300blk pdw build questions

[berserk686]

I'm posting this here because my login wasnt working on .300blktalk.

Background:
I want to build a PDW in 300blk that is as compact as possible without sacrificing reliability. After much deliberation, I concluded that it would be easiest to buy a stock 300 aac blackout pistol and (after registering as an sbr legally) put a LWRC UCIW stock on it. It seems to be compatible with 300blk and reliable in general. The UCIW reduces length by 1" in comparison to a standard buffer tube (allegedly 8.5" long as opposed to 9.5"). I was looking at the NEA compact carbine stock, but found that some users experienced issues with reliability. If I go with another stock, it will be a magpul CTR. I currently have an AAC cyclone in purgatory, however I am considering buying a quick detach silencer thats a few inches shorter, because the cyclone adds a whopping 8.75" to overall length. I am thinking AAC, Silencerco/SWR suppressors for this build.

An sbr that when all put together has a barrel and overall length greater than or equal to 16" and a standard AR15 overall length is a waste of time and money IMO. I definitely don't want that. Also, please don't make suggestions based on price. I don't really care if I save 1-200$ on a griffin armament. Thanks!

Goals:
-Have a shortest barrel+suppressor length as far under 16" as possible (because thats the point of forking out 200$ for an sbr)
-Determine the most prudent/efficient choice for a 300blk suppressor for this purpose (willing to compromise between functional and practical)
-Have the decibel level of suppressed, subsonic fire approximately equal to that of an MP5. So ~126dB ideally.
-Determine overall length of build

Specific questions:
-Would a gunsmith be able to shorten the 9" barrel of the stock aac pistol down to say, 6-7"? How short would you go before you were concerned about reliability? (I've looked this up, but just wanted to get some opinions here)
-How long would this overall setup be before I added a suppressor? (I dont have my 5.56 AR handy for measurements so I'd appreciate this a lot, even if you can just get me the length of a standard stripped upper receiver)
-What .30 suppressor is both compact and efficient enough to be considered the optimal choice for a compact PDW build?

references:
http://300aacblackout.com/resources/300-BLK.pdf
http://www.ar15.com/forums/t_6_51/40990 ... nces_.html

product links:
http://www.advanced-armament.com/300-AA ... p_645.html
https://www.lwrci.com/p-361-uciw-ultra- ... stock.aspx

[jlwilliams]

Have you considered going integral as a way of optimizing OAL?

[eastern_hunter]

A possible caution ... I would think that the rational use for a 300 BLK SBR would be subsonic. If that is the case one would like to go with the heavier projectiles 220 to 240 gr.

When I built mine I ask the question of twist and it was noted that long bullets in short barrels suggest a twist faster than a 16". Especially important if you're going to put an expensive can on it!!! Thus I built mine with a 1:7 8.5" barrel. Does stabilize things nicely!

I started with a CMMG pistol gassed barrel which luckily was concentrically threaded. Port has been opened to 0.120" Am using an Octane 9 can and a 9 1/2" free floating forearm. The actual muzzle is shorter than the forearm. I first tried using a 5/8x24 fixed adapter for the can to minimize length.

Unfortunately, the adapter would unthread from the can when it was removed. So I put a TROS 3 lug adapter on the barrel. Added some length to things but the new muzzle is just beyond the length of the forearm and mounting/dismounting of the can is slick as a whistle.

OAL with the SOPMOD collapsed is 25 3/4" with out the can and 33 1/2" with the can mounted.


If one were to go with a shorter (8.5" or less) forearm and use the fixed thread adapter rather than the three lug, you'd lose an inch or so of OAL.

The SBR as I built it is pretty handy and easily "hearing safe" even in a shoot house.

[ncorry]

-What .30 suppressor is both compact and efficient enough to be considered the optimal choice for a compact PDW build?

Liberty Chaotic- made especially for 300BLK SBRs. http://libertycans.net/centerfire-rifle ... s/chaotic/

[rckshrk]

I'm working on a similar PDW type build. I was initially going to use the NEA stock on this future build but after installing the LWRC UCIW stock on my current SBR project, I'm going to stick with it for my PDW build too.

As far as the barrel, I was planning on going with a CMMG barrel. Mainly because it's inexpensive enough I don't feel bad having ADCO shorten and thread it to 6 to 7 inches like I would with my Noveske barrel. That would also take care of any concentric thread issues.

Finally, the Gemtech 300 BLK is what I plan to use to top it all off. It's short (6.7 inches), direct thread, light (14oz), super and sub safe. Hopefully Gemtech starts shipping those things soon.



edited for readability

[berserk686]

Thanks for the responses so far. I have a few more questions.

eastern_hunter, the AAC pistol is 1:7" and I'm pretty sure that twist will accommodate 6-7" barrels, although I appreciate the heads up. Btw, I am currently waiting on an octane 9... you and Emilio's posts pretty much sold me on one.

rckshrk, how is the UCIW performing??

I just realized that I might have to sell that KAC URX rail... anybody know how much clearance the URX will provide, in case I'll have to have the suppressor partially covered?

I also was wondering if it would be a bad idea to register a sbr with a shortened buffer tube, in case I want to switch uppers. I don't really feel like messing with staked castle nuts, and an inch is potentially worth sacrificing if it means a more versatile lower. What do you guys think?

Man, I wish AAC would've gone with a 6-7" barrel right out of the gate on this pistol. I think it was a good idea to release a pistol, and I get it that 9" + a standard suppressor comes out to roughly 16", but that's a real shame to add inches unnecessarily... ASSUMING that it is unnecessary. Not to tell them how to do their job, but with all of their product placements I would assume there would be a high demand for a more compact, honey badger-esque pistol. I wonder if could put them into production at 2.5k price point or less... probably. Slap on some sweet paint, a 6" barrel, and a compact, hk style stock and it'd be great... if it ran.

[strobro32]

I wanted to go got the shorter 6.5 inch barrel too but you loose velocity on HV.

[rckshrk]

I wanted to go got the shorter 6.5 inch barrel too but you loose velocity on HV.

What is the minimum velocity needed for the 110 TTSX bullet to expand? The answer to this question will determine if my future 6 incher is relegated to cool, toy status.

OP, I was surprised how much I like the UCIW stock. Even with it's noticibly smaller size, it's still comfortable for me and I am able to establish a normal cheek weld. I don't think that will be the case with the NEA stock. LWRC did a great job balancing size and functionality.

[berserk686]

strobro32, what do you mean by HV? What barrel length did you end up with? I'm afraid I don't understand how a 6" barrel would be completely acceptable in a honey badger but not for other guns. Cool graph, but what am I to make of it? The AAC powerpoint I attached to the OP discusses that after a certain point the length of the barrel is mostly redundant. While certainly on the short end, it was my (limited) understanding that you will get full powder burn in a 6" barrel.

[strobro32]

High velocity.

I have the 8.2" Noveske barrel. I loose 350 fps on my Barnes 110 compared to people using 12-16" barrels. I'm not sure of the ballistics at that speed. I have seen what Nosler 110 gr. bullets do at 2050 fps and I load them for home defense.

I love the idea of the Honey Bagger but if I think if it was ideal, they would have released some version of it. Who knows for sure.

I've repeatedly read Robert saying full powder burn is at 9". He also said they tested down to 4. 5" but he did not say what the results were.

If I build a super shorty, I'm going to do something just for fun.

[Pyrex238]

I made a 6" barrel for my 300 blk gun. With a standard 9" .30 cal can my guns barrel is 14.5". Its perfectly reliable and accurate.

Here is a quick video I did that should answer some of your questions:

https://www.youtube.com/watch?v=0M6ibP_k6pc

Some pics:







Forget about getting MP5SD quiet, aint gonna happen. They are much quieter. But, you can get close. As for the HV theorizing, who cares? This caliber is designed for subsonic use.

[MCKNBRD]

Anyone have any numbers for pressure for the .300BLK at the muzzle? I'm wondering what supersonic loads have as far as uncorking pressure, based on barrel length. Trying to figure out some basic info for a Form 1 can that will be dedicated to a bolt gun; most use will be subsonic, but I'd like to build it strong enough for supers, too.

Byrdman

[LawBob]

I'm posting this here because my login wasnt working on .300blktalk.

Background:
I want to build a PDW in 300blk that is as compact as possible without sacrificing reliability. After much deliberation, I concluded that it would be easiest to buy a stock 300 aac blackout pistol and (after registering as an sbr legally) put a LWRC UCIW stock on it. It seems to be compatible with 300blk and reliable in general. The UCIW reduces length by 1" in comparison to a standard buffer tube (allegedly 8.5" long as opposed to 9.5"). I was looking at the NEA compact carbine stock, but found that some users experienced issues with reliability. If I go with another stock, it will be a magpul CTR. I currently have an AAC cyclone in purgatory, however I am considering buying a quick detach silencer thats a few inches shorter, because the cyclone adds a whopping 8.75" to overall length. I am thinking AAC, Silencerco/SWR suppressors for this build.

An sbr that when all put together has a barrel and overall length greater than or equal to 16" and a standard AR15 overall length is a waste of time and money IMO. I definitely don't want that. Also, please don't make suggestions based on price. I don't really care if I save 1-200$ on a griffin armament. Thanks!

Goals:
-Have a shortest barrel+suppressor length as far under 16" as possible (because thats the point of forking out 200$ for an sbr)
-Determine the most prudent/efficient choice for a 300blk suppressor for this purpose (willing to compromise between functional and practical)
-Have the decibel level of suppressed, subsonic fire approximately equal to that of an MP5. So ~126dB ideally.
-Determine overall length of build

Specific questions:
-Would a gunsmith be able to shorten the 9" barrel of the stock aac pistol down to say, 6-7"? How short would you go before you were concerned about reliability? (I've looked this up, but just wanted to get some opinions here)
-How long would this overall setup be before I added a suppressor? (I dont have my 5.56 AR handy for measurements so I'd appreciate this a lot, even if you can just get me the length of a standard stripped upper receiver)
-What .30 suppressor is both compact and efficient enough to be considered the optimal choice for a compact PDW build?

references:
http://300aacblackout.com/resources/300-BLK.pdf
http://www.ar15.com/forums/t_6_51/40990 ... nces_.html

product links:
http://www.advanced-armament.com/300-AA ... p_645.html
https://www.lwrci.com/p-361-uciw-ultra- ... stock.aspx

AAC makes theirs in 9" for a reason. Best of both worlds (sub/sonic).

You could wait until troy makes their PDW Kit available (and that means buy their upper and stock)

http://www.troydefense.com/firearmsaccessories/