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243 Conversion (khyber pass RPK)


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As you may know, a 243 winchester cartridge is simply a necked down 308, a smaller faster bullet, FTW

 

Mag compatability is a non-issue.

 

I just finished this last night, It started out as a sporter saiga 308 (7.62 X 51mm).

I removed the rear trunnion and installed a side folding bulgarian stock and USA pistol grip. With a G2 trigger group.

Then, converted it to 243 Winchester with a brand new 22 inch stainless steel barrel. (got it off gunbroker, for cheap, and lathed it down to fit)

It has a flash hider and bayonet lug , of course.

 

Range Update

 

It ejects strongly, and like a lot of other saigas, it seems to damage the rim of the soft brass casings about every 5th round, and I think the bolt needs that mod to prevent severe case damage from the (bolt carrier?) denting the shoulder of the casing. I don't know exactly were to mod, anybody know?

 

It groups nicely, I was getting about 1" inch at 30 yards. But It was me, not the gun, I was wobbling a bit, cause of the shitty range I was at didn't have a good bench.. I'll bet the gun can do better than 2 inches at 100 yards, If I do my part. Mostly it was just function test. And it worked perfectly.

 

A few of the brass casings had the rim ripped off, I suspect it is normal, as I have seen factory 223 saigas do the same thing (soft brass). It ejected fine though, even though the rim got ripped off a few times.

 

And you can see where the ejector hit the head. again, I have seen this on normal guns, so I'm not concerned.

 

I doubt my gas port is to big, as it's at 0.065 (1/16"), as opposed to factory 0.055 but that was the closest size I could get here in the city, as 3/64" would have been to small.

 

IF I do this again though, I'll try a 3/64 first, just to see. I plan on doing a 24" barrel next time, so a 13/64" should work fine, due to the longer barrel and increased gas linger time.

 

Anyways, the gun works fine and other than damaged rims and dented shoulders..... it's all good.

 

I didn't even need to make a ramp on the barrel, just cut to extractor depth and GTG,

 

I'm really happy with it, and I'd like to try some light weight loads. The 100 grainers work good, but they don't have the spectacular velocity that was my main reason for doing this conversion. I'd like to find some ~55 grainers, and hand load them, just to see what it'll do.

 

Vaporization of metal targets was my main goal here, as well as a wicked long range deer gun.

 

243_RPK_santanatwo.jpg

 

bayo.jpg

 

barrel.jpg

 

1internals.jpg

 

1side.jpg

 

308_243.jpg

Edited by santanatwo
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Very nice conversion!! Awesome workmanship.

 

What was the original barrel length if you don't mind me asking? I am looking for a long 308 barrel for my 308.

 

16" sorry.

 

I believe the gas port is to big, cause I used a 1/16" and I should have used a 3/64. not much difference, but enough.

 

the carrier is hitting the recoil assembly hard enough to cause a mark. I'm gonna have to install piece tire sidewall to act as a buffer.

 

bummer.

 

next time I'll use a 3/64 for the gas port.

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I came up with a novel sollution.

 

I screwed the gas piston in as far as I could without limiting carrier travel, (about a 1/2") this reduced the pressure inthe gas block and slowed bolt carrier travel, now it ejects normaly, and does not rip off case rims, also the cases aren't getting dented as bad when the bolt rides back over them. (now it's just a little ding, instead of a 1/4" dent.

 

next time I'll use a 1/32" drill bit to start with, then, IF it doesn't cycle, go up to a 3/64"

 

1/16" is just to big for that setup

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Instead of a makeshift buffer I would try a heavier spring (wolf sells'em). It seems even though the 308 spring is stiffer than say a Romy G those brand new stiff wolf springs really slow down your bolt. Also, I would maybe think about increasing the weight of the bolt carrier, maybe turn urself a new piston with a thicker shaft etc. I say this beause bumpers are hard on your rear trunnion and as nice as that build is, the less stress the better. Another idea might be to somehow silver solder and partially plug the gas port. Just a thought. Regards

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Instead of a makeshift buffer I would try a heavier spring (wolf sells'em). It seems even though the 308 spring is stiffer than say a Romy G those brand new stiff wolf springs really slow down your bolt. Also, I would maybe think about increasing the weight of the bolt carrier, maybe turn urself a new piston with a thicker shaft etc. I say this beause bumpers are hard on your rear trunnion and as nice as that build is, the less stress the better. Another idea might be to somehow silver solder and partially plug the gas port. Just a thought. Regards

 

well, this was the cheaper sollution, just screwing in the piston deeper. And it worked, it cycles perfect now. ejects them about 15 feet to the right.

 

but I had considered a custom thicker piston, to add weight.

 

I didn't know wolf sold heavier springs for the AK.

 

There aren't to many good sollutions when you drill the port to big.

 

1/16" is about .0612", factory is 0.055" acording to my calipers.

 

not much of a difference. I suspect the smaller bore or perhaps the higher velocity of the bullet made the difference, along with the longer barrel made for some energetic ejection, top say the least.

 

so, in the future, anybody want to do this, start off smaller than 1/16" for your port.

 

I'm guessing 3/64 would be ideal, but start at 1/32 to be safe.

 

I knew better than to start at the size I thought it would be. but it was late on a friday night and I wasn't wanting to wait till monday to finish the build... doh!!!

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Wow.. stainless barrel on a saiga looks sharp. :wub:

 

My loading manual lists 55gr BT at 4,058 fps. Burner!! I think you might be sending some of the fastest pills fired from a Kaloshnikov.

 

The bayo is in case the deer doesn't want to cooperate right. :ded:

 

Overall very nice, kudos.

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I've got (2) 16' 308-1 Saiga's. They are great...however, I got to thinking how cool it would be to have one rebarreled to the 358 Winchester. It should be fairly straightforward. The only problem I can envision would be a slight modification of the gas flow to ensure proper cycling. To my mind it would be an almost perfect large hog or black bear hunting tool.

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  • 11 months later...
Instead of a makeshift buffer I would try a heavier spring (wolf sells'em). It seems even though the 308 spring is stiffer than say a Romy G those brand new stiff wolf springs really slow down your bolt. Also, I would maybe think about increasing the weight of the bolt carrier, maybe turn urself a new piston with a thicker shaft etc. I say this beause bumpers are hard on your rear trunnion and as nice as that build is, the less stress the better. Another idea might be to somehow silver solder and partially plug the gas port. Just a thought. Regards

 

well, this was the cheaper sollution, just screwing in the piston deeper. And it worked, it cycles perfect now. ejects them about 15 feet to the right.

 

but I had considered a custom thicker piston, to add weight.

 

I didn't know wolf sold heavier springs for the AK.

 

There aren't to many good sollutions when you drill the port to big.

 

1/16" is about .0612", factory is 0.055" acording to my calipers.

 

not much of a difference. I suspect the smaller bore or perhaps the higher velocity of the bullet made the difference, along with the longer barrel made for some energetic ejection, top say the least.

 

so, in the future, anybody want to do this, start off smaller than 1/16" for your port.

 

I'm guessing 3/64 would be ideal, but start at 1/32 to be safe.

 

I knew better than to start at the size I thought it would be. but it was late on a friday night and I wasn't wanting to wait till monday to finish the build... doh!!!

 

Is the 0.055" measurement from the 16" take off barrel, or from a factory 22" Saiga barrel. Looks like it was taken from the 16" barrel that you took off when you rebarreled.?

 

Excellent idea by the way! I've been wanting to do this myself. I was thinking that it would reduce muzzle jump, and shoot flater ect...

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  • 3 weeks later...

I took the measurement for the gas port from the 16 barrel that I took off. I see it was way to big. I'll be needing a new barrel anyways though, the smithy I had trim down the barrel did NOT do it to my specs, as he removed the face of the breach, lik eI told him NOT to. I went with it anyways, but it lets the extractor slam the barrel on an empty chamber.... and aside from the ding building up on the breach face, the extractor will be getting weakened and eventually break, I am sure... so next time I'll be buying a lathe and doing it myself. I thought I could get away with the way he did it, but it isn't going to fly int he long term, and extractors are a bit hard to come by. The good news was that I didn't need any kind of feed ramp cut ont he barrel like the factory had, as the bullet goes right into the chamber. very nice.

 

Not exactly back to square one, but I guess the next time I'll be doing it the RIGTH way, correct size gas port and proper breach face.

 

I haven't posted pics but I nickel plated all the parts that aren't attached to the barreled receiver, it's hawt! I'll see if Ican find my cord to my cell phone so I can download them.

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Just FYI, a smaller bore means higher pressure for a longer distance. So if the .30 cal bore had a .055" port, and you want to drill your gas port at the same distance from the breech for a 6mm bore, then you'd want a smaller gas port. You solution was pretty clever though. A lot of these Saigas built in US calibers are overgassed and could do with smaller ports/ less pressure.

 

Lovely build, great initiative to put this together. supprised you didn't plate the trigger though.

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