AR15 pistol 7.5in. barrel PDW-SBR best of everything?

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AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by Poboyspecial » Tue Aug 04, 2015 3:07 pm

I have been testing my Head Down Provectus AR15 pistol with a 7.5 in. barrel and have been amazed at the versatility and ability of this little fire breathing beast. I had to tame the flame with a Noveske KX3 and now it has NO flame and directs all the blast straight forward... just awesome! This is a must have.

I wanted to post this because I have found that not all rounds perform as advertised because of the short barrel. I have tested just about everything I could get my hands on, and have documented most of it. You can check out all the testings on YouTube...
https://www.youtube.com/playlist?list=P ... UsJjo5RWPd

There are several videos now of people shooting 200-500 yards with this short barrel. I don't know if I would recommend that, but it is an amazing thing to have it be effective at those ranges. The whole purpose of the PDW is close quarters and medium ranges just like regular pistols. It is very maneuverable, tactical, and ammo is plentiful. It makes a great compliment to an M4.

This is the perfect all around choice in weapon in my opinion... what is yours?
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by LowKey » Tue Aug 04, 2015 3:46 pm

Poboyspecial wrote:I have been testing my Head Down Provectus AR15 pistol with a 7.5 in. barrel and have been amazed at the versatility and ability of this little fire breathing beast. I had to tame the flame with a Noveske KX3 and now it has NO flame and directs all the blast straight forward... just awesome! This is a must have.

I wanted to post this because I have found that not all rounds perform as advertised because of the short barrel. I have tested just about everything I could get my hands on, and have documented most of it. You can check out all the testings on YouTube...
https://www.youtube.com/playlist?list=P ... UsJjo5RWPd

There are several videos now of people shooting 200-500 yards with this short barrel. I don't know if I would recommend that, but it is an amazing thing to have it be effective at those ranges. The whole purpose of the PDW is close quarters and medium ranges just like regular pistols. It is very maneuverable, tactical, and ammo is plentiful. It makes a great compliment to an M4.

This is the perfect all around choice in weapon in my opinion... what is yours?
Give thought to switching to a caliber that makes better use of the barrel length you have, unless you just enjoy the light show.
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by Poboyspecial » Tue Aug 04, 2015 3:51 pm

The best so far, has to be the DRT 79g. It was most devastating, and penetrated well.
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by Doctorr Fabulous » Tue Aug 04, 2015 5:11 pm

A caliber change would go a long way. The ballistics testing doesn't look great, even with the DRT. About the same as i'd expect from a segmented .22LR, but with a lot more flash and noise. Any standard 9mm HP would produce a better wound channel, and by the looks of it so would .45 ball loads, again, with less noise, concussion, and flash. IMO, that barrel length is the worst combination of everything. You can't conceal it in a holster, reloads are big, ammo is bulky, lots of flash and bang, but you're not outperforming a duty handgun in terms of terminal ballistics. Adding five inches of barrel gets you a lot in terms of terminal ballistics with a big reduction in kaboom.

You say "effective" 200-500 yards, but I disagree outright. Your terminal ballistics are non-existent, your drop ridiculous at those distances. Your fastest loadsa will be transonic at the far end, and while making this with a transonic round is possible, you have little or nothing to sling on the ass end. Slower, heavier rounds like the DRT will be transonic much sooner. Further, a video of someone dinging known-distance targets on a practiced range is not an indication of effective accuracy, especially under duress or unknown-distance targets. Your drop tables will be more rainbow-y than an AK, and as always, the effective range of the weapon is mainly determined by what you can do behind it, not what someone else did in a video.

Also, you're incorrect about the Flaming Pig deucing the flash. http://i1196.photobucket.com/albums/aa4 ... tPig-1.jpg

You probably don't see it by daylight, but that's a lot of flash and concussion in close quarters, in darkness, or in both.

TL:DR neat toy, but a Glock 34 makes a better poor-man's PDW. The next step up, IMO, is something like a Scorpion EVO, a 5.7 AR pistol, or .300 Blackout in an eight-inch barrel. I have a 7.5" SBR, but it's pretty much a dedicated rimfire upper.

For reference, 9mm 147gr PDX-1 from a Glock: http://i.ytimg.com/vi/rBIDnzDDx6Q/maxresdefault.jpg

Fragmenting 5.56 from an M-4: http://i859.photobucket.com/albums/ab15 ... iginal.jpg

.300 Blackout 125gr SMK https://www.ar15.com/ammo/project/Self_ ... KOTMBG.jpg
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by Poboyspecial » Wed Aug 05, 2015 7:06 pm

I understand what you are saying, but it really isn't that accurate. The AR pistol from 50 yds. and less has 500-800 ft/lbs of energy depending on grain and brand. No 9mm, 45, 40, 357 can compare to that. The AR pistol has the same performance as the M4 from 300 meters. NO, I would not recommend this platform farther than 100 yds, but it does have some great ballistics, had an MK318 expand to .43 inches. I did not use the flaming pig, I went with the Noveske 4pc. It is heavier, but look at the video I did and you will see that it tamed the flame from 5.56 AR and the 7.62 AK. (YouTube- Poboyspecial channel) playlist of 7.5 inch barrel.
Yes, I agree that it is obnoxiously loud, but it can be wielded a little easier than a full size barrel.
I appreciate your opinion and input.
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by Doctorr Fabulous » Wed Aug 05, 2015 8:48 pm

Poboyspecial wrote:I understand what you are saying, but it really isn't that accurate. The AR pistol from 50 yds. and less has 500-800 ft/lbs of energy depending on grain and brand. No 9mm, 45, 40, 357 can compare to that. The AR pistol has the same performance as the M4 from 300 meters. NO, I would not recommend this platform farther than 100 yds, but it does have some great ballistics, had an MK318 expand to .43 inches. I did not use the flaming pig, I went with the Noveske 4pc. It is heavier, but look at the video I did and you will see that it tamed the flame from 5.56 AR and the 7.62 AK. (YouTube- Poboyspecial channel) playlist of 7.5 inch barrel.
Yes, I agree that it is obnoxiously loud, but it can be wielded a little easier than a full size barrel.
I appreciate your opinion and input.
.45 ACP makes a bigger hole than the Mk318 without expanding at all, and every law enforcement-designed hollowpoint will get at least a half-inch, most get more. The ballistics are shit. The ballistics you're seeing are impressive compared to rimfire FMJ from a pistol barrel, but pale in comparison to LE-loads from a duty-sized handgun or what you'd get with even a ten or twelve inch barrel instead of a seven-inch.

Have you fired it at an indoor range? Done a side-by-side timed drill against an AR?

What's a Noveske 4pc? I can't find it on their website, just the KX3 and whatever the other one is that's the same design but bigger. KX5?
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by Paladin1 » Wed Aug 05, 2015 10:10 pm

I don't mean to piss in your beer, have fun with what you have.

But from a practical point of view, I never understood why people built 7"-9" AR's in 5.56.

You lose velocity, range, effectiveness, there freaking loud as shit, throws fireballs that blind you for any follow up shots or transitions.

My solution (using the attributes you described) is my 300BO with 8.5" barrel. Designed from the ground up to operate out of a short barrel and be suppressed.
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by LowKey » Thu Aug 06, 2015 12:01 am

Paladin1 wrote:I don't mean to piss in your beer, have fun with what you have.

But from a practical point of view, I never understood why people built 7"-9" AR's in 5.56.

You lose velocity, range, effectiveness, there freaking loud as shit, throws fireballs that blind you for any follow up shots or transitions.

My solution (using the attributes you described) is my 300BO with 8.5" barrel. Designed from the ground up to operate out of a short barrel and be suppressed.
Ditto. I have the same .300 blackout set up.
Doc's suggestion of 5.7 would also be better in a short barrel than 5.56 would be.
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by Doctorr Fabulous » Thu Aug 06, 2015 6:52 am

As I said, I built my SBR initially on the cheapest shorty upper I could. Mismatched parts, largely, and it's maybe fired a hundred rounds of 5.56 total, mostly it's a rimfire upper as far as I'm concerned, and fairly accurate suppressed. Heavy, though. For doody use moving to a ten inch makes a big difference all around, and if you're already rocking a buffer tube or stock, adding three inches of barrel is fairly negligible.

I have a 9mm AR pistol that was a recent build, and other than currently sporting a FUBAR free-float, it's shaping up pretty well. Heavier than a standard in the same barrel length, a bit snappier recoil, and it took more tuning. Uses Colt mags instead of Glock, but that's not a huge problem for me. Cheaper than HK stick mags by a long shot. It's a six-inch barrel, nudging slightly ahead of most duty handguns, and while the 17L I used to have was more accurate with shitty ammo, the AR is more stable in rapid fire, sports an Aimpoint, and whenever I'm sitting flush with spending money and in a different state, I can add a three-lug adaptor to run a quick-detach SMG can on it. I have more faith in this one to put down an animal or person than I do a super-short AR.

I sold my Blackout upper, but I'll end up rebuilding one someday I'm sure. It was a good compromise, aside from ammo cost, between a traditional pistol-caliber PDW and a carbine with a ridiculously short barrel. RSilvers did work on that project, even if most of the work was just finishing what JDJ never had the ambition or desire to do. Performance ammo is either extremely costly, or is on par with older .30-30 loads.

My old man has, or maybe had a 5.7 upper that ejected out the mag well. A bit front-heavy, but as long as you didn't use a gutted AR mag as a brasscatcher the whole thing was very low profile, especially with a micro RDS mounted low, no irons, and a shortened grip. About the same profile as an Obrez with the bolt locked back, more or less. Mostly a toy, but ammo is about the same as Blackout costwise. Really can't be reloaded, though.
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by Poboyspecial » Thu Aug 06, 2015 2:55 pm

I agree with the 300 blackout set up, the ballistics are awesome, however, you have to buy another kind of ammo.
I did not like the AR pistol with the regular muzzle break, it shot flames to the side and backwards which is HELL for anyone next to you that may be helping to defend you. I found the flash hider at CNC warrior http://www.cncwarrior.com/product-p/23959.htm
I also agree with the 45 acp, I love my Kimber Ultra Carry II. I love the 45. I also understand that the 40 has very good expansion and penetration from various brand names. I have had good success with Hornady Critical Defense.

If I didn't already have an M4 and an AR pistol, I would get an M4 and pistol in the 300 blackout. Since I do have the combination of rifle and pistol in 5.56, then that is what I am going with for now. Yes, you lose a lot of velocity from a short barrel, but it still has a lot of useful punch behind it, even through cinder blocks, wood, and car doors..... just saying!

I know I am not agreeing with your opinion totally, and I don't want to sound like a know it all or smart***, I am just throwing some things out there to try, test and discover. I really do appreciate looking at and weighing different opinions, even ones that are completely opposite. That's what makes the world better.

Thanks for your input.
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by LowKey » Thu Aug 06, 2015 3:23 pm

If you are having to accept the constraint of sticking with 5.56 this set up is adequate. It would certainly be unpleasant to be on the receiving end if someone emptied a magazine.
Nothing to be ashamed of, It's just not "the best of everything".
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by Poboyspecial » Thu Aug 06, 2015 4:46 pm

Very good points...

If you would like to see the results of my testing from a 7.5 inch barrel of many different rounds on this platform, then you can download it for free on my website. Scroll down a bit and you will see it in a PDF format. Enjoy!

http://www.thenothingbox.tv/index.html
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by AS556 » Sun Aug 09, 2015 7:24 am

http://www.ar15.com/ammo/project/Self_D ... Rounds.htm

The 50gr TSX is clocking over 2600 from an 8"..possibly 2700 in an 8.5". The wound channel between the 8" test and 20" test is IDENTICAL. The 70gr TSX from a 9" clocks 2375fps, expands down to 1800 and is still within its expansion threshold at 230m. Not so anemic, eh? Comparing that to .45 ball is a joke. 55gr Gold Dot and 55gr V-max (yes, V-max. The low MV prevents fragging and the bullet just mushrooms. http://mousegunaddict.blogspot.com/2014 ... l.html?m=1 )


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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by Doctorr Fabulous » Sun Aug 09, 2015 10:14 am

I love data, but that DocGKR is lacking some important data, like permanent wound cavity, accuracy, and drop tables. What i see if a big temporary cavity, a recovered diameter about .5" or smaller, and a maximum penetration depth of fifteen inches. You know, about like another gimmick that was highly derided by industry experts:

Image

If you've got actual wound channel diameter data I'd love to see it. Remember that the barrier penetration rounds, and particularly solid-copper expanding loads aren't chosen for their instant-stop ability, but for their ability to penetrate barriers while still producing acceptable lethal ballistics.

The GDSP and VMAX in the videos you link all perform about the same as the DRT load I compares to ball ammo in the OP: small but consistent wound channel, smaller than you would get with HST or Gold Dot out of a duty handgun.

Do you have data that shows ubershort 5.56 outperforming service handguns? Because so far, I haven't seen it.
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by gun toting monkeyboy » Thu Aug 27, 2015 6:36 pm

Truthfully, I wouldn't bother using a .223/5.56 in anything under 10.5". The ballistics just aren't good enough to warrant the muzzle blast below that. Here in California, where SBRs are basically non-existent, we have spent a lot of time playing with AR pistols. I have probably half a dozen different uppers in 5.56 and 6.8. And I have tested their accuracy and velocity often. I would take a 6.8 with a short barrel any day of the week. And for all practical purposes, I would take a .300 Blk instead as well. 5.56 just doesn't pack as much of a punch out past about 60-75 yards. It is simply the nature of the beast. About the only thing that the shorter barrels are good for is making noise and putting on a light show. Especially if you have a brake on them. I had a simple Cavalry Arms brake on a 10.5 inch one for a while. It would clear your sinuses in three rounds of less. And poor buggers next to you on either side would get stuff knocked off of their benches by the blast. People thought it was at least a .308. And the 5-6 foot, blinding white fireball was a sight to see. Literally. That was all you saw, and it took a couple of seconds for your vision to clear, even shooting outside in daylight. That was with a 10.5" barrel. I shudder to think what a 7.5" barrel would do. I have since converted all of my pistols to Smith Enterprises vortex flash hiders to make them more functional.

In terms of ballistics, they have done multiple studies showing that anything under 10.5" is a waste of powder. You move from centerfire rifle velocities down to .22 WMR velocities. For what it costs to shoot a .223/5.56 these days, I can't really see myself wasting money on it, when .22 WMR is so much cheaper.

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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by Rugger » Thu Aug 27, 2015 11:58 pm

.300 BLK is much better in a pistol or SBR configuration. Hands down, end of story. That being said, I too have a 7.5" 5.56 upper. I went with it because I already have a bunch of 5.56, several rifles in 5.56, don't want to reload for just one caliber, don't want to buy another caliber, and understand that it's useful in a very limited capacity. As long as you understand the limitations you put on yourself when using such a short barrel, I say you're good. For me, it's a very specific tool and with limited roles in which it'd be useful. Inside of 50 yards, I'd take my 7.5" pistol every day, over an actual handgun. Mine travels in the vehicle or is by my bed, as that's where it's most useful for me and where it's negatives are minimized by the likely close quarters. Anything beyond 50 yards, I'd prefer a rifle. If it's over 100 yards, I wouldn't want to have to use it.
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by Kutter_0311 » Sat Aug 29, 2015 6:25 am

You know, for less weight, you could just buy a G35...
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by PistolPete » Wed Sep 30, 2015 4:22 pm

Kutter_0311 wrote:You know, for less weight, you could just buy a G35...
Verily.
I'm with other people here, after having crunched the numbers and shot some shorty .223's, I'd pick a long pistol any day. Glock 34, 35, 17L, 24, etc. Toss in an extended barrel in it even. 357 Sig out of a 6" barrel is pushing 1,600 fps with bullets twice the weight of your standard 5.56 loads. Even 9mm gets a velocity boost in longer barrels, but rounds like 357 sig and 10mm really perform nicely.

On top of that you get way, way less flash in dim situations out of a pistol with a longer barrel. And a lot less noise as well. A lot of people here have considered shorty AR's and things like the PLR-16 (which I've shot a fair bit) and even with a fancy flash hider they are oppressive to shoot indoors. Something like a Noveske Pig helps, but it's still a lot to deal with.

Switch the caliber to 300 BLK and it starts to make more sense, better ballistics out of short barrels, reduced noise and flash, plus viable can use. For something PDW size, my money is either in a short 300 BLK or a long pistol.

But hey, it's an AR. If you decide it's not for you at some point you sell the upper and put something else on it without losing your ass. Lots of people run those 7.5" barrels, you just won't find many of them here. :-)
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by brothaman » Thu Oct 01, 2015 7:47 am

Answer your PDW needs with a Glock 40 and a RDS. Carry a hate-stick for the bad days. Done and Done. Probably stupid reliable, too.
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Re: AR15 pistol 7.5in. barrel PDW-SBR best of everything?

Post by woodsghost » Thu Oct 01, 2015 12:36 pm

Poboyspecial wrote:I understand what you are saying, but it really isn't that accurate. The AR pistol from 50 yds. and less has 500-800 ft/lbs of energy depending on grain and brand. No 9mm, 45, 40, 357 can compare to that. ...

This I think is a key misunderstanding, and I misunderstood this for quite a while. "Foot-pounds" of energy is a number which requires some interpretation and filtering.

1) There is the raw energy, which we see in the numbers like "500" or "800." But this is NOT all delivered to the target. If the round exits the target, then not all the energy was transferred to the target. The round continues to move, so it still has energy left, and therefore not all was transferred to the target medium. In the case of 5.56 rounds which fail to fragment, most of that energy is still in the bullet upon exiting the target.

Think of it this way: If a bullet has 800 ft pounds of energy when striking a paper target, how much energy was the target hit with? Answer: 800.

Ok, so the bullet continues on after punching a hole in the paper target. It strikes some measurement device and the device records 799 ft pounds of energy. That is because the bullet imparted 1 ft pound of energy to the paper. Bullets do not magically impart all their energy to a target upon striking it. You do not fully impart 800 ft pounds of energy to a piece of paper. You impart a small portion of that energy to the piece of paper, and the same with living targets.

2) Temporary tissue cavitation does not count for much. Folks thought it did, but found it only matters with a very few organs in the human body. Most organs are elastic, and deal quite well with being stretched.

3) Looking at what a bullet does to ballistic gelatin does not tell you anything about what the bullet does to flesh. Read Martin Fackler's stuff (the guy who gave us most of what we know about bullets). Ballistic gelatin itself does not tell us about the wound. Rather, we can learn about the effect a bullet will have on flesh from knowing A) penetration depth, B) retained weight, C) and fragmentation [if any]. There might be a few more important variables, but gelatin does not simulate the wound, it simulates the effect of flesh on the bullet, and from knowing what happens to the bullet we can know about the wounding potential of a bullet. The slow-mo shots of bullets hitting gel are fun, but otherwise worthless.

4) So what is needed is not "hey! Look at the ft pounds and how big a hole in the gelatin it made when it hit it," but rather we need a way to translate effects on bullets from hitting gel into effects on flesh. This data would seem to exist, given Fackler's work, but is likely not public. His articles and means of testing are, however, public.

5) If you want to know what weapon/ammo combinations are the best, look to the hog hunters. Hog flesh is as similar to human as we can find, and there are plenty of hogs which match humans for weight. If hog hunters are not using 7.5 inch barreled ARs in 5.56, then you can bet that platform will not do what you want it to do in a bad situation.

...but if you DO find hog hunters using 7.5 in barreled ARs, do please share. I would LOVE to watch that!
*Remember: I'm just a guy on the internet :)
*Don't go to stupid places with stupid people & do stupid things.
*Be courteous. Look normal. Be in bed by 10'clock.

“It's a dangerous business, Frodo, going out your door. You step onto the road, and if you don't keep your feet, there's no knowing where you might be swept off to.” -Bilbo Baggins.

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