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Sound Mitigation Buffer SMB H3 (5.6 oz Equivalent)
Want a smoother recoil cycle and less buffer spring noise without overcomplicating your build—this is the drop-in route. The SMB is a single-stage captured system designed to keep the spring from rubbing the inside of the buffer tube, which helps the action feel more refined.
At a glance
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Platform: AR-15
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Variant: H3 (5.6 oz equivalent)
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Complete assembly weight: 6.71 oz
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Made in USA + Lifetime Warranty
Why choose the H3 option
H3 is the heaviest AR-15 option in the SMB lineup (excluding the 9mm version). Choose it when you want the most mass in this family and you’re intentionally steering your setup toward a heavier buffer class.
What’s included
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1x Polymer base guide rod
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1x Spring
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1x Buffer
Specs
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Equivalent weight: 5.6 oz (H3 class)
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Actual weight (complete system): 6.71 oz
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Compatibility: AR-15
Optional spring tuning
The SMB includes adjustable spring weight guidance: the main spring can be trimmed 0.25 lbs per coil, up to 12 coils max, to reduce tension. Make small changes and test between changes.
Installation overview
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Insert polymer base with guide rod into the buffer tube
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Insert desired spring on the guide rod
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Insert the buffer over the spring
Compare SMB weights (equivalent)
| Variant | Equivalent weight |
|---|---|
| Carbine | 3.3 oz |
| Heavy | 3.8 oz |
| H2 | 4.7 oz |
| H3 | 5.6 oz |
| 9mm | 6.9 oz |
Need a replacement weight?
Individual SMB H3 weights are sold separately (ARM159-H3), which can be handy if you’re rebuilding an existing setup. (armaspec.com)
FAQ
What does “5.6 oz equivalent” mean?
It’s the buffer weight class this model is designed to match from a tuning standpoint. The complete captured assembly has its own listed actual weight.
Why is the complete assembly weight different?
Because the full unit includes additional captured-system components beyond a standard buffer body, so the “actual” number is higher than the tuning-equivalent class.
Will this fit a standard AR-15?
Armaspec lists SMB compatibility as AR-15. If your build uses a non-standard receiver extension or proprietary recoil parts, verify your configuration before ordering.
What comes in the box?
A polymer base guide rod, spring, and buffer.
Can I tune spring tension?
Yes. The spring can be trimmed in small steps (0.25 lbs per coil), up to 12 coils maximum, to reduce tension.
What’s the part number and UPC?
ARM258-H3 and 810048492466.
WARNING: This product can expose you to Lead, which is known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to - www.P65Warnings.ca.gov.
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