SBR barrel length

[rbird7282]

Well - ok I suppose there is no advantage to registering multiple length uppers but you can if you want. Not sure about different calibers, but maybe you are not interested in that anyways.

You don’t register uppers. The only thing registered on an SBR is the lower.
You can SBR one lower and have 20 different uppers of different lengths and/or calibers for it as long as you can return it to its original configuration.


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[outrider58]

You don’t register uppers. The only thing registered on an SBR is the lower.
You can SBR one lower and have 20 different uppers of different lengths and/or calibers for it as long as you can return it to its original configuration.


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I've heard of people registering the upper instead of the lower. It has its advantages and drawbacks.

 

[rbird7282]

I've heard of people registering the upper instead of the lower. It has its advantages and drawbacks.

Well apparently I’m mistaken, didn’t know you could do that.
What would the advantage be?


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[outrider58]

Well apparently I’m mistaken, didn’t know you could do that.
What would the advantage be?


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It was once explained to me by erwos IIRC. I can't remember all the intricacies. When you go that route, you engrave the barrel.

It made sense for doing it that way. I decided it wasn't for me though.

 

[boothdoc]

Thanks again for all those who have responded.
I am going to take a bit and make my decision then do the paperwork

 

[atblis]

You could do a 15.9” barrel.

 

[calicojack]

or send a "please amend my form 1 with these additional configurations" letter, and swap whatever uppers you want whenever you want. I sena a letter with a list of the uppers I might swap to, and just keep a copy of the letter with a copy of my NFA forms in my range bag. You are only required to Notify rhe ATF if you change the configuration permanently, and there is a bit of grey what that means, swapping uppers at the range, swapping at home, etc. I just mail a letter, cheap insurance IMO, and i can just keep my SBR lower on whatever upper I want. https://www.guntrustguru.com/how-do-i-change-the-registered-configuration-of-my-short-barreled-rifle.html

This is exactly what I do, although not mandatory. The place I got my trust from has a form wizard you fill out and it emails you the letter.

 

[outrider58]

There are 2 ways to go about it. Either keep the original upper with you, or send a "please amend my form 1 with these additional configurations" letter, and swap whatever uppers you want whenever you want. I sena a letter with a list of the uppers I might swap to, and just keep a copy of the letter with a copy of my NFA forms in my range bag. You are only required to Notify rhe ATF if you change the configuration permanently, and there is a bit of grey what that means, swapping uppers at the range, swapping at home, etc. I just mail a letter, cheap insurance IMO, and i can just keep my SBR lower on whatever upper I want. https://www.guntrustguru.com/how-do-i-change-the-registered-configuration-of-my-short-barreled-rifle.html

If you are stuck with the 29" OAL thing, that is a 10.5 or larger. A 10.5 is a fine 5.56' barrel length, especially with heavier bullets or suppressed. Ends up about the same size as a 14.5-16" AR with a can, and will clear a 9" handguard. 11.5 and 12.5 are hot now, they add about 100fps per inch in that range( 10.5 is about 2500FPS with 55gr), once you get to 14.5" there isn't a ton of barrel length saved for the $200 tax stamp. 300BO really starts to get fun under 10", and subs are awesome down to < 7" barrels, but they are too shory for MD. 22 uppers are a ton of fun, especially suppressed, and you can tuck a 5" can in 7" handguards pretty well with a 4.5" barrel.

This is exactly what I do, although not mandatory. The place I got my trust from has a form wizard you fill out and it emails you the letter.

Why? As long as you are able to reconfigure your SBR to its original state, that is all the BATFE requires.
Now if you were to leave Merrylandistan, and wish to reconfigure your barrel length permanently, then I can see writing that letter. Otherwise, totally unnecessary.

 

[outrider58]

an a5 intermediate buffer like vltor, solgw, and bcm will take some of the harshness out of it similar to a rifle buffer, but still keep carbine stock compatibility. helps with the short barrel gas issues.

Meh. Harshess? It's a gun. Grab ahold and shoot. If you are shooting and SBR suppressed, you should already have an adjustable gas block on it, one way or the other.

 

[calicojack]

Why? As long as you are able to reconfigure your SBR to its original state, that is all the BATFE requires.
Now if you were to leave Merrylandistan, and wish to reconfigure your barrel length permanently, then I can see writing that letter. Otherwise, totally unnecessary.

Just for my own edification; is this also the case if you want to run different calibers like (e.g.) 300 Blackout and 5.56?

 

[teratos]

Just for my own edification; is this also the case if you want to run different calibers like (e.g.) 300 Blackout and 5.56?

Yes. Doesn’t matter. 9mm with endo mags….50 Beo. Go for it.

 

[outrider58]

Just for my own edification; is this also the case if you want to run different calibers like (e.g.) 300 Blackout and 5.56?

Yes. Doesn’t matter. 9mm with endo mags….50 Beo. Go for it.

...and if you throw on a rimfire upper, the 29" rule doesn't apply.

 

[boothdoc]

Can you register it as a rim fire setup under the 29” and switch it over afterwards provided you maintain the 29” length with a center fire upper attached?

 

[boothdoc]

So,
I can do a form 1 for an existing stripped lower I have and send it out to have my name, city and state engraved on it? What if I was doing two or a second one. Would I need to engrave the second one with something different for ATF registration?

 

[alucard0822]

It isn't just velocity per se , it's the dwell time .

10.5 to 11.5 is modest change in velocity , but significant % increase in dwell time . This can allow for the gas system configuration to be more flexible and forgiving for better reliability and consistency .

Yes, on paper, but port tuning matters, and the short dwell from carbine gassed 10.5s and mid-gassed 12 5's gives a really smooth cycle. Runs well on quality barrels, and less gas to the face suppressed, with less buffer needed. Not as much incentive to go that short if not running a can though.

Why? As long as you are able to reconfigure your SBR to its original state, that is all the BATFE requires.
Now if you were to leave Merrylandistan, and wish to reconfigure your barrel length permanently, then I can see writing that letter. Otherwise, totally unnecessary.

For me, it's convenience. If I head out of state with a form 20, or take an SBR to a match a couple hours away, I don't need to bring the original upper with me. Pretty much 0 chance you will get checked, but takes 5min to send a copy of the email to the ATF fax line to "notify" about additional configurations and keep a copy. The theory is if a local PD wants my "papers", I have the F1(serial# matches, but length/caliber doesn't), F20, and the config list to show the current config. 99.9% chance it's unneccesary, and might bot be a requirement, but cheap insurance vs getting hounded by a field office somewhere far from home.

So,
I can do a form 1 for an existing stripped lower I have and send it out to have my name, city and state engraved on it? What if I was doing two or a second one. Would I need to engrave the second one with something different for ATF registration?

Yes, assuming it is a factory lower, not 80% need name, city, state("MD" is OK) at least .003" deep and 1/16" letters. Can engrave the same thing on as many lowers as you plan on F1-ing. I usually order a few lowers at a time from places online, and just get them to engrave it before shipping. That way they are all ready to go soon as I pick it up from my local FFL if I want to F1 it down the road. If I want to do a lower not previously engraved, I strip it and run it to my NFA shop( Lanco Tactical), they can engrave it on site and print out a copy of fingerprints for me at the same time for $50

 

[boothdoc]

Are the gas port locations different on a 10.5 & a 11.5” or 12.5”

 

[outrider58]

Are the gas port locations different on a 10.5 & a 11.5” or 12.5”

In 5.56/.223? They shouldn't be. You would want them all to be carbine length gas. This is just my personal preference.

 

[outrider58]

Can you register it as a rim fire setup under the 29” and switch it over afterwards provided you maintain the 29” length with a center fire upper attached?

Yes.

 

[teratos]

In 5.56/.223? They shouldn't be. You would want them all to be carbine length gas. This is just my personal preference.

Carbine length is the way…

 

[boothdoc]

Yes, assuming it is a factory lower, not 80% need name, city, state("MD" is OK) at least .003" deep and 1/16 letters. Can engrave the same thing on as many lowers as you plan on F1-ing. I usually order a few lowers at a time from places online, and just get them to engrave it before shipping. That way they are all ready to go soon as I pick it up from my local FFL if I eant to F1 it down the road. Or If I want to do a lower not previously engraved, I strip it and run it to my NFA shop( Lanco Tactical), they can engrave it on site and print out a copy of fingerprints for me at the same time for $50

So they do it while you wait?? Seems reasonably priced also for $50.00