The Lock-N-Load® Headspace Comparator extends brass life, improves accuracy, and enhances safety. The gauge measures variations in brass before and after firing or re-sizing. It allows for headspace comparison between fire-formed brass and re-sized brass.

The five bushings that come with the Lock-N-Load® Headspace Comparator provide the ability to check most bottleneck cases, from .17 Rem through belted magnums. Ackley Improved chambers use the same bushing size as the parent case. See chart provided or consult product instructions for cartridge/bushing size details.


  • This is for the bushing only, the comparator body and that are required for the set to work are sold separately
  • All bushings are interchangeable with the Comparator
  • Must be used with Calipers.


    • 5 bushings

    Body with 5 Bushing Set Item #HK66

    5 Bushings Only Item #HK55

    Lock-N-Load® Headspace Bushings

    F .188"
    Bushing blank with .188 diameter hole
    G .240"
    17 Hornet
    A .330"
    17 Remington
    204 Ruger
    221 Remington Fireball
    222 Remington
    222 Remington Magnum
    223 Remington
    220 Swift
    B .350"
    22 PPC
    22-250 Remington
    6mm PPC
    6mm Bench Rest Remington
    250-3000 Savage
    7mm Bench Rest Remington
    300 Blackout
    6.5 Grendel
    C .375"
    6mm Remington
    257 Roberts
    25-06 Remington
    270 Winchester
    7 X 57mm Mauser
    280 Remington
    30-30 Winchester
    30-06 Springfield
    300 H & H Magnum
    7.62 X 39 British
    6.5 X 55mm
    7mm Winchester Short Magnum
    30-40 Krag
    6.5 Creedmoor
    6.5mm X 47 Lapua
    D .400"
    223 Winchester Super Short Magnum
    243 Winchester
    243 Winchester Super Short Magnum
    260 Remington
    270 Winchester Short Magnum
    7mm-08 Remington
    300 Savage
    308 Winchester
    35 Remington
    E .420"
    284 Winchester
    7mm Remington Magnum
    7mm Remington Ultra Magnum
    300 Winchester Short Magnum
    300 Weatherby Magnum
    325 Winchester Short Magnum
    338 Winchester Magnum
    350 Remington Magnum
    375 H & H Magnum
    264 Winchester Magnum
    7mm Remington Short Action Ultra Magnum
    7mm Shooting Times Westerner
    300 Remington Short Action Ultra Magnum
    300 Winchester Magnum
    300 Remington Ultra Magnum
    8mm Remington Magnum
    338 Remington Ultra Magnum
    35 Whelen

    Hornady Lock-N-Load Headspace Comparator Kit (HK55)

    Out of Stock