Maxim Defense PDX:SD SBR .300 Blackout
Model: MXM-47843
Maxim Defense PDX:SD SBR .300 Blackout
Model: MXM-47843
Full Specifications
About This Firearm
The Maxim Defense PDX:SD SBR is an integrally suppressed .300 Blackout short-barreled rifle built for home defense and duty use. It has an MSRP of $3,695. Its 5.5 inch barrel runs inside an integral M-Kore suppressor that Maxim tunes to the PDX platform, so the finished gun is 23.75 inches long with the can counted.
The upper carries an HK height rail, which Maxim fits for a more rigid receiver, and the trigger is an ALG unit. The .300 Blackout build uses the Maxim CQB stock. Maxim does not sell the suppressor separately, so nothing has to be mounted or timed before the rifle is shot suppressed.
If you're cross-shopping, the Maxim Defense SDX RFLX SBR carries the same MSRP of $3,695 and uses an 8.5 inch barrel, which puts it at 33 inches and 8.2 lbs, so the extra 3 inches of barrel cost 9.25 inches of length and 0.8 lbs. The Sig Sauer MCX Rattler is no longer made and is a used buy now, with the same 5.5 inch barrel at 23.5 inches but 5.7 lbs and a bare muzzle, which is where the PDX:SD's extra 1.7 lbs went.
Best For
Strengths & Limitations
- The suppressor is tuned to this barrel and gas system, so there is no mount, shim or alignment check to work out.
- The .300 Blackout barrel uses a 5/8x24 thread pitch, the common pitch for the caliber.
- Maxim's materials list runs to 6Al-4V titanium, 17-4 stainless steel and 7075 and 6061 aluminum.
- These are built to order on a four to six week lead time, so there is no walking into a shop and leaving with one.
- The can is tuned to the PDX platform, so barrel length is fixed and a different barrel is not an option.
- A barrel this short gives up velocity to the 8.5 inch barrel on Maxim's own SDX RFLX SBR, which is the cost of the short package.
Compatible Ammunition
Find the best prices on compatible .300 Blackout ammunition.
Shop .300 Blackout Ammo →Ballistics Calculator
Calculate trajectory, drop, and energy for .300 Blackout ammunition.
.300 Blackout Ballistics →Where to Buy
No prices available at this time.
Frequently Asked Questions
Can the suppressor be taken off?
Maxim sells it as integral and does not offer it as a separate product, so treat it as part of the rifle instead of a can you could move to another host.
What other versions are there?
The PDX:SD is also chambered in 5.56 NATO and 7.62x39. Those two use the Maxim SCW stock, and the 5.56 barrel is threaded 1/2x28, so the stock and the thread pitch both follow the caliber.
What does the HK height rail do for optics?
It raises the mounting surface above a standard AR flat top, which puts a red dot closer to a natural head position with a bulky suppressor body underneath it. Riser-free AR mounts will sit too low to use.
