Washington Objective: Non-SBA AR-9/EPC 9mm pistol for home defense

[FnM]

This is my first build and although I have been able to find ample information on the 'how to', I've been unable to find general dimensional specifications for typical builds' LOP, LOA. If you know of a resource that provides dimensional specs, please share.

Relevant parts summary for my build:
Complete EPC/pistol caliber upper w/11" 9mm barrel
9mm bolt
EPC stripped lower
My objective will NOT have a brace or stock. I never wanted to use either in the build so that's not an issue. My question concerns the buffer tube length.
Carbine length tube, spring, buffer
OR
Rifle length tube, spring, buffer
I understand a carbine length spring and buffer are not interchangeable and vice versa. BUT the regulation specific to the buffer tube is my issue of concern.

The current federal and state regulation defines/limits a pistol to:

Buffer tube only w/out brace
LOP <13.5 inches
LOA >26 inches

Commercially available buffer systems are Rifle length Or Carbine length. There is no 'Pistol' length system however 'Pistol' style tubes are available, are the same length as carbine, and thus require the use of carbine buffer and spring. The pistol style is distinguished by a slightly larger diameter and is a plain tube w/out a positioning rib. i.e. the pistol style presumably will not accept a commercially available stock or brace.
If the 'Pistol Style' is not required…
-Is a 'rifle length' buffer system permissible?
-If yes then will a rifle length buffer tube exceed parameters?
-Will a standard 'carbine length' buffer tube meet parameters?

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[drstrangelove]

Best bet is a bare Kak pistol tube and an attachment point for a single point sling. You will need to use the recommended 9mm buffer and spring for your blowback system.
IDK if your frame is set up for Glock or PMags with inserts, but the Glock mag system is MUCH more foolproof. Have experience with both.

 

[FnM]

Best bet is a bare Kak pistol tube and an attachment point for a single point sling. You will need to use the recommended 9mm buffer and spring for your blowback system.
IDK if your frame is set up for Glock or PMags with inserts, but the Glock mag system is MUCH more foolproof. Have experience with both.

It's a Glock style lower
Curious… why single attachment point presuming you mean the back plate.

 

[drstrangelove]

It's a Glock style lower
Curious… why single attachment point presuming you mean the back plate.

Because single point slings are super quick to deploy and have nearly the same red dot aim stability as a stock. Yes, the rear plate with the sling attachment.

 

[Member 34319]

Have you purchased anything yet?

If not, turn a 180 and start looking at bufferless designs.

For 9mm there are a few out there now. CMMG being one example. They utilize a stripped down bolt carrier that allows for recoil springs to be utilized inside the upper receiver and zero need for any sort of buffer tube.

 

[FnM]

Have you purchased anything yet?

If not, turn a 180 and start looking at bufferless designs.

For 9mm there are a few out there now. CMMG being one example. They utilize a stripped down bolt carrier that allows for recoil springs to be utilized inside the upper receiver and zero need for any sort of buffer tube.

I already purchased lower, buffer, and spring but no tube. I'll take a look but I'm on a budget. Thanks for the tip.

 

[Member 34319]

I already purchased lower, buffer, and spring but no tube. I'll take a look but I'm on a budget. Thanks for the tip.

For straight blowback without one of the bufferless uppers you'll want as much tube as you can get. Weight can only do so much, whereas the spring will be the key to reducing recoil. Longer the spring the better. Not that you can't tune a shorter spring with a stronger spring rate, its that there are usually more options that use longer buffer tubes.

 

[bradsteen]

If you're running a bare tube, pretty sure you don't need to worry about LOP. It's not equipped with a stock or brace, the tube is just an extension of the receiver, and is a part necessary for the weapon to function. It's not like you're shouldering the tube.

 

[FnM]

For straight blowback without one of the bufferless uppers you'll want as much tube as you can get. Weight can only do so much, whereas the spring will be the key to reducing recoil. Longer the spring the better. Not that you can't tune a shorter spring with a stronger spring rate, it's that there are usually more options that use longer buffer tubes.

All my parts have been purchased from and recommended by Aero for their EPC 9mm.
Complete upper
9mm EPC BCG
EPC lower, stripped
EPC buffer
EPC buffer spring
I would have bought a complete buffer system which includes the tube but both the tube and kit are not in stock.
Ideally my build would include the use of a rifle length buffer system purely for balance. As both system are the same ID, a spacer could be first installed inside the rifle length tube to allow for the use of a carbine length spring and buffer.
Without specs which are not ordinarily published by the commercial sector, I'm engineering in the blind.

 

[FnM]

I found this which is very helpful but doesn't answer my question about regulated buffer tube length

What 9mm buffer do I need??? (and spring)

Let’s look at a little quick history and then get to what works best for most typical 9mm ARs. NOTE: None of this applies to the CMMG Banshee. It uses a different operating system. This infor…

blowback9.wordpress.com

 

[Member 66129]

Why though? If you aren't putting a brace/stock on it then what benefit does it offer over a G17 with an optic?

 

[Member 53328]

Why though? If you aren't putting a brace/stock on it then what benefit does it offer over a G17 with an optic?

This is my thought as well…..

 

[drstrangelove]

Why though? If you aren't putting a brace/stock on it then what benefit does it offer over a G17 with an optic?

This is why I'd rather have a 16" 9mm with a stock… way way better accuracy, capable of bouncing golf balls at 50yds… not something you are going to pull off with a G17.

 

[Member 53328]

This is why I'd rather have a 16" 9mm with a stock… way way better accuracy, capable of bouncing golf balls at 50yds… not something you are going to pull off with a G17.

You must have a much longer hallway in your house than I do….

 

[Member 66129]

This is why I'd rather have a 16" 9mm with a stock… way way better accuracy, capable of bouncing golf balls at 50yds… not something you are going to pull off with a G17.

You must have a much longer hallway in your house than I do….

Beyond 50 yards, if I'm using something with a 16" barrel I would rather use a rifle caliber.

A 16" PCC makes sense when you're trying to meet the rules requirements for competition. Outside of that, it's about as practical as one of those California legal AR "Grips" that give you eye herpes with even the slightest look at it.

Hell, I can even buy the idea of an AR9 "pistol" with a nekkid tube and a single point sling, but certainly not with anything longer than an 8-11" barrel. 6-8" makes more sense.

 

[drstrangelove]

you guys are moving out of the fun zone of competition and plinking into self defense… different story… I guess I missed the title purpose. Oopsie.

for that purpose, I'm using a 12ga 00 and a Glock 21 with a light.
if I need more stand-off, I'm using a rifle, not a PCC.

 

[arakboss]

This is my first build and although I have been able to find ample information on the 'how to', I've been unable to find general dimensional specifications for typical builds' LOP, LOA. If you know of a resource that provides dimensional specs, please share.

Relevant parts summary for my build:
Complete EPC/pistol caliber upper w/11" 9mm barrel
9mm bolt
EPC stripped lower
My objective will NOT have a brace or stock. I never wanted to use either in the build so that's not an issue. My question concerns the buffer tube length.
Carbine length tube, spring, buffer
OR
Rifle length tube, spring, buffer
I understand a carbine length spring and buffer are not interchangeable and vice versa. BUT the regulation specific to the buffer tube is my issue of concern.

The current federal and state regulation defines/limits a pistol to:

Buffer tube only w/out brace
LOP <13.5 inches
LOA >26 inches

Commercially available buffer systems are Rifle length Or Carbine length. There is no 'Pistol' length system however 'Pistol' style tubes are available, are the same length as carbine, and thus require the use of carbine buffer and spring. The pistol style is distinguished by a slightly larger diameter and is a plain tube w/out a positioning rib. i.e. the pistol style presumably will not accept a commercially available stock or brace.
If the 'Pistol Style' is not required…
-Is a 'rifle length' buffer system permissible?
-If yes then will a rifle length buffer tube exceed parameters?
-Will a standard 'carbine length' buffer tube meet parameters?

There should be no length of pull restrictions on a handgun as handguns are not designed to be shouldered. Use whatever buffer tube you need to accommodate the buffer or buffers you will be using.

 

[arakboss]

As for why an AR "carbine" style handgun over a Glock 17? Longer barrels are cheaper, cheaper to switch back and forth to rifle from handgun, more optic options including adding scope, potentially stronger and capable of regular use of +p+ ammo.

 

[FnM]

Why though? If you aren't putting a brace/stock on it then what benefit does it offer over a G17 with an optic?

Every choice is a compromise. I'd only use a pistol if I couldn't reach my carbine first. Punching holes in paper tends to make one over confident. Nobody knows just exactly how a home invasion is going to go down but I'd bet my lilly white bubblegum I wont be standing in my hallway with safety glasses, earmuffs, and adjusting my stance while my heart is pumping piss. It will be terrifying and traumatic, that much I'm certain.
I'm not the only one in the house. My wife and 12 year old son better be able to defend the home and themselves in my absence and they stand a much better chance with a carbine than a handgun or shotgun. The latter two would definitely end up in misplaced shots or worse. 9mm is a better than average cartridge for a pistol and doubly so for a carbine. There are loads of good defensive rounds to choose from, practice AMMO is relatively cheap, recoil is not intimidating, and most of all because 9mm is the number one choice of professional action movie directors.
Next there's the matter of indoor shooting without a suppressor. .22LR isn't fun without hearing protection, I don't have an NFA stamp but if I did I would still choose 9mm and 6-8" barrel would be the ticket. In fact I tried to get an 8" upper but for some odd reason they seem scarce. Maybe the 11" drops a decibel.
If I accidentally shoulder my buffer tube defending my family, we all live, and the feds come for me, I'll face the music.

 

[Hueco]

Sprinco offers various strength springs for carbine length tubes. I'm running their regular strength these days with a 10oz buffer for ~23.9oz total reciprocal mass. (Note, in post below I tested and ran for a time their heaviest. Saw no difference when switching to the lighter spring in terms of bolt bounce so went lighter)

I recommend you turn right around on that Aero bcg and buy something else. (https://www.northwestfirearms.com/threads/wtf-happened-here-pew-go-boom.396062/).

The list of Aero compatible drop in triggers is in my post above, though I found success with a Triggertech AR9 trigger.

You want to shoot for 21-25oz total reciprocal mass. So bust out the scale and measure away to determine buffer weight.

Also, this works as advertised and is a worthwhile addition to a build: https://maconarmory.com/product/aero-epc-mag-catch-upgrade/