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Review: Daniel Defense DDM4 ISR .300 Blackout

Review: Daniel Defense DDM4 ISR .300 Blackout
The Daniel Defense M4 ISR represents an ideal close-quarters combat rifle given its stout chambering and nimble handling characteristics.

One of the quirks of being a gun writer is that now and then you forget you don't know it all. Even a company that you've been paying attention to for a long time can surprise you. Thomas Carlson of Daniel Defense had flown up to Gun Abuse Central to show me the new DDM4 ISR. In talking with him to ferret out the details, he mentioned that "This was, in effect, the ISR 2.0" What? There had been a previous ISR?

ISR is the acronym for Integrally Suppressed Rifle and Daniel Defense had built the previous one as a hog-hunting tool. Well, not really hunting, as hogs threaten to swarm the landscape in rural Georgia (and other locales as well) and it isn't hunting in the traditional respect. It is full-blown whack-as-many-as-you-can-regardless-of-size-or-age population control.

To that end, Daniel Defense took the DDM4, chambered in .300 Blackout, and made it a better tool. They shortened the barrel and then installed a suppressor on it, one that fit underneath the free-float handguard. And then they found they were so busy with all the other new products that it sort of got lost in the lineup. Within a couple of years, Daniel Defense found they had only made enough ISR V1.0 rifles to equal about a months' worth of regular AR production. So, if you have one of the originals, you have a pretty rare rifle. You also have the option of upgrading it, as the ISR V2.0 is improved but not in such a way as to make the old obsolete.

What then did Daniel Defense do to make the new ISR?

First, the barrel. It is one of DD's cold hammer forged barrels, trimmed to 9.3 inches, chambered in .300 Blackout, chrome-lined and to which the designers have installed a pistol-length gas system. This means that while it will thump you a bit harder when you use supersonic loads, it will cycle reliably when you are stuffing it with the heavyweight subsonics. This is a direct-gas system, not a piston, system, so you will have the normal-for-DD (read: best quality) bolt-carrier assembly on the inside of the upper receiver.

The suppressor takes up most of the 16-inch length of the
The suppressor takes up most of the 16-inch length of the "barrel." The barrel itself is a mere 9.3 inches.

The bore has a twist of eight inches, and the barrel profile DD selected is their "strength-to-weight" profile. It is a contour they selected to keep the barrel as light as possible, while maintaining as much strength as possible.

The barrel has the suppressor mount and tube welded to it, creating an assembly that is just longer than the 16-inch minimum for rifle barrels. Combined with the receiver and buttstock length, this also keeps it over the overall minimum length, so your paperwork problems are minimized.

A short-barreled rifle requires an approved transfer, and tax payment, from the ATF. A suppressor also requires an approved transfer and tax. Were you to put a suppressor on an SBR, you'd have two transfers, and a total of $400 in transfer taxes. Ouch. What Daniel Defense has done with the ISR, by making the overall and the barrel lengths over minimum, is pare that down to one transfer and tax; that of the suppressor. If the barrel is permanently attached to the suppressor, and the entire assembly is over 16 inches, then the ATF considers them just one NFA device.

Daniel Defense then slides that into their MFR XL 15.0 handguard, a trim and lightweight handguard that is as rigid as a bridge beam. This is essentially the SLiM handguard, with a profusion of Keymod slots, a top Mil-Spec 1913 rail running the length of the top, and a forward protrusion on the bottom to keep your hand away from the suppressor tube. The mounting system is not your usual clamp-onto-the-barrel-nut design. Instead, it uses four large bolts, and it sandwiches the barrel nut flange between a rear clamping plate and the rear of the handguard. DD sent me one of these for a different project, and once I'd had a chance to inspect it and install it on another rifle, I told Thomas that they weren't getting it back. He seemed neither surprised nor disappointed.

The rifle, from the barrel nut to the rear, is basically the DDM4 V4, with Daniel Defense stock, pistol grip, Mil-Spec or better parts, and all properly assembled. I know that because I've been to the factory and watched them assemble rifles.

The MFR XL 15.0 handguard is a free-floated unit that offers a solid foundation for light and other accessories.
The MFR XL 15.0 handguard is a free-floated unit that offers a solid foundation for light and other accessories.

The ISR is then done up in Cerakote, the suppressor tube in black, and the rest of the rifle in bronze, applied over a Mil-Spec hard anodized finish.

Everyone knows that Daniel Defense makes their own rifles. They do not outsource the critical parts, and they make their own barrels, bolts, carriers, receiver, handguards, and so on. It should not come as a surprise to find that they also make the suppressor in-house. When the ISR was unveiled at the SHOT Show, I'd heard grumbles from some "insiders" that DD was out-sourcing the suppressor, and that they were made by a particularly low-rep suppressor maker. What was a real scream was that I heard this rumor three times, from three people, and they each named a different "bad can" maker. And all three were suppressors I owned and knew to be good. So much for rumormongers at trade shows.


One of the upgrades from V1.0 to V2.0 is the baffle stack design. The engineers at Daniel Defense fussed and tested, and came up with a quieter design, and also made it backwards compatible with V1.0. So, if one of you lucky owners of the earlier ISR happens to think you need a few more decibels pared off the signature, you can have the old stack replaced with the new stack.

The interior of suppressors, in some calibers and with some loadings, can get pretty grubby, and require cleaning. If the ISR suppressor is nestled down inside the handguard, and welded-in to boot, how are you supposed to clean it?

The front cap of the ISR suppressor is the disassembly point, using the DD-made wrench. You unscrew the front cap, and slide the all-stainless (17-4PH) baffle stack out of the tube. You could, if you wanted (I don't know why) shoot the

The grip is of Daniel Defense's own device and features rubber grips and a steep rake that's ideal for close-quarters action.
The grip is of Daniel Defense's own device and features rubber grips and a steep rake that's ideal for close-quarters action.

ISR with the stack out, and the cap off. Please don't, as you'll just put powder residue in the threads, and make your cleaning job even more difficult. Plus, you aren't going to need to do this very often. Daniel Defense recommends cleaning the baffle stack at 10,000-round intervals. Considering that a good barrel is going to last you twenty thousand rounds or so, you'll clean the suppressor once, and then at the twenty grand point send it in to Daniel Defense for a new barrel. You can clean the suppressor before you ship, or leave the cleaning to the armorer who does the barrel swap.

And all this comes in a package that is 7¾ pounds, bare. In a world where everyone who makes an M4gery is proud to state it weighs "only" seven and a half pounds (and they usually are fudging that weight, to boot) to have an integrally suppressed, carbine-length rifle that is 7¾ is amazing.

I had to change my usual process for testing because I only had Thomas and the rifle here for one day. Luckily it was a beautiful day, but it still meant a lot of hurry-up. So, I only did five-round chrono results. I took an extra few minutes to crosscheck the chrono results with a couple of the loads and recorded 10-round averages. That was a waste of time and ammo, as they both produced 10-shot averages that were within 3 fps of the 5-shot averages.

I did not change my five, 5-shot groups for accuracy standard, but I shot them at 50 yards instead of 100. Not because I wanted to show off, or out of laziness, just that the extra time walking meant less time shooting. That turned out to be a fortunate decision.

The process was simple; grind through each ammo recording muzzle velocity, and then sit down at the bench, and with a Champion rest, shoot groups. The scope was my trusty Leupold 1.1-8x, in LaRue mount. Things proceeded reasonably well, but then the groups started getting, well, dodgy. And then I tried the Gemtech subsonic. The groups were so big and so irregular, I wasn't really sure which strays were with which groups. I've never seen such ammo-hate from a rifle before. And just to be clear, this is not an indictment of Gemtech. I've had brilliant results with it in other rifles.

I had a thought. "Thomas, how many ISR V2.0 samples are there, right now?"

"Well, we're ramping up production, and we'll have them in full supply when the shipping date in July arrives. But right now? Two."

"Two? And do they both get shot?"

"No, the show gun we keep off the range, so it looks good in the display rack."

"So this is the rifle from the SHOT Show media day, then?"


On range day at the SHOT Show Daniel Defense had this upper installed on a select-fire lower and a crew of magazine loaders. Gun writer after gun writer would step up, get the ISR and a mag, and do a full-mag full-auto mag-dump downrange. They did this to demonstrate that the suppressor-inside-the-handguard design would not make the handguard too hot to hold. That, and it was truly giggle-worthy fun.

In this instance it simply was Gemtech's turn to be the designated "bad" ammo, despite its excellent results in other rifles. It could as easily been anyone else's ammo. I've had barrels in .223/5.56 last up to 20,000 rounds. The .300 Blackout should be easier on a bore than 5.56, but there was all that full-auto firing, you see.

What all this meant was that I was accuracy-testing a barrel that had obviously reached the end of its service life, and a lot of that life had been spent in full-auto gun writer entertainment. It wanted to shoot, as the very good groups that it did produce can attest to. But it also shot groups that would be marginal at 100 yards (for a new rifle) and miserable at 50 yards. But, and I want to make sure you are clear on this; while a new rifle that shoots a two-inch group at 50 yards is one that needs to go back to the maker right now, if it does that once in a day's shooting, after 20,000+ rounds, life is normal. This barrel has to have had much more than a mere twenty grand of bullets sluiced through the bore.

And yet the ISR still produced brag-worthy groups. Groups under three-quarters of an inch are not cause for scorn and mocking at the gun club.


While I could feel warmth in the handguard, especially after the supersonics loads (and bench-testing can warm up a barrel/suppressor, don't kid yourself) it was never so hot I felt the need for a glove.

The felt recoil of the two types of loads were noticeable. The subsonics were soft in recoil, while the supersonics were more vigorous in thumping my shoulder. The power factor and the momentum of the loads were not dissimilar. A 220-grain subsonic, going 929 fps, has a PF of 204. A 115 going 1,950, has a PF of 224. That's a nine percent increase, more or less, but the supersonic loads thump more than that, which is due to the pistol-length gas system. If you want to reliably cycle subsonics, you have to have the pistol-length gas tube up top. No

matter how good your lawyer is, you can't evade the laws of physics, and here you'll simply have to pay the price.

Speaking of price, the full up, suggested retail price of the ISR may seem a bit steep. But, for that you're getting a lot. DDISR-SpecsYou get a Daniel Defense rifle, which is in itself a pretty stellar piece of gear. I have not shot one yet that has let me down in any way. I even used one, right out of the box, to shoot a clean score on an LE Patrol Rifle qualification course, and didn't even have to change the sights. With the ISR you get the DD suppressor factory-installed.

With a regular carbine, you can install a suppressor, but you end up making the whole package as long as a full-sized AR, not a carbine. If you shorten the barrel, you now have the suppressor tax, and the SBR tax, and that extra tax is a lot of money that could be spent on ammo. With the ISR you get a suppressed carbine, still carbine-length, for the cost of only one stamp tax. It is lightweight, durable, will last a long time (unless, of course, you let all your friends do full-auto full-mag dumps with it) and it will deliver the goods for years to come.

Look at it this way: If a barrel has a service life of 20,000 rounds (full auto, a semi-only rifle will last even longer) the ammunition cost over that service life will be, at a minimum, $6,000. Add in the costs of going to the range, the gun club membership, match fees, accessories, and you come up with a pretty impressive total spent on the improvement of your skills and the enjoyment the effort brings. Measured against that investment the

difference between the "expensive" Daniel Defense rifle, and a "more affordable" other option becomes pretty much nothing. Plus, if that "more affordable" other rifle malfunctions even once (say, in a match) then you just lost a big chunk of the difference between DD and the non-DD rifle.

If the track record the rest of us have built up is any indication, you will end up owning a bunch of ARs. Own at least one that your friends will envy, own a Daniel Defense ISR.

Hogs beware.

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