Bimetal Jacket Effect on Steel Targets

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  • Doco Overboard

    Ultimate Member
    Odd fact: my large frame AR in .308 runs more reliably suppressed on a lower gas setting with steel cased ammo than it does with brass cased ammo. Not sure why that is.

    Next time you have cause to think about it, or if you even care to do it, check your (brass/ steel) cartridges with a protractor before and after firing and use a comparator. Especially the sharp angle at the shoulder neck juncture.
    What you may be able to determine is that differences in the sharp shoulder, (brass vs. steel) have a pronounced effect on pressure and internal ballistics. These same characteristics also have a degree of influence on throat erosion and were a concern for wildcatters and early developers of high velocity cartridges. Not that they used steel cases but you get the picture.

    In your rifle, all that may be happening is that the steel cased ammo does not have the elasticity of brass and the turbulence of the expanding gases reacts differently with the steel case, at the steeper shoulder angle, than the brass, working with the lower gas setting more reliably as the gas is moved forward towards the case mouth, the bore and until the projii is clear of the entire vessel and could be partly responsible for your observation.
     

    Zorros

    Ultimate Member
    Dec 10, 2017
    1,407
    Metropolis
    I just returned from the range and sprayed my shoot steel 1/4” target. For the first time i noticed tiny dimples on the face . i suppose due to the angle and light. I only shoot 380,38 sp,357 sig, 9mm, 45 acp and 45 colt. From about 15 yds. I have shot this often for 6 years. Have used 9mm bi metal and 45acp bi metal. Target owes me nothing, and shoot steel says don’t use bi metal...could shoot thru the target!
    Any danger coninuing to use this target.
    !
     

    Gcs7th

    Ultimate Member
    Jan 26, 2012
    1,280
    AGC
    I’ve chornographed wolf steel case 223 and it was appropriately 500fps slower than wolf Gold. That 500fps does more damage than XM855 to steel.
     

    lazarus

    Ultimate Member
    Jun 23, 2015
    13,678
    I just returned from the range and sprayed my shoot steel 1/4” target. For the first time i noticed tiny dimples on the face . i suppose due to the angle and light. I only shoot 380,38 sp,357 sig, 9mm, 45 acp and 45 colt. From about 15 yds. I have shot this often for 6 years. Have used 9mm bi metal and 45acp bi metal. Target owes me nothing, and shoot steel says don’t use bi metal...could shoot thru the target!
    Any danger coninuing to use this target.
    !

    Unlikely to be dangerous. If you start to notice a serious bend in it, maybe retire it. Same if serious pitting starts occurring. Eventually after throwing enough lead at it, you can anneal the steel and change the hardness. At that point you can get the target itself spalling or splashing, which would be bad at close distance as you are likely to get fragments back at you or ricochets instead of the bullet shattering.

    That said, it is likely still safe. Pistol rounds don’t do nearly the damage rifle rounds do.
     

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