M14 Firing pin bridge saftey test method
- Thread starter Savage
- Start date
looks like my rifle is around the .165" mark.... should I be concerned?
If the bolt go this far, why wouldn't it drop the rest of the way? I don't think there is any more forward motion once it drops off. There would almost need to be something under the roller, or op rod not fully extending to pull it down.
If it got this far, wouldn't an oversized case no longer be an issue?
The Operating Rod will force the bolt to fully seat
This is not an issue with Factory or properly sized or Reloaded Ammunition
The bolt may or may not fully seat or close all the way when a improperly resized reloaded case is used. This can result in a headspace issue and there is a chance that the case will be unsupported which can lead to a problems when fired .
At the risk of being flamed, I'm going to submit this.
I unintentionally fed one of these mistakes (I know.. what a dumb ass) to my M305. The bridging mechanism saved my butt, as all that I got was a click. When I inspected the situation at the range, it looked to me that a round was fully chambered, so the round was pretty close to being in full battery. End result is that a round was in the chamber and it was pretty hard to extract!
The incident woke me up in terms of checking the final result of each and every bullet seating operation.
After hearing about the "MY NORC BLEW UP" episode, I tried every conceivable out of battery test I could think of using a dummy round, and then I repeated the tests with a primed empty casing. The only time I could coax the M305 into firing was in full battery.
To this end, I'm not going to loose any sleep over THE INCIDENT and will continue to shoot and tweek my M305 to it's fullest potential.
I unintentionally fed one of these mistakes (I know.. what a dumb ass) to my M305. The bridging mechanism saved my butt, as all that I got was a click. When I inspected the situation at the range, it looked to me that a round was fully chambered, so the round was pretty close to being in full battery. End result is that a round was in the chamber and it was pretty hard to extract!
The incident woke me up in terms of checking the final result of each and every bullet seating operation.
After hearing about the "MY NORC BLEW UP" episode, I tried every conceivable out of battery test I could think of using a dummy round, and then I repeated the tests with a primed empty casing. The only time I could coax the M305 into firing was in full battery.
To this end, I'm not going to loose any sleep over THE INCIDENT and will continue to shoot and tweek my M305 to it's fullest potential.
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I have been gone the past couple of days (clearing and building a 500 meter rifle range out at the cabin before breakup hits...woohoo!) and thus missed all the action in this thread....
My perspective on Savage's test as follows:
This is a well thought out test that provides a good indication regarding the engagement tolerances of the receiver bridge safety with a particular bolt/firing pin/receiver combination. In theory it should give a good indication about how far out of battery a bolt can be while forward motion of the firing pin is unhindered by the receiver bridge.
I like his initial test even better....prime a couple of empty reloaded cases, set a dime under the bolt, and drop the hammer to see if the primer fires. Draw your own conclusions after you see how far out of battery your rifle is (if at all) capable of being fired.
One thing the threads on the norinco kablooie has really drove home to me is the degree to which people really don't understand how their rifle is designed to work. Nothing wrong with this at all and I've been encouraged by the spirited discussion as people start to explore these things.
Something that discourages me though is the notion that only an expert can have a valid opinion. What is it that makes Jerry K an bona-fida certified expert on the M1A? Is it just that he wrote a book? Hardly. For the record I do happen to think that Jerry K is a bona-fida expert on the M1A but that is not based on his internet certified pedigree...it is based on me reading his book, carefully thinking about everything he's written in there and thus drawing my own conclusions regarding the merit of his work. Another guy who gets no press here and, IMHO, has highly relevent observations and options relating to what can go wrong with an M14 type rifle is Glen Zediker (Google for his article titled "Reloading for the Match M14"). But back to my original point which is to question the notion that we must always defer to the benevolent knowledge of a learned sage who will do all our thinking for us.
People who handload for these rifles should have a better-than-average understanding of how they work.
People who tweak these rifles should have a better-than-average understanding of how they work.
This better-than-average understanding should include at the minimum (if not more) thinking and evaluating everything anyone ever tells you about the gun...you yourself is responsible (and will have to deal with the consequences of a kablooie if it happens to you or someone you care about when they fire your rifle)....do youself a favor and THINK.
Based on my own observations and experience I believe that the receiver bridge safety feature of the M14 type rifle (norincos more than others) is unreliable. Does Savage's test above support this opinion? I think it does but don't take my word for it...again try it on your own rifle and draw your own conclusions. Does the fact that 2/3rds of my norinco M14 type rifles will fire a sized & primed case with the bolt only halfway into battery keep me from shooting thousands and thousands of handloads a year through them? No way jose. I love and shoot my M14 type rifles regularly.
I am anal though about how I manage my reloading practice (ie: small base dies, recessed primers, tonnes of inspection etc etc etc) AND ADDITIONALY how clean I keep the chamber of my guns. This last point on chamber cleanliness is, in my opinion, equally important to the use of small base die. In order to be reasonably safe we need to make sure that the case can move freely and completely into the chamber. It's also based on this last point that I disagree with Savage's opinion that the same thing would not have happened with factory loaded ammunition.
If the chamber is very dirty and the case hangs up or get's wedged at some weird angle based on some combination of brass shavings, ejector plunger force wedging, cosmoline and powder residue the bolt might hang up a bit before going into battery. While this is less likely with factory ammunition (ie: smaller brass - more space between brass and chamber wall) it is not hard to imagine that it is very possible with a dirty chamber all grimed up with a bunch of cr*p.
This is especially relevent on a gun with ultra-tight headspace (ie: the sometimes-CGN-sought-after-1-thou-crush) How much cr*p does it take to keep the bolt from closing half way? My measurements (taken with stripped bolts on guns headspaced right on 1.630 SAMMI spec; measured with a set of numerous headspace gauges that grow in 1 thou increments) indicate that 50% bolt engagement is at about 5 thou (1.635). At 9 thou (1.639) the bolt is only about 15% closed! So how much brass-shaving-impregnated-grease does it take to plug up the chamber shoulder that far? Your guess is as good as mine but the moral of my story is to keep your chamber clean and to size your brass small. This is less an issue on liberally headspaced guns such as most of the norincos I've seen...one could even speculate that the chinese purposely cut their headspace this long as an additional safety feature.
Bottom line: if the case can't go completely into the chamber the bolt will likely not close the whole way. Whether this is from an oversized case that was not resized properly, a bunch of stuff in the chamber that hung the case up, or a combination of the two does not matter....if the bolt does not completely closed you can't bank on the receiver bridge to save your bacon.
Anyway....time to shut off the rant.
Good luck everyone and happy shooting.
Brobee.
My perspective on Savage's test as follows:
This is a well thought out test that provides a good indication regarding the engagement tolerances of the receiver bridge safety with a particular bolt/firing pin/receiver combination. In theory it should give a good indication about how far out of battery a bolt can be while forward motion of the firing pin is unhindered by the receiver bridge.
I like his initial test even better....prime a couple of empty reloaded cases, set a dime under the bolt, and drop the hammer to see if the primer fires. Draw your own conclusions after you see how far out of battery your rifle is (if at all) capable of being fired.
One thing the threads on the norinco kablooie has really drove home to me is the degree to which people really don't understand how their rifle is designed to work. Nothing wrong with this at all and I've been encouraged by the spirited discussion as people start to explore these things.
Something that discourages me though is the notion that only an expert can have a valid opinion. What is it that makes Jerry K an bona-fida certified expert on the M1A? Is it just that he wrote a book? Hardly. For the record I do happen to think that Jerry K is a bona-fida expert on the M1A but that is not based on his internet certified pedigree...it is based on me reading his book, carefully thinking about everything he's written in there and thus drawing my own conclusions regarding the merit of his work. Another guy who gets no press here and, IMHO, has highly relevent observations and options relating to what can go wrong with an M14 type rifle is Glen Zediker (Google for his article titled "Reloading for the Match M14"). But back to my original point which is to question the notion that we must always defer to the benevolent knowledge of a learned sage who will do all our thinking for us.
People who handload for these rifles should have a better-than-average understanding of how they work.
People who tweak these rifles should have a better-than-average understanding of how they work.
This better-than-average understanding should include at the minimum (if not more) thinking and evaluating everything anyone ever tells you about the gun...you yourself is responsible (and will have to deal with the consequences of a kablooie if it happens to you or someone you care about when they fire your rifle)....do youself a favor and THINK.
Based on my own observations and experience I believe that the receiver bridge safety feature of the M14 type rifle (norincos more than others) is unreliable. Does Savage's test above support this opinion? I think it does but don't take my word for it...again try it on your own rifle and draw your own conclusions. Does the fact that 2/3rds of my norinco M14 type rifles will fire a sized & primed case with the bolt only halfway into battery keep me from shooting thousands and thousands of handloads a year through them? No way jose. I love and shoot my M14 type rifles regularly.
I am anal though about how I manage my reloading practice (ie: small base dies, recessed primers, tonnes of inspection etc etc etc) AND ADDITIONALY how clean I keep the chamber of my guns. This last point on chamber cleanliness is, in my opinion, equally important to the use of small base die. In order to be reasonably safe we need to make sure that the case can move freely and completely into the chamber. It's also based on this last point that I disagree with Savage's opinion that the same thing would not have happened with factory loaded ammunition.
If the chamber is very dirty and the case hangs up or get's wedged at some weird angle based on some combination of brass shavings, ejector plunger force wedging, cosmoline and powder residue the bolt might hang up a bit before going into battery. While this is less likely with factory ammunition (ie: smaller brass - more space between brass and chamber wall) it is not hard to imagine that it is very possible with a dirty chamber all grimed up with a bunch of cr*p.
This is especially relevent on a gun with ultra-tight headspace (ie: the sometimes-CGN-sought-after-1-thou-crush) How much cr*p does it take to keep the bolt from closing half way? My measurements (taken with stripped bolts on guns headspaced right on 1.630 SAMMI spec; measured with a set of numerous headspace gauges that grow in 1 thou increments) indicate that 50% bolt engagement is at about 5 thou (1.635). At 9 thou (1.639) the bolt is only about 15% closed! So how much brass-shaving-impregnated-grease does it take to plug up the chamber shoulder that far? Your guess is as good as mine but the moral of my story is to keep your chamber clean and to size your brass small. This is less an issue on liberally headspaced guns such as most of the norincos I've seen...one could even speculate that the chinese purposely cut their headspace this long as an additional safety feature.
Bottom line: if the case can't go completely into the chamber the bolt will likely not close the whole way. Whether this is from an oversized case that was not resized properly, a bunch of stuff in the chamber that hung the case up, or a combination of the two does not matter....if the bolt does not completely closed you can't bank on the receiver bridge to save your bacon.
Anyway....time to shut off the rant.
Good luck everyone and happy shooting.
Brobee.
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300Spartans
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