FN FAL caliber?

[DrDucati]

I have a Century Arms FN FAL that I've been shooting 7.52x51 fmj out of. It's what was sold to me years ago when I bought the rifle.

Now that I'm reloading multiple calibers and want to start reloading for the FAL, I'm stuck trying to figure out if it can handle 308. I have looked the gun over everywhere and no indication of this. Are all century arms fals made to handle 308?

[Scharfschuetze]

Dr,

The 308 Winchester was brought out after the US Military adopted the 7.62 NATO in what... 1957 I think. It is basically the same cartridge and Winchester saw the advantage of producing the civilian version of the NATO round for commercial sale. All of the US Military's small arms rounds have gone to give sterling service as civilian rounds.

You're safe in using 308 rounds in your FAL, although you may need to adjust the gas port depending on your loads. Civilian brass may not last as long as GI brass in the FAL, but hopefully you saved all of your GI brass (if boxer primed) for reloading.

[Artful]

7.62x51 NATO and 308 WCF are interchangeable - no issues

[DrDucati]

Those answers are what I "want" to hear, but if I may....
why do I keep reading that NATO brass and guns can face excessive pressures when shooting 308 rounds?

[castalott]

IfI remember correctly... Canada had a pierced primer scare with the FN and then mandated that the 7.62 pressures were limited to about 42,000 CUP. ( Maybe 40,000) . I think like you as I don't run full power loads thru any of the older rifles. You can drop down 10,000 CUP and still have an amazing cartridge.

I really don't know how strong the guns are. I did watch a video of a manufacturer run 20 blue pills thru his full auto FAL in just a second or three. It was implied that the gun wasn't harmed...

And I believe that some ball ammo is loaded very hot....Some South American stuff comes to mind.

Another thought is which receiver your gun is built with. Imbel ( the FN approved manufacturer in Brazil) has a sterling reputation. Some others are spotty.

Bottom line for me....I don't run hot or even warm loads thru older rifles.

I hope this helps... Dale

[Petrol & Powder]

Externally 7.62 x 51mm NATO is identical to .308 Winchester. Military brass may have thicker case walls which results in reduced internal volume. If you're reloading near the max limits it is wise to avoid mixing commercial and military brass. Both cases can be used but you may end up with using less powder to achieve the same pressure with the military cases.
I put much more effort into achieving consistency with rifle ammunition than I do with handgun ammunition and segregate my rifle cases by manufacturer and sometimes even by lot number. You can interchange NATO and Commercial brass but you should work up to a specific powder weight for each type of casing separately.

And by the way, I shot both commercial and NATO surplus cartridges in a FAL without issue and then reloaded that brass and shot it repeatedly through that same FAL without problems. I ended up using the same charge weight in both types of casings BUT I approached those loads separately and I was a little below maximum when I settled on a load.

[runfiverun]

the 308 win is loaded to a higher pressure than the NATO round is.
the nato round is held low in deference to the Spanish FR-8 rifles.
the 223 is the opposite where the 5.56 is the higher pressured round.

one more thing.
the 308 win round hit the civilian market before it became a military round, it hit at least a year sooner.
Winchester done most of the developmental work with the governments assistance and seen the potential for a whole new case size that would just about duplicate the venerable 30-06.
airc the developmental round was called the T-48 [M-48 sumthin like that] then come out on market first as the 308 win then the 7.62X51 for the M-14/M-60 rifles, then the NATO designated round was adopted later as other country's seen it's potential.

[bouncer50]

A simple answer to a simple question. The fn fal has a adjustable gas system for different country spec. I have four of them mine run best at 3 setting

[Artful]

Those answers are what I "want" to hear, but if I may....
why do I keep reading that NATO brass and guns can face excessive pressures when shooting 308 rounds?

I think you are hearing it the other way around -
in a NATO chamber you can shoot 308 but in a tight 308 with short throat you may have
high pressure if shooting 7.62 NATO (T-65 was developmental)

The 7.62x51 NATO chambers have more generous dimensions than the commercial 308 chambering.

[HangFireW8]

the 308 win is loaded to a higher pressure than the NATO round is.
the nato round is held low in deference to the Spanish FR-8 rifles.
the 223 is the opposite where the 5.56 is the higher pressured round.

Spain became part of NATO in 1982. By that time, both 308 and 7.62 standards were well established. I can't see anybody holding back any standards to please the Franco regime.

[JSnover]

I hate these threads but here's how I understand it: The MilSpec chamber is loose (shoulder is about .013" further out). The cases are externally identical, with MilSpec brass being thicker. High-pressure .308 may cause a problem in a MilSpec chamber, though I haven't actually seen or heard of it happening. My FAL shoots both without a problem.

[Artful]

Spain became part of NATO in 1982. By that time, both 308 and 7.62 standards were well established. I can't see anybody holding back any standards to please the Franco regime.

While the 7.62mm NATO cartridge has a maximum chamber pressure of approximately 50,000 pounds per square inch (psi), in the SAAMI book the .308 Winchester has a MAP (maximum average product) pressure of approximately 62,000 psi* (each by conformal transducer measurements, and therefore comparable). This is not to say that all .308 Winchester loads will develop such pressures, merely that they would be within manufacturing tolerances if they did so. But I have fired many commercial 308 WCF cartridges in my FAL's without a hitch - I have had to pound open a few 308 bolt guns using surplus ammo (7.62x51 NATO)

[Petrol & Powder]

I hate these threads but here's how I understand it: The MilSpec chamber is loose (shoulder is about .013" further out). The cases are externally identical, with MilSpec brass being thicker. High-pressure .308 may cause a problem in a MilSpec chamber, though I haven't actually seen or heard of it happening. My FAL shoots both without a problem.

/\ This is pretty close to answering the OP

There are dimensional differences between chamber specs and cartridge specs and not all chamber specs are the same. There are also pressure differences between commercial ammunition and military ammunition. It's important to keep it all in perspective and remember which differences are critical and which ones are not all that important.

[DrDucati]

Thanks for the responses. What I'm understanding is that while there are small differences and people do argue back and forth, practically speaking they are identical. And in fact the Lyman cast bullet handbook has just one set of loading data for both.

This is music to my ears. Thank you.

So I would like to ask what is everyone's preferred mold for this caliber for this gun?

[WineMan]

I had a Win Mod 70 Featherweight in 308 who's SN# was from 1953. Hatcher's Notebook of 1947 describes the new 7.62 NATO as being adopted in 1957 and the 308 Win in 1952. As a cast bullet load there should be no difference other than the usual small variance in components. I am not sure the pressure but competitive M14/M1A shooters routinely push the limits on 600 yard ammo. Have fun!

Dave

[Dutchman]

.308 Winchester chamber headspace gauges:
GO: 1.630"
NOGO: 1.634"
FIELD REJECT: 1.638"

US Army 7.62x51 chamber headspace gauges:
GO: 1.635"
FIELD REJECT: 1.6455"

SAAMI .308 Winchester chamber pressures:
MAP: 62,000 psi
MPSM: 66,000 psi
Minimum Proof Pressure: 83,000 psi
Maximum Proof Pressure: 89,000 psi

US Army 7.62x51 chamber pressures:
Maximum: 50,000 psi
Proof pressure: 67,500 psi

7.62x51 NATO pressure data from: TM 43-001-27 "Army Ammunition Data Sheets Small Caliber Ammunition" and headspace data from Kuhnhausen's M1/M1A shop manual.

.308 Winchester data from ANSI/SAAMI document Z299.4-1992, "Pressure and Velocity, Centerfire Rifle Sporting Ammunition".

[Petrol & Powder]

I had a Win Mod 70 Featherweight in 308 who's SN# was 1953. Hatcher's Notebook of 1947 describes the new 7.62 NATO as being adopted in 1957 and the 308 Win in 1952. As a cast bullet load there should be no difference other than the usual small variance in components. I am not sure the pressure but competitive M14/M1A shooters routinely push the limits on 600 yard ammo. Have fun!


Dave

Wow, Hatcher was able to predict the future in 1947....?
Or, more likely, that was a later edition published after 1957.

[Mk42gunner]

Winchester kind of jumped the gun by bringing out the .308 Win before the 7.62 NATO round was finalized. Not that it isn't a decent cartridge, but it would be nice if the headspace dimensions and chamber pressures were the same.

A couple of other thoughts:
1. If Gen MacArthur had let the M1 Garand be built in .276 Pederson, there probably would be no such cartridge as the .308 Win/ 7.62mm NATO.

2. IIRC the FAL was being developed for a 7mm British round in the Post WWII era, but the US Military was adamant that the NATO ammo compatible rifle was going to be a thirty caliber. The big pocketbook won the argument, then the US went to mostly the 5.56 in the 1960's anyway. (The U.S. Navy was still using mostly M-14's until I retired in 2004).

Robert

[Petrol & Powder]

.308 Winchester chamber headspace gauges:
GO: 1.630"
NOGO: 1.634"
FIELD REJECT: 1.638"

US Army 7.62x51 chamber headspace gauges:
GO: 1.635"
FIELD REJECT: 1.6455"

SAAMI .308 Winchester chamber pressures:
MAP: 62,000 psi
MPSM: 66,000 psi
Minimum Proof Pressure: 83,000 psi
Maximum Proof Pressure: 89,000 psi

US Army 7.62x51 chamber pressures:
Maximum: 50,000 psi
Proof pressure: 67,500 psi

7.62x51 NATO pressure data from: TM 43-001-27 "Army Ammunition Data Sheets Small Caliber Ammunition" and headspace data from Kuhnhausen's M1/M1A shop manual.

.308 Winchester data from ANSI/SAAMI document Z299.4-1992, "Pressure and Velocity, Centerfire Rifle Sporting Ammunition".

That's all fine and dandy.

The acceptable chamber dimensions are close but not the same.

The maximum allowable pressures are different but that doesn't mean all commercial cartridges are loaded to maximum pressures OR that the military rifles WILL fail if exposed to the higher (but within SAAMI specs) commercial pressures.

It does mean the military standards are lower but it doesn't necessarily mean the rifles themselves are actually weaker than commercial rifles. It could just mean the military has a larger margin of safety created by maximum pressures well below the commercial limits.

I'm not advocating people ignore standards but I am saying that those lower military standards don't automatically translate into weaker rifles. There is a possibility that the military guns could withstand the higher commercial proof pressures but they chose to build a large margin of safety into the data by setting the standards lower.

I'm here to tell you that you can fire commercial .308 Winchester ammunition in a FN FAL without concern. In fact, you can fire a LOT of it without concern. That doesn't mean the commercial .308 ammo is operating at 62,000 psi and it doesn't mean that a military FN FAL will fail at 67,501 psi. It means those numbers represent standards and not necessarily absolute limits.

NOW, I wouldn't take NATO brass and load it to the maximum data for commercial .308 Winchester. That would be asking for trouble. But I would take factory loaded .308 Winchester ammunition off the shelf at a gun store and fire it in a military FN FAL without concern.

[yovinny]

Those numbers are skewed and cant be taken at face value like that.

#1. the USGI 'field reject' gauge is used only with a special test bolt for determining stretched receivers...It is not used like a standard HS 'field reject' gauge. The USGI 'no go' of 1.6375" is actually used as a standard 'field gauge'.

#2. Those pressure numbers are from 2 different testing systems. One being plunger crusher and the other being transducer. When the same system is used, the resulting pressure numbers are very similar.

USGI "field reject" FSN# 4933-647-3698 (sized 1.6455")
USGI "no go" FSN# 4933-916-9275 (sized 1.6375")
USGI "go" FSN#4933-916-9271 (sized 1.6355")
*referenced from USGI manual #TM 9-1005-223-34