into the trunnion. Using the Saiga trunnion as a model, I modified a M70 trunnion to accept the M-14 magazine. That was as far as I got.

    I drilled out what metal I could, and then used a dremel for the rest.

    Now that I have decided to build a 8MM Yugo using the M70 parts.....I am really looking forward to following your steps (and mis-steps if any). It is always nice to let someone lead the way when you aren't really sure which way to go.

    If you think I will be keeping a close check on your progress.........you are right. So...lots of pictures, please.

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    Gunco Veteran jreifsch80's Avatar
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    sure thing i'll try to give updates as often as i can, as far as the saiga .308 having the mag in the trunnion 3/4 of an inch is that from the very back of the trunnion where the mag is already a little between to begin with? or is that an additional 3/4 of an inch farther in the trunnion than normal? i guess i shouldn't say i'm not into the trunnion at all. I've massaged my trunnion just in front of the mag a little to tighten up the mag but nothing too serious, just a little light grinding at the bottom. looking at things i might not even need to shorten my trigger gaurd if i relocate my mag latch pin closer to the gaurd and cut a slot in the middle of the safely lever stop all so the bolt catch at the back of the mag can nestle it's self into the mag latch a little more snug. these mags might be about the tightest mags for this application but not sure i hope romanian surplus steel core ammo isn't much longer than my wolf gold i test filled my mag with haha though the wolf is a bit longer than most commercial ammo it's right about 3 inches. if anyone has some romy 8x57 i would love hearing how long it measures lol but i'm sure it would work or that i could find a way to make it work haha. so how long are m1 mags? also anyone know how long mg-13 mags are? long as in front to back that is. just want to see if there is something tighter than the 7.5 french in case i need it later

  6. #6
    Gunco Regular Shadow Walker's Avatar
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    The cut for the magazine stops .20 inch from the rear of the barrel. That makes the cut 1.10 inch long measured from the rear of the trunnion. While the cutout for the magazine lip is just .09 inch from the barrel.

    The .308 Saiga uses a standard length AK-74 style bolt.

    The front to rear length of the .308 magazine body is 3.10 inches. This doesn't include the magazine lip or the magazine catch part.

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    Gunco Veteran jreifsch80's Avatar
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    cool, thanks i think that would move my mag forward about a half an inch from where i am (i modified the mag to get it as far forward as i can) I set up the front mag claw to grab inbetween the receiver and front trunnion as that works best with these mags otherwise they would be too high (even with a new claw all the way at the top of the mag) i cut a little of the bullet retaining ears on the mag a little in the front mainly to help with feeding, might not be totally needed with a mag in the normal location but if i move into the trunnion it would be needed to allow the bolt to rotate and lock. i mocked things up roughly again and it looks like if i move my mag into the trunnion and massage the rear of the mag and mag bolt hold open i will be able to use a standard receiver and will not need to lenthen my bolt in fact it looks like the hammer will strike just fine though i still need to figure out where to put my cross brace and will probably need to massage my hammer to fit bit that shouldn't be hard.

    I'm such a planner i like mocking things up and taking care of potential problems if i can before doing most anything so i need to get a flat still haha anyone know how long till ak builder is ready to release his new yugo flats? if i have to i know a local gunsmith that has 3 tapco yugo underfolder flats he's been sitting on for ages and looking to sell i could always fill the underfolder holes and be in business.

    another thing i thought about was bending flat steel and making my own blank, cutting the front off where needed and grafting my blank to the cleaned up demilled front section that came with my m70 (it's fairly long and in very good shap) I've made some measurements to it and once i cut off the melted part from the torch it seems it's not warped but the torch might have made it brittle, I could always weld a partial home blank to it and see how it is even if i decide not to use it.

    another good thing is on my new m76 barrel the gas block and hg retainer (when i get one) will be almost in the same place as my m70 so i shouldn't have to lengthen my gas tube if i massage it right or if i do it would only need lengthening by about 1/8th inch at most but that might mean my piston needs readjusting, might have enough thread on it to back it out of the carrier and drill a new pin hole but if i needed to do that i might as well get a new us made one for another us part. i'll let you guys know how it goes.

    anyone ever make a new hg retainer from scratch? wouldn't be too tough i might give it a try also is there any thread here where someone makes their own gas block? i've searched but couldn't find anything. i'll probably make one when i have time just to make one but might not use it anyways. i was thinking a section of tube reamed to press fit on my barrel, another section of tube welded at an angle connecting my gas chamber. inside the gas chamber i'll have a sleeve that fits snug inside the gas chamber that i'll drill 3 holes of different sizes for adjusting my gas system all at 12:00 3:00 6:00 and the 9:00 i'll leave undrilled to have no gas to the system, then install a threaded ring the the end of the sleeve pin it in place or a few little spot welds so it stays for good, cut notches in the collar to tell me what setting i'm at and the gas tube will mount on the end of the sleeve like it would the gas block. that would fill the 1/8th inch or so gap i have between my gas tube and gas block and might work just fine. (from what i understand my home gas block would be kind of like an m76 gas block) i'll make my gas block angled so i can drill my gas port on my barrel with the block installed minus the adjustment sleeve. my goal is to have adjustments for romy surplus ammo, my commercial ammo i like and then whatever reload my rifle likes best. maybe it's overkill but that's why i'm building my own rifle

    I really wish max schmelling (my chocolate lab) wouldn't have destroyed my digital camera. maybe this weekend i'll get a cheapo camera to show everyone a few pictures (my wife has been wanting me to get a new camera for a while anyway). I'm not fancy (this is my first ak) but i'm meticulous, i research and plan quite a bit

    if anyone thinks of anything i might have missed so far or has ideas let me know.

  8. #8
    Gunco Regular Shadow Walker's Avatar
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    It looks like you are taking on a lot for your first AK build. I ain't that brave, or that smart.

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    Gunco Veteran jreifsch80's Avatar
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    haha yeah it is a bit of an undertaking but there is alot of info and help here from what i've found. also like i said i am pretty meticulous and i am a planning nut with my projects. not to mention if there is anything i don't feel comfortable doing on this build i have friends that are amazing with working metal that could help me and i have a gunsmith i've befriended ages ago that is an amazing fabricator (he specializes in ARs) also i sometimes bounce ideas off him and see what he thinks (especially with safty issues) I wouldn't mind sometime building an ak with an AR type gas system but am not sure how safe that would be. or an sks system wouldn't be too hard to make and i'm sure it's been discussed here. I'm excited to see how my rivets turn out, I'm going to heat the shanks and press them or maybe for fun i might get a harbor freight air rivet hammer (or even try using one of their 10$ regular air hammers with home made rivet dies) I love to tinker lol

    But anyway I'll let you guys know how things go and the new ideas

  10. #10
    No Hope For Me 1biggun's Avatar
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    Lots of Ideas and info on doing a build like this in the calibur conversion section here. . A old 8mm mauser barrel can be had pretty cheap under $40 or much less and then be turned down to fit you barrel parts BTW.

    Watch the pressures on surplus 8mm ammo as its a lot hotter than the Commercial stuff sold in the USA

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