11-21-2011, 06:29 PM
Whelenon Wrote:Could you boys explain some of your gobbly guck for the ignorant masses, CHF, HP/MPI, M203 groove, bolt traceability? Sorry, you're over my head and would like to get a feel for the discussion. Design has always tripped my trigger so a brief explanation would be appreciated. Thanks
CHF: Cold Hammer-Forged. Totally different barrel manufacturing process that is recognized for its strength, minimal residual stresses, and accuracy. Very common in Europe.
HPT/MPI: High-Pressure Tested/Magnetic Particle Inspected. A 170% proof load in the 5.56 military bolts, barrel extensions, and barrels is discharged. Then magnaflux is introduced and inspected with electric current run through the parts, to see if they attract to an area of weakness that resulted from the high-pressure load, giving an indication. One argument is that the test itself reduces the life of the parts. MPI'd bolts usually fail after high-volume shooting at the lug areas, while non-MPI bolts used in high-volume fail at the cam pin hole in 5.56 guns.
M203 Barrel Profile (M4): There is a step down to a smaller profile just forward of the Front Sight Base on the M4, so the M203 mounting bracket could be secured in-place without sliding forward.