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Old 09-19-2018, 07:17 AM
pocketshaver pocketshaver is offline
Join Date: Mar 2018
Posts: 98
Default chamber safety

Heres something im actually interested in from you guys, I admit it is a modern hash up of the ancient debate.

if its "unsafe" to use 5.56x45 55 grain FMJ in a .223 Remington, despite the original specifications of the two cartridges BEING THE SAME THING,

how is it SAFE to use that ammunition and chamber comibination AFTER merely using a reamer to alter the chamber leade to the .223 Remington chamber...

should one NOT actually be considering the SAAMI "standard" of using an ideal 150% MAP strength ?

ie, if a gun is going to be chambered in a cartridge creating 20,000 PSI,,,, the should be able to digest 30,000 PSI laods all day long with out issue.

Ive just read so many damned "expert" articles stating I can merely ream the chamber leade out in a .223 Remington and I can use any and all modern pressure level 5.56nato..
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Old 10-30-2018, 02:02 AM
Bill K Bill K is offline
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Join Date: Aug 2012
Location: N.E. Commie Kalifornia
Posts: 4,357
Default Chamber safety

Shooting it in a standard 223 chamber will caused pressure spike and that could damage the rifle and/or the shooter if the action ruptures.
The difference is in the leade as you mention. Now if you did give your standard 223 chamber a little more leade/Freebore, then you could safely fire either 5.56 or 223 rounds.
Despite what many will say, about pressure, leade, etc. manufactures of both the rifles and ammunition, all state not safe too fire 5.56 ammo in a standard 223 chamber. They know and have tested and sure know more about it than most of the home grown experts do.. So heed their warning and be safe and sane. Bill K
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Old 11-01-2018, 06:00 PM
squirrel_slayer squirrel_slayer is offline
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Join Date: Jan 2013
Posts: 450

there were tests done by a private operation with .223 and 5.56 and from what I gathered the lead/throating difference acts as an artificial expansion chamber(thusly increasing available capacity).

The best example I have come up with when others ask about the difference is think of a cartridge as a bomb. if we loaded the same powder charge inside the same size vessel with the only difference being one has a cork that pops (the bullet) and the other be sealed. 1 will explode and generate a lot more pressure until it reaches the yield strength where it ruptures. the other is a controlled explosion that propels the bullet down the barrel rapidly dropping pressure as it travels down the bore thus increasing internal volume.

I've seen pictures and horror stories about bullet setback (mostly in pistol rounds) nothing changes but the available space for the ignited powder to expand in yet by shrinking the vessel's size pressure goes up dramatically.

I'm sure some of the mathmaticians here could find the relative increase in volume between .223 and 5.56 chambers, but for theoretical sake lets say there is 2gr's of extra space created from the case mouth to the point where the bullet seals. that effectively is like increasing case capacity by 2gr's. the smaller the case the higher the %'age ratio.

one thing I've learned playing with these little cartridge is a small increase=big changes. things can go from zero pressure signs to whoa that was close in as little as .2-.3gr

Just as an experiment 1 time I loaded some 9mm rounds with the same charge with a light charge ~4.5gr unique with 124gr bullet I then loaded several rounds but seated bullets .030" deeper from 1.17" to 1.05" and it went from sooty case to normal operation and picked up 150 ft/sec with bullet seating depth being the only variable.

Last edited by squirrel_slayer; 11-01-2018 at 06:06 PM.
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