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Thread: Romi RPK for .308Win

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    Gunco Member alpine44's Avatar
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    Default Romi RPK for .308Win

    Is the Romi RPK strong enough for a .308Win conversion?

    I know this has been done with Yugo RPKs but how does the Romi RPK bolt and trunnion measure up to the Yugo RPK?

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    No Hope For Me 1biggun's Avatar
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    WELL ITS A UNKNOWN. GUYS HAVE DONE 308 WIN ON ROMMYS . I THINK HCPOOKIES BULLPUP IS ON A R0MMY TRUNION. (I THINK) THERE IS A HUGE TREAD ON DOING A 308 CONVERSION AND THERE IS A TON OF DISCUSSION ON THE MATTER. WITH NUMBERS ON BOLT THRUST AND CHAMBER PRESSURES. I STARTED IT AROUND 4 YEARS AGO.

    IF I WERE GOING TO GO THROUGH ALL THE TROUBLE AND TIME TO DO A CONVERSION I WOULD START WITH A YUGO TRUNION. IT OFFERS SOME EXTRA STRENGTH AT LEAST ON PAPER. I HAVE NEVER FOUND ANY DOCUMINTATION ON THE STRENGTH OF ONE TRUNION VERSUS ANOTHER ONE.

    WITH THE COST OF KITS GOING THROUGH THE ROOF A 308 SAGIA BECOMES A MORE ATTRACTIVE CHOICE. FOR A EXTRA $200 OVER A $300 ROMMY KIT YOU CAN GET A SAIGA WITH THE THREE LUGS. I RECENTLY PICKED UP A SAIGA TO CUSTOMISE INTO A POSSABLY A 260 REMINGTON OR MAYBE EVEN A 6.5-284 OR SOME OTHER LONG DISTANCE WONDER.

    READ THIS THREAD.
    http://www.gunco.net/forums/f244/308-ak-18443/

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    Gunco Member alpine44's Avatar
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    Thanks for the input and links.

    Ultimately, there is no better proof than proof testing. In Germany all guns are proof tested with well defined over-pressure loads. At worst, the potentially dangerous "device" is destroyed, at best you have peace of mind.

    (You may check your HK or Mauser. The proof marks look like an Eagle with an "N" or "V" under it, followed by a 2 digit year code, and lastly an antler, horse, or crest)German Proof Marks

    I will try to get some recipes for these proof loads and share the info if I get it.

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    No Hope For Me 1biggun's Avatar
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    THERE ARE SOME PROOF ROUND RECIPES POSTED SOME WERE HERE. i CANT RECAL IF THEY WERE 308 OR 7.62X39 OR 7.62X51. ON MY CONVERSIONS I RELOAD ONLY I USE THE WINCHESTER POWDERS SLIGTLY UNDER MAX. EVEN COMPRESSED THE WINCHESTER POWDER PRODUCES WELL UNDER THE SAMMI LIMITS. ITS MY UNDERSTANDING THAT THE FACTORY POWDER AND THE STUFF THEY SELL IS THE SAME (DONT QUOTE ME ON THIS) SO A COMPRESSED LOAD HAS TO BE LIKELY UNDER A FACTORY LOAD.

    THE HOTEST 150 GRIN BULLET LOAD WITH WIN 748 POWDR AT 50 GRAINS IS 43,200 CUP THAT IS UNDER THE LIMIT OF A 7.62X39 LOAD AS I RECALL. THAT IS A COMPRESSED LOAD AND AS ABOUT MUCH POWDER AS YOU CAN GET IN THE CASE. THAT LOAD IS LISTED AT 2996 FPS BY THE WAY. KEEP IN MIND THAT THE 308 HAS A LARGER RIM/BASE THAN THE 7.62X39 SO BOLT THRUST WILL BE HIGHER THAN A COMPARABLE 7.62X39 ROUND WITH THE SAME PRESSURE.

    FOR WHAT ITS WORTH A STARTING LOAD WITH THE SAME POWDER OF 44 GRAINS IS ONLY MAKING 32,700 CUP WELL UNDER THA SAFE PRESSURES OF THE AK AND MAKES 2690 FPS WITH A 150 GR BULLET. A HUGE IMPROVMENT OVER THE 7.62X39.

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    Gunco Member alpine44's Avatar
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    Thanks 1biggun

    Your pressure values sound low compared to other published data: 308 Winchester Load Data - Handloads.Com

    Maybe we should take this to the reloading section.
    I just got new WW748, fresh .308 cases, bullets and the weather is terrible here...

    The bottom line: A reloader would not need to loose much sleep over strenght issues for the .308Win as he/she is in control of the pressure. The buyer of surplus or commercial hunting ammo is in a different pickle.

    My M77 Yugo (factory .308Win) has three gas port settings. I only shoot ammo that fails to cycle on the smallest port. Most mil surplus ammo will fall in that category. Any ammo that cycles on the smallest port will be banned from the Yugo and will be "disposed of" in my M98 bolt action. Several commercial hunting loads went that way.

    This may be a very conservative approach but the M77 is such a nice gun that it would be a shame to beat it up. In fact, I got the thread started because I want to build a M77 clone from a suitable RPK kit.

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    Gunco Member alpine44's Avatar
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    I found something concerning proof loads:

    "M 60 (HIGH PRESSURE TEST)stannic stained case
    Bullet : 173gr.
    Powder : IMR4475 - 41grs.
    Used only to proof test weapons. This thing develops something like 70,000 psi! Don't even think about it...."

    and

    "...called Lake City Arsenal in the early '70's and talked to an engineer involved with load development and accuracy testing. He said their 7.62 NATO proof loads were essentially the same as the Navy's Mexican Match. The difference was they used a 172-gr. match bullet instead of the 147-gr. ball version in the same case with the same 42-gr. of IMR4475. He said he'd heard about the USN and USAF using "blue pill proof loads" in their (7.62x51) Garands and ... shuddered just thinking about it..."

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    Gunco Member alpine44's Avatar
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    Does anyone want to donate a bolthead and trunnion for a worthy scientific cause?

    I have the other required components including tree and string and will report the results with photos and video.

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    No Hope For Me 1biggun's Avatar
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    Your pressure values sound low compared to other published data:
    interesting my loads come straight from the lyman 48th edition. some were i have a actual winchester book i can check


    I have considerd doing that myself. now that kits are going for over $300 its not likely. as stated the build has been done before. i have no intention of shooting any surplus or unknown ammo in mine.

  9. #9
    No Hope For Me 1biggun's Avatar
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    Your pressure values sound low compared to other published data: 308 Winchester Load Data - Handloads.Com

    HMMM MY LYMAN BOOK DOES SHOW LOWER PRESSURES THAN MY WINCHESTER BOOK. IT ALSO SHOWS USING MORE POWDER AS WELL. NOT SURE DIFFERNT TESTS AND BARRELS, BULLETS. IT ALSO SHOWS SOME LOADS WITH 760 POWDERS THAT ARE EVEN LOWER


    from my 2006 Winchester book 150 gr fs(ct) bullet 748 powder 43 gr 748 powder 2540 fps = 45,100 CUP

    150 GR SP 50 GR 760 POWDER 2700 FPS = 40,500 CUP THIS IS WELL UNDER FACTORY AK SPECS!!!!!!! AT LEAST CHAMBER PRESSURE YOU STILL HAVE TO CALCULATE THE DIFFERANCE IN RIM SIZE TO GET COMPARITVE BOLT THRUST VALUES. SEE THE 308 AK LINK.

    150 GR SP 48.5 742 POWDER 2865 FPS = 48,000 CUP

    180 GR FMJ BT 46.6 760 POWDER 2535 = 43,000 CUP

    IT ALSO SAYS TO USE 748 TO DUPLICATE FACTORY 308 BALLISTICS AND 760 FOR 30-06 BALISTICS

    KEEP IN MIND THAT CUP PRESSURES ARE GENERALY LOWER THAN PSI READINGS WITH THE SAME LOAD AND BARREL.

    A 147 GR FMJBT WITH 45.2 GRS OF 748 MAKES 27,300FPS AND MAKES ONLY 45,500 PSI NOT CUP

    THESE ARE SUSPOSED TO BE MAX FROM WINCESTER. AND THE 748 LOADS SHOULD EQUIL A FACTORY ROUND. IF THESE WERE DOWN LOADED SAY 5% I FEEL IMOO THAT THEY WOULD BE SAFE ON A 2 LUG TRUNION.

    AGIN THIS IS ONLY MY OPINION AND IM NO ENGINER. BUT THERE ARE PLENTY OF 50,000 PSI LOADS SHOT IN 7.62X39 AND I HAVE LOADED UNTILL THE PRIMERS WERE GOING FLAT WELL OVER 50,000 PSI (DONT DO THIS AT HOME ). SO I AM CONFIDENT THAT THE AK WILL HANDEL OVER 50,000 PSI WITH A .447" BOLT FACE.

    THE SAME BOOK HAS 7.62X39 LOADS AT 44,700 CUP BUY THE WAY THAT IS OVER SOME OF THE 308 LOADS.

    ALL OF THIS HAS BEEN COVERD IN THE ORIGINAL 308AK THREAD.

    IS THE ROMMY RPK TRUNION BULGED LIKE THE YUGO?? IF SO IM GUESSING THERE COMPARABLE IN STRENGTH. THERE HAVE BEEN 308 BUILT ON ROMMY G STANDARD TRUNIONS BTW. I AGREE THAT HAND LODING IS THE SAFE BET HERE.

    MY BUILD ACTUALLY USES TURNED CASES TO MATCH THE ORIGINAL .447 BOLT FACE THIS PREVENTS ACIDENTAL USE OF VERY HOT HAND LOADS FOR MY 308 BOLT ACTION THAT WOULD BE AROUND 60,000 PSI. I USE MY BUILD STRICTLY FOR HUNTING AND HAVE ONLY RAN AROUND 50 ROUNDS THROUGH IT. I HAVE SEEN NO HEAD SPACE CHANGE WITCH I MONOTOR VERY VERY CLOSLY.

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    Happy Camper hcpookie's Avatar
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    I've shot both surplus loads and hand loads out of my Romy .308 conversion and while the surplus is stout, the problems I have had have NOT been with the bolt, rather with the over-sized gas port I drilled. I made it larger than what it should have been, so I had to compensate with more bleed holes in the gas tube.

    The surplus is STOUT with this larger hole, probably more akin to what a FAL would feel like with its gas port adjusted larger.

    I am trying to get this to be more of a scoped build than a "blaster" and so I've taken to hand loads that are lighter than surplus loads. I've recently identified and fixed the issue that caused my scope mount to wobble, and I need to get back to the range to see how she groups.


    IMO - 2 things here:

    1. yes it appears you can use a Romy bolt. Look again at those 308 conversion threads, and find those pics about the bolt head comparisons. You'll find they are close enough.

    2. it will be cheaper, and less hassle, to buy a Saiga .308 and tweak it to however you wish. I would either build the RPK or sell it, since RPK kits have basically dried up and you'll definitely get more for your money out of it!

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