Gunco Forums banner

RBTHNTR64's .243 AK build

9K views 64 replies 12 participants last post by  allesennogwat 
#1 ·
Guys, I thought I would start a thread since Aloharovers .308 conversion deserves a thread of it own and I kind of injected my build into his thread.
SORRY ABOUT THAT ROVER! So over the next couple of days I will be moving my posts form there to here.:thumbup1:
 
#29 ·
Back burner at the moment. +$200 of needed parts from K-var slowed it up.
 
#31 ·
Jeez,I'm glad I looked at this thread.Thanks,rbthntr64.As you can see in the antelope thread I'm doing basically the same thing.My big puzzle was which way to shift the mag-that RSA TG takes care of that.Nothing to it now.Thanks much!
 
#35 ·
Back to work on mine. Massaged the mag to get it to feed. I would like to see your bullet guide and rifle.

 
#37 ·
It is an Ed's custom stock set. I will probably be offering it for sale as soon as I get my custom dragunov furniture done.
 
#39 ·
It is set up for the PSL. I will have it up for what I paid for it. $139 +S&H. I will not take a penny less. If you are still interested drop me a PM.
 
#41 ·
rbthntr64,
nice build, Im not that far behind you . a few "Q" if you dont mind.
#1 did you change the triger bow back hole or did you mod the bow it's self. I just got done cutting out a 1/4" and welding mine back.
#2 did the psl gas tube fit on a rommy RSB with no mod's if so what did you do.
#3 with the slector stop plate in and no mod's to the plate the bolt looks like it will ride over the case in the mag. if I leave the plate out the bolt head looks like it will catch the case at the primer. did you have this problem and what did you do to fix.

here is ware Im at in the build. I still need to hand fit the mag to mag well but thats for later.
muttman
 

Attachments

#42 ·
you should really think about this. The bolt on a saiga 308 has 3 lugs, not two. There is a third lug for a reason. Higher pressures. IT is good you are using the RPK style trunion, Muttman, you are using a normal AK trunion, I would be very concerned. :nono: :scared:

WIth the OP's bulged yugo trunnion, I am only slightly concerned. :dunno:

Nice project BTW, I'm doing a 243 conversion on my 308 saiga, 24" stainless steel barrel, doing a AKS74 series AK clone.

I chose the saiga 308 because, obviously, it only needs a barrel change, and also because the 308 action was modified (thid lug, etc) for the higher pressures of the 308 round.
 
#43 ·
There is a third lug for a reason. Higher pressures.
Yes we've talked that through pretty much to completion. We really need a sticky about that!
 
#47 ·
The earlier 308 AK's such as the Valmet, Galil and Yugo have only two bolt lugs. The Russians first tried to pass the newer CIP proof pressure test of 125% standard chamber pressure limit with two lugs and failed the 25% overpressure test and this why the 308 Saiga has three lugs. To pass CIP proof testing. With standard pressure ammo the two lug bolts seem okay but it does go to show how close to failure they are.
now keep in mind that 7.62x51 nato is susposed to be loaded 10,000 PSI BELOW comercial 308 Winchester and you should have an even larger comfort zone. IMOA IMOA.

this is why I have stayed a way from roundls like the 22-250 ect that are over even the 308 win Sammi pressures.

there are a few full pressure hand loads using winchester powders that are not much above the 7.62x39 pressures. this is the route I will be taking. for what it worth. the winchester powder is susposed to be the same that winchester uses in its comercialn ammo. if this is so then commercial wincheser is no were near the SAMMI limit. as hand loads will equil or excede the factory stuff at a advertised lower pressure.

the maximum load with 748 powder with a 150 grain bullet for a 308 win is. 50 grains powder COMPRESSED (this means thats all winchester is going to get in the case!!. this load makes only 43,000 CUP (right at the 7.62x39 SAMMI LIMIT). the velocity BTW is 2996 litterlay kicking the 7.62x39 ass in every area. the starting load for this powder 44 GR and makes only 32,700 CUP. Bellow the 7.62 x39 limits. FWIW that load is doing 2690 FPS still kicking the 7.62x 39, as an with a 150 grain bullet to boot!

if you want to use the same weight bullets as the x39 then the MAXIUM load of 51.2 grains of 748 powder COMPRESSED will make ONLY 41,600 cup !!! this round is way below ANY 7.62 x39 round and the bolt thrust is likely slightly more due to the larger case head factor.
that load will do 3034 PSI complety blowing away the X39 round by like 800 FPS. this is a HUGE improvement ythis load is also listed as the most accurate load in the 125 bullet group. and these are MAXIMUM LOADS. you will likely end up around 5% under these.

I am likely exceding the 308 loads with my 7.62x39 hand loads all the time. some of them are at 50,000 PSI and have been reliable. I am possably taking a bigger risk with these than a 7.62 NATO conversion?????

If you want to load for the maximum and play around in the 65,000 PSI world that any of these 308 based caliburs can do then by all means I would want a three lug action. (if you trust the current saiga quality ) No one on this sight has even mentiond trying to shoot those pressures. if I do a 22-250 or 260 remington and want its maximum it will be a three lug set up.

IF any one wants to check my numbers there from LYMAN 48TH EDITION RELOADING HAND BOOK.

BOTTOM LINE IS JUST BECAUSE THE SAMMI OR CIP LIMITS ARE AT 61,000 PSI DOSENT MEAN THE AMMO IS ACTUALLY MAKING THOSE PRESSURES!

WARNING dont assume I know any thing or that these loads are safe. always follow a manual not something off the internet. these are my opinions. I am not an expert on any thing.
 
#48 ·
Didn't SAAMI recently *UPGRADE* the 7.62x51 specs to higher proof pressures? I'm sure I read that somewhere, and it was suggested that was the reason behind the motivation for 3-lug bolts? I'm sure I read that... just not going to look it up :)
 
#50 ·
SAAMI changed from CUP copper crusher to transducer PSI years ago. This made a "higher" number PSI, CUP is also a measure in PSI. The two methods can't be directly compared. The US military stayed with copper crusher PSI for many years.

The military pressures and SAAMI/CIP pressures can't bedirectly compared due to differences in chamber dimensions.

Recently NATO has switched to transducer measurements using the SAME method and even the SAME pressure limit as European CIP for 308 Winchester but remember this is in a military 7.62x51 chamber

US military CUP = 50,,000 PSI (CUP)

old SAAMI CUP = 52,000 CUP

current SAAMI transducer = 62,000 PSI - 430 MPa (metric)

current CIP transducer = 415 MPa = 60,190 PSI

new NATO transducer = 415 MPa = 60,190 PSI

Note CIP/NATO transducer is a different measurement method than SAAMI transducer.

Note while CIP and NATO transducer use the same measurement method, CIP uses a minimum CIP commercial 308 Win. chamber and NATO uses a minimum military 7.62x51 chamber.
 
#49 ·
Didn't SAAMI recently *UPGRADE* the 7.62x51 specs to higher proof pressures? I'm sure I read that somewhere, and it was suggested that was the reason behind the motivation for 3-lug bolts? I'm sure I read that... just not going to look it up
I havent heard of that. It does make sense that requirng any weapons made that are marked 7.62x51 should be able to pass a higher PROOF test. is almost a certain that at some point someone would try to shoot comercial 308 in them.
I assume you are talking about upgrading the test on weapons not increasing the pressures of the ammo itsself that is sold. as I recall there are a few weapons that are not safe to shot comercial 308 in.
 
#51 ·
Most commercial 308 Winchester ammo is loaded about 8,000 PSI UNDER maximum SAAMI maximum pressure. This is to allow for converted 100 year old receivers, temp differences. The military loads for performance and isn't worried about being sued. The military loads for and uses modern, well maintained firearms. Usually military ammo is loaded closer to military maximum pressure limits. Firing commercial ammo in a military chamber will drop pressure and firing military ammo in a commercial chamber will increase pressure. The larger military chamber will have a lower pressure using the same amm compared to the tighter commercial chamber.
 
#53 ·
SO IS IT CORRECT TO SAY THAT NATO IS NOT LOADED LIGHTER/SPECD THAN COMMERCIAL ??? DAM Mi COULD SWEAR THAT THE NUMBERS i LOOKED AT SHOWED BOLTH 308 AND 7.62 IN PSI NOT CUP??? i WAS CERTAIN i WAS COMPARING APPLES TO APPLES BEFORE AND THE MILITARY WAS 10,000 PSI UNDER THE COMMERCIAL SAMMI LIMIT. WTF

THIS SEEMS TO SAY THE OPPOSITE OF allesennogwat. IM NOT SAYING HE IS WRONG IN FACT FAR FROM IT JUST QUESTIONG WERE THE MISS INOF COMES FROM. iM AWARE THE CHAMBERS ARE DIFFERANT.

WHAT IS THE SAMMI PSI LIMIT ON 308 WIN (NOT CUP)??

WHAT IS THE CURRENT DIRECTLY COMPARABLE iF CAN BE COMPARED DIRECTLY MILLITARY PSI LIMIT?

IT IS MY UNDERSANDING THAT EVEN THOUGH THE CHAMBER IS DIFFERANT THE CASE IS EXACTLY THE SAME OUTSIDE DEMINSIONS. JUST THE THICK MILLITARY BRASS WOULD WORK IN THE LOOSER CHAMBER AND THE THIN MIGHT NOT LIKE IT AND SPLIT OR RUPTURE.

IS THE INFO ON PRESSURES IN THIS SITE WRONG???????

7.62x51mm NATO or 308 Winchester? What's the Difference?
 
#55 ·
SO IS IT CORRECT TO SAY THAT NATO IS NOT LOADED LIGHTER/SPECD THAN COMMERCIAL ??? DAM Mi COULD SWEAR THAT THE NUMBERS i LOOKED AT SHOWED BOLTH 308 AND 7.62 IN PSI NOT CUP??? i WAS CERTAIN i WAS COMPARING APPLES TO APPLES BEFORE AND THE MILITARY WAS 10,000 PSI UNDER THE COMMERCIAL SAMMI LIMIT. WTF

THIS SEEMS TO SAY THE OPPOSITE OF allesennogwat. IM NOT SAYING HE IS WRONG IN FACT FAR FROM IT JUST QUESTIONG WERE THE MISS INOF COMES FROM. iM AWARE THE CHAMBERS ARE DIFFERANT.

WHAT IS THE SAMMI PSI LIMIT ON 308 WIN (NOT CUP)??

WHAT IS THE CURRENT DIRECTLY COMPARABLE iF CAN BE COMPARED DIRECTLY MILLITARY PSI LIMIT?

IT IS MY UNDERSANDING THAT EVEN THOUGH THE CHAMBER IS DIFFERANT THE CASE IS EXACTLY THE SAME OUTSIDE DEMINSIONS. JUST THE THICK MILLITARY BRASS WOULD WORK IN THE LOOSER CHAMBER AND THE THIN MIGHT NOT LIKE IT AND SPLIT OR RUPTURE.

IS THE INFO ON PRESSURES IN THIS SITE WRONG???????

7.62x51mm NATO or 308 Winchester? What's the Difference?

There is some confusing info on that site. It says "SAAMI field". There is no such standard. SAAMI has a minimum (Go) and a maximum (No-Go). Field is a gauge used by the military. The headspace gauge companies do sell field gauges but there is no "Field" standard set by SAAMI. Normally the gauge companies double the difference between Go and No-Go to get Field. There are differences in dimension other than headspace that also differ between commercial SAAMI 308 Winchester and military 7.62x51. It's not just headspace that can be larger.

The US military sets limits on cases by weight. Sometimes I find military cases from other NATO countries that are outside of US case weight specs and these would have been rejected to load for US military ammo. Some FN 7.62x51 cases are over the weight limit set by the US military and are even thicker in some areas of the cases.
 
#54 ·
The US military until very recently used the copper crusher method that SAAMI expresses as "CUP" but the units are in fact PSI and the military states it as "PSI". When SAAMI switched to the transducer method of measurement the measurements were expressed in "PSI". This causes confusion with US military PSI (which is CUP) and transducer PSI. Both copper crusher and transducer are expressed in units of PSI but SAAMI used "CUP" to show the method of measurement. Using the CUP method the old military limit was 50,000 and old SAAMI was 52,000, for a difference of 2000, BUT MILITARY IS MEASURED IN A LARGER, LOOSER CHAMBER.

To complecate matters more the load guides with "service rifle" loads would use military pressure measurement limits(with the lower number) measured in a tight commercial chamber. This makes the published loads a bit wimpy.

The transducer measurements are performed slightly differently between SAAMI and CIP. This keeps their numbers from being directly compared. But the very new NATO standard now uses the CIP method of transducer measurement. The pressure limits are now exactly the same numbers between NATO 7.62x51 and CIP 308 Winchester but CIP uses a tighter chamber when measuring pressure.
 
#56 ·
HMMM WELL SO MUCH FOR THE 10,000 PSI SARTY CUSHION I THOUGHT I HAD. YEA i HAVE ALWAYS BEEN VERY CAREFULL TO DIFFERENATE BETWEEN CUP AND PSI SPECIFICATIONS. THANKS FOR UPDATING THE 308/7.62 NATO.

I GUESS IT IS SAFE TO SAY THEN THAT WE ARE DEALING WITH A 61,000 PSI LOAD IF IT IS LOADED BY ANY ONE COMMERCIAL OR NATO. ( i RELIZE THAT COMMERCIAL MAY NOT ACTUALLY BE THAT HIGH BUT COULD BE IF THAY WANTED IT TO BE)

NOW I AM STARTING TO QUESTION MY NUMBERS IN MY LYMAN BOOK ALTHOUGH MOST ARE IN CUP. ERRRRRRRRRRRRRRRR
 
#57 · (Edited)
Most of the data in the Lyman manual is good but if the powder hasn't changed in 20 years or the powder company keeps listing a higher load, Lyman doesn't update the data for that powder. The IMR powder in the Lyman manual hasn't changed for more than 20 years. Maybe 30 years. The powders that have changed or if the powder company now list a lower max load Lyman will USUALLY update the data for that one powder in that one cartridge. It's best to cross reference many load guides.

Hornady has wimpy "service rifle" loads in it's latest manual #7. They use thin Winchester cases with the now not so good Winchester primers.

The best data I've seen is from Accurate Arms but it's only for their powder and they haven't updated in a long while. Accurate Arms has 7.62x51 data using older heavy military thickness and capacity IMI cases loaded to military pressure using transducer PSI. Their 2495 is similar to IMR-4895. I think their data is for 168 and 175 grain match buullets only but it gives the best idea of pressures.

Accurate Arms 308 Winchester in commercial cases

http://accuratearms.com/data/PerCal...l(7.82mm)/308 Winchester Pages 260 to 262.pdf

Accurate Arms 7.62x51 Match

http://accuratearms.com/data/PerCaliber2Guide/Rifle/NRAcartridges/7_62 51 Match page 378.pdf

Accurate Arms 308 Win 155 grain Palma bullet in Lapua case

http://accuratearms.com/data/PerCaliber2Guide/Rifle/NRAcartridges/308 Win Sierra PALMA page 385.pdf

Accurate Arms 208 Win Long Range

http://accuratearms.com/data/PerCaliber2Guide/Rifle/NRAcartridges/308 Winchester page 381.pdf


New 7.62x51 NATO standards

7.62x51mm NATO - Wikipedia, the free encyclopedia

NATO pressure testing

NATO EPVAT testing - Wikipedia, the free encyclopedia

If there was a 10.000 PSI difference from 50,000 that would an increase of 20% !!!!

The newest M118LR pressure which is higher than M80 is rated by US military at around 55,000 PSI which 10% higher than 50,000 but I don't know the testing method.
 
#59 ·
Here are some US military 7.62x51 cartridges. The M80, M852 and the early version of the M118LR which has since been updated. Note the pressure is copper crusher CUP expressed in PSI. The M80 and M852 are loaded to US military standard pressure limit of 50,000 PSI (CUP). The M118LR is loaded to SAAMI CUP pressure spec of 52,000 PSI (CUP). The current M118LR uses transducer measuring and the powder has changed. The powder charge is considered too much for a standard unmodified M-14 and it's gas system. The M118LR case has slightly more capacity than the standard military 7.62X51 case but not much. It still has less capcity than a Lapua case and the Lapua case has less capacity than a Winchester case. The M118LR pressure, even though equal to SAAMI is measured in it's own specially dimensioned chamber.
 

Attachments

#60 ·
GOOD INFO i WILL NEED TO DIGEST IT. I WOULD LIKE TO KEEP MY LOADS SOME WERE IN THE 50,000 PSI RANGE OR SLIGHTLY UNDER. IF THE LYMAN CHARTS ABOVE ARE CORRECT A MEDUM LOAD WILL STILL GET A 165 GR BULLET GOING FASTER THAN A STANDARD 7.62X39 123 gr. AND THAT IS A HUGE IMPROVEMENT. AROUND 47 GR OF IMR 4350 WOULD LIKELY BE CLOSE TO WHAT i WANT WITH A 165 BULLET. EVEN THE STARTING LOADS AT 38,600 PSI ARE BETTER THAN THE AK LOAD. AND THAT S PUSHING A BULLET WEIGHING 30 GRAINS MORE. A 260 REMINGTON WIOTH STARTING LOADS WOULD KICK THE CRAP OUT OF THE 6.5 GRENDAL AS WELL.
 
#63 ·
You might not want to use IMR-4350. That's what the commercial 308 ammo does is use slow powders to keep down pressure and get velocity but the slow powders are hard on gas operated rifles. the US military M118LR uses a hot load of RL-15 which is restricted to auto rifles with it's special chamber and bolt actions. IMR-4350 is difficult to measure also as it's very large. I found both RL-15 and Varget borderline slow for the M-14. the really work the gas system. I use mostly IMR-4895 with 168 grain bullets and H-335 with a 147 - 150 grain bullet for my plinking load.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top