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Rifles, Reloading, Optics, Equipment
Reloading
"Rebounding" NATO 7.62 brass???
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<blockquote data-quote="Hummer70" data-source="post: 2729680" data-attributes="member: 85770"><p>Several things come into play. First off I am not aware of any machinegun and lets loaded rounds sit in a barrel be it hot or cold. Think about it, you have a barrel that is really hot and you chamber you are begging for a "cook off" which occurs when the round gets to around 400 deg F.</p><p></p><p>In the cook off tests we did at Aberdeen Proving Ground 500 rounds were fired in 500 seconds in M16 and 501st round chambered immediately and stop watch was started. A cook off will occur about 8 to 10 seconds later. In belt fed guns if you get a failure to fire you have to open bolt within 5 seconds of stoppage with a chambered round. If the gun crew does not open bolt in 5 seconds of less the testing is stopped and bolt not retracted for 30 minutes IIRC.</p><p></p><p>Machineguns chambers are not match dimension chambers and has the gun is fired there is wear on the locking surfaces and the base to shoulder length can increase a tad.</p><p></p><p>Military cases are designed for enhanced performance for many rounds and the they can get dents etc you will never see with a bolt action rifle.</p><p></p><p>Commercial dies can be a blessing or a curse in loading. For instance I have multiple sets of dies for 308 and 30.06. If you have a good set of calipers you and measure the inside diameters at the base of the die. Don't be surprised with dies made by the same vendor resize fired cases from .466 to .469.</p><p></p><p>I had custom chamber reamers made up to that restricted the amount of expansion in my cases. For instance 308 cases in unfired ammo can range from .466 to .469 diameter. Fired cases and measure upwards of .4734" and still be in SAAMI specs. Factory ammo can have a base dimension of .4703 and delivered with .4603 diameter loaded ammo and still be IN SPEC.</p><p></p><p>Think about it, you have a commercial 308 case that is .465 at the base and you shoot it in a chamber that can be .008" larger and you size it back down and first thing you know you get a case coming out that is only 1/2" long because the case was over worked. On my match rifles my cases only expand the base .002 to .003 and I don't the the "bulge"at the base which shortens case life.</p><p></p><p>I have never bought a small base die as if your rifle has the correct dimensions the ammo will go in and fire. Where the ship hits the sand is the makers of the dies have their reamers made on the large end of the range so they can be resharpened several times in the life of the reamer.</p><p></p><p>Another thing I have run into on multiple occasions is the dies are chambered too deep so the die does not contact the shoulder enough to set the shoulder back enough. I have 57 sets of dies and I have had to trim the bottoms off about 1/4th of them to get them to size the fired cases correctly. One die I had to take of .030" material to get them to size correctly. This is not restricted to one vendor either.</p><p></p><p>As well milspec cases are generally thicker in the wall areas because of the chamber sizes.</p><p></p><p>Back when primers/powder were cheap I ran tests. I have one 30.06 Match case I have loaded and fired 157 times and it is still waiting on me to get back to feeding it. I have run two milspec 7.62 cases to 90 reloads and still going fine.</p><p></p><p>I used to shoot with a buy named Marty Tyska, he was a ammo engineer at Frandford and Picatinny Arsenals and a highpower shooter and he made a statement I have remembered for the last 40+ years which was "You should never lose a case from a split neck, if you do you have not cared for your cases." You should only lose a case from the primer pocket getting loose which occurs quickly in commercial cases because they are designed to be made for the least cost possible. MILSPEC cases are heavier than commercial cases because the case walls are thicker and there is a hardness requirement so they can be run in semi and full auto weapons without a problem.</p><p></p><p>I had friends in the ammo industry and some cases are only good for two reloads and the primer pockets get loose quick. Yes they can still be reloaded but if you do so you will start to see where there is gas leakage around the primer edge that will cut a groove in your bolt face.</p><p></p><p>Now small base dies, why does this term come up. Remember above I said that the chamber reamers are resharpened. Once they get down to a certain point they are "under spec" and the vendors use them one more time and call them "small base dies" which is a money maker.</p></blockquote><p></p>
[QUOTE="Hummer70, post: 2729680, member: 85770"] Several things come into play. First off I am not aware of any machinegun and lets loaded rounds sit in a barrel be it hot or cold. Think about it, you have a barrel that is really hot and you chamber you are begging for a "cook off" which occurs when the round gets to around 400 deg F. In the cook off tests we did at Aberdeen Proving Ground 500 rounds were fired in 500 seconds in M16 and 501st round chambered immediately and stop watch was started. A cook off will occur about 8 to 10 seconds later. In belt fed guns if you get a failure to fire you have to open bolt within 5 seconds of stoppage with a chambered round. If the gun crew does not open bolt in 5 seconds of less the testing is stopped and bolt not retracted for 30 minutes IIRC. Machineguns chambers are not match dimension chambers and has the gun is fired there is wear on the locking surfaces and the base to shoulder length can increase a tad. Military cases are designed for enhanced performance for many rounds and the they can get dents etc you will never see with a bolt action rifle. Commercial dies can be a blessing or a curse in loading. For instance I have multiple sets of dies for 308 and 30.06. If you have a good set of calipers you and measure the inside diameters at the base of the die. Don't be surprised with dies made by the same vendor resize fired cases from .466 to .469. I had custom chamber reamers made up to that restricted the amount of expansion in my cases. For instance 308 cases in unfired ammo can range from .466 to .469 diameter. Fired cases and measure upwards of .4734" and still be in SAAMI specs. Factory ammo can have a base dimension of .4703 and delivered with .4603 diameter loaded ammo and still be IN SPEC. Think about it, you have a commercial 308 case that is .465 at the base and you shoot it in a chamber that can be .008" larger and you size it back down and first thing you know you get a case coming out that is only 1/2" long because the case was over worked. On my match rifles my cases only expand the base .002 to .003 and I don't the the "bulge"at the base which shortens case life. I have never bought a small base die as if your rifle has the correct dimensions the ammo will go in and fire. Where the ship hits the sand is the makers of the dies have their reamers made on the large end of the range so they can be resharpened several times in the life of the reamer. Another thing I have run into on multiple occasions is the dies are chambered too deep so the die does not contact the shoulder enough to set the shoulder back enough. I have 57 sets of dies and I have had to trim the bottoms off about 1/4th of them to get them to size the fired cases correctly. One die I had to take of .030" material to get them to size correctly. This is not restricted to one vendor either. As well milspec cases are generally thicker in the wall areas because of the chamber sizes. Back when primers/powder were cheap I ran tests. I have one 30.06 Match case I have loaded and fired 157 times and it is still waiting on me to get back to feeding it. I have run two milspec 7.62 cases to 90 reloads and still going fine. I used to shoot with a buy named Marty Tyska, he was a ammo engineer at Frandford and Picatinny Arsenals and a highpower shooter and he made a statement I have remembered for the last 40+ years which was "You should never lose a case from a split neck, if you do you have not cared for your cases." You should only lose a case from the primer pocket getting loose which occurs quickly in commercial cases because they are designed to be made for the least cost possible. MILSPEC cases are heavier than commercial cases because the case walls are thicker and there is a hardness requirement so they can be run in semi and full auto weapons without a problem. I had friends in the ammo industry and some cases are only good for two reloads and the primer pockets get loose quick. Yes they can still be reloaded but if you do so you will start to see where there is gas leakage around the primer edge that will cut a groove in your bolt face. Now small base dies, why does this term come up. Remember above I said that the chamber reamers are resharpened. Once they get down to a certain point they are "under spec" and the vendors use them one more time and call them "small base dies" which is a money maker. [/QUOTE]
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"Rebounding" NATO 7.62 brass???
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