OK, FINE,
This is one of the very few actual KABOOMS we have ever had with any M-14 rifle here in Canuckistan, so let’s look at it carefully:
First of all, there is no firing pin spring in an M-14.
The firing pin is cammed in and out of engagement by the bolt turning and the receiver bridge allowing or blocking the firing pin tail through the slot in the receiver. This is called receiver/bolt/firing pin timing. When this timing is properly set up, the firing pin can NOT go forward until the bolt is most of the way into the locking lugs. This is one of the built in safety devices of the M-14, and in every M-14 type rifle I've ever checked [ and this is DOZENS ] this mechanism was working as designed.
SO,
possible reasons for a closed chamber KABOOM:
1.] Bullet to neck fit aka” “draw” not enough, allowing the bullet to be pushed back into the case and creating massive pressure jump on firing.
2.] Obstruction in bore …
as in - the first bullet did not have enough powder to get out of the barrel.
But, this usually would also mean there was not enough gas to cycle the action, and loading the second round would require manual activation of the op rod.
3. ] Reloads too long for chamber or dirty chamber
4.] Soft primers ... the inertia of the bolt slamming closed will usually leave a slight dimple in the primers [ SLIGHT dimple = just barely noticeable ]. Check your unfired rounds once in a while, and you will probably see the mark ]. This should happen ONLY when the bolt is fully home, and the round is fully chambered.
what IaninVic said:
The M 14 is designed to fire military ammunition with hard primers
Federal primers and reloads without a really heavy crimp will go bang badly. Also the brass must be full length resized for each reload, you can't neck size for a semi. The loading cycle for these guns really slams the loaded round up the ramp and more or less jams it into the chamber, without a strong crimp the bullet sets back into the case.This reduces the case capacity and drives pressures through the roof. With the M14 if you're reloading use CCI milspec primers and a very strong crimp, also use projectiles similar to the military weight (147-168 for 7.62) and select a powder with a similar burn rate (same velocity) to military spec.
This is very good advice,
However,
I have personally shot literally thousands of rounds of FACTORY LOADED Federal 168 Gr HP BT Match .308 ammo out of properly built M-14s without a problem.
Possible reasons for an OPEN bolt Kaboom [ which this sounds more like ]
“ … when I looked at the ground i realized what had happened. After the first round went off, the bolt came back and loaded the next shell, but not all the way. It was struck by the firing pin before the round was properly placed and caused it to explode which was directed downwards and caused 2 other rounds to go off in the mag …”.
1.] Primers not seated fully [ MOST LIKELY CAUSE for reloads ]
2.] Firing pin extrusion too large, again with the M-14 built in safety mechanisms, this is not usually a problem, but if the rear tip of the firing pin is worn, or chipped,then this could be significant.
3.] broken firing pin or dirty filthy firing pin slot …
same as # 3 above and another likely cause
5.] Hammer following and slam fire … but again, if the timing is correct, this should NOT happen.
Prevention:
What Brobee said … every bit of it valuable and proven advice
PS: while I have reloaded for the M-14, I no longer do so. When I did reload, I used my own once fired MILITARY brass [ not pickups from the range that may have been fired though an MG with horrendous headspace]. I would NOT recommend reloading fired commercial brass, especially not if you don’t KNOW FOR CERTAIN that your headspace is right for .308. Read the stickies on M-14 headspace …
most of the current crop of 14s that I have checked recently, new out of the box, are running about .012" - .014” thou GREATER THAN 7.62 NATO GO … which is already .0005” greater than SAMMI specs for .308 Winchester NO GO.
Case head separation on reloads from long chambered rifles is a very real possibility. Although, even with these very long headspaces, I have no personal knowledge of case head separation with NEW factory loaded .308, and none with thicker walled 7.62 NATO ammo.
As usual,
with any advice you get from the internet,
your personal mileage may vary.
PS: I have thre Norc M-14 rilfes, all with longer than spec headspace, and I trust thesde over almost any other Mil Surp type rifle.
[;{)
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