Correct Ammo For Fn Fal

45calmuzzleloader

What is the proper ammo to use in an Israelli Heavy Barrel Fn Fal? I have read that 7.62x51 NATO is not the same as 308 Winchester and that 308 ammo is loaded to much higher pressure. My buddy says "but the rifle has an adjustable gas system" to correct this situation. I say it is only safe with 7.62 NATO ammo. Any help is greatly appreciated.

mark christian

The differences between the .308 Winchester sporting cartridge and the 7.62X51 NATO STANAG cartridge have been discussed in this forum many times. Essentially, both cartridges were based on the T65 experimental cartridge; itself an offshoot of the old .300 Savage. Winchester introduced the T65 as the .308 Winchester in 1952 and began commercial sales. In the meantime the T65 underwent minor design changes until emerging as the 7.62X51 NATO cartridge. The result is that the dimensions of the two cartridges, while very close, are not exactly the same. Generally speaking, the 7.62X51 can be fired safely in rifles chambered for .308, but the reverse isn't always true. .308 sporting rounds can sometime rupture in rifles chambered for the 7.62 NATO cartridge. The cartridge case is the issue and not chamber pressures, so an adjustable gas system is irreverent.  Your rifle will work fine with any 7.62X51 NATO military ammo.

This was a very brief overview of a complex subject. We have members- including one of our forum moderators, who are far better versed in ballistics than myself. Hopefully they will come by to fill in the gaps.  

nononsense

As with any question regarding ammunition and safety, it's always best to ask first then set about acquiring the correct ammunition for any firearm.

Mark is correct in the understanding of the differences. Here is another way of explaining those differences:

"Commercial .308 Win. came first. The two ended up differently. Similar to the 5.56 NATO vs. .223 Rem., the difference between .308 Win. and 7.62 NATO is in the chamber, but it’s in a different place. The difference in these two isn’t the throat, it’s the headspace. NATO is ridiculously longer. Although there are different pressure-testing standards used by NATO and SAAMI, .308 Win. commercial ammo is normally loaded to a higher-pressure maximum than mil-spec NATO. It’s safe to shoot NATO rounds in a .308 Win. chamber, and .308 commercial ammo in a NATO chamber. The difference is in what comes back out. The case (either case) will have been stressed, a whopping lot. A softer or thinner commercial case might be hopelessly contorted."

As for numbers, SAAMI spec headspace for a .308 Win. is a minimum (shortest allowable or “GO” figure) of 1.6300 inches, and a “reject” (too long) figure of 1.6340. Well, the number given as a minimum for NATO is 1.6380. The “reject” on NATO is 1.6455. I’m not at all clear on why anyone thought that was a good idea, but that’s what was done. It’s also the reason NATO cartridge case specs call for considerably thicker-walled brass and associated hard alloy. It has to endure that much more expansion. It’s a big reason not to purchase “surplus” 7.62 brass for reloading. That’s my advice at least. Cases fired through a true NATO chamber will be patently worthless to anyone owning a .308 Win. They’ll be blown beyond all reasonable repair.

If you are a handloader for a 7.62 NATO chamber, get a cartridge case headspace gauge and subtract 0.004 inches from the spent case reading to use as a figure to set your sizing die (case shoulder set-back). So, be sure not to take it down to .308 Win. specs—or it’s liable to break on next use. Actually break.

Please pay close attention to the chamber description on any firearm's chamber. This is especially true with our nation's military firearms and civilian ammunition. If you have a question, always ask first before simply loading and shooting.

Best.

45calmuzzleloader

Thanks again for the expert advice. I'm not planning on reloading for this rifle. But I am going to purchase additional ammo. I want to find either Federal or Winchester 7.62 NATO.