School me, .223 vs. .300 AAC SBR?

[DarkRose]

So I've been getting ready to submit a Form 1 for an SBR, and been doing some shopping for parts, and realized that it's a LOT more reasonable (price AND availability) to get a 12.5" .300 AAC barrel than a 12.5" .223/5.56 barrel...

Good thing I haven't submitted or gotten signatures... Lower is already marked "Multi", just need to change caliber on Form 1...

My understanding is the only thing I need different are barrel and bolt.
Ammo cost for factory isn't too much over the premium match I've been shooting in my AR now. (and with just a set of dies, reloading is already available)
Mags are the same...

I've heard snippets of reliability issues with the .300 when running unsuppressed, which mine will be (at least for a while). Carbine length gas system. Would I need an adjustable gas block? Heavy buffer?

This wouldn't be a precision gun, more fun gun and "lighter and easier to carry through the woods for random varmints than my 26" heavy barreled behemoth" gun.

And I've still got the option down the road of an additional .223 SBR upper with letter to inform to ATF, correct?

Am I missing any glaring issues?

Am I missing any issues?

 

[Bfish]

Can you get a 300 BLK barrel that is carbine length? You will want to buy a pistol length and you should be good to go... Go with the adjustable gas block, the heavy buffer is more so when suppressed as you keep so much more gas "in the gun" but you really should be fine. The only reason I would say don't go 300blk is if you don't reload.

 

[ParaManAR15]

300 and 5.56 will use the same BCG since you're using the same case size, just necked down for the 300. I would also suggest using an H2 buffer.

Now, I'm not an NFA guru but to my understanding you do not need to notify ATF when having multiple SBR uppers as long as your lower is registered as and SBR. Someone more experience will sure chime in with more experience on this.

 

[romad7]

Upper swaps are a temporary modification so no notification needed. I have a 8.2" 300 BLK and 16" 5.56 uppers for my SBR lower. In fact, swapping to a 16"+ upper removes NFA restrictions if you don't have the parts to convert it back in your possession.

So, you can get whatever upper you want first then get another upper later for a different caliber.

Here is some good info. https://www.atf.gov/firearms/faq/na...arreled-rifles-shotguns.html#removal-from-nfa

300 BLK reliability issues happen when using subsonic ammo with an improperly set up gas system. Since you won't be using a suppressor yet then subsonic doesn't make sense. 300 BLK doesn't make sense to me in a longer barrel over 5.56. It does great and was designed for a 9" barrel. 12.5" and over, I would stick with 5.56.

 

[DarkRose]

I just don't get why in a 12.5" barrel, .223/5.56 averages $100+ more expensive than the .300

I had read other places that since the ATF no longer allows "multi" as caliber on a Form 1, if you get a 2nd upper it's nice to notify. Or is that only if you sell the original upper and replace it with one of a different caliber?

Might just stick with .223, if I was going 9" barrel, I'd just straight go pistol. I've got a specific idea in mind and 12.5" barrel fits that idea. Most if not all the .300 barrels I found last night while I was "window shopping" seemed to have carbine length gas systems... I'd have to go back and double check.

 

[MontereyC6]

You only notify the ATF on PERMANENT changes. So if you registered it a 300 BO, and change your mind, buy a same barrel length 5.56, just notify in writing of the change.

 

[romad7]

I just don't get why in a 12.5" barrel, .223/5.56 averages $100+ more expensive than the .300

I had read other places that since the ATF no longer allows "multi" as caliber on a Form 1, if you get a 2nd upper it's nice to notify. Or is that only if you sell the original upper and replace it with one of a different caliber?

Might just stick with .223, if I was going 9" barrel, I'd just straight go pistol. I've got a specific idea in mind and 12.5" barrel fits that idea. Most if not all the .300 barrels I found last night while I was "window shopping" seemed to have carbine length gas systems... I'd have to go back and double check.

110 grain VMax is 2150fps from a 9" barrel, why would you prefer a pistol caliber?

edit: do you mean pistol gas system? If so then yes, thats the way to go.

 

[cop car]

Only changes that are needed are the barrel. Bolt is the same for 5.56 and 300blk. 10.5 is the shortest you want to go with 5.56. No point in going longer than 10.5 with 300blk. On the form I put it as you are building a 50 beauwolf, with a 4 in barrel. That way it's pretty much the shortest barrel you'd ever have and biggest caliber. Deciding between 5.56 and 300blk for an upper is hard. So just get both. If you already have 5.56 rifles and no 300blk, get the 300blk to start. 10.5-7.5 inch barrel length would be my suggestion.

 

[Davecz]

8.5" with pistol gas is what I suggest

 

[DarkRose]

I went back and checked all the barrels I found for the .300, and they were all pistol length systems. The 5.56 I had in mind needs a 12.5 to look right with the handguard I want, but It's also available shorter, so I might just end up with one of each...

Got passport photo taken today, so hope to have my Form 1 in soon. (Unfortunately I have to get the form printed and take it somewhere as my printer only does 1 sided, and not even that reliably, then to the CLEO, etc...)

Probably end up eventually with a 10.5" in .300 to go with the 12.5" .223/5.56 upper I'll start with.

Side Note: Anyone in Columbus had any problems/issues with getting the chief to sign off on NFA items?

 

[wsenefeld]

The 12.5" barrels aren't hard to find or more expensive.

A high quality, 4150 cmv, nitride treated, for $150.
12.5" 5.56 Government Profile Carbine Length CMV Barrel | Ballistic Advantage, LLC

 

[DarkRose]

The 12.5" barrels aren't hard to find or more expensive.

A high quality, 4150 cmv, nitride treated, for $150.
12.5" 5.56 Government Profile Carbine Length CMV Barrel | Ballistic Advantage, LLC

That's the one I'm looking at, same price as Faxon, but no one has Faxon in stock (they may be an AIM Surplus exclusive?). I emailed Faxon and they've got another batch going, said they should be available in a few weeks.

Those are the only two places I found barrels for that price, where I found several sub-$200 Blackout barrels.

 

[deanald2pt0]

Here you go. 12.5" 5.56 Government Profile Carbine Length Barrel | Aero Precision
Although if you aren't set on 12.5" you could save a few bucks on a 10.5 or 11.5 barrel as they are more commonly availble.

 

[DarkRose]

The 12.5" barrels aren't hard to find or more expensive.

A high quality, 4150 cmv, nitride treated, for $150.
12.5" 5.56 Government Profile Carbine Length CMV Barrel | Ballistic Advantage, LLC

Well hell... Decided to go with the 12.5" 5.56... AND a 10.5" .300 Blackout...

Just have to store them offsite as soon as they show up... Got printed today, forms dropped off waiting for CLEO sig, should be ready to pick up and mail Monday or Tuesday...

 

[cop car]

Should have just had a pistol lower then you could even try them out!

 

[DarkRose]

I know right? Not sure if my lower is classified, think I got it when they added the "other" category?
Does a pistol buffer make it a pistol or does it actually need to be classified such on the 4473?

Couldn't try them yet anyway, still deciding on comps and handguards... but have both upper, barrels, tubes, stock, and blocks ordered.
Handguards, comps, and a BCG and I'm good to go.

This site is a bad influence... lol.

I hate my hours, but love my paychecks...

 

[Vamptepes]

STRIPPED BARRELS

I've bought from them recently and in the past. they have good prices and good barrels.

 

[cop car]

I know right? Not sure if my lower is classified, think I got it when they added the "other" category?
Does a pistol buffer make it a pistol or does it actually need to be classified such on the 4473?

Couldn't try them yet anyway, still deciding on comps and handguards... but have both upper, barrels, tubes, stock, and blocks ordered.
Handguards, comps, and a BCG and I'm good to go.

This site is a bad influence... lol.

I hate my hours, but love my paychecks...

most lowers now are transferred as lowers. Not as pistols or rifles... I spent extra money for mine to be transferred as actual pistols.. In all honesty you probably wouldn't have issues with a pistol buffer tube on a lower, since legally no one would really care as well as it would be super hard to prove what it is and isn't. Not advising anyone to break the law, but the way laws are written and enforced make for some very grey areas. Personally I didn't want there to be gray areas, and made sure they transferred mine as pistols. Even though there isn't really a point in it, as well as all paperwork associated with the sale should be gone in the next 5 years.

 

[DarkRose]

most lowers now are transferred as lowers. Not as pistols or rifles... I spent extra money for mine to be transferred as actual pistols.. In all honesty you probably wouldn't have issues with a pistol buffer tube on a lower, since legally no one would really care as well as it would be super hard to prove what it is and isn't. Not advising anyone to break the law, but the way laws are written and enforced make for some very grey areas. Personally I didn't want there to be gray areas, and made sure they transferred mine as pistols. Even though there isn't really a point in it, as well as all paperwork associated with the sale should be gone in the next 5 years.

That's what it was... I couldn't remember if the category was "lower" or "other" but knew it wasn't Long Gun or Handgun...

Well when I have enough parts on-hand to actually complete the uppers, I'll have to see what the timeline looks like and decided if I want to grab a pistol buffer tube...

 

[Trigger Time]

I'd be careful who you let "school" you here. I heard .300 blackout is no good past 300 yards the other day