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Thread: AK.45 work (well, sort of...)

  1. #1
    Master Endmill Breaker Rhino_66's Avatar
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    Default AK.45 work (well, sort of...)

    I wanted to get something done with the .45 conversion, so I figured I'd go ahead and get the bolt and carrier mostly finished over the holiday.

    My first task was to open up the cup in the bolt to fit the head of the .45ACP case. I decided it would be easiest to open the cup to 0.500" with an end mill. The 0.500" cup will have just a little slop, but not too much.

    With the 16" Thompson barrel, there is about 0.150" of case sticking out of the breech. The depth of the standard AK bolt cup is about 0.130". If the cup is milled much deeper than 0.150", the firing pin hole will start getting larger, as you will be cutting into the taper of the hole.

    First, I clamped the stripped bolt in the vise. Because of the grooves in the bolt stem, I had to keep turning the bolt to get it to clamp evenly in the vise.

    Once it was solid, I centered the firing pin hole with the mill head using a drill bit. I know there are tools for this, but I don't have one... I tweaked the position until the bit would go into the firing pin hole without dragging or flexing. I switched the mill on and ran the bit straight down to the shank. There was no drag and the bit went in without so much as a squeak.

    I changed out the drill chuck and 1/2" collet for the 5/8" collet that fits the carbide end mill. I grabbed the 0.500" carbide 4-flute end mill and tightened it in the collet. I touched off on the bolt face to set for zero. A couple drops of cutting oil and the chips started flying.

    The carbide mills are an absolute necessity when cutting the bolt, it's too hard for high speed steel. I took small cuts and used plenty of oil. The cut actually only took a couple of minutes.

    I checked the depth and it was dead on, so I took the bolt out of the vise and cleaned it up for the test fit.

    Well, I should have looked at the actual dimension on the cutter instead of what was printed on the plastic sleeve. The cutter was not the 1/2" cutter I assumed. It was actually a 17/32" cutter! The hole I milled wound up around 0.530", way too big for the .45 case. Damn. It may still be usable, but it pisses me off that I didn't check the cutter. This minor fiasco ruined my mood for the evening, so I cleaned up my mess and packed it in.

    I may be able to use the bolt as-is, but it's a lot more play than I want. I could braze in a couple pieces of steel shim stock to take up some of the extra space. I may just use another bolt... Again, damn. At least I know how much trimming the extractor will need.
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    Gunco Regular Oldgunner's Avatar
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    Remember the old saying, ?Measure twice, Cut once.? Better get a new bolt; don?t trust your gun and your life to a make-do fix. If you don?t you won?t be happy later.
    "Moss Isley spaceport. You'll not find a more wretched hive of scum and villainy"
    (Actually this better describes Washington than Moss Isley)

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    Gunco Member spray & pray's Avatar
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    Have you considered using the bolt from a .308 saiga? I think I recall that the case head of a .308 is the same as a .45 auto. If it was you would be good to go with bolt-extractor-and firing pin without mods. Is a spring loaded firing pin important for your build - are pistol primers hard for non sring loaded pin use? I think that EAA sells replacement parts for Saigas, but they have a rep for being slow and unresponsive.

    s & p

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    Gunco Veteran Toten Kopf's Avatar
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    Another saying is, "We always have ime to do it right the second time". If nothing else, a valuable lesson was learned, not just for you but for everyone who reads this.
    The machining looks good otherwise.

    Thanks for posting this "mistake", I will remember it.

  5. #5
    Master Endmill Breaker Rhino_66's Avatar
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    Quote Originally Posted by spray & pray
    Have you considered using the bolt from a .308 saiga? I think I recall that the case head of a .308 is the same as a .45 auto. If it was you would be good to go with bolt-extractor-and firing pin without mods. Is a spring loaded firing pin important for your build - are pistol primers hard for non sring loaded pin use? I think that EAA sells replacement parts for Saigas, but they have a rep for being slow and unresponsive.

    s & p
    I'm going to be shortening the bolt by just under an inch, so that precludes me from using any standard spring-loaded AK firing pin. I considered using a spring-loaded one, but I'm going to have to shorten the firing pin by about an inch as well. The pin is going to be approximately the same weight at the Makarov firing pin when it gets shortened. The Mak pin isn't spring loaded, so I'm going to try it without a spring-loaded first. If it slam fires or dents any primers, I'll have to fabricate a custom pin.
    The most damning evidence is the truth.

    That which does not kill you, really really really hurts...



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  6. #6
    Gunco Regular tarawa's Avatar
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    Is this going to operate like a standard AK or will is be straight blow back?
    gtbehary........ ak builder, hack machinist, nuclear worker and violin huckster!

  7. #7
    Master Endmill Breaker Rhino_66's Avatar
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    Operation will be straight blowback. The bolt will be moved back (about where it is when you start to install it in the carrier) and will be repositioned to orient the stripper lug pointing straight down. It will be welded in this position. The bolt will be cut flush with the back of the carrier and the triangular tab on the back of the carrier will be removed.

    The cocking handle will be cut off and moved back so that it's flush with the face of the bolt. If the cocking handle isn't moved, the empty casings will bounce off the carrier back into the receiver.

    The gas piston will be replaced with a steel rod to add a little more mass to the carrier/bolt assembly. It will only be a small amount of added weight, but will help to delay blowback.

    The receiver will be shortened by approx 3/4". This is the amount that will be cut off the bolt stem. This shortening of the receiver will allow the back of the carrier to align with the hammer and function properly during firing.
    The most damning evidence is the truth.

    That which does not kill you, really really really hurts...



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  8. #8
    Master Endmill Breaker Rhino_66's Avatar
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    Got a new (used) bolt on the way and my end mills showed up today. I bought carbide and TiN 0.500" cutters (I'll try both and see what likes the hardened steel of the bolt). I won't get a chance to work on it this weekend, but next weekend should be a go. I've got a few more cutters on the way for some of the carrier mods. I've got a brand spankin' new trunnion and a pile of RPK barrel blocks waiting for me to get my arse in gear and get busy.
    The most damning evidence is the truth.

    That which does not kill you, really really really hurts...



    Gunco Member #21

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