Well unless you talk to someone who worked at HK at the time in the stamping department I doubt you will ever get the absolute truth. (And I would be highly skeptical of anyone who posts anything here as absolute truth! )

I know that some HK91's are marked 7.62 and some are .308. You may have just gotten one of each and 911/91 thing has nothing to do with it.

Out of curiosity, what will the definitive answer tell you? Since they both can take either .308 or 7.62 there is no real difference what it's marked as. Much like the SL8 is marked .223 and the G36 is marked 5.56, the receivers are (virtually) the same and both can eat either ammo.

Also, the title of your post seems to indicate you think that the chamber is actually different. It's not, they have the same chamber, they are just marked differently. HTH.

 

Just like My PSG-1 is marked 7.62X51
and the hand book is printed cal 308

who knows why they stamp it the way they do...:901:

 

They're all capable of firing either.

Sometimes they're marked .308 instead of 7.62 to make it sound more "sporting", that is the ONLY reason. Same thing with marking a gun .223 instead of 5.56.

Here is a really good one: UMPs are marked .45 AUTO, where as USCs are marked .45 ACP.

So based on that you should be able to conclude that the markings really has nothing to do with what the chamber spec is, it has more to do with what sounds more politically correct.

I do love the 7.62x51 marking on my HK911 over the typical .308, it just sounds soooo...military and evil

 

Thanks all but....

I know that I can fire both .308 Winchester and 7.62 NATO ammo through the guns, but there is actually a small dimensional difference between the .308 versus and 7.62 x 51 mm cartridges. This has got me wondering if this dimensional difference is reflected in the chambers too.

This is why I am curious about the .308 versus the 7.62 x 51 mm stamping on the receiver.

I posted this question on HK USA website forum, but I never got a straight answer.

Could these 7.62 x 51 mm receivers have originally been planned for making into German G3's and the .308 cal. receivers made for the civilian market into HK91's?

I guess only HK would really know the answer. It would be really nice to know.

Thanks again,

SJ

 

The actual HK chambers are no different they are all 7.62 Nato (dimensionally) and can handle the (supposed) extra pressure of .308 rounds. Thus, while .308 and 7.62 should NOT be used interchangeably in all rifles they can be in the HK91/911.

Other notes:
Do not use the Hornady "Light Mag" .308 in any SA firearm (per Hornady).

You should NOT use .308 in some rifles that were designed only for use with 7.62 to be totally safe, though I'd bet the chances of you having a problem are remote and I can't even find an anecdote on the internet of someone blowing up a good condition 7.62 rifle with .308.

The 7.62 vs .308 debate will rage on the internet long after I am gone but as long as you own an HK 91/911 it will not be a problem for you.

762 has spoken.

PS where are the pics of these three beauties of which we speak????

 

use any military 7.62x51 you will be fine.
you can even use the fed 308 150gn soft point

 

I suspect that, especially for the 9x series, HK used the same tools to bore out the barrel and chamber as they did for the military rifles. I can't see HK making separate tooling for military and civilian 91/G3 barrels.

 

7.62 NATO is different than .308 . The free bore is opened up slightly in the NATO chamber to accept a larger varity of ammo from other nations. We have both reamers and if you bore scope the chamber you can see the difference.

 

I was trained that you can use .308 in a 7.62 chamber but the reverse is not a good idea because the cartridge case at the base and lower sides of the 7.62 is thicker than the .308 and the 7.62 is a military designation used primarily for machinegun ammunition. As alluded to by 75B, the tolerances are greater in the 7.62 to accomadate this dimensional discrepancy and if i am not mistaken the throat of the 7.62 chamber is longer than that of the commercial .308 and the potential increase in CUP pressure related to the absence of that small space in the .308 chamber is potentially hazardous.

 

As far as I know: 7.62 Nato compared to .308 is probably the same as 5.56x45mm compared to .223. In the US, SAAMI specs for ammunition say that .223 Remington is a little different than 5.56X45, mostly as far as chamber pressures. I suspect this is the same for .308 and 7.62X51. The NATO round can develop higher chamber pressures, so anything chambered and designed for 7.62X51 will shoot .308 without any problems, but probably not the reverse.

I suspect anything made in Europe is really designed for the NATO round (7.62X51) rather than .308.

Any others have any ideas?

 

Right, so the rounds are different (slightly), but the chambers of the HK rifles marked 7.62x51, and the ones marked .308 are the same, and you can shoot either one...

 

I would say anything marked 7.62X51 would shoot either 7.62X51 or .308 without any problem.

Also, anything manufactured in Europe (even marked ".308") would shoot either 7.62 or .308 without any problem.

 

Years ago, when I was closer to the gun manufacturing arena, I knew of custom gun makers that would chamber a barrel and shoot max pressure cartidges out of it to form the brass to that particular chamber and then use those cartridges to tinker with different loads and bullets to get the better accuracy out of the rest of the barrel. (rifling, bullet shape, bullet fit with rifling, barrel thermal expansion, barrel thermal warping tendencies, straightness, etc.)

Accuracy is a trial and error method AFTER you have accomplished certain milestones. Of course, even the aforementioned milestones are infinitely variable. Ponder that!

 

can you shoot 308 or 7.62x51 out of you Hk..
yes ..yes you can...and have fun doing it

 

My Thoughts...

First of all, thanks to all of you for your comments.

The HK91 .308 chamber versus the HK911 7.62x51 NATO chamber topic is an interesting topic.

We all know that one can shoot both 7.62 x 51 mm and .308 Winchester in the same rifle, but the topic is about why there are two different HK91 calibers.

It may be that the 7.62 x 51 mm chambers on these HK911's are dimensionally the same as the .308 model 91s, and that HK just stamped 7.62 x 51 mm on the receiver, but knowing that HK prides itself on its engineering and workmanship, I would expect, strictly from an engineering point of view, that HK would stamp the proper chamber caliber on the receivers.

Assuming that HK uses proper engineering nomenclature, the HK911’s marked as 7.62x51mm would indeed have 7.62x51 mm dimensioned chambers and HK91’s marked as .308 cal. would have .308 Winchester dimensioned chambers. Even though the 7.62x51 mm and .308 Winchester dimensions are close, they are in fact dimensionally different.

It is interesting and puzzling that the last true Hk91's ever made and imported into the US, and later turned into hk911's, have 7.62x51mm chambers.

I’m guessing here, but maybe HK knew the end was coming for the HK91, and retooled the production line for military 7.62x51mm G3’s. Then shortly after retooling for G3’s, decided to make one last run of HK91’s for import into the US. If this was the case, then HK would have most likely used 7.62x51mm G3 receivers taken off the G3 production line to make the last run of HK91’s.

If this was the case, and from a collector’s point of view, they may have some significant value because they are closer related to military G3’s than the civilian HK91’s.

SJ

 

Sorry Sam308, there's nothing interesting or puzzling, there ARE NO differences between the chambers of a HK91 that's stamped .308 or a Hk911/SR9/PSG1 that's stamped 7.62x51.

It COULD be due to a variety of reasons, it could be political, it could be they just decided to change the way they mark the caliber, ore MOST likely, it could be done to appeal more to the American public who may be clueless of the metric system.

what we're sure is that HK uses .308 and 7.62x51 interchangeably, which is very much the case with their firearms, they can shoot both.

And consider that most of the 7.62x51 markings are found on POST BAN rifles, they'll never have collector value more than a true pre-ban firearm, a simple caliber marking won't suddenly cause the firearm to become collectable.

The CHAMBERS ARE THE SAME REGARDLESS OF WHETHER IT SAYS .308 OR 7.62!

HK isn't the only company that does this, FN, SIG, IMI, BERETTA have ALL in the past marked their 5.56 firearms w/ .223 or their 7.62x51 firearms with .308!

Gun companies tend to mark their guns sold to the U.S. in a caliber designation that most people would be familiar with. You'd be surprised to find out how many people don't know what 7.62x51 is but they know .308!

Heck, if you've seen one of the CZ75s made in the 80's, they come in a box that says 9mm/.38! Now there's no such thing as a .38 CZ75, they were in fact, referring to 9mm except converted to inches!

 

Nobody has found the answer yet as to why HK made the switch?

 

i bet it was the Guy who was stamping the Gun..and just used the 7.62x51
all My Hk91's say 308. But My PSG-1 is 7.62

but when it comes to the Military /LE Guns. Not Types it's Posted 7.62x51
i bet when the Hk91 went to the way side so did the stamping of 308.

and every thing after that was 7.62

just a gess.. remember think like you making alot of something in a run and a marking part gets lost or tossed..what are you going to do?