Sig Rattler .300 Blk PDW

Discussion in 'AR15' started by TACAV, Sep 12, 2020.

  1. TACAV

    TACAV G&G Evangelist Forum Contributor

    This is my new truck/travel "get home" gun. / pistol...

    Sig Sauer MCX Rattler in .300 Blackout.

    As configured it is 24" with brace extended (replaced the Sig one with a SB Tactical SB1913 brace with aluminum strut) and only 16" folded.

    It folds up nice to fit in a small pack.

    5.5" barrel but still giving far better ballistics than either a short barreled 9mm PCC or shorter barreled 5.56/7.62x39 or 5.45x39 pistol which would require an even longer barrel. the .300 blackout wont spit fireballs like the other intermediate calibers either.

    The defensive ammo load Im using is the SigSauer 120 grain supersonic expanding copper SBR loads that were loaded for use in shorter barrels.

    Other accessories are an SLR Rifleworks M-Lok handstop, Streamlight TLR1 HL weapon light with the rifle mount kit and pressure switch, Sig Romeo 3 open reflex site and an HSP sling.

    The brace stays put when folded but only requires you to easily pull/snap it out with a little pressure. Once opened it locks in solid until you pull it up out of its cam locking notch to close it again.

    I currently have the optic and folding BUIS sights zeroed in at 50 yards but after some recent training etc and experience with the .300 blackout round Ill be switching it to a 30 yard zero as it will give me the flattest trajectory with minimal hold overs from 0-180/200 yards (180-200 depending on each load out there since there are so many different ones). And lets be real here, distances you could legally justify using this in a defensive shoot would probably be far less than that anyways. The idea is to avoid trouble at all cost first.

    A 30 yard zero with .300 blackout super sonics is sort of similar to a 50-200/223 yard zero with 5.56.

    This setup is designed to be a concealable and easily packable PDW that will give me as much bang for the buck as I can in a small platform.

    I keep a 20 rounder in the gun with a couple extra 30 rounders with it. Using Lancer AWM .300 blackout specific magazines.

    The Rattler is basically a gen 3 Sig MCX piston system rifle with an adjustable gas block for suppressor use if you want it. It has an ambi mag catch and charging handle and no forward assist. Accuracy is pretty good.

    .300 blackout is a bit hard to come by these days but Im set for my carry setup and some extra of the good stuff.
    Rattler Right.jpg Rattler Left.jpg
    Last edited: Sep 12, 2020
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  2. blaster

    blaster G&G Evangelist

    very nice!!
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  3. ChaZam

    ChaZam G&G Evangelist Forum Contributor

    Nice, and if I was to jump on the 300 BO wagon, something like that is probably what I would be considering and investigating.
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  4. TACAV

    TACAV G&G Evangelist Forum Contributor

    Supersonic .300 blackout with good ammo is hands down the superior round to .223/5.56 for 200 yards and in for soft tissue ballistics, punching through windshield glass etc but also not over penetrating either. Depending on the round, .300blk actually punches through windshield glass making a bigger hole than .308 does.

    Outside of 200 yards it drops to fast. But going back to the 30 yard zero you can keep everything pretty tight within that distance.

    If it wasnt for the cost difference in ammo, for a defensive carbine, I'd go straight supersonic .300 blackout with a suppressor vs a 5.56 gun.
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  5. ItstheHOFF

    ItstheHOFF G&G Evangelist

    I got a ghost 7.5” 300blk upper on the way that I can just swap out on my AR when I feel like it. If I’m not mistaken, any standard .233/5.56 AR mag will work with 300blk. Why did you go with a 300blk specific?
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  6. TACAV

    TACAV G&G Evangelist Forum Contributor

    Because .300 blackout optimal barrel length is 9" but its doable down to the 5.5" and its still accurate and has viable ballistics and you wont have ungodly muzzle blast.

    vs 5.56 which the shortest you can go barrel length without getting completely useless ballistics is like 10.3" and even then you are spitting fireballs from all the unburned powder and muzzle blast.

    7.62x39 is also unglodly blasty and with horrible ballistics in short barrels and 5.45 about the shortest id go is 8.5" and its going to be mighty blasty as well with compromized ballistics.

    So the .300 blackout lets you have super short barrel, decent ballistics over the other intermediate rifle calibers or a pistol caliber for the matter and you dont have a daylight visible flame thrower every time you shoot it.

    regarding the mags, it depends on what bullets you are using in .300 blackout.

    The differences in .300 blackout ammo range from 110 grain to 220 grain which is a 110 grain bullet size difference vs 5.56 where you can have anything from usually 50 grain to 77 grain which is only a 27 grain difference.

    If you are using the longer/bigger sub sonic bullets in a standard 5.56 mag it can cause feeding issues with the rounds getting hung up. This problem is much less prevalent in the lighter .300BO rounds.

    Magpul and Lancer both make dedicated .300 blackout P Mags and AWM mags respectively.

    The mag bodies have some subtle but noticeable differences to help visually and tactfully differentiate between the 5.56 and the .300 BO mags.

    Phyiscally the mag bodies, feed lips and follower are ever so slightly different but enough where it solves the feeding issues that the heavier .300 BO rounds can have in the standard 5.56 mags.

    Supposidly if you only have 5.56 mags and you are shooting heavy subsonic .300 BO you can mitigate the probability of a feeding issue by either downloading your 30 round mags by a few or by using 20 round mags but I have not tested that. I have just bought a bunch of dedicated .300 blackout mags and have not had a problem.

    The standard aluminum USGI mags seem to be another factor. they seem to have more issues with .300 BO subs than some of the other polymer mags like the P Mags or the lancers.

    Some people can run subs in (subsonic loads are typically high 90 to 200-220 grain pills) and never have a problem with 5.56 mags fully loaded and some people def. have problems depending on the ammo they are using.

    I just didnt want to have to worry about it so I went with the dedicated mags.
    Last edited: Sep 12, 2020
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  7. Ranger4

    Ranger4 G&G Evangelist

    The folded size of your Rattler is impressive. Congrats on the Cadillac of defensive pistols.

    For my RV camping gun, I built a 300 pistol with a 10.5 inch tube. I have not had any feeding issues with any magazines with any load including Viet Nam era Colt mags with original springs. I also have an AR carbine with a 16 inch tube and never had any feeding issues.

    I put BUIS on mine but I also put a BDC 3 x 9 x 40 scope on it, with those quick detach lever activated mounts, so it comes off in about one second. Just wanted the ability to lay it across the truck hood and take a long shot if I wanted. I also have a small light that works very well at 50 yards, all that I need. The only option I do not have but might consider would be a tritium from sight. If you have ever seen a bear at 10 feet in the dark, it is a frightening experience and the cost of a glowing front sight would be pretty small if it happened again.

    I do shoot with a suppressor most of the time, but do not keep it on the gun as I do not want to carry it across state lines. Not a problem with the federal side, but I do not want to have to worry about any state restrictions on suppressors.

    That being said, if you have the option of shooting suppressed it is worth the cost and wait, I just wish I had them when I was much younger. Enjoy that cool gun.
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  8. Junction15

    Junction15 G&G Evangelist

    Mine is a 10.5 inch "home-built" gun with a SBH brace. And I have to say -just like TACAV and others have said - the ballistics and accuracy of the 300 Blackout is impressive. I have it fitted with a light and a laser, and it is the primary weapon kept ready to go.

    After watching mediocre shooters PCC score as high as top handgun shooters at USPSA matches, I am convinced that - other than a shotgun - a short barreled carbine or an AR pistol are very efficient self defense weapons. They are faster on target than any handgun.

    As for ammo, I have found I get good results with forming 223 brass into 300 Blackout.
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  9. TACAV

    TACAV G&G Evangelist Forum Contributor


    Nice, your's sounds pretty nifty too.

    This is my other .300 blackout gun which is almost run exclusively suppressed.

    Its a Noveske lower with a Noveske/VLTOR upper. 8.5" barrel with a PDW Stock (Its SBR'd).
    AAC SDN-6 suppressor, Aimpoint Micro T1, Surefire Mini-scout light, ALG Defense ACT trigger, BCM grip, RailsScales G10 keymod covers, Radian Raptor Ambi Charging handle and Ranier Arms low pro BUIS.


    Ive had this one for about 8 years now. Its almost always been shot with sub sonics suppressed more as a range toy but after seeing how well .300 blackout does in person though FBI ballistics gel, windshield glass and all that recently (ive always heard about it but never got to see it in person and then everything just clicked lol).... Ill probably be making this one shoot supers as well and tweak the zeros a bit for the sights and optics.

    As I used this as a range toy, probably 80% of my stockpiled ammo is subsonics (another reason why I have so many dedicated .300 blackout mags) and the rest being supers... but when the ammo drought stops and ammo is easier to find Ill probably be flipping that ratio around and investing more in supersonic ball ammo for plinking and defensive supersonic ammo.
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  10. Ranger4

    Ranger4 G&G Evangelist

    Yep the ammo supply is an issue, I reload so not a short term issue. If Biden gets elected expect ammo to be a big issues. They will try to ban all lead ammo and restrict the rest. Check out the scalpers prices today.
    Remington, 220 grain ammo $2.85 per round plus shipping and maybe tax depending on your state. Guess I will be molding toms 30 cal bullets and loading for a while. Who woulda thought?
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  11. Ten Man

    Ten Man G&G Evangelist

    I got my 300 BLK primarily to get away from the AK47, because I reload all my ammo (except for PD ammo). I wanted to be able to use the same .308 bullets for ALL my "30 Cal." rifles. All my 300 BLK ammo is supersonic. I have no need for a subsonic load. I basically treat my 300 BLK as a "mini" AR10. :usa2:
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  12. TXplt

    TXplt Gun Toting Boeing Driver Forum Contributor

    Wow--that's pretty nice and looks like a fantastic setup !

    I'm a fan of the .300 -- mostly super -- but I DO occasionally use suppressed subs though for hunting (especially at night where something loud might be disturbing) -- using the 190gr Hornady expanding load. It's really accurate at range for a sub and doesn't seem to bounce around when hitting rocks or steel like the other subs.
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  13. TXplt

    TXplt Gun Toting Boeing Driver Forum Contributor

    The .300 is a great round to run suppressed. I've found nil change of POI when running open vs. suppressed in either the subs or supers.

    What I've done on one specific upper is index (it's running a mildot sight which is OK but I'll probably change out someday due to some light bounce issues under low light with light sources in the background) the mil-dot to known ranges with subs and supers (it's right now running a 25 yard zero with subs which gives me about 1 dot up at 100 yds subsonic) and keep this on my card with the upper. This gives me about two dots down for supers at around 100 yards as a zero if I switch to them. Since it's mostly exclusively used at the farm and cabin the ranges to various stuff are all well known.

    The other version has the .300 ACOG (with the diamonds) so I kinda do the same thing with this (knowing the graduation and diamond width).

    This lets me switch between supers and subs without re-zeroing (putting a stake in the ground by zeroing for the round that's mostly going to be used as the go-to round for the rifle/pistol).

    ONE THING I have found--think I've mentioned this on a few occasions--is that unlike just about everything else I shoot at steel (angled down, AR-500, good quality, yada yada) the subs DO seem (at least the 220-ish grain ones) to have more of a propensity to bounce than just about anything else I shoot. This includes hitting rocks, etc. Not sure why; just something I've observed. No problem with the supers and the Hornady 190 round doesn't do it. So I avoid shooting the heavier FMJ subs at steel and harder targets these days. No idea why this has been the case but I've observed it both at my steel range in PA as well as when shooting at targets in TX which have rocks I didn't see behind them. No damage to anything but hearing the whirrrrrr on a couple of occasions was enough to make me stop doing it.
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  14. ItstheHOFF

    ItstheHOFF G&G Evangelist

    887A3959-0F83-4991-97A9-D463BC60CE5D.jpeg My upper came in today! Looks solid, can’t wait to get ammo for it and see how it feels, but it may be a while. This purchase probably could have waited, but oh well.