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I took my son shooting for his birthday and brought my M1 rifles and some military surplus (maybe?) FN 66 ammo.

I only shot one of these two M1's that day (the one with the bayonet, of course) and after a few rounds I noticed that 50% of the cases had primers that were "proud" or slightly backing out.
I immediately switched to other ammo (commercial Remington) - no problems. I now wish I had shot a few rounds of the suspect ammo in the other M1 just see if the problem also happened in that gun.

Questions:
1)
Is this a sign of overpressure ammunition, slightly off rifle headspace (the second type of ammo didn't show the same problem), or something else?

2) Does that fired primer (besides being backed out) look overly "flat" to you given that unfired it was "rounded" (see the second picture).

3)
Is there any scuttlebutt (good or bad) on FN 66 .30-06 ammo? I couldn't find any?

Any advice would be appreciated.
3752822
3752823
 

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the unfired ammo looks to have original primers, so I would postulate it is not reloads. Fired case definitley looks like a tad to much pressure - flattened primer etc.... I have no history with the FN66 ammo, but generally the ammo from FN has been good. The problem with surplus these days is that we have no idea how it has been stored.
 

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Can happen with LOW pressure rounds as the case is pushed forward by the primer strike the primer moves rearward on ignition, but the case does not move or stretch on firing to reseat it.
Not saying this is the case here, but the thickness/strength of the FN case vs the Remington may be significant. Weigh each case.

I have never see this with FN 1960s 30-06.
 

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The ammo is too short or the chamber is a bit too long or a combination of both.
The pressure looks ok.
 
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FN 1966 .30-06 is going to be good for the FN49 .30-06 which was their standard rifle, and was also probably for export to other .30-06 M1 Garand users of the period (France, Italy, Netherlands, Greece, to name a few). The primers are BERDAN, and very likely corrosive and mercuric anyway, not reloadable. The gas pressure curve on your ammo is slow, so the primer backs out a bit rather than "sticking" in the pocket with an higher initial spike - note the other ammo had "normal" primers. Nothing to be concerned about, other than the corrosive salts in your bore from the priming. The FN primers are a slightly small Berdan that looks like a large rifle, but is a few thousands larger. Many countries and even lots of FN ammo have a primer sealer to keep out moisture and even assist in primer retention - lots of issues with MGs when the primers fall out in the action.
 

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Why is there no mention about checking head space? I have a problem blaming the ammo unless all other causes are eliminated. An unfired case should be checked with a min/max case length gage.
 

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Why is there no mention about checking head space? I have a problem blaming the ammo unless all other causes are eliminated. An unfired case should be checked with a min/max case length gage.
Probably because the issue was only happening with this particular ammo. He used Remington ammo without any issues.
 

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Why is there no mention about checking head space? I have a problem blaming the ammo unless all other causes are eliminated. An unfired case should be checked with a min/max case length gage.
Odds are pretty good that FN ammunition, no matter what the caliber or year, is going to be high quality stuff. VERY unlikely that the cases would be out-of-spec.

That being said, there MIGHT be storage issues.

Proud primers are a symptom of LOW pressure, not one of excessive headspace.

Typically what happens is upon firing, the case is pushed as far forward in the chamber as the firing pin can push it. The primer when it fires (either crimped or uncrimped, high pressure or low), will blow to the rear as the round is fired, being stopped by the boltface (the pressure from the priming compound in that small primer pocket before the gases vent into the case causes it).

The primer will remain 'proud' until the internal pressure in the case itself is sufficient to overcome the elasticity of ythe brass, and stretch the brass in the case web area. This 'allows' the case head to be driven back to the boltface. When the case head moves rearward, it will slide back over the primer, making everything to appear flush once again.

A few days ago, somebody posted an animation in one of the threads about what a .303 round goes through upon firing. I can not locate it now, or I would post it here. It is basically the same thing that would happen to a .30-06.

If someone remembers where it is, it might be useful to post here.
 

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Both of those Garands are real lookers. Just sayin. I know it's no help.
 

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Both of those Garands are real lookers. Just sayin. I know it's no help.
Thanks, yeah they are nice. The one with the bayonet is a Springfield Armory Nov. 1940 (80,xxx SN), and the other is a Springfield Jun 1942 (675,xxx SN). I bought them both 20+ years ago so they've been a good investment. I hope to not blow them up due to an ammo or headspace problem.
 

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My thanks to everyone for all the comments so far.
A friend loaned me some nice .30-06 case gauges. The unfired FN 66 ammunition dimensions look fine in both types of gauges.
He also loaned me some surplus US Ordnance Cal 30 headspace gauges, I'll disassemble the M1 and let you know what I find. I'd rather use some new commercial gauges but let's see what these "oldies" tell me.
3753159

3753160
 

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My thanks to everyone for all the comments so far.
A friend loaned me some nice .30-06 case gauges. The unfired FN 66 ammunition dimensions look fine in both types of gauges.
He also loaned me some surplus US Ordnance Cal 30 headspace gauges, I'll disassemble the M1 and let you know what I find. I'd rather use some new commercial gauges but let's see what these "oldies" tell me.
View attachment 3753159
View attachment 3753160
Will those gauges accept your FIRED cases? See if they now go further into the gauge after firing...where do the base of the case vs extended primers lie on the gauge.
 

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Discussion Starter #13 (Edited)
Will those gauges accept your FIRED cases? See if they now go further into the gauge after firing...where do the base of the case vs extended primers lie on the gauge.
Ah, that's a good question. No, a fired "FN 66" case from the M1 would not go all the way into the gauge as the section just above the base had expanded too much. What does that indicate? Is it normal for a fired case to stay expanded like that?
3753293
 

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Yes it is normal...your gauge is a cartridge gauge. This indicates ctg “max”. Your case needs sizing to chamber, so it will not enter the gauge. They do make fired case gauges I think.
 

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I took my son shooting for his birthday and brought my M1 rifles and some military surplus (maybe?) FN 66 ammo.

I only shot one of these two M1's that day (the one with the bayonet, of course) and after a few rounds I noticed that 50% of the cases had primers that were "proud" or slightly backing out.
I immediately switched to other ammo (commercial Remington) - no problems. I now wish I had shot a few rounds of the suspect ammo in the other M1 just see if the problem also happened in that gun.

Questions:
1)
Is this a sign of overpressure ammunition, slightly off rifle headspace (the second type of ammo didn't show the same problem), or something else?

2) Does that fired primer (besides being backed out) look overly "flat" to you given that unfired it was "rounded" (see the second picture).

3)
Is there any scuttlebutt (good or bad) on FN 66 .30-06 ammo? I couldn't find any?

Any advice would be appreciated.
View attachment 3752822 View attachment 3752823
Remington might be higher pressure than FN and slaming the case harder into chamber rear thus re-seating the primer. I suggest checking the headspace in your gun.
 

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ive had the same issue with fn 66 and fn 67 ammo, never had a problem with any other ammo in my multiple garands, but they are berdan primed, so they just got tossed into the brass bucket
 

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Yep, low pressure.
Have the same situation with my 7.9mm reloads.
In my case, though, I know the loads are light.
I generally do not exceed the midpoint on the recommended load range for the chosen powder, for example, currently I'm loading 42 grains of IMR4895 behind a 198 grain FMJ projectile in mixed headstamp brass.
42 grains is the midpoint in the range (39 to 45 grains) listed for a 200 grain projectile.
All fired cases show some amount of primer protrusion, some more, some less depending on the temper of the brass.
Rifle is a 1918 dated 98A mixmasters.
Keeping the load on the light side allows the rifle to shoot to point of aim at 100 yards using the 300 yard battle sight.
It is not the best solution but this particular rifle spews 150 (ish) grain projectiles all over the map, it definitely has a taste for heavy weights.
If this dry season ever ends and supplies become more abundant I will continue to experiment.

Question I have is how does this (apparently) underpowered ammo perform in the Garand?
Does the action cycle properly?
 

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Yep, low pressure.

Question I have is how does this (apparently) underpowered ammo perform in the Garand?
Does the action cycle properly?
To make the rifle reliable, the Garand was built with a pretty large gas port (and VERY robust parts to be able to withstand the beating they were going to take). From the evidence presented by the OP, he typical Garand is likely going to work with a low enough gas port pressures to cause primer protrusion.
 
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