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biy lower rails for .308

2K views 18 replies 5 participants last post by  muttman 
#1 ·
did or hase sombody made a guess as to ware the ejector should go I have the print off of hcpooikes page and the hook is 29.xxmm from the front end and this is too short to eject a non fired round. if I put the ejector at 50mm that should be close to were it needs to be right?

thanks muttman
 
#2 ·
I can check a little later today... to be honest, I hand-measured it so that a loaded non-firing round can be ejected, and compared that to my other rifles' ejector locations doing the same thing. I think I gave it an extra .25 inches, but I'll check to be sure. I just got back from a flight and I'm running a little behind.
 
#4 ·
Sorry for the delay.


A few points to make -

- I set the ejector back far enough that the tip of the bullet is just at the front of the locking lugs on the trunion. That gives adequate clearance, even if you're using a non-spec longer bullet.

- The ejector was made just like the AK-47 style ejector, same length to centerline, but only farther back.

- Note the top cover had to be cut away for the longer cartridge, otherwise it will hit it and possibly cause stovepipes. I left a tab when I cut it and will heat it and hammer the edge inward so that the final result is a rolled edge just like factory. For now, I have to watch it when I cycle the action because it is still sharp! :)

I didn't get a chance to actually measure it, but hopefully this helps you out:


http://pookieweb.dyndns.org:61129/AKM/AK_308/rails/100_0694.JPG

http://pookieweb.dyndns.org:61129/AKM/AK_308/rails/100_0695.JPG

http://pookieweb.dyndns.org:61129/AKM/AK_308/rails/100_0696.JPG
 
#5 ·
Here's a blurry pic of mine. I was going to measure it at lunch and forgot. I can measure it tonight and post in the morning if you still need it.

 
#6 ·
Hc does your build dent up the brass on the edge of the cover during ejection? I have had to resort to gluing a piece of vacume line cut down the center on my covers edge to save the brass from being dented. I didnt roll the edge and its not trimmed back very far. was wondring if trimming it back more would help or if it still hits . Im positive it is hitting the cover were it curves down. does the siaga 308's dent brass?
 
#7 ·
Yes, mine dents it but the dent is a very thin crease. I have not yet attempted to fix it, but the rubber hose trick is on the list, as I have no intention of buying a Valmet buffer. The crease is small enough that I can still reload it with no problem. I normally full-length resize anyway.

Based on other peoples' work with PSL ejectors, I would expect that you could modify the ejector enough to alter the direction of the ejection path, and therefore reduce the amount of force that it hits the top cover.
 
#8 ·
I forgot to mention that I had to modify the back end stem of the bolt so that the stem won't drag along the relocated ejector and cause misfeeds. It took some eyeballing to get just right. I hit it with the dremel until it no longer rubbed.
 
#11 ·
the vacume line on the cover edge works ok but it will wear out. I used 3m weather stripping adhesive to hold it in place after cutting away the rolled edge. about 500 rounds on the 223 it shows wear and not many rounds on the 308 but for now it is a solution but looking for a better cover modification. possably nylon or perhaps a differant cover design
what is the story with the valimet buffer??? have any picks does this affect case denting.
I need to come up with a solution before building my 260 rem. brass is pricey, the 223 dents I could live with but, even if you resize the dent is still there and it affactes case capacity and likely accuracy,
 
#12 ·
Here's the factory Valmet buffer.

Valmet Ejection Port Buffer

They are even more expensive on Gunbroker.


Note that the buffer is THICK. It attaches to the back of the ejection port on the top cover. I think it actually has a metal clip that snaps it on and keeps it there.

I have considered talking to BlackjackBuffers about making some of these, and he would need a sample of one to get started. I worked with him to create the Uzi and FNC buffers, and at taht time all he needed was a shape and thicknes. Perhaps we could just design one from scratch. A metal clip would be easy to find I would think from some place like MSC or McMaster. The thickness makes it "semi permanent" if you get my meaning.

For your application, you may want to see how it dents before investing in one. My dents are honestly a small crease about as wide as my fingernail, and they have reloaded and fired no problem. The 2nd firing tends to act as a fire form, and other than cosmetics it doesn't seem to be a big deal. Now if you don't want to tweak the ejector on your build (aka grind and reweld it) then a buffer makes sense.


 
#13 ·
First off, thanks guys SOO much for this info. I've been gathering it up for a while now for my own .308 project, and hopefully within a month or two will start on it(Thanks for the inspiration Pookie!!)

Would it be possible to use a standard AK47 ejector, but just set it further back in the reciever for shell clearance, or will a whole new ejector rail have to be made/manufactured?

My idea is to use a 20 in raw in the white chambered barrel blank from Numrich(got that already), and in some way make an adjustable gas system for it (maybe fal type, not sure yet), all the while wrapped into bullpup form. Will use FAL mags as a base, but G3 mag is a possibility as well(Again, thanks Pookie!)

Thanks again for all the advice guys!!
 
#14 ·
I would sure like to have one of those buffers to hold and and see up close.
i would also like to no what proflie the modifed ejectors have that some kick the shell out differantly. on the 223 varmit build I was getting severe denting/crease in the middle of the case. it was bad enough that I was afraid that the case might rupture due to the thining of the brass there. I opend up the port are of the cover and used the vacume line and it worked but it will not hold up forever. On the 308 it is not as bad but anoying none the less the nato brass is thicker and seems to resist denting. I need tp open the cover more however.

Would it be possible to use a standard AK47 ejector, but just set it further back in the reciever for shell clearance, or will a whole new ejector rail have to be made/manufactured?
You would end up with a gap at the trunion and the area for the center support is a issue . it is best to just make a new one out of some correct metal. I milled my first one from solid bar stock as it was all I had on hand. but for the rebuild I will use sguare tubing cut into angle per HC pookies idea else were in this sight. air craft spruce has it.

make an adjustable gas system for it (maybe fal type, not sure yet),
A FAL GB will work. so will a non adjustable standard AK or siaga one. the nice thing about the FAL block is the larger ID allows a heavier barrel. Its a bit of work to use them but not too bad there is also some misalignment of the carrier but they can be made to work. I bought a couple from Tapco when they were dirt cheap wish I had bought all they had now.
I would also recomend a much smaller Gas Port than HC used to avoid high pressre to the GB. IMOA around .065 would be a good starting point and go up in steps. of course if you make it adjustable the hole can be larger. I like to keep the hole as small as possable for accuracy reasons so I avoid adjustable blocks on my varmit stuff. If you dont shoot a large variety of ammo with differant pressures an adjustable block is not nessacry. if you hand load and want to do some light recoil stuff then make it adjustiable.
 
#15 ·
Muttman the rail lacks reaching all the way to the front trunnion by a hair or two. The ejector tip is 1.750" back from the left rear side of the trunnion or 2.750" from the chamber end of the barrel. Which is less than the OAL spec for the .308 of 2.810". I just used mil-spec ammo and a loaded round is clear of the chamber when it hits the ejector.
 
#16 ·
Ditto to what Biggun said about the rail - just cut a new one. My cut-and-reweld appraoch was really a pain.

Also totally agree on the smaller gas port - I seriously shut off my brain and didn't stop to double-check what I was doing when I made it the same size as the standard AK-47 gas port. A smaller port would work wonders on my setup. In fact I have been planning from the start that I might need a brand-new barrel, and I will drill that one with the correct size port ;)

Are there any FAL gas blocks to be found these days? I remember when they were all $2.00 or something from Tapco...
 
#17 ·
Are there any FAL gas blocks to be found these days? I remember when they were all $2.00 or something from Tapco...
I havent seen any cheap lately. tapcos were about $12 for ALL the parts to complete one. I got some of the last ones they claimed to have and also got the last FAL gas tube they had just to see what it looked like. They had over 900 blocks(as I recall from talking to them) when the thread on gunco was being posted. I toyed with the idea of buying a large quanity and reworking them for ak Use with a ecentric bushing to adjust the miss alignment and reselling them. several months later they were about out I bought a couple. Im guessing someone bought out there entire stock. they had FAL flash hiders for a buck or so as well. I bought one of there last rommy kits it is the nicest I have new with perfect wood, Im keeping it for a authentic build some day when I decide to rivet correctly.
What I really would like to find is a source for 20 guage Siaga gas blocks. they would be perfect for heavy barrel builds.
 
#18 ·
On the gas port stuff. my 223 runs at .075 if I remeber correctly. I figure the pressure of my loads are at around 50,000 CUP (likely close to 59,000 PSI) very close to the chamber pressure of the 5.56 nato. I would think that 50,000 cup in a .22 bore and a .308 bore with a same size would be directly comparable. I am not a mathamatiton or a enginer but a hole into a pressure source should be comparable. IMOA the port on the 7.62x39 is made for upmost reliabilty with 44,000 PSI ammo or less. it,s large so it will not foul easily under continues fire. with my HEAVY hand loads (dont ask) will cycle the action way to hard.
On my current 7.62x39 build with a .308 bore 24" stainless barrel I plan on using a smaller than normal 7.62x39 port. this will be a hand loaded with .308 bullets only and I plan to load it on the hot side Im hoping to get away with a considerably smaller port.
 
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