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[Review+Video] Daniel Defense DDM4ISR: Best Suppressed .300 BLK?

Daniel Defense's DDM4ISR is a .300 Blackout integrally suppressed rifle built on the AR-15 platform...but is this pricey rifle worth the cost? We find out.

What do you get when you pair an integrally suppressed rifle with the .300 Blackout cartridge?

The Daniel Defense DDM4ISR, of course.

Daniel Defense DDM4ISR
Daniel Defense DDM4ISR

Though this premium rifle from Daniel Defense steps it up with that .300 BLK chambering and a suppressor, is it worth the price of the rifle AND $200 NFA tax stamp?

We wanted to find out…so we grabbed a DDM4ISR, some boxes of .300 BLK, and headed out to the range and a local shoot house.

at Daniel Defense

Prices accurate at time of writing

Prices accurate at time of writing

Available Coupons

After almost a thousand rounds downrange, we think we have the answer…so keep reading to see if the DDM4ISR is worth the cash and wait time…

Want to see us take this gun to the range and shoot house? Check out the full video review below.

As always, be sure to head over to Pew Pew Tactical’s YouTube page for more gun and gear reviews.

Table of Contents


Why .300 Blackout?

Before diving into the gun, it probably makes sense to give a little bit of context for what .300 Blackout is.

For those not acquainted with .300 BLK, it’s a cartridge that can be fired out of an AR-patterned rifle with minimal modifications.

.300 BLK 123gr vs 200gr
.300 BLK 123gr vs 200gr

First and foremost, you’re going to need a barrel that’s chambered for the chunkier round.

Though .300 BLK fits into 5.56 magazines and will chamber in a 5.56 gun, it leads to catastrophic consequences if you accidentally mix it into your 5.56 goods.

Ok, maybe not this dramatic…but it’s still bad.

So, uh, don’t do that.

AAC first developed it to bridge the gap between the ergonomics of the M4 system of rifles and the shorter length and suppressability of the MP5 family.

The idea here is pretty simple.

Very Simple

5.56 generally requires a 12-inch barrel to fully burn its powder charge and minimize muzzle flash. But .300 BLK utilizes fast-burning powder that drops that number to 9-inches.

But…there are tradeoffs.

.300 BLK is a much slower, chunkier round than 5.56. As a result, its time to the target, drop at distance, and effective range are significantly reduced.

Daniel Defense DDM4 ISR 300 BLK

While .300 BLK performs reasonably well against pistol-class body armor, it lacks the oomph to penetrate rifle plates given its lead core construction.

So what am I getting at?

.300 BLK is a reasonable intermediate alternative to 5.56…if your primary concerns are being sneaky with an AR-like platform and you don’t need to punch out further than 300-yards or so.

300 BLK
.300 BLK

DDM4ISR Specs & Features

With that bit of cartridge context out of the way, let’s jump into the Daniel Defense DDM4ISR.

The DDM4ISR features a 9-inch cold hammer-forged barrel with an integrated suppressor that brings the overall barrel length to 16-inches.

Daniel Defense DDM4ISR Barrel Suppressor
The gun comes with a suppressor basically built-in.

This means that while this is an NFA firearm because of that suppressor, it is not a multiple NFA firearm.

Its overall length keeps it out of the SBR category.

The suppressor features a user-serviceable baffle core that can be removed for cleaning.

Daniel Defense DDM4ISR AR Optics

And the gun runs on a standard pistol-length gas block, all housed inside a 15-inch MFR XL Keymod handguard.

Its handguard has attachment points along its sides and bottom and a full-length Picatinny rail up top.

While the DDM4ISR is available in several finishes, ours featured an attractive bronze-y “mil-spec” FDE anodized hard coat finish.

 Daniel Defense DDM4ISR Keymod
Keymod attachment points line the handguard.

It sported Daniel Defense’s standard ergonomic 6-position stock, low-angle pistol grip, and rubber over-molded stubby Keymod vertical grip.

Daniel Defense DDM4ISR Stock

The fire selector is ambidextrous, and the charging handle features oversized wings on both the left and right sides.

Outside of that, the DDM4ISR, intentionally built on the AR-15 platform, feels overall…like an AR-15.

Daniel Defense DDM4ISR Charging Handle
DDM4ISR charging handle

Depending on your personal feelings towards ARs…that might be positive or negative.

With the nitty-gritty out of the way, let’s talk range time.

Daniel Defense DDM4ISR

At the Range

We had the opportunity to run close to 1,000 rounds of .300 BLK through the DDM4ISR during our time with it.

Easily, the most notable takeaway is just how slow that chunky projectile is…gauged by the noticeable hang time it’s got even at 50-yards before impacting the target.

Daniel Defense DDM4ISR Range Shooting

Aside from the obvious fact that we’re firing subsonic projectiles, this is also because .300 BLK, on average, is around 1,000 feet per second slower than 5.56.

Subsonic .300 Blackout
Subsonic .300 Blackout

Granted, that’s contingent on the actual grain of the projectiles and barrel length, so don’t treat that number as gospel.

Daniel Defense DDM4ISR Barricade Shooting

Point is…it’s slow.

That said, once we had the ISR ready to go with our Sig Sauer Romeo5 zeroed, hitting steel at 50-yards was a breeze.

Brutally Tested Budget Red Dot
at EuroOptic

Prices accurate at time of writing

Prices accurate at time of writing

Available Coupons

Although .300 BLK should have a felt recoil a bit heavier than 5.56, the difference felt negligible.

All in all, the DDM4ISR ran great, and we had no notable problems during our time with it.

Daniel Defense DDM4ISR Range Shooting

Even with a select-fire lower attached with a throwable fun switch, the ISR delivers easy, controllable bursts that at no point felt off-target.

Daniel Defense DDM4ISR Range Shooting
It ran great at the range.

Shoot House Fun

The folks at ALERRT and Broaddus Defense were even kind enough to let us go embarrass ourselves in their shoot house – which is arguably the exact kind of environment the gun excels in.

Daniel Defense DDM4ISR Shoot House
Shoot house…sign us up!

If you watched our review of the DD MK18, we’re in familiar territory here.

Daniel Defense’s approach to a low-angle pistol grip works quite well when you’re maneuvering and snapping a rifle through tight confines.

Daniel Defense DDM4ISR Shoot House
That grip angle makes sense in this environment.

Overall, this changed my attitude towards the pistol grip compared to my previous time with it on static, flat ranges.

I still maintain that it’s not the most comfortable grip on the market if all you’re doing is static line drills or bench shooting.

But after a ton of runs through the shoot house, I understand the grip much better, and my wrists were thankful for the relief.

Daniel Defense DDM4ISR Shoot House Night Vision

The ISR handled just about as smoothly in the shoot house as it did out on the range.

Again, I didn’t feel a noticeable difference between the ISR’s .300 BLK or the suppressed DD MK18 we ran immediately prior.

If you’re designing an entire cartridge around an AR-15 platform, that’s the outcome you’re after.

Daniel Defense DDM4ISR Shoot House

It’s probably worth noting that .300 BLK penetrates soft objects like drywall to a much more significant degree than does 5.56.

Depending on your desired outcome or use-case scenario, that’s either a good thing or a bad thing.

Daniel Defense DDM4ISR Range Shooting

But keep in mind that the projectile does have quirks that make it a good choice for a very narrow set of circumstances.

As such, it shouldn’t be viewed as a 1:1 replacement for just adding a suppressor to your short-barreled 5.56 AR.

Daniel Defense DDM4ISR Range Shooting

By the Numbers

Reliability: 5/5

We had no problems whatsoever during our testing. This rifle loaded, fired, and ejected perfectly.

Ergonomics: 4/5

So, the grip angle feels odd at a regular range, running regular drills…but take this gun to a shoot house, and the ergonomics start to make a lot more sense.

Daniel Defense DDM4ISR Shoot House
Ergos work best in CQB scenarios.

Accuracy: 5/5

Both at our static range and the shoot house, the DDM4ISR hit targets with no issues.

Customization: 4/5

Though it’s an AR-based platform, it also sports Keymod…which isn’t our preferred attachment method. That said, you can still throw an optic and Keymod compatible accessories onto it.

Value: 3/5

I’m going to go out on a limb and say that $3,400 plus the NFA stamp plus ammo that’s roughly twice the cost of 5.56 makes this too rich for our blood — even if that means we’re missing a hell of a lot of fun as a result.

at Daniel Defense

Prices accurate at time of writing

Prices accurate at time of writing

Available Coupons

Overall: 4/5

I had a blast with the ISR, especially considering it was my first real time getting to run a .300 BLK platform across a variety of environments and scenarios.


Daniel Defense’s DDM4ISR seems to be a decent way to snag an integrally suppressed gun chambered for the .300 BLK cartridge intended to do a very specific job…if that’s what you’re after.

Daniel Defense DDM4ISR
Daniel Defense DDM4ISR

Remember, you do need a tax stamp, though, because of its integral suppressor. So, factor that into the overall cost.

at Daniel Defense

Prices accurate at time of writing

Prices accurate at time of writing

Available Coupons

While this gun is a little out of our price range, if you have the funds and want the cool factor of an integrally suppressed rifle, the DDM4ISR fits that bill.

To see this gun in action, make sure to peep the full video review below.

What do you think of the DDM4ISR? Let us know in the comments. For more Daniel Defense rifles, check out our reviews on the MK18, DDM4 V7, and DDM4 PDW.

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4 Leave a Reply

  • Commenter Avatar
    sound awake

    is a $3260 daniel defense anything twice as good as the same thing by anybody else for $1630
    for most people most of the time

    November 6, 2021 12:54 pm
    • Commenter Avatar

      I find that most guys that say "is it worth twice as much" don't do much shooting. If they did, they'd know the rifle is just the entry fee. After ammo, optic/accessories, mags, range fees, travel, licenses/tags, fine jewelry/divorce lawyer, etc. spread out over 5-10 years (at least) that extra is a drop in the bucket. Unless it sits in your safe than it's prob not worth it.

      But to answer your question, I replaced my PSA 9 inch SBR and YHM can (about $1,500 with the SBR stamp included) for the ISR and yes, it is at least twice as good. More accurate, more reliable, MUCH less gas face, no need for different buffers/springs or AGB to shoot between subs and supers, no walking-off or baffle strike fears, don't need to ask the ATF's permission when I move or hunt/travel out of state, MUCH better fit and finish with hilariously better quality built entirely by DD with excellent customer service. I paid $2,650 (plus $200 free gun case promotion) when I bought mine but would still pay full price today in a heartbeat.

      March 2, 2022 4:27 pm
  • Commenter Avatar
    Douglas L Dicketts

    I'll stick with a .45 +p hp and gun light thanks. By the way much as I hate to say it this build on a bullpup would make more sense for cqb.

    November 6, 2021 6:44 am
  • Commenter Avatar

    Just another weapon not available in California! Penal Code 33410 PC. Thanks again Democrats!

    November 4, 2021 11:18 pm
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