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308 ak

49K views 321 replies 44 participants last post by  1biggun 
#1 · (Edited)
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#103 ·
1biggun said:
I am still working on this project. just wanted to move the post up as there was a lot of go info here that some new guys may have missed unfortunatly some of the info was deleted by people who left this site. my plan is turn the case heads down on the 308 brass and use the stock AK bolt diamiter and hand load this will prevent hot 60,000 psi 308 rounds from acidently being chamberd and possably blowing something up. also this would make using a romy kit possable I can control the pressures my self.
Brass mods seem like a ton of work.

Recommend to open up the bolt face - you can do it with a dremel, it really isn't that much to open up.

My (lathed) bolt pics are here:
http://pookieweb.dyndns.org:61129/AKM/AK_308/bolt_308.htm
 
#104 ·
I think the idea was to prevent accidental chambering of a full pressure 308 round. However, I agree that having to make such a mod for each piece of brass seems to defeat the purpose of chambering for a particular round, apart from the fact that dies can be had and loads developed more cheaply than for other wildcats.
 
#106 ·
Well, I moved this summer and most of my stuff is still in storage totes. I am in the process of running wire to my newly-built workbench and once I paint it, I'll be ready to start unpacking the "junk". :)

In fact, I have been spending most of my time on guns-and-ammunition.com so I've put the last update (just before I moved) there... in short, I managed to mod a G3 mag so that it engages like an AK (more like a Galil I think) and it works really nice. Lots of milling was done to the trunion.

I have now to mod the remaining 9 mags I bought :) Then sleeve the G3 barrel. Then press the G3 barrel. Then install the barrel components. Etc.
 
#113 ·
im lookind at machining some front trunions and bolts to match, that way you can get the lock up and the length right, but ive got sooooooooo many project i dont know how long its going to take me to get around to it

dont worry as soon as i start ill post everything
 
#116 ·
#121 ·
Today I did some measuring between a 7.62 AMD, 7.62 Romy, and a 5.45 Bulg. bolt lugs. The AMD and Romy were within .001 of each other so we will just call them the same. The 5.45 has the smaller stem then the 7.62. What I'll call the small lug is the one away from the extractor. The width and height are the same between them on either caliber. The difference is in the length. The AMD/Romy is .402 long and the 5.45 is .551 long. The large lug where the extractor is located is .611 long on the AMD/Romy and .720 long on the 5.45. The bolt face hole on the AMD/Romy is .458 and the 5.45 is .400. Both would need to be opened to around .475 for the 308.

Rbthntr64, does that sound like the measurements on the Vepr? Also didn't the Saiga 308 use a small stem bolt?
 
#122 ·
Math isn't my greatest subject either so, someone check these figures.

In the other thread 1biggun asked about bolt thrust at 42,000 cup on a .308 and 50,000 cup on a 7.62x39. I found a formula to convert cup to psi. Now this will only be a ballpark figure as there are +/- in both cup and psi. So hitting either end of the +/- could give different results. The formula is Cup x 1.516 -17902 = PSI. So, taking your .308 at 42,000 cup should be around 45,770 psi. The 7.62 at 50,000 cup should be around 57,898 psi. Now we need to figure the square inch we have touching the bolt head. The .308 is .473 inch across so, the radius is .2365. We take .2365x.2365x3.14=.175 square inch of area (I think). The 7.62 is .444 inch across so the radius is .222. So .222x.222x3.14= .154 square inch of area. Now we can take the psi x the area to find the amount of pressure on the bolt. For the .308 at 42,000cup/45,7700psi the force on the bolt is 8009 pounds. The 7.62 at 50,000/57,898psi the force is 8916 pounds. If we bumped the .308 up to 60,000 psi the force is 10,500 pounds. Now none of these figures take in to account the friction between the brass case and steel camber. These are just pressure figures at a certain pressure on a certain area.
 
#124 ·
Saiga 308 uses the small stem.Extractor side lug is the same as Bulgy 74 ~.720.The ejector side lug is .100 longer on the 308-.645.Most of that is a ramp to help rotate the bolt.Bolt face hole looks like .478.Bottom part that strips the rounds is the same as a 47 width/depth wise, of course the Saiga has the little (third)sorta lug projecting down off the rear left side .The Saiga bolt was ~.050 wider across the two main lugs with little reliefs cut into the lugs to clear the upper rails as it would have been to wide to fit the ~.980 width opening for the bolt carrier.It would not enter a regular AK trunnion until I milled off the .025 per side in a rotary table.
 
#126 ·
im going to talk with a couple of the engineers tomorrow at work and get them to do some calculations with the trunnions and bolts and see if they can come up with some shear numbers for the parts. ill post what they come up with asap, they do this stuff every day for industrial equipment, and i would put a lot of faith in whatever they come up with

then we can compare those numbers to the bolt thrust numbers we've come up with

has anyone tried to find out what kind of numbers the "strict european pressure tests" used in deciding the romy 308's couldnt be sold to the public
 
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