Description Modular Headspace Comparator Inserts Introducing the Modular Headspace Comparator Insert for Precision Measurement The Modular Headspace Comparator Insert offers unparalleled accuracy for cartridge headspace and bullet measurements. This innovative insert works seamlessly with the Modular Headspace Comparator Body, which must be purchased separately, to deliver a highly adaptable tool for precise measurements. Designed with the user in mind, this modular insert simplifies the process of measuring headspace with exceptional accuracy. Why Choose the Modular Headspace Comparator Insert? Short Action Customs has reimagined its original headspace comparator, made from 6061 aluminum, to create a superior Modular Headspace Comparator. This updated version supports cartridges up to 338 Lapua Magnum, providing greater versatility and ease of use. Each bullet and headspace insert is precision machined from 17-4 Stainless Steel, ensuring maximum durability and corrosion resistance. Compatibility and Usage Our inserts are designed to measure relative headspace accurately. For those needing headspace measurements based on reamer prints, we recommend our Datum Gauges. If you’re uncertain about which insert to choose, we encourage you to verify your shoulder angle or datum size through the SAAMI Cartridge and Chamber Drawings. Precision-Engineered for Reliability The Modular Headspace Comparator ships with your choice of headspace comparator insert, selected conveniently from the dropdown menu. These inserts are crafted with precision, bringing you the highest quality in headspace and bullet measurement tools. Whether you are a professional or an enthusiast, the Modular Headspace Comparator Insert offers dependable accuracy for every measurement task. Please Use This Compatibility List To Determine Which Headspace Comparator Is Right For You. The Headspace Comparator Model Is Listed First, The Compatible Cartridge Is Listed After. 204 Ruger 204 Ruger 223 Rem 223 Remington and 5.56mm NATO 222 Remington Wildcat Cartridges necked down from the 223 Remington 22 Cal x 28° 22-250 Remington 22 WSSM Wildcat Cartridges necked down from the 22-250 Remington 22 Cal x 30° 22 Creedmoor 224 Valkyrie 22 ARC 22 PPC 22 Cal x 35° 22 GT (6GT necked down to 22 caliber) FN 5.7x28mm 22 Cal x 40° 22 Dasher (Non-Alpha Chamber) 22 BRA 22-250 Ackley Improved 223 Ackley Improved 22 Alpha Dasher .22 Cal Dasher with an Alpha Legacy Reamed Chamber 6mm x 20° 243 Winchester Wildcat Cartridges necked down from the 243 Winchester 6mm x 23° 6x45mm (223 Remington necked up to 6mm) 6×47 Remington (222 Remington necked up to 6mm) 6mm x 26° 6mm Remington 6mm x 30° 6mm Creedmoor 6 x 47 Lapua 6BR 6BRX 6mm Super LR 6 ARC 6 PRC 6 XC 6 PPC 6mm x 35° 6GT 6mm x 284 Winchester 6mm x 40° 273” Neck Diameter, .060” Neck Shoulder Radius 6mm Dasher 6BRA (6mm BR Ackley Improved) 243 Ackley Improved Any 6mm Cartridge with 40° Shoulder and a fired neck diameter smaller than .273” 6mm x 40° .275” Neck Diameter, .060” Neck Shoulder Radius 6mm Dasher 6BRA (6mm BR Ackley Improved) 243 Ackley Improved Any 6mm Cartridge with 40° Shoulder and a fired neck diameter smaller than .275” 6mm x 40° 279″ Neck Diameter 6mm Ackley Improved cartridges with a fired neck diameter over .275″ 6mm Alpha Dasher 6mm Dasher with an Alpha Legacy Reamed Chamber 25 Cal x 30° 25 Creedmoor 25 x 47 Lapua 25 PRC 25 SAUM 25 SST 25-06 Remington 25-06 Remington 257 Weatherby 257 Weatherby 6.5mm x 20° 260 Remington 6.5mm x 25° 264 Winchester Magnum 6.5mm x 30° 6.5 Creedmoor 6.5 x 47 Lapua 6.5 PRC 6.5 SAUM 6.5 Grendel 6.5mm x 35° 6.5 Winchester Short Magnum 6.5 x 284 Winchester 26 Nosler 6.5mm x 40° 260 Ackley Improved 6.5mm Wildcat cartridges with a 40 degree shoulder 6.5-06 Springfield 6.5-06 Springfield 6.5mm x 55mm Swedish 6.5mm x 55mm Swedish 270 Winchester 270 Winchester 27 Cal x 30° 277 Sig Fury 6.8x51mm 27 Cal x 35° 6.8 Western 270 WSM 280 Remington 280 Remington 7mm x 20° 7mm-08 7mm x 25° 7mm Remington Magnum 7mm STW 7mm x 30° 7mm SAUM 7mm Creedmoor 7mm LRM 7mm PRC 6.5mm PRCW 7mm SPRC 7mm SAW 7mm x 35° 28 Nosler 284 Winchester 7mm WSM 7mm/300 WSM 284 Shehane 7mm x 40° 7mm-08 Ackley Improved 280 Ackley Improved 7mm Wildcat cartridges with a 40 degree shoulder 7 TCU .30 Cal x 20° 308 Winchester Wildcat Cartridges necked down from the 308 Winchester .30 Cal x 30° 300 Remington Ultra Mag 300 SAUM 300 PRC 30 BR .30 Cal x 35° 300 Winchester Short Magnum .30 Cal x 40° 300 Norma Magnum Ackley Improved .30 Caliber Wildcat cartridges with a 40 degree shoulder 300 Blackout 300 AAC Blackout 30-06 Springfield 30-06 Springfield 300 Winchester Magnum 300 Winchester Magnum 300 Norma Magnum 300 Norma Magnum 300 Norma Magnum Improved 33° 300 Norma Magnum Improved 33° 338 Cal x 20° 338 Federal 338 Cal x 25° 338 Winchester Magnum 338 Cal x 30° 8.6 Blackout 338 RCM 338 ARC 338 Cal x 35° 33 Nosler 338 Cal x 40° 338 Lapua Magnum Ackley Improved 338 Norma Ackley Improved 300 Norma Ackley Improved 338 Lapua Magnum 338 Lapua Magnum Wildcat Cartridges necked down from the 338 Lapua Magnum 338 Norma Magnum 338 Norma Magnum Wildcat Cartridges necked down from the 338 Norma Magnum 33XC 33XC 37XC 37XC 375 Cheytac 375 Cheytac 375 Enabler 375 Enabler 375 Cal x 15³ 375 H&H Magnum 375 Cal x 30³ Any .375 Cal Cartridge with a 30° Shoulder Datum Inserts Use the table below to choose the correct Datum Insert for your comparator. If measuring for headspace off of a reamer print please select an insert from the below Datum gauge list Datum A .330″ 17 Remington 204 Ruger 220 Swift 221 Remington Fireball 222 Remington 222 Remington Magnum 223 Remington Datum B .350″ 22 PPC 22-250 Remington 6mm PPC 6mm Bench Rest Remington 250-3000 Savage 6mm ARC 6.5 Grendel 6.8 SPC 7mm Bench Rest Remington 300 Blackout Datum C .375″ 6mm Remington 25-06 Remington 257 Roberts 6.5 X 55mm Swedish 6.5mm X 47 Lapua 270 Winchester 7 X 57mm Mauser 7mm Winchester Short Magnum 280 Remington 30-40 Krag 30-30 Winchester 30-06 Springfield 300 H & H Magnum 7.62 X 39mm, M43 32 Special Datum D .400″ 223 Winchester Super Short Magnum 243 Winchester 243 Winchester Super Short Magnum 260 Remington 6.5 Creedmoor 270 Winchester Short Magnum 7mm-08 Remington 300 Savage 303 British 308 Winchester 35 Remington Datum E .420 257 Weatherby 6.5mm-284 264 Winchester Magnum 7mm Remington Magnum 7mm Remington Ultra Magnum 7mm Remington Short Action Ultra Magnum 7mm Shooting Times Westerner 8mm Remington Magnum 8×57 Mauser 8x68mm 284 Winchester 300 Winchester Short Magnum 300 Weatherby Magnum 300 Remington Short Action Ultra Magnum 300 Winchester Magnum 300 Remington Ultra Magnum 7.62x54R 325 Winchester Short Magnum 338 Winchester Magnum 338 Remington Ultra Magnum 35 Whelen 9.32x62mm 375 H & H Magnum
