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Old September 13th, 2018, 10:06 AM   #1
clandestine
AR15 Technical Instructor
 
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Join Date: Oct 2008
Location: Cecil County, MD
Posts: 33,919
Info Topic: AR/M4/M16 Bore Straightness Gages

Tool Topic (Gauges)

These are a few of my 5.56MM Barrel Straightness Gauges.

The barrel should be clean to use these gauges. A fouled barrel will prevent an accurate reading and cause accelerated wear off the gauges. Don't let them hit hard surfaces and wipe them down with oil after every use. They corrode VERY easy if not protected.

I use these on new barrels and used barrels.

On a new barrel, it will tell you of the bore has a bend, a burr on the gas port, or if the bore is constricted. On a used barrel it checks for bends and can also tell you if too much copper fouling is present.

Top)
U.S.G.I. RIFLE 5.56MM GAGE BORE STRAIGHTENESS 8448202
Instructions on Gage:
A - REMOVE RIFLE BOLT
B - INSERT GAGE INTO MUZZLE END OF BARREL.
C - RIFLE WILL NOT ACCOMPANY TROOPS OVERSEAS IF GAGE DOES NOT PASS FREELY THROUGH BARREL.

Middle)
Pacific Tool & Gauge 5.56 Barrel Straighteness Gauge .215 (.001 Tolerance)

Bottom)
Pacific Tool & Gauge 5.56 Match Barrel Straighteness Gauge .215 (.0001 Tolerance)

I own another Military BSG (Not Shown) but the laser engraving is worn off. I also have the BSG's in .22 LR, 6.5 Grendel, 6.8 SPC, .308/.300 Blackout/7.62NATO, 7.62x39mm, and 9mm Luger.

A standard BSG from PTG runs between $35 and $45. The Military ones are quite difficult to get. The PTG units perform the same way as the Military Gage.
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