Low velocity AR pistol build for HD?

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Low velocity AR pistol build for HD?

Postby Scratch on Fri May 15, 2020 5:20 pm

I had recently seen some cool AR pistol builds come in like the Saint Edge pistol, a certain BCM pistol, and a few others, and I really liked how lightweight and modern looking they were. Some of my AR's still have quad rails on them. I like them, but they seem dated now with the smooth M-Lok, and Keymod stuff out there. plus the smallest AR pistol I have has a 14" barrel and I've always thought I'd like to go really small like 10 inches.

I had a customer come in yesterday who upgraded barrels and he decided to give me his old 7" barrel... who was I to say no...

After he left, I got to thinking and realized I had enough take off's, extra parts, and prize table pickups to build a complete pistol so I put one together last night.

This is built on a PSA lower and a mystery upper. It has an SBA3 brace, H2 buffer, Raptor charging handle, Magpul BUS, MOE+ pistol grip, Mystery BCG, Mil Spec trigger, B.A.D lever, Primary Arms AMD, Sharps Bros ultralight handguard, mystery low pro gas block, and a Lancer Nitrous comp.

I was worried about such a short 5.56 barrel causing cycling issues, so I took it out today and put about 300 rounds through it with absolutely zero problems! I did chronograph my reloads (Berrys 55gr FMJ's) and they were running about 1905 FPS. (These loads run 2785 out of a 20" IIRC) I was getting about 2-3" groups at 50 yards with the red dot, but decided to try stretching it's legs a little, so I put on a PA 1-6 ACSS scope and went for my 20" gong at 250 yards. After finding my POI, I was able to hit it 8-10 times which is OK I guess...

I do really like how lightweight it is. Every time a new, nice looking, lightweight, AR pistol comes in, I weigh it and record it so I have something to base my future build on. They were coming it at 5 pounds 10 ounces, 5 pounds 13 ounces, etc... Mine is 5 pounds 8 ounces so I'm very happy with that! I also really like the Lancer comp. The barrel barely moves, although it is pretty loud. I did tune it with the adjustable jets, and found I like having two of the small orifice jets installed in the comp best.

I like the gun so much... I'm thinking I might want to use it for my home defense gun.

Of course I need to run a bunch more rounds through it for reliability testing, probably swap over to a matching black pistol grip, and trigger guard because it bugs me, and I think I'm going to try a Holosun HS515GM, but I'm wondering if I should be concerned with such a short barrel on a 5.56. So far it's running perfectly, but using it as a HD gun with hollow points, could I have expansion, or fragmentation problems with a velocity of only 1905?

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Re: Low velocity AR pistol build for HD?

Postby Holland&Holland on Fri May 15, 2020 5:38 pm

Sbr them.
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Re: Low velocity AR pistol build for HD?

Postby warrlac on Fri May 15, 2020 5:58 pm

Holland&Holland wrote:Sbr them.


I hear that a lot and am curious why? Is the issue that the ATF will change its policy on stabilization braces?

I have a couple of AR pistols (300 Blackout and one like the one above). With the brace they are really fun and I don't want to see them go. Is SBR really the inoculation against future problems?
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Re: Low velocity AR pistol build for HD?

Postby Scratch on Fri May 15, 2020 6:35 pm

Holland&Holland wrote:Sbr them.

I see no reason to SBR anything at this time. So many more benefits to not SBR'ing them. If braces go the way of the bump stock, I'll deal with it then.

I'm more curious as to the low velocity in a 5.56 for a HD weapon.
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Re: Low velocity AR pistol build for HD?

Postby Holland&Holland on Fri May 15, 2020 6:59 pm

warrlac wrote:
Holland&Holland wrote:Sbr them.


I hear that a lot and am curious why? Is the issue that the ATF will change its policy on stabilization braces?

I have a couple of AR pistols (300 Blackout and one like the one above). With the brace they are really fun and I don't want to see them go. Is SBR really the inoculation against future problems?

A real stock.
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Re: Low velocity AR pistol build for HD?

Postby Holland&Holland on Fri May 15, 2020 7:00 pm

Scratch wrote:
Holland&Holland wrote:Sbr them.

I see no reason to SBR anything at this time. So many more benefits to not SBR'ing them. If braces go the way of the bump stock, I'll deal with it then.

I'm more curious as to the low velocity in a 5.56 for a HD weapon.

Why low velocity?
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Re: Low velocity AR pistol build for HD?

Postby mc762x54R on Fri May 15, 2020 7:12 pm

That's gotta be crazy, crazy loud for HD no? You could load a 9mm carbine / SBR and get that same muzzle energy with less powder, noise, etc.
I'm getting 1320fps with a 124gn JHP 9mm in my little CZ Scorpion...480 ft-lbs
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Re: Low velocity AR pistol build for HD?

Postby brad3579 on Fri May 15, 2020 7:14 pm

Scratch wrote:
Holland&Holland wrote:Sbr them.

I see no reason to SBR anything at this time. So many more benefits to not SBR'ing them. If braces go the way of the bump stock, I'll deal with it then.

I feel the same way, as long as the SBPDW braces stay legal no reason to go thru the paperwork.
I have a 9mm and .45 ACP. have parts to complete a .300 BO and .223.
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Re: Low velocity AR pistol build for HD?

Postby Scratch on Fri May 15, 2020 9:02 pm

Holland&Holland wrote:
Scratch wrote:
Holland&Holland wrote:Sbr them.

I see no reason to SBR anything at this time. So many more benefits to not SBR'ing them. If braces go the way of the bump stock, I'll deal with it then.

I'm more curious as to the low velocity in a 5.56 for a HD weapon.

Why low velocity?

Its such a low velocity because of the short barrel length. 7" short.
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Re: Low velocity AR pistol build for HD?

Postby Scratch on Fri May 15, 2020 9:09 pm

mc762x54R wrote:That's gotta be crazy, crazy loud for HD no? You could load a 9mm carbine / SBR and get that same muzzle energy with less powder, noise, etc.
I'm getting 1320fps with a 124gn JHP 9mm in my little CZ Scorpion...480 ft-lbs

It's not unbearably loud. just a little louder than a normal AR according to my wife. My 20 year old daughter was in the house while I was shooting off the deck. She came out to water the plants and was surprised to see that I was shooting. She thought it was weird that so many birds were hitting the windows today. :o
So it must have not been "that" loud.

I know that a 55gr bullet will have a lot less force at 1900 FPS than a normal 2500 FPS bullet, and a 1320 FPS 124gr bullet may be a lot better. I don't know that. That's what I'm hoping to find out from this thread.
I do have an AR9 build on order, but it could be up to a couple more months.
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Re: Low velocity AR pistol build for HD?

Postby Lumpy on Fri May 15, 2020 9:48 pm

Scratch wrote:
mc762x54R wrote:That's gotta be crazy, crazy loud for HD no? You could load a 9mm carbine / SBR and get that same muzzle energy with less powder, noise, etc.
I'm getting 1320fps with a 124gn JHP 9mm in my little CZ Scorpion...480 ft-lbs

It's not unbearably loud. just a little louder than a normal AR according to my wife. My 20 year old daughter was in the house while I was shooting off the deck. She came out to water the plants and was surprised to see that I was shooting. She thought it was weird that so many birds were hitting the windows today. :o
So it must have not been "that" loud.

I know that a 55gr bullet will have a lot less force at 1900 FPS than a normal 2500 FPS bullet, and a 1320 FPS 124gr bullet may be a lot better. I don't know that. That's what I'm hoping to find out from this thread.
I do have an AR9 build on order, but it could be up to a couple more months.
If you're going to cut the performance down to pistol levels, wouldn't starting with 7.62x39mm make more sense?
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Re: Low velocity AR pistol build for HD?

Postby Ghost on Fri May 15, 2020 9:52 pm

A suppressed SBR is a thing of beauty.
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Re: Low velocity AR pistol build for HD?

Postby Holland&Holland on Fri May 15, 2020 11:06 pm

Scratch wrote:
Holland&Holland wrote:
Scratch wrote:I see no reason to SBR anything at this time. So many more benefits to not SBR'ing them. If braces go the way of the bump stock, I'll deal with it then.

I'm more curious as to the low velocity in a 5.56 for a HD weapon.

Why low velocity?

Its such a low velocity because of the short barrel length. 7" short.

Ah, I thought you were saying you wanted a lower velocity load for HD that still cycled.
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Re: Low velocity AR pistol build for HD?

Postby Holland&Holland on Fri May 15, 2020 11:07 pm

brad3579 wrote:
Scratch wrote:
Holland&Holland wrote:Sbr them.

I see no reason to SBR anything at this time. So many more benefits to not SBR'ing them. If braces go the way of the bump stock, I'll deal with it then.

I feel the same way, as long as the SBPDW braces stay legal no reason to go thru the paperwork.
I have a 9mm and .45 ACP. have parts to complete a .300 BO and .223.

Once you go with a real stock you will never go back.
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Re: Low velocity AR pistol build for HD?

Postby Bearcatrp on Sat May 16, 2020 7:29 am

Do your homework and research minimal expansion fps on the ammo you want to use. Subsonic ammo will reduce the noise a bit but not great. Put a can on it and it will be quiet. My 300BO 12 inch shoots 190 subs about as quiet as a mouse fart, almost.
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