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8mm on a romy kit?

4K views 38 replies 11 participants last post by  Sprat 
#1 ·
what is everyones opinion on building one of these
 
#3 ·
pretty long shell you would most likely need to increase the length of the reciver as the mag well would be getting pretty close to the trigger if left as is. the bolt Is to short, it needs to be able to extend to the back of the mag well in order for the hammer to clear the mag and still have proper geomitery to contact the end of the bolt. the 8mm has an over all length of 3.250 compared to a 7.62x51 of 2.810 that .44 of an inch has to go some were. doing a 308 requires some grinding on the hammer as it is. not saying it is not doable but you would need to extend the bolt some how or find a bolt for a m76 or some other gun. the SAMMI max pressure for this round are 35,000 psi however there are loads out there much hotter than that and hand loaders load way above that in modern rifles. The 30-06 saiga or a Dragunov in 7.62x54r would probably make a a better canidiate for a bulid. I think Ohio rapid fire makes a m77 milled reciver for an AK but you would still need the the bolt and other parts and a thick wallet. I toyed around with the thought of extending a bolt and moving the trunion forward but the work to shoot the 8mm round was not worth it when you compare what the 308, 338-08 0r the 358 win can do wich can be done on a AK bolt length. If 8mm was dirt cheap and non corrosive it might be worth it IMOA
 
#4 ·
i got 960 rnds for $60, but it is corrosive. i was wondering about 8mm because i had a romy kit and figured 8mm pressures would be ok in it as long as you stayed away from the machinegun stuff with the higher pressures

i know about the mods i would have to do, i was really wondering about the romy bolt and trunnion for pressure, they arent as built as the yugo (308 as soon as i get a yugo kit)
 
#7 ·
Wasn't this discussed about half a year ago?

If memory serves, the consensus reached was that a 7.62x39 assembly would not be strong enough to handle 8mm pressures, and a .308 assembly may be strong enough. The model to emulate is the Yugo sniper model.
 
#9 ·
i've read through the other post but didnt seem to see a conclusion as to what to build off of and what not to, maybe im just being blind and dense, i never can tell

im planning on doing a 308 on a m70 or bigger later and had the romy kit sitting here
 
#12 ·
8mm comercial rounds in the US are way under what the 308 is loaded at. europeans however factory load the 8mm to full potential. there are to many pr 98 mauser bolt actions that will not handel the pressures so the US loads weak. the hotest load in my lyman book is 48,000 PSI not CUP simiular loads rated with the cup meathod are around 35,000-40,000 CUP, About the same or less as 7.62x39 the hotest hand load shown for 7.62x39 is 44,700 cup if it were rated in PSI it would likely be around 50,000 psi based on other loads listed but dont take my word for this. 8mm bolt thrust would be higher as the case head is slightly larger and the same as the 308. bolt thrust is what I feel should be considerd most important. for example there are max loads listed in the book for the 223 at 51,800 CUP, not PSI but the smaller.378 case head means there is less bolt thrust than a 308 WIN with the same PSI in the chamber as it has a .473 case head. some were on this site I think it was posted on my 308 AK post there is a formula for figuring out bolt thrust. It involves square route and math I dont know how to do. It would be great if some one could figure it out and post some numbers here. 8mm mauser barrels can be found on ebay for around 10- dollars I bought 4 one time for $15 for all.
 
#15 ·
Bert o1 great link. the steel is likely very simular to 4130 no clue as the hardness. I think just knowing the bolt thrust of each round would be a good place to start. by knowing 7.62x39 one could compare others to see were they rate. we know the action is good for 7.62x39 and 223. what I want to know is how much higher the 308, 8mm are as well as the 223. I would also like to be able to figure out the 6mm ppc 6,5 grendal 6.8 rem 458 socom 50 beowulf the last 2 have a rebated rim I am guessing you would use the largest ID of the casing?? MY math skills are poor or i would have been an engineer or somthing else in life. tony at Tromix lead delivery built a 458 SOCOM on a milled ak reciver with a standard AK bolt.
 
#16 ·
If you checked last week I asked for the chamber pressures for 7.92 kurtz vs 7.62 x39mm
unless you have a romak 3 kit or a trunnion for a 308, the pressure will be too great for 8mm. you will need a 308 bolt or open the 7.62x39mm bolt face, you will need to convert a existing 8mm mag to the ak design, and a 8mm barrel. After a lot of thought and in possession of a Romak 3 kit, I am going to keep it in 7.62x54R.
I decided to go 7.92 x 33 kurtz, as the chamber pressure is simular to 7.62 x 39mm. I have a lot of 7.92 kurtz (EG) plus Partizan has started producing it again (reloadable). I got the 8mm barrel and a polish trunnion, I saw one of the companys selling the front sight and gas block's, mags will work.

some good post above, shame two pages and few good answers

sprat
 
#17 ·
unless you have a romak 3 kit or a trunnion for a 308, the pressure will be too great for 8mm
.

Sprat there are a lot of guys bulding 308's on AK 47 trunions. the 8mm has less chamber pressure than the 308 so I dont feel that this is an issue .If the 308 is safe that is. the m77 trunion and boltface appear almost identical to the m70 trunion and bolt face, only the stem of the bolt is longer and face is enlarged there were pics on my 308 post but that member removed them when he left this site the are on another site now. opening up the bolt face is not a big issue the mag can be used from a m76 if it can be found as it is a 8mm AK, or some type of 30-06 mag as it is slightly longer,. most of the build problems are adrdessd here.
the one question that myself and every one would like to know is what can a AK bolt and trunion handel as far as bolt thrust. the saiga 308 has three lugs and I have seen posted that that is due to the very high pressures that the europeans test at (higher than the SAMMI). some were this info must be puplic. there are however numerous military AK variants that have only 2 lugs
 
#18 ·
bert01 said:
i've read through the other post but didnt seem to see a conclusion as to what to build off of and what not to, maybe im just being blind and dense, i never can tell

im planning on doing a 308 on a m70 or bigger later and had the romy kit sitting here
We came to the consensus that either a ROMAK-3 kit or Saiga .308 donor rifle would be the best place to start... since these are built for 7.62x54r or .308, respectively, they are already "reinforced" from the factory for the more powerful rounds.

That will be closest to the already-in-use Yugo 8mm Sniper model. OR just buy a Yugo 8mm kit and alter it.

I know that I would not want to be the first one to try it! :eek:

HTH,
- Jerry
 
#20 ·
im looking 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
 
#21 ·
When this came up before someone posted pics of their saiga .308 trunnions and they were much bigger than a regular ak, I think they also had 3 locking lugs, not 2, I'm sure they did that for a reason. It was determined then after careful study of what was available that the yugo kits would be the best to experiment with.
In otherwords, exactly what hcpookie said.
 
#22 ·
I didn't post to debate, but I just think that standard 7.62x39mm trunnion may not be strongh enough, yah I know commerical 8mm is low and you can reload for it. I just feel more comfortable with a 308/7.62x54r trunnion and a RPK/Romak3 reciever or blank .60 in thickness. over large mag well is included in the Romak 3 design
mags you can use that are existing 8mm mags ex. mg13, hakim, cz or bar mags

the romak 3 54r bolt can be utilized for a 303 british conversion ( thought about this as only the barrel is a problem 308 vs 312 almost a shame the romak3 kits were like new not shot out? the 303 barrel would also allow you to convert to 7.7 jap with a 308 bolt

Sprat is losing it did he say 7.7 jap AK -47!!!!!!!!!!!

once the kits start coming in without barrels you will not find these post funny

sprat
 
#23 ·
. a 303 british on a romak would be cool allthough 303 has a smaller bolt face .540 vs .570 . dont the 303 british and the 7.62x54 both fire a .311 bullet? I have read that there is a large variance in bores on the 303 from.308 up to .317. I bought some 180 grain bullets designed for the 303 british to try to do a 7.62x39 whisper and they mic'd out at .310. the romak .570 bolt face would be a problem on a 8mm or 308 build with a .473 bolt face. the romak mag most likely would be to short on a 8mm 3.037 vs 3.250 OAL length

the saiga has three lugs on the 308. the yugo m77 and the m76 (308 and 8mm full auto AK,s) have only two I Think (could be wrong) the valamet 308 has only 2 and advertises it uses the full auto trunion some were on ther site.

I am going to build a 7.62x51/308 on a Yugo M70. I am going to use the military 7.62x51 brass with the smaller case capacity due to thicker brass. I will hand load middle of the road loads for it as well and will not use surplus ammo in it.
I also am going to find some one who knows math better than my self and figure the bolt thrust of the 7.62 x 39 loaded at 50,000 CUP ( there are published loads at this pressure) and the bolt thrust of the 308 rounds loaded at around 42,000 cup ( a middle of the road published load) and compare them. I have concerns as well if the bolt shear strength of the AK is safe thus my first post here around a year ago.
 
#26 ·
I have always used .312 when reloading 303. Depending on wear, yes 303 could/should run .310 to .312 plus.
I have loaded 308 147gr gi pull in 7.62 x 39mm cases, yes they shot fine but the projectiles always came loose, not much to crimp to.

yes the romak3 mag is too short for 8mm, but 303 fits, wonder if 303 bren mags can be adapted

as far as the bolt face, I fitted a 303 live case into the bolt and a 7.62 x54r live case, the was very little play and the 303 round was tight and required a little tension to peel off the bolt face.

because of the overall length of standard military 8mm the romak 3 design would have too be enlarged in the front & reduced at the rear so that the top cover fits

sprat
 
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