User Panel
Posted: 10/8/2014 8:15:24 PM EDT
Prose details on the build itself and the ammo I designed will follow.
SIG SB-15 Brace Looped receiver plate KAK Industries buffer tube Billet lower G.I. 20-round mag Magpul K2 Grip KNS non-rotate pin set ALG Combat Trigger Forged flat top upper VLTOR charging handle Palmetto State Armory flip-up rear sight Yankee Hill Diamond handguard Ergo rail covers Magpul AFG2 10.5” heavy barrel, .223 Wylde chamber Yankee Hill FSB, H&K flip-up front sight Smith Enterprises Vortex FH Streamlight TLR-4 light/laser http://i27.photobucket.com/albums/c195/numero_6/000_Full_LHS_no_sling_zps44e9814b.jpg 8.2 lbs in home defense trim, loaded. 28.5" OAL, 26.5" to end of bbl threads. http://i27.photobucket.com/albums/c195/numero_6/002_LHS_front_zps1d87095a.jpg http://i27.photobucket.com/albums/c195/numero_6/003_LHS_front_sight_down_zps84a39890.jpg http://i27.photobucket.com/albums/c195/numero_6/004_TLR-4_AFG2_detail_zps70d74a11.jpg http://i27.photobucket.com/albums/c195/numero_6/005_hold_LHS_zps4015bd36.jpg |
|
An AR-based Personal Defense Weapon (PDW) concept firearm - Part 2
http://i27.photobucket.com/albums/c195/numero_6/006_hold_RHS_zps3681e201.jpg http://i27.photobucket.com/albums/c195/numero_6/007_hold_RHS_zpsc0ce64f0.jpg Activating the TLR-4 http://i27.photobucket.com/albums/c195/numero_6/011_SB15_zpsf0d011a3.jpg A little addition http://i27.photobucket.com/albums/c195/numero_6/012_single_point_zps04007640.jpg A single point OPTION http://i27.photobucket.com/albums/c195/numero_6/014_top_zpsc60056b3.jpg http://i27.photobucket.com/albums/c195/numero_6/015_top_zps02c5676e.jpg |
|
I agree on the quad rail. CDNN has a great deal on LWRC rails which are the ones that I chose to go with on my build.
|
|
Quoted:
I agree on the quad rail. CDNN has a great deal on LWRC rails which are the ones that I chose to go with on my build. View Quote $90-100 are fantastic prices for a quality quad rail handguard. I had a LWRC midlength a while back, but decided it was too heavy and opted for a modular handguard. My currently pistol build is getting a Samson EVO 7" for a 8" 300BO. |
|
|
Quoted:
Think I'm covered on AR-based PDW's for now http://i241.photobucket.com/albums/ff206/devtucker/2013-03-04_17-36-46_163.jpg .45 DI SBR work in progress http://i241.photobucket.com/albums/ff206/devtucker/AR-45/IMG_20140920_170459_612.jpg View Quote Where'd you get that rail? Lower right pic. |
|
Quoted:
Think I'm covered on AR-based PDW's for now http://i241.photobucket.com/albums/ff206/devtucker/2013-03-04_17-36-46_163.jpg View Quote I am curious of the forward charging handle of the SBR with the Nordic CRS. |
|
Quoted:
Where'd you get that rail? Lower right pic. View Quote View All Quotes View All Quotes Quoted:
Quoted:
Think I'm covered on AR-based PDW's for now http://i241.photobucket.com/albums/ff206/devtucker/2013-03-04_17-36-46_163.jpg .45 DI SBR work in progress http://i241.photobucket.com/albums/ff206/devtucker/AR-45/IMG_20140920_170459_612.jpg Where'd you get that rail? Lower right pic. That's an ARMS Swan Sleeve for an AR10. |
|
Quoted:
I am curious of the forward charging handle of the SBR with the Nordic CRS. View Quote View All Quotes View All Quotes Quoted:
Quoted:
Think I'm covered on AR-based PDW's for now http://i241.photobucket.com/albums/ff206/devtucker/2013-03-04_17-36-46_163.jpg I am curious of the forward charging handle of the SBR with the Nordic CRS. Built my own bufferless upper with a non-reciprocating charging handle. Original pistol configuration: More recently: |
|
Spend the extra $200 if you can. You lose the whole "compact" thing when the brace is on there.
CHRIS |
|
10.5" seems kinda long for a "PDW."
Seems most factory PD dubs are 7-8." |
|
|
Thought you guys would like to see how I added the GG&G universal loop to
the SB-15. Probably never need it for my application (house gun). More to see if it could be done than anything else: http://i27.photobucket.com/albums/c195/numero_6/001_GGG_zpsa95e88de.jpg Loop must be located low enough so the screws don't hit the tube! I chose the position shown, 1.5" from the back of the butt to the centerline of the back mounting screw. This rubber cuts like butter with a utility knife or X-acto, go slow. I finished up with a Dremel. http://i27.photobucket.com/albums/c195/numero_6/002_GGG_zps74098174.jpg Measure FIVE times, cut once. http://i27.photobucket.com/albums/c195/numero_6/003_GGG_zps97adee9f.jpg I think I used 1.5" #8 dark plated screws from the hardware store. Each screw goes all the way through the open area and just starts in on the far end. I also used rubber contact cement on the loop before this step. Tighten screws only far enough to press loop into the rubber a little. http://i27.photobucket.com/albums/c195/numero_6/004_GGG_zps8edeb8f8.jpg Contemplated many solutions for a retainer/stiffener: threaded dowel, threaded aluminum piece, etc. Then it hit me - good ol' JB-Weld. Love that stuff. Just kept glommin' it in until it went under and over the screws. In use, the loop has proven plenty solid. As you know, the SB-15 tends to rotate on the tube. IMHOP you really must glue it on. I used a little two-element epoxy. This mod does not interfere in any way with the brace function of the SB-15 and it gives me a way to carry my firearm comfortably to the range. |
|
Quoted:
the KNS non-rotate pin set was a waste the rest seems fine View Quote My reasoning on the pin set -- Even though I was careful to "sneak up" on the pin hole diameters by drilling first then hand-reaming they still came out just a tad looser than I would prefer. It's hardened steel (albeit very smooth) against aluminum, so I figured what the heck, it couldn't hurt. I keep the wrench in the grip. |
|
Quoted:
My reasoning on the pin set -- Even though I was careful to "sneak up" on the pin hole diameters by drilling first then hand-reaming they still came out just a tad looser than I would prefer. It's hardened steel (albeit very smooth) against aluminum, so I figured what the heck, it couldn't hurt. I keep the wrench in the grip. View Quote View All Quotes View All Quotes Quoted:
Quoted:
the KNS non-rotate pin set was a waste the rest seems fine My reasoning on the pin set -- Even though I was careful to "sneak up" on the pin hole diameters by drilling first then hand-reaming they still came out just a tad looser than I would prefer. It's hardened steel (albeit very smooth) against aluminum, so I figured what the heck, it couldn't hurt. I keep the wrench in the grip. Any reason you reamed them by hand instead of using the drill press / jig? |
|
Quoted:
I like the two tone look, hate quad rails though. View Quote At first, I left the lower alone because I was too busy using it and trying out different ideas. Now the appearance is growing on me too. The lower came bead-blasted so it isn't too shiny. May leave it as-is. The quad rail was what I had, and I wanted some weight to start with anyway. I find the grip shown to be very natural. But I think the next upper I build will be in completely the opposite direction - how LIGHT can I make it. .625" BBL, Magpul guard, add rails only where I need 'em, etc. |
|
My reasoning on the pin set --
Even though I was careful to "sneak up" on the pin hole diameters by drilling first then hand-reaming they still came out just a tad looser than I would prefer. It's hardened steel (albeit very smooth) against aluminum, so I figured what the heck, it couldn't hurt. I keep the wrench in the grip. View Quote View All Quotes View All Quotes My reasoning on the pin set --
Even though I was careful to "sneak up" on the pin hole diameters by drilling first then hand-reaming they still came out just a tad looser than I would prefer. It's hardened steel (albeit very smooth) against aluminum, so I figured what the heck, it couldn't hurt. I keep the wrench in the grip. Any reason you reamed them by hand instead of using the drill press / jig?
The drill press I used appeared to have more run-out than I liked, so I felt much better doing it by hand. I carefully reamed through before milling the inside so I knew the holes would be aligned. If you have a high-quality drill press you can certainly use a chucking reamer in it. Even when you use a good drill press, bits tend to bore a couple thousandths over their nominal size. More with bigger bits if your press is like mine. Especially true with the safety hole! If you just use a 3/8" (.375") drill right off, it'll work, but you won't like the way your safety wobbles. I used the 3/8" bit through the jig to make a dimple, then drilled thru with a "U" bit (.368") before using a .375" hand reamer. The safety fits and works like factory. |
|
I don't use jigs and I do all my work on my Bridgeport mill...
Be glad you don't have the old style 80% where you had to tap the buffer tower, I paid about $60 for that tap, and I would hate to have to ream and tap it without a mill. |
|
the around the house thing is part of why i build my 7.5, but im sure it would just light walls on fire.... its nice and short though. and it fits in a vehicle i can pivot from side window to side window in my fiero even... the ramcharger might as well be a pill box tho
|
|
Quoted:
I don't use jigs and I do all my work on my Bridgeport mill... Be glad you don't have the old style 80% where you had to tap the buffer tower, I paid about $60 for that tap, and I would hate to have to ream and tap it without a mill. View Quote You're way aheada me! Sorry about the machining 101 tutorial. I finished mine on a friend's mill - an old but still solid Bridgeport BTW, beautiful piece of equipment. I'm amazed you found a tap that big for $60. Can't even imagine having to do that operation without the right equipment. That area of the lower is the only part of the whole weapon that's always bothered me - just not enough meat. I wonder about the possibility of getting a forging with an internal fault that just happens to be in that tower area. Solution: pay more and get a good billet lower! |
|
Quoted:
I wonder about the possibility of getting a forging with an internal fault that just happens to be in that tower area. Solution: pay more and get a good billet lower! View Quote Much less likely to happen in a forging compared to one of the crappy cast 80% lowers that still pop up from time to time. |
|
Further comments on my pix above, split over six posts since newbies get
2000 chars per post to start. Twenty years ago or so after building my first AR, I considered building up a compact semi-auto AR-based personal defense weapon. It seemed to me that sort of AR would be ideal for home defense. It would be relatively lightweight, handy, and suited for the job of moving around inside and through doors. It seemed like it would be easier to shoot well than a handgun, especially for someone who has plenty of shooting experience but minimal formal combat training. Another consideration was the fact that we are seeing more and more home invasions by perps wearing body armor of the Threat Level IIa or II variety. The bad guys know homeowners are more likely to be armed and willing to defend themselves, and they're raising the stakes. I didn't think of the requirement to penetrate body armor back then, but times have changed... This was all assuming the right 5.56 ammo. I had thoughts about that, too. But the pistol buffers seemed awkward and I backburnered the idea. In the meantime, semiauto versions of PDWs like the PS90 began appearing but, good grief, are they expensive! And in most cases it would have meant a new caliber or specialized cartridge (or both). It also meant different, more expensive, tougher to get spare parts. That meant changes I really didn't want to mess with in my my nice, steady AR-15 logistics chain. Then the Sig SB15 Pistol Brace appeared on the scene, and the thoughts started percolating again. What could be done with the standard AR platform to meet my PDW requirements? The result of that percolation is presented here for your consideration. |
|
Part 2:
The basic weapon is 8.2 lbs, unloaded. This could be reduced somewhat if desired by using a lightweight ("pencil") barrel assembly and a plastic handguard like the Magpul instead of the quad-rail. I built this first effort a little heavy on purpose. Easy to build any sort of upper you like. Everything I did here had a reason. May not have been the BEST reason - but there was a reason. The idea was to design to the task at hand, but no more. In keeping with that philosophy, I knew I needed to come up with a suitable 5.56 variant for the ammo. A quick aside. I realize .300 Blackout has been mentioned more and more often for the PDW concept and, I believe, for good reasons. For now the author is limiting himself to 5.56 because that's his current self-imposed logistics chain. Shooting military loads or full-patch hot reloads out of a short barrel in the home defense application is unsatisfactory IMHOP for several reasons: 1) The flash and blast in confined spaces is often disorienting, not something you want to deal with under the circumstances, if possible. In some instances you can permanently damage your hearing. The idea here is presumeably to take down the bad guy without wrecking yourself. 2) With the powders most often used in mil cartridges and by reloaders in 16" and longer barrels, a good proportion of the powder is wasted producing flash and blast as it burns outside a shorter barrel. 3) The highest possible velocity and bullet energy may not be the best goal, since the result may be overly-penetrative. |
|
|
|
Part 3:
So the requirements for my 5.56 house gun load became: 1) Reduce the flash and blast enough to partially mitigate the effects of firing 5.56 inside a home. 2) Within requirement #1, pick a projectile and move it fast enough to reliably penetrate Threat Level II and IIa body armor while retaining enough energy to stop the perp. 3) Within requirements #1 and #2, the load should not be overly penetrative. 4) Finally, within all three requirements above, the load must cycle the action with as close to 100% reliability as practical. 4a) Had to add this in - ALL STANDARD PARTS, no shortened buffer springs, lightweight oddball buffers, etc. I began by doing a survey to get an idea of the ballistics I needed to match. Looking at military cartridges that have been developed for short barrels like the U.S. Mk 318 round can be misleading since they have to dance around the Hague Convention restrictions concerning expanding bullets. Ironically, we as civilians can use bullet types our fighting men and women can't. The FN "Duty" SS190 5.7x28 cartridge that defeats body armor has a steel core and has been deemed armor-piercing by BATF. The SS197SR (sporting round) uses a Hornady 40gr V-Max bullet at 2100 fps when fired from the P90's 10.5” bbl. There is conflicting data on whether this cartridge will defeat Threat Level II vests: This from Wikipedia: "The SS196 was classified by the ATF as not armor-piercing, and in testing by FNH USA it did not penetrate a Level II vest when fired from the Five-Seven." No mention of whether the round will penetrate when fired from the P90's 10.5" barrel. But then there is this link: http://www.eliteammunition.net/multi_media_page.html Scroll down to "5.7x28 ProtecTOR One Level II Vest 15% Gel Test". They show the bullet penetrating the vest and then an additional 9" into ballistic gelatine. I tend to believe what I see with my own eyes. |
|
Part 4:
There are many powders for .223/.556 out there. I did my preliminary development with these three: Accurate Arms 2230 - #83 out of 145 on my burn rate chart, sort of a standard powder for .223/5.56. Not sure it's made any more but it's what I have. IMR 4198 - quite a bit faster at #71 on the chart, IMR's fastest rifle-specific powder. IMR 4759 - faster still at #66, IMR actually lists it in the pistol column, and as a "reduced load propellant for rifle cartridges". I'm extremely wary about using any pistol-SPECIFIC powders in a rifle cartridge. I began by trying to approximate the ballistics of the FN SS197 cartridge (40gr V-Max, 2100fps, 392 ft-lbs). It became obvious that a lot of the 2230 was burning outside the barrel even with this reduced load... 20.6gr Accurate 2230 powder, 40gr V-max Velocity: 2050fps Bullet energy: 373 ft-lbs ...so I didn't even bother to keep going after this point. To shorten the story, I eventually arrived at these two loads, both are 2.25" OAL, Winchester silver primers, US mil brass (LC and WCC): 17.5gr of IMR4198, 55gr V-Max bullet Velocity: 2218 fps Bullet energy: 601 ft-lbs 15.5gr IMR 4759, 55gr V-Max bullet Velocity: 2283 fps Bullet energy: 636 ft-lbs No FTFs or FTEs now with either of these loads. AT FIRST when the weapon was new, the SR4759 load failed to hold open on the last shot about 50% of the time. However, after the first 100 rounds or so of testing, I could no longer reproduce the fault. Between the 40gr and 55gr V-Max and 60gr Nosler Ballistic Tip, the 55gr bullet had the highest bullet energy using the faster powders. Ejection was positive, although not as energetic as full-patch loads. The cases did not appear to hit the deflector. Rather, they came out at a slight angle to the rear and 6 - 7 feet out. |
|
Part 5:
There are many powders for .223/.556 out there. I did my preliminary development with these three: Accurate Arms 2230 - #83 out of 145 on my burn rate chart, sort of a standard powder for .223/5.56. Not sure it's made any more but it's what I have. IMR 4198 - quite a bit faster at #71 on the chart, IMR's fastest rifle-specific powder. IMR 4759 - faster still at #66, IMR actually lists it in the pistol column, and as a "reduced load propellant for rifle cartridges". I'm extremely wary about using any pistol-SPECIFIC powders in a rifle cartridge. I began by trying to approximate the ballistics of the FN SS197 cartridge (40gr V-Max, 2100fps, 392 ft-lbs). It became obvious that a lot of the 2230 was burning outside the barrel even with this reduced load... 20.6gr Accurate 2230 powder, 40gr V-max Velocity: 2050fps Bullet energy: 373 ft-lbs ...so I didn't even bother to keep going after this point. To shorten the story, I eventually arrived at these two loads, both are 2.25" OAL, Winchester silver primers, US mil brass (LC and WCC): 17.5gr of IMR4198, 55gr V-Max bullet Velocity: 2218 fps Bullet energy: 601 ft-lbs 15.5gr IMR 4759, 55gr V-Max bullet Velocity: 2283 fps Bullet energy: 636 ft-lbs No FTFs or FTEs now with either of these loads. AT FIRST when the weapon was new, the SR4759 load failed to hold open on the last shot about 50% of the time. However, after the first 100 rounds or so of testing, I could no longer reproduce the fault. Between the 40gr and 55gr V-Max and 60gr Nosler Ballistic Tip, the 55gr bullet had the highest bullet energy using the faster powders. Ejection was positive, although not as energetic as full-patch loads. The cases did not appear to hit the deflector. Rather, they came out at a slight angle to the rear and 6 - 7 feet out. |
|
Quoted:
Built my own bufferless upper with a non-reciprocating charging handle. Original pistol configuration: http://i241.photobucket.com/albums/ff206/devtucker/AR%20Pistol/DSCN0363.jpg More recently: http://i241.photobucket.com/albums/ff206/devtucker/IMG_20130704_231500_079.jpg View Quote View All Quotes View All Quotes Quoted:
Quoted:
Quoted:
Think I'm covered on AR-based PDW's for now http://i241.photobucket.com/albums/ff206/devtucker/2013-03-04_17-36-46_163.jpg I am curious of the forward charging handle of the SBR with the Nordic CRS. Built my own bufferless upper with a non-reciprocating charging handle. Original pistol configuration: http://i241.photobucket.com/albums/ff206/devtucker/AR%20Pistol/DSCN0363.jpg More recently: http://i241.photobucket.com/albums/ff206/devtucker/IMG_20130704_231500_079.jpg You have the ugliest feet. |
|
|
Quoted:
>>1) Reduce the flash and blast enough to partially mitigate the effects of firing a rifle inside a home. You need a flash can. https://dl.dropboxusercontent.com/u/302245/300blk_sm.jpg View Quote How are you liking that light? |
|
Quoted:
Quoted:
>>1) Reduce the flash and blast enough to partially mitigate the effects of firing a rifle inside a home. You need a flash can. https://dl.dropboxusercontent.com/u/302245/300blk_sm.jpg How are you liking that light? I don't like the fact that is rechargeable or that up close it looks plasticky, but I like the size, light weight and that it doesn't need a tailcap and is easy to remove/replace Overall I like it - but at the discounted price I got it at - not at $99 ETA - might have to put it on a riser of some kind because sliding it backwards to come off the mount would interfere with any rail panels - hence you can see the rail behind it is bare. |
|
Part 6
Picked the 10.5" barrel for several reasons: 1) The 7.5" I tried at first was distasteful to shoot, even with reduced loads - excessive flash and blast. Far too much powder wasted outside the bore. 2) Extraction was violent with standard mil loads - at least on my example - and tore up the case rims to the point it interfered with reloading. 3) Shortest standard length that allowed use of a carbine gas system and a standard-size gas block. 4) Shortest standard length that resulted in 26"+ OAL to the bbl threads, using the SB15 configuration I wanted. I picked the bottom-mount position for the TLR-4 because operation was natural with the AFG2 (for me anyway). Jury is still out on the charging handle. Definitely easier to operate from the chest-ready position with the off-hand (no shredded palm syndrome) but it jabs me sometimes when slung and gets caught on things. Since the intent for the primary home defense application is to keep the weapon in Condition 1 anyway, the utility of the bigger handle may be moot. I went on the heavy side to start with, maybe a little too heavy. The great thing about ARs is you can experiment until you get blue in the face (or run outta moolah). The Vortex just plain flat works. The real deal. Last thought: Something like this but built lighter and firing downloaded .300 Blackout 125gr ballistic tip just might be the ultimate house gun. Oh well, yet another money sink... |
|
View Quote Roger that. But the main thing here was to see if I could match the ammo to the intended purpose without having to adopt yet another caliber. Eg: could I make the 5.56 behave like a current PDW load? Maybe not a new concept, but another project to mess with. It's what makes this all so interesting. I tried posting in the SB15 thread but goofed somehow and it ended up here. |
|
Quoted:
>>1) Reduce the flash and blast enough to partially mitigate the effects of firing a rifle inside a home. You need a flash can. https://dl.dropboxusercontent.com/u/302245/300blk_sm.jpg View Quote I considered that, but since the main reason for the project was to see if I could come up with a .556 load that behaves like a PDW load, I decided to go with the Vortex instead. (See multi-part writeup). Also, the flash can won't do much for the blast, right? That's my concern in closed spaces. Doesn't mean I won't try one at some point! |
|
With the flash can the blast is also directed forward rather than out to the side so if your partner is beside you less cutting gas hitting them.
By the way mine is in 300 Blackout and I intend to experiment as you suggested with various subsonic rounds for HD. My barrel is 8.5 inch. |
|
Quoted:
With the flash can the blast is also directed forward rather than out to the side so if your partner is beside you less cutting gas hitting them. By the way mine is in 300 Blackout and I intend to experiment as you suggested with various subsonic rounds for HD. My barrel is 8.5 inch. View Quote I'll be HIGHLY interested to hear what happens. Is your shorty hard on the case rim? If not you may be half there already. That 125gr Nosler Ballistic Tip would be one bullet to try. I have no experience yet with .300 AAC but I see it has an actual diameter of .308 so all sorts of bullets are out there. I wonder if anyone makes a 100gr .308 ballistic tip? The challenge would be to see if you can get over that 1600fps beginning expansion velocity and still stay away from pressure signs, while lowering blast and flash. 4198 will also work, but not quite as well in my 10.5", so probably a lot less well in an 8.5". But like everything else technical, you just don't know until you try. It's a bummer, but I think IMR is discontinuing 4759 yet again as of next year. I say "yet again" because I think they've yanked it at least twice already and brought it back when enough people squawked. |
|
Not bad.
Personally I'd go with lighter weight components and suppressor. And move the weapon light to 12:00. |
|
|
|
for now ill stick to takeing the upper and lower apart... i just need a nicer aluminum lower, not the poly omni i had in the safe.... if i wouldnt have found my fnx45 this weekend i was gonna buy one
|
|
|
|
Sign up for the ARFCOM weekly newsletter and be entered to win a free ARFCOM membership. One new winner* is announced every week!
You will receive an email every Friday morning featuring the latest chatter from the hottest topics, breaking news surrounding legislation, as well as exclusive deals only available to ARFCOM email subscribers.
AR15.COM is the world's largest firearm community and is a gathering place for firearm enthusiasts of all types.
From hunters and military members, to competition shooters and general firearm enthusiasts, we welcome anyone who values and respects the way of the firearm.
Subscribe to our monthly Newsletter to receive firearm news, product discounts from your favorite Industry Partners, and more.
Copyright © 1996-2024 AR15.COM LLC. All Rights Reserved.
Any use of this content without express written consent is prohibited.
AR15.Com reserves the right to overwrite or replace any affiliate, commercial, or monetizable links, posted by users, with our own.