Description
AR9 Dead Blow Bolt Weight — Pre-Cut
A dead blow weight for 9mm blowback AR bolts, machined to final length and ready to install. No cutting, no measuring off a raw blank, no guessing at how much to take off. It drops into the bolt tail bore and pins in place.
The Build
8620 case-hardened steel. The dead blow action comes from free-moving mass inside the body — on the rearward stroke it lags behind the carrier and lands a fraction of a beat late, which spreads the impulse out instead of delivering it all at once. The result is a softer, flatter cycle and less bolt bounce than a solid weight of the same mass.
Pre-cut is the point. Every one comes off the machine at the same length, so the part you get is the part that was tested.
What You Need To Run It — Measure Your Bolt First
This is the one thing to check before ordering. AR9 bolts vary between manufacturers, and this weight is cut for a specific tail geometry. Your bolt must have:
- Ø0.636″ bore in the rear of the bolt
- Ø0.250″ cross hole, through, with its centerline 0.950″ from the rear face of the bolt
Overall bolt length doesn’t matter, and the slot orientation doesn’t matter — neither is controlled. What matters is the bore diameter and where that cross hole sits. Pull your bolt, measure those two dimensions, and compare against the diagram below.
If your bolt doesn’t match, this part will not fit, and it isn’t something that can be made to fit by forcing it.
What It Fits
9mm blowback AR-pattern bolts meeting the dimensions above. That covers a lot of common bolts, but not all of them — the measurement is the answer, not the brand name.
Not for use in delayed or locked-breech 9mm systems.
Specifications
| Material | 8620 case-hardened steel |
|---|---|
| Type | Dead blow, captive internal mass |
| Condition | Pre-cut to final length |
| Required bolt bore | Ø0.636″ |
| Required cross hole | Ø0.250″ through, 0.950″ from rear face to centerline |
| Bolt OAL | Not controlled |
| Slot orientation | Not controlled |
| Platform | 9mm blowback AR only |
Function Check
Changing bolt mass changes how the gun cycles. After installing, function check with the ammunition you intend to run before relying on the firearm for anything. If you see short-stroking, failures to feed, or failures to eject, stop and reassess — buffer weight and spring rate work together with bolt mass, and a change to one can require a change to another.
Legal Responsibility
It is the buyer’s responsibility to verify that this component is legal to own and use in their jurisdiction. This product is sold as an individual mechanical component for lawful use in appropriately configured firearms. VoidSpec does not provide legal advice. If there is any doubt about whether this part is appropriate for your situation, consult a firearms attorney in your state before purchasing.
