Rimfire suppressors sit among the cheapest National Firearms Act items and often ride backyard plinkers. Low-pressure .22 loads deposit lead, lubricant and powder that stay inside because muzzle blast cannot purge them as centerfire gas does. In a 2016 TFB evaluation Pete checked an A-TEC CMM4 by weight and X-ray at 500-round intervals and saw residue reach the exit by 3,000 rounds, so many owners prefer user-serviceable stacked or monocore cans over sealed welds that Gemtech later converted on Outback II units for $249.