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View Full Version : Israeli Mauser K98K 7.62/.308 worries


daktaklakpak
06-24-2012, 4:31 PM
Hello all,

I am new and just jumping into this as a hobby recently. I recently purchased a Israeli Mauser K98K rebarreled for 7.62x51 NATO, and will be picking it up soon from my FFL.
Here are some pictures: http://i15.photobucket.com/albums/a397/Muppetbrain123/8b127d83.jpg
http://i15.photobucket.com/albums/a397/Muppetbrain123/a72e7be9.jpg
http://i15.photobucket.com/albums/a397/Muppetbrain123/ff13db50.jpg
http://i15.photobucket.com/albums/a397/Muppetbrain123/9f08b963.jpg
http://i15.photobucket.com/albums/a397/Muppetbrain123/522ad40c.jpg

My concern is the difference between 7.62x51 NATO and .308 WIN. Almost everywhere I look for ammo, they have bundled the searches of 7.62x51 with .308 win, so that results all look like "7.62x51/.308 win" at places like ammoseek.com. I've done a few google searches, and the main arguments for differences seem to be the pressure differences and headspace differences between 7.62x51 nato and .308 win. I've browsed a few discussions, and I have come across these points as well:

A) http://thefiringline.com/forums/showthread.php?t=399226
B) http://dutchman.rebooty.com/1895Chile.html
C) http://thefiringline.com/forums/showthread.php?t=326877

In point A), there was a comment that seems to have some faith in that firing .308 WIN should be okay due to 8mm Mauser (which the gun and action were originally working with) being a more powerful round.

Point B) is what scares me. Will my rifle eventually be destined to come apart, even with the marked 7.62x51 nato ammo?

Point C) the detailed document FALPhil wrote says the pressure differences are negligible, which throws me back into the endless loop of questioning the differences again.

My main questions, I guess, are:
1) Is it safe to buy .308 win for my Israeli k98k 7.62 considering the above points?
2) If I have to buy 7.62x51 and not .308 win, where can I do so in larger quantities (200+ rounds) cheaply without reloading them myself?
3) Is my Israeli Mauser going to be okay with either round in the long run?

I just want to have fun and shoot, but safely of course.


Thanks guys!

ps. the best deal I found, if .308 is okay, is http://www.aimsurplus.com/product.aspx?item=ABB308FMJ&name=Brown+Bear+.308+145grn+FMJ+20rd+box&groupid=26 wondering if I can do better elsewhere

smittty
06-24-2012, 5:42 PM
Under 40 cents a round is a good price for 308 but thats still expensive imo for just having fun. To me 223 is good cheap fun but the guns cost a lot more.

weber_2
06-24-2012, 5:46 PM
Correct me if I'm wrong but 308 is to 762x51 like 556 is to 223. If your chambered for 308 then any ammo is good, not always the case if your chambered for 762x51.

smittty
06-24-2012, 6:00 PM
Correct me if I'm wrong but 308 is to 762x51 like 556 is to 223. If your chambered for 308 then any ammo is good, not always the case if your chambered for 762x51.

No, 7.62x51 is not same as 308 but both fit in the same rifles. 308 is higher pressure. I couldn't say if it's ok in the isreali Mauser or not. I almost bought one but couldn't get a definitive answer on this so I didn't buy one.

You might want to look into reloading to really enjoy that rifle!

6mmintl
06-24-2012, 6:10 PM
Will be fine in the 98 action, they have been chambered in higher pressure cartridges.

Richard Erichsen
06-24-2012, 10:35 PM
No, 7.62x51 is not same as 308 but both fit in the same rifles. 308 is higher pressure. I couldn't say if it's ok in the isreali Mauser or not. I almost bought one but couldn't get a definitive answer on this so I didn't buy one.

You might want to look into reloading to really enjoy that rifle!

.308 is not higher pressure. This is a common misconception caused by differences in measurement. NATO was originally speced using the now obsolete Copper Units of Pressure (CUP) where the specific copper alloy "measurement device" (the amount it is crushed tells you how much pressure it was exposed to) is located in a different part of the chamber than the more modern method of using a piezo pressure transducer closer to the case mouth. The two methods do not covert well from one into the other and sometimes CUPs is substituted haphazardly for PSI, even from some well known publications.

When 7.62 NATO (you don't need the x51 at the end, there is only one NATO 7.62 mm caliber) is tested using the more modern piezo pressure transducer instrumented in the same manner as the .308 Winchester, low and behold the typical M80 ball ammo and similar 150 grain .308 spire points are compared, very similar pressure is observed (usually in the 51K PSI range). You can see they are close in pressure despite all the hubub when you compare published muzzle velocities at sea level with similar projectile weights.

As a result, 7.62 NATO and .308 Winchester have very similar peak pressure and proof (test) pressures. This isn't where folks need to be worried. It's actually pretty hard to overpressurize the case unless you used pistol or shotgun propellent by mistake during a reload.

The differences to be concerned with and scrutinize, or call for confirmation about are in the case length specs and chamber specs. The 7.62 NATO is just a bit longer and this is where problems can occur. When the .308 Win case stretches during firing to fill the longer void of the 7.62 NATO chamber, it can cause case failure, mostly case head separations that require a broken case extractor to remedy, or a really long rod to knock out the pieces. Very tight 7.62 NATO chambers don't have this problem and are so close to the .308 win (where max .308 Win is very close to the min for NATO) that both can be used without problem. Many rifles have chambers that can use both, including Springfield M1A, DSA FALs, PTR91 and most if not all the modern (if proprietary to a given company) AR10 models.

The best way to be sure is to call the manufacturer and ask. If you replace your barreled upper with a new upper, or rebarrel a rifle that doesn't use an "upper" (PTR91, FAL, M1A), then you need to confirm the chamber specs for the barrel you have purchased.

The rebarreled 98K's are early rechamberings, similar to what Spain did with their FR7 and FR8 rifles for much the same reason. Because of this, most of these rifles are deemed suitable primarily for 7.62 NATO surplus ammo, or reloads using NATO spec cases. The best way to be absolutely sure is to use a set of go, no go and field gauges for .308 Win and see where you end up. I'd also check throat erosion with an erosion gauge while I was at it and have one, if not two gunsmiths look over the rifle and render an opinion on suitability for modern higher pressure (near max pressure, like some long range target and hunting loads) and .308 Win compatibility specifically. If any two experts don't agree, go with the more conservative opinion of the two, it will keep you out of trouble.

If you like the rifle and you plan to keep it for awhile, rebarreling it with a modern barrel and a known chamber spec that can safely shoot either may be prudent. Old surplus rifles can be dangerous primarily because of a certain degree of unknown in the quality of the barrel that might require sophisticated tools to spot (magnetic particle and other methods to reveal cracks, poor metallurgy, etc.). Given that a new barrel can often be had for $150-$250 or so installed, it might be the better, more prudent choice regardless of how well your gauges suggest everything should fit.

Stay safe.

R

daktaklakpak
06-24-2012, 10:44 PM
Thanks guys, giving all these replies a good read :)