BPM Inc. Technical Document-
Topic– Maintenance of SBR type weapons platform with “Stoner Type Gas Impingement system,” i.e., Mk18 type uppers, as well as “AR-style Pistols” that are common in commercial firearms industry, including 7-1/2” to 11-1/2” barrel length configurations.
Scope of Topic– It is known in the industry that increased Severity of gas pressures /heat cycles in these “SBR” (Short Barreled Rifles) type weapons – which are also commonly considered
pistols with proper ATF approved armbrace usage , and combined with more and more common legal suppressor usage , requires considerable more attention to maintenance details by the end-user /consumer, to include earlier intervals of part/component inspection/evaluation-to prevent catastrophic failure of critical components, and or degradation of reliability and or complete failure/malfunction of weapons platform. It has been a common practice for consumers /users of the Common “AR” weapons platform, in various configurations –lengths, to include rifle/carbine/pistol, etc., to use the common M16/M4 field manual for basic field maintenance.
While this is acceptable relative to the basic understanding of the Stoner design /platform, to include controls as in the safety selector, bolt latch, magazine latch, etc. But consumable component/parts Life expectancy between different lengths/configurations is where that similarity ends. Industrywide – Gas Impingement Type SBR/Pistol usage, with shorter barrels /gas
systems, as defined previously, can be expected to have considerably shorter usage /life expectancy than the longer barreled ( with similar /longer gas systems) standard M16/M4/AR variants that exist in DOD and or Commercial industry.
In the DIG/SBR(Direct Impingement Gas/Short Barreled Rifle ) configuration – including 7-12” to 11-1/2” barrel length range, round count/life expectancy is generally half of what a standard AR15/M4 barrel length –carbine gas system length is with standard training usage. This may be exacerbated with elevated/continued high round count training. As always- per physics, “Rate of fire” (HEAT CYCLES) dictates component lifespan, to include gas port erosion/barrel life -not total round count.