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A baffle strike on a big .375 caliber can is an expensive lesson, and the frustrating part is that most of them are preventable. Suppressors are long, and even a tiny bit of runout at the barrel threads or muzzle device gets multiplied by the time you reach the end cap. Stack a couple of small tolerance deviations together and a bore that looked fine at the muzzle can be noticeably off center at the exit hole. That is exactly what this gage is made to catch before you ever send a round.
The process is simple. With the suppressor mounted on the rifle, slide the 17 inch rod down the bore from the muzzle end and watch how the gage sits in the suppressor's exit aperture. Centered means you are good to go. Rod touching or crowding one side of the end cap tells you something in the stack, whether it is the barrel threads, the muzzle device, or the mount itself, is pushing the can off axis. Because the gage is so long, the bore itself aligns the rod, so it does not need a piano wire tight fit to give you a trustworthy reading.
Geissele machines this gage from hardened steel ground 0.002 inch under nominal bore diameter, which they have found to be the sweet spot for fitting the widest range of real world .375 barrels. The outside diameter is finely finished and straight to 0.001 inch over the entire length. The hardening matters more than you might think. It keeps abrasive powder residue from wearing the surface, prevents burrs if the rod drags on a misaligned baffle, and stops grit from embedding in the gage and scratching your bore later.
If you run a can on a 375 CheyTac, 375 H&H, or similar big bore rifle, a quick alignment check every time you swap the suppressor to a new host or install a fresh muzzle device is cheap insurance. Made in the USA by Geissele Automatics, part number 10-1639-F.
With your suppressor mounted and the rifle verified clear, slide the gage down the bore from the muzzle end until it passes through the can. Look at where the rod sits in the suppressor's exit hole. If it is centered, your alignment is good. If the rod is touching or clearly favoring one side of the end cap, something in your barrel threads, muzzle device, or mount is off and needs attention before you shoot suppressed.
Barrel bores vary in diameter and straightness from one manufacturer to the next, and Geissele found that 0.002 inch under nominal is the size that fits the widest range of .375 barrels. The 17 inch length is what keeps the reading accurate, since the long bearing surface aligns the rod to the bore without needing a super tight fit.
No, that is exactly why Geissele hardens it. The hardened, finely finished surface resists wear from abrasive powder residue, will not pull burrs if it contacts a misaligned baffle, and keeps grit from embedding in the rod where it could scratch your bore on future checks. Treated with basic care, it will give consistent readings for years.
This size is made for barrels with a nominal .375 bore, so think 375 CheyTac, 375 H&H Magnum, 375 Raptor, and similar big bore cartridges. If you are running a different caliber, Geissele makes the SAG in a range of sizes from 5.56mm on up, so grab the one matched to your bore for an accurate reading.
| UPC | 817953029718 |
|---|---|
| Manufacturer | |
| Manufacturer Part Number | 10-1639-F |
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