Discussion of how to get an 8.5" Barrel SBR AR15 to 29" OAL

Hawkeye · Dec 3, 2015

First, thanks again for taking the pictures. I'd take this as fairly decent proof that you can get to 29" with the 7 position A5 tube and either the eMod or the ACS with the extended buttpad.

screamingeagle said:
Sorry ran out of time to post these last night.

Here us my LWRC 8.5 first pic is with the Magpul stock with .70 thickest pad,with the VLTOR 7 position buffer tube.

Makes 29 inches but have to measure from angled portion of the buttpad where it extends the furthest.

Th second stock is the one that comes with the VLTOR. It measures 29 also from the furthest angled portion of the buttpad.

I would think that you'd measure to the point on the stock or buttpad that is furthest to the rear, just like you start at the furthest forward part of the barrel.

dementlr · Dec 24, 2015

Is it typical that a 10.5" 9mm barrel would measure be 10.5" from the tip of the muzzle to the front edge of the upper receiver? Likewise would an 8.5" measure 8.5" from the tip of the muzzle to the front of the upper receiver? I ask because when I contacted quarter circle ten about their 10.5" barrel they indicated that the actual measurement from muzzle to receiver will be 9.45".

Hawkeye · Dec 24, 2015

dementlr said:
Is it typical that a 10.5" 9mm barrel would measure be 10.5" from the tip of the muzzle to the front edge of the upper receiver? Likewise would an 8.5" measure 8.5" from the tip of the muzzle to the front of the upper receiver? I ask because when I contacted quarter circle ten about their 10.5" barrel they indicated that the actual measurement from muzzle to receiver will be 9.45".

That makes sense to me. There is a portion of the barrel which sits inside the upper receiver, so you're going to "loose" that length if you measure from the muzzle to the front of the upper.

Hawkeye · Dec 24, 2015

Also, I just broke in my new trust and e-filed a Form 1 to SBR my 8.5" .300BLK pistol. Waiting game begins!

smdub · Dec 24, 2015

dementlr said:
Is it typical that a 10.5" 9mm barrel would measure be 10.5" from the tip of the muzzle to the front edge of the upper receiver? Likewise would an 8.5" measure 8.5" from the tip of the muzzle to the front of the upper receiver?

No. Barrel length is barrel length. From muzzle to breach. Some of it extends into the upper receiver. Just like a pistol barrel length isn't just to tip you can see sticking out the front but the whole thing as if it was taken out of the gun. The ATF procedure allows sticking a rod down the barrel until it contacts the closed bolt IIRC. Gives you an additional fraction of an inch on some guns due to the bolt recess.

dontpanic · Dec 24, 2015

Hawkeye said:
I would think that you'd measure to the point on the stock or buttpad that is furthest to the rear, just like you start at the furthest forward part of the barrel.

OAL is measured along the bore axis.

Hawkeye said:
Also, I just broke in my new trust and e-filed a Form 1 to SBR my 8.5" .300BLK pistol. Waiting game begins!

Pretty easy isn't it. I had myself all worked up about it until a couple weeks ago. I've now done 3 SBRs and a SBS. Thinking about a 7.62 suppressor.

I did one in .22lr with a OAL of 22". That will be fun.

Good luck on your build. :thumbsup:

dementlr · Dec 24, 2015

smdub said:
No. Barrel length is barrel length. From muzzle to breach. Some of it extends into the upper receiver. Just like a pistol barrel length isn't just to tip you can see sticking out the front but the whole thing as if it was taken out of the gun. The ATF procedure allows sticking a rod down the barrel until it contacts the closed bolt IIRC. Gives you an additional fraction of an inch on some guns due to the bolt recess.

So if I use the rod method to measure my colt 6920 and subtract the flash hider I get a barrel length of a little over 16". If I also measure the barrel from tip to front of the upper receiver, less the FH, I get the same measurement. So I am just wondering if the quarter circle barrel is sized differently than other barrels. Bottom line is that I am trying to determine the actual exposed barrel length as it contributes to the OAL.

Hawkeye · Dec 24, 2015

dontpanic said:
OAL is measured along the bore axis.

Crap, you're right. I totally forgot about that. Lucky for us, the furthest extension of an AR stock is usually in line with the bore axis anyhow.

Pretty easy isn't it. I had myself all worked up about it until a couple weeks ago.

With a PDF of the trust documents it really, really is.

I've now done 3 SBRs and a SBS. Thinking about a 7.62 suppressor.

I did one in .22lr with a OAL of 22". That will be fun.

Good luck on your build.

Yeah.... I have some others that will be done eventually. My next item is a Silencerco Omega to go on the .300 BLK SBR though.

Pinecone · Dec 24, 2015

smdub said:
The ATF procedure allows sticking a rod down the barrel until it contacts the closed bolt IIRC. Gives you an additional fraction of an inch on some guns due to the bolt recess.

This is the official way of measuring barrel length to meet BATFE requirements.

lsw · Dec 24, 2015

About 3 inches when extended I would say...

fabsroman · Dec 29, 2015

I am waffling between sadness and anger here. Between crying and wanting to choke somebody. Having to spend the entire night trying to figure out which parts to put on a SBR build to get it to 29"+ is just frustrating.

So, I read this thread, a thread started in 2014, and the thread that resulted in this thread.

I currently have one rifle with a Magpul MOE carbine stock on it, and the rifle measures 18.5" to the top of the upper receiver without the barrel. I am guessing that I would need to run an 11.5" barrel on this thing to get to 29" OAL. 11.5" isn't very common in 5.56, .300BLK, or even .458 SOCOM. Think I can get 12" in .458 SOCOM

Thing is, I want to use the new Magpul MOE SL-K stock on my SBR builds, which is supposedly .4" shorter than the Magpul MOE carbine stock. However, if I have to use a Vltor 6 position buffer tube or 7 position buffer tube, that defeats the purpose of the SL-K stock. I am guessing that I need a 12" barrel at the minimum if I go with the SL-K stock.

Anybody have any advice for me? Thanks

Markp · Dec 29, 2015

It's simple... just weld on a 12" folding bayonet and call it done.

Pinecone · Dec 30, 2015

Fabs, why not just put in the barrel length you want and the OAL at 29.1"

Then, when you build it, make the decision, and if it needs a longer barrel, then make it that way. As I understand it, BATFE is not picky about a longer barrel than on the Form 1, only a shorter one.

Just make sure you do not assemble a less than 29" SBR. You can always make up the longest buffer tube/stock setup, with a 10.5" barrel, and measure that combo. Then you can figure out where you want to do from there. You can measure the stock setup differences, and decide what barrel length will work.

fabsroman · Dec 30, 2015

Pinecone said:
Fabs, why not just put in the barrel length you want and the OAL at 29.1"

Then, when you build it, make the decision, and if it needs a longer barrel, then make it that way. As I understand it, BATFE is not picky about a longer barrel than on the Form 1, only a shorter one.

Just make sure you do not assemble a less than 29" SBR. You can always make up the longest buffer tube/stock setup, with a 10.5" barrel, and measure that combo. Then you can figure out where you want to do from there. You can measure the stock setup differences, and decide what barrel length will work.

That is what I actually did. I went 10.5" on the .300 BLK, 12.5" on the .223 Wylde, and 12" on the .458 SOCOM. However, I screwed up on the serial number for the .223 application and will be canceling that application somehow. Then, after applying for all three, I found a 11.3" 5.56 Wilson Combat barrel that I like. So, I am going to resubmit that application for a 11.3" 5.56 barrel.

Since e-forms are down on Wednesday, I will try to figure out how to cancel it tomorrow and resubmit, or just resubmit it anyway and hope everything gets worked out and this only costs me $600 instead of $800.

thai · Dec 30, 2015

Hahaha! Fabs, you are NOT the one person that I would picture muffing up his first eform 1. :lol:

I found a you tube video to walk me through my first form. It took me a while on my first because I didn't realize that the first page you open was some other form other than the Form1. I didn't realize that the form pages scroll sideways.

fabsroman · Dec 30, 2015

thai said:
Hahaha! Fabs, you are NOT the one person that I would picture muffing up his first eform 1.

I found a you tube video to walk me through my first form. It took me a while on my first because I didn't realize that the first page you open was some other form other than the Form1. I didn't realize that the form pages scroll sideways.

Yep, I am not happy with myself. That much is for sure. Realized my mistake as soon as I got to the serial number on the second receiver (i.e., all three receiver are sequential). However, the fix is pretty simple. Another member told me that there is a method to cancel the e-file form online. So, I will look at that tomorrow. Then, I will resubmit it and for a different, nicer barrel, that I came across. Even if I cannot get this fixed and have to cancel that tax stamp, it is only a $200 lesson and it is better that I make the mistake on my own behalf than a client's.

Wonder if I should start buying parts slowly for the builds "assuming" that the three Form 1 applications will be approved, or if I should wait for the stamps. Probably going to wait for the stamps and then give my wife a heart attack on the build cost. lol

pwoolford · Dec 30, 2015

fabsroman said:
Yep, I am not happy with myself. That much is for sure. Realized my mistake as soon as I got to the serial number on the second receiver (i.e., all three receiver are sequential). However, the fix is pretty simple. Another member told me that there is a method to cancel the e-file form online. So, I will look at that tomorrow. Then, I will resubmit it and for a different, nicer barrel, that I came across. Even if I cannot get this fixed and have to cancel that tax stamp, it is only a $200 lesson and it is better that I make the mistake on my own behalf than a client's.

Wonder if I should start buying parts slowly for the builds "assuming" that the three Form 1 applications will be approved, or if I should wait for the stamps. Probably going to wait for the stamps and then give my wife a heart attack on the build cost. lol

I don't believe you can correct an e-filed form 1 but cancelling it should be no problem. You will get your $$ back but it may take a month or two for the refund. I would just submit a new form 1 and cancel the incorrect one. The BATF is really pretty easy to deal with by phone and email.

fabsroman · Dec 30, 2015

pwoolford said:
I don't believe you can correct an e-filed form 1 but cancelling it should be no problem. You will get your $$ back but it may take a month or two for the refund. I would just submit a new form 1 and cancel the incorrect one. The BATF is really pretty easy to deal with by phone and email.

Yep. No way to correct it, because I looked for that option for ten minutes after I realized my mistake. Now, I need to figure out how to cancel it. Submitting another Form 1 shouldn't be a problem at this point with the experience I have from the previous three, and luckily I can live without the $200 for a couple of months. My wife pointed out to me how lucky we are that we can do so. She was preaching to the choir.

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