My dad and I are building a 6.5 caliber AK. This has become one of his pet rounds and we've talked about it so long I just want to see if we can do it :)
He wants to base the build on a PSL style rifle.
While the Swedes did have a BAR-styled MG, the magazines are simply impossible to find. So we had to research a suitable replacement. We determined that his particular load - using 100 grain bullets - would work in a .308 magazine. However the most ubiquitous load uses 140 grains, and some load even larger for extreme long-distance shooting. Therefore we are going to attempt the use of French 7.5mm LMG (25 round!) magazines as they are slightly longer than .308. 8mm magazines are simply too long and cause rounds to tilt in the mag.
Parts are mostly from a Yugo M70 kit and various PSL parts we scrounged.
Current Status is that the rifle fires and feeds from a modified magazine.
Calculated 6 US-built 922r part requirement for the build:
We used a Mauser barrel which is already chambered. We profiled it into the PSL profile. The barrel profile was too thin in the front for the Yugo front sight. I had an old 3/4" bolt that we used to make a sleeve and thread adapter. The barrel was uniformed to .560".
- Bolt Carrier
Added a bolt and carrier extension to accommodate the converted 7.5mm mags. Comparing to the PSL, the 7.5mm mag is longer still. I used a block of steel welded on the end to extend it the extra 1.6" the mags require. The final bolt carrier is not as heavy as it looks! I may lighten it some more based on the newer bolt carrier designs.
Of paramount importance was the hammer spur (unsure if that's its actual name) on the end of the bolt carrier. Its purpose is to prevent an out-of-battery discharge in the event the disconnector does not disengage the hammer. I messed mine up a little as it isn't centered perfectly, but it DOES contact the hammer which is what is important. If the disconnector does not disengage the hammer, the firing pin won't be contacted until the locking lugs begin to engage the trunion.
I used a length of an actual machine bolt, drilled it out larger to accommodate a firing pin spring, and put a step on the front to interface with the end of the Yugo bolt. The end of the Yugo bolt was notched for the step and welded together. The step helped me keep it centered much better than just butting the two pieces together. Lastly the notches for the ejector were machined in. Test fired successfully.
- Firing Pin
You'll notice that the firing pin is just a long length of steel tapered at the tip. I left the end of the pin larger to allow for the firing pin spring. I used small sections of spring to adjust the pressure so it would not be SO hard that it could cause weak primer hits. It works really well! I also had to notch the rear stock trunion to allow the longer pin to install properly.
- Recoil Spring
The recoil spring retainer has a piece of tubing welded to it to let a normal AK spring work in the longer action. It is about 1.7" long. Others have lengthened the end of their piston to do the same thing, but I am using a factory PSL piston and so this was the easier route. I made sure to remove it from the spring before welding so as not to weaken the spring!
- Top Cover
Since my receiver and RSB configuration is slightly longer than the PSL (since I'm using AK parts) I had to weld two top covers together. I have plans for the other top cover so it isn't a total waste.
There isn't a convenient way to clamp both pieces together for welding... I used vise grips and a drill bit to keep the pieces aligned. It worked! Sanding them smooth is a real challenge.
I used my old Galil AR bipod. Custom extension built from a chunk of steel then welded to the RSB. Notched the handguard to match.
The bipod is intended to be stored captive in the Galil handgards for carry purposes, but I could not use that design with the PSL handguards. I welded the area of the body where the arms are in the "carry" position and notched grooves so that the bipod will stay fixed in place. You must squeeze the bipod arms to move them to the "open" position. It keeps the bipod from flapping around when carrying it!
Again from the Galil parts I had laying around that I won't ever use. Attachment point is modeled after the Valmet squad support model's carry handle... just welded to the side of the rear sight block. I will install a 2nd cross-pin on the RSB to strengthen the area.
The 7.5mm magazines work with a bit of modification. Had to hammer the feed lips down to gain more purchase against the rounds. The extra surface area helps, and the lips are now long enough to hold the round until the tip enters the chamber. This seems to have eliminated the stovepipe feed problems.
The follower tilts rather easy, so I welded an arm to the back of the follower. This seems to have eliminated tilting problems altogether, even with the shorter rounds.
Here you can see the before and after pics of the feed lip mods:
Adjustable Gas Port
The adjustable gas port was easy due to the use of the Yugo M70 front end parts. I simply drilled divots at regular intervals between the "1-0" positions of the grenade launcher shut-off for a total of 5 settings, counting the shut-off position. Doubtful he'll ever need to use the "0" position but it could prove useful.
The indicator is a piece of cut-off saw blade that I shaped on the grinder and dimpled the tip to mate with the relief divots. I stamped 0-2-4 only because it was somewhat crowded with the size of stamps I have.
The indicator is pretty snug! I welded a ring to the right side so a bullet tip, screwdriver, etc. could be used to adjust the settings.
She runs! Took a little tweaking on the magazine feed lips, but it works great. In the 2nd pic you can see the ejected bullet flying past the ammo can :)
We are going to Duracoat the finish and I think refinish the wood with a conventional wood finish to replace the original shellac. Dad is going to get a standard reticle scope - that's my scope and he can't have it :)