Help me pick an evil black rifle

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doctorjj

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Geez, your one of those guys huh
By pressure, I suppose you mean gas pressure? So, in that case, the pressure is working for you to unlock the bolt from barrel extension, so it's helping, as opposed to a piston system that just forces it off. Piston guns keep your BCG and lower parts cleaner and cooler. That's where the advantages end. There is no accuracy advantage. There is no reliability advantage. In fact, there is a lot of real world data that shows they are less reliable.
 

rc508pir

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By pressure, I suppose you mean gas pressure? So, in that case, the pressure is working for you to unlock the bolt from barrel extension, so it's helping, as opposed to a piston system that just forces it off. Piston guns keep your BCG and lower parts cleaner and cooler. That's where the advantages end. There is no accuracy advantage. There is no reliability advantage. In fact, there is a lot of real world data that shows they are less reliable.
I didn't say there was a reliability improvement in pistons over DI. A bolt in a DI gun will break before it does in a piston gun, because of the heat and pressure, inside the BCG. I'm not saying the bolt is going to break after a few hundred rounds. The service life on a M4 bolt is 8 to 10k. After that, its replaced do to fatigue from the heat and pressure from carbine gas sys. The M16 bolt service life was 18Kk+ service life. You don't have that issue with a piston AR.

You have to remember, the gas expanding in the BCG is also forcing the bolt forward as the Carrier is forced to the rear. That pressure and heat stresses the bolt and over time, especially if you're getting it hot.
 

doctorjj

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I didn't say there was a reliability improvement in pistons over DI. A bolt in a DI gun will break before it does in a piston gun, because of the heat and pressure, inside the BCG. I'm not saying the bolt is going to break after a few hundred rounds. The service life on a M4 bolt is 8 to 10k. After that, its replaced do to fatigue from the heat and pressure from carbine gas sys. The M16 bolt service life was 18Kk+ service life. You don't have that issue with a piston AR.

You have to remember, the gas expanding in the BCG is also forcing the bolt forward as the Carrier is forced to the rear. That pressure and heat stresses the bolt and over time, especially if you're getting it hot.
Wrong again. This has all been looked at. The temperature difference is minimal in comparison so what it takes to actually affect the steel these are made of. The mechanical difference is not minimal. Piston system bolts fail before DI bolts will. Been proven over and over again. Look at the High Round Count M4/AR thread on Ar15.com for the truth. Real world experience.
 

rc508pir

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Wrong again. This has all been looked at. The temperature difference is minimal in comparison so what it takes to actually affect the steel these are made of. The mechanical difference is not minimal. Piston system bolts fail before DI bolts will. Been proven over and over again. Look at the High Round Count M4/AR thread on Ar15.com for the truth. Real world experience.
First off, AR15.com is not proof of anything. I might as well look at 1 and 5 star ratings on Amazon and accept them as gospel.Both Colt and FN did testing on this very matter and the difference of carbine, mid and rifle length gas systems have on the effect of bolt service life.
There is no force on the bolt that weakens the bolt during any part of the cycle, except for the;
1. Cartridge discharge, forcing the bolt rearward (never saw a bolt lug break off in 22 years of service, they always break at the cam pin slot).
2. Gas expansion inside the BCG

In any case, I am obviously not going to change your mind, so I'm not going to worry about it
 

doctorjj

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First off, AR15.com is not proof of anything. I might as well look at 1 and 5 star ratings on Amazon and accept them as gospel.Both Colt and FN did testing on this very matter and the difference of carbine, mid and rifle length gas systems have on the effect of bolt service life.
There is no force on the bolt that weakens the bolt during any part of the cycle, except for the;
1. Cartridge discharge, forcing the bolt rearward (never saw a bolt lug break off in 22 years of service, they always break at the cam pin slot).
2. Gas expansion inside the BCG

In any case, I am obviously not going to change your mind, so I'm not going to worry about it
Never said I had "proof". But at least there is data. Not just your anecdotal experience. The fact that you've never seen a bolt out break is proof you of your limited experience. And there are other forces going on than just those 2 but you're never going to change your mind.
 

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