Will Insulation Stop a Bullet?

   03.11.19

Will Insulation Stop a Bullet?

When talking about overpenetration in home-defense scenarios, the main concern is that bullets may pass through walls and cause injury to someone on the other side. And apparently there are folks who attribute fiberglass insulation with bullet-stopping capabilities. So Paul Harrell has decided to demonstrate for all to see whether the most-common wall insulation in the USA (fiberglass “wool”) has any value for stopping bullets.

There are people who strenuously assert that this stuff is some kind of bullet stop. Well… let’s put that to the test.

To give the fiberglass its best chance, he starts with a wimpy round: 25 ACP — firing hollowpoints, which should penetrate less than “hardball” (a.k.a. FMJ) bullets. Predictably, it fails.

He then fires a typical small 9mm personal-defense pistol through a chronograph with and without insulation “slowing” the bullet. With average velocities of 1100 vs. 1081 fps, we can see that the bullet is — maybe — slowed by a mere 19 feet per second… which ain’t much.

Insulation as a bullet stop? Yeah, no.

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