Starting a 300 Blackout Build

[MarcSpaz]

As many of you know, I have been trying to figure out what to do to get a nice SBR or high powered long barrel pistol for brown fan moments (like Ferguson). I got a lot of feedback from everyone an some members were kind enough to let me try their hardware. I really took my time on this because I have a habit of rushing into purchases and making mistakes. I am sick of wasting money and really only want to do this once. After kicking this around for almost 5 months... I finally made a decision.

I decided to start building my 300 Blackout pistol. I got the first two pieces today. I'm committed now... I have to finish it. LOL

I'll document the build here for those interested and for new folks looking to learn from my mistakes. I'm new to AR's too (about 2.5 years), but hopefully I'll be able to help someone with my experience and asking you guys questions.

I got the Sig SB15 stabilizing brace and the Sig SB15 buffer extension tube. Next time I get a check... gonna grab a lower and a cheap lower parts kit, but a nice trigger.

I'm not settled on the lower yet. Likely whatever recognizable name my normal "go to shop" has in stock that is reasonably priced. I don't know that the brand of the LPK is "critical" for my application, but I'll likely use one of the well known brands, such as PSA, RRA, Stag, Bravo Company, etc. Plan on the Geissele Super Dynamic Enhanced trigger though.

[bryanrheem]

Are you going to build your upper or buy a complete? Since your goal is to SBR it (meaning it will be engraved and permanent), are you going to first submit the Form 1 under 5.56 or 300blk?

I agree with going with whatever "mil spec" LPK and upgrading the Trigger group and grip. PSA has deals for LPKs minus trigger group and grip btw.

I'm too will embark on building a 300BLK rifle (once I finish some 762x39 builds). I finally got to hear subsonic ammo through a suppressed rifle and was sold!!!

[bryanrheem]

PS. Are you planning on reloading the ammo?

[0ne5hot]

I'm in the middle of building a 300 blackout pistol too. Great minds think alike
Only I started with the upper first going to pick up a lower next weekend at the gunshow. Mine is a 9" AAC barrel, a BRT Linear Comp, with the vltor VIS-2 upper, which only 1/2 of the linear comp sticks out past the handguard. I will post up some pics for you tomorrow, when I finish this 24hr shift.

[MarcSpaz]

Are you going to build your upper or buy a complete? Since your goal is to SBR it (meaning it will be engraved and permanent), are you going to first submit the Form 1 under 5.56 or 300blk?

I agree with going with whatever "mil spec" LPK and upgrading the Trigger group and grip. PSA has deals for LPKs minus trigger group and grip btw.

I'm too will embark on building a 300BLK rifle (once I finish some 762x39 builds). I finally got to hear subsonic ammo through a suppressed rifle and was sold!!!

I am going to build it. I know I am going to use a AAC 9: bbl, and extension, but I am not sure about the rest of the parts yet. Gonna get the lower done and tested with my 16" upper first, then go from there.

I am not sure about the Form 1. I have never done one before, so I am not sure of the ins and outs. Do you know what the difference is between either or?

PS. Are you planning on reloading the ammo?

I am going to test with OTC ammo, but long-term, I'm going to reload in the near future.

I'm in the middle of building a 300 blackout pistol too. Great minds think alike
Only I started with the upper first going to pick up a lower next weekend at the gunshow. Mine is a 9" AAC barrel, a BRT Linear Comp, with the vltor VIS-2 upper, which only 1/2 of the linear comp sticks out past the handguard. I will post up some pics for you tomorrow, when I finish this 24hr shift.

Nice!!! Sounds good. Looking forward to the pics.

[bryanrheem]

For a Form 1, you will need to indicate the caliber. There was a time when you could submit 'Multi' but recently there is news of the BATF rejecting applications with that written. Seems the safest route is to simply put the caliber of the lower you intend to SBR (most likely 5.56) and then swap on the 300 blackout upper.

I believe you can send a note to the ATF to indicate the change, but that MIGHT not be necessary. It's always a question of great debate regarding all things NFA.

PS. I am not a lawyer!

[MarcSpaz]

Ah, good to know. Appreciate it.

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[Siffer703]

[0ne5hot]

For a Form 1, you will need to indicate the caliber. There was a time when you could submit 'Multi' but recently there is news of the BATF rejecting applications with that written. Seems the safest route is to simply put the caliber of the lower you intend to SBR (most likely 5.56) and then swap on the 300 blackout upper.

I believe you can send a note to the ATF to indicate the change, but that MIGHT not be necessary. It's always a question of great debate regarding all things NFA.

PS. I am not a lawyer!

...And that my friends is why I'm going to leave mine as a pistol

[bryanrheem]

The Form 1 process is very painless if you have a TRUST (minus the $200 fee). Has anybody been arrested because of an incorrect caliber? No. Could it happen… Nothing would surprise me these days.

With the advent of the Sig brace, why spend the $$$ to SBR? Because some even think the Sig Brace is iffy…. Who knows.

Marc, Never built an upper from scratch before… might as well go with a side charging upper!!

[MarcSpaz]

I thought about that ambi 2VA side charge upper, but my gut is telling me to go traditional old-school modular upper for access to parts and pricing. Plus... could care less about the forward assist, but I really like my dust cover.

[ShotgunBlast]

I'm not sure why you need any forms for a pistol.

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[jdonovan]

For a Form 1, you will need to indicate the caliber.

Then he shouldn't put 300 Blackout down. Thats not a caliber... .30 is; 300 blackout is a cartridge.

There are no stories of anyone getting into any federal law violation problems for having a different caliber on a form 1/4 vs what the firearm was configured in, if it was a readily changeable caliber firearm.

There was a time when you could submit 'Multi' but recently there is news of the BATF rejecting applications with that written.

There was a time multi was approved, I've not heard of may getting approved in the last 10 years, in fact I've probably heard many many more storied of multi getting rejected than approved.

I believe you can send a note to the ATF to indicate the change, but that MIGHT not be necessary.

Sure you can but they won't send anything back to you to keep with the form... so whats the point?

[0ne5hot]

The total package

Using a monolithic upper is not an "easy" build when you go this short, but it is doable if you take your time.

This is what a 9" barrel looks like with a 9" handguard

[MarcSpaz]

I'm not sure why you need any forms for a pistol.

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You don't for a pistol. However, I am building a pistol, and then (possibly) submitting the form to make it an SBR, so I can put a telescoping butt stock and other rifle related items on it. This way I get to buy an SBR, for all intensive purposes, but I get to keep the weapon while the paperwork goes through. As long as I don't convert it before the paperwork is in order, I'm completely legit. I like that better than spending $1,500 - $2,000 for a nice SBR, but leaving it at the store for a few months (or more).

The only thing I can't get past is, if I leave it in a pistol/handgun format, I can legally conceal carry it (if so desired) since I have a CHP. That may actually have more value to me than the adjustable stock. Plus I get to save $200. I really need to think about it.

The total package

image

Using a monolithic upper is not an "easy" build when you go this short, but it is doable if you take your time.

image

This is what a 9" barrel looks like with a 9" handguard

image

Nice! I like it. I was wondering how those monolithic rails opened. That is a sharp design.

I am fairly certain that I am going to use a poly cover to keep weight down to 5 lbs or less (without a mag and can). With a quad rail, it will be over 5 lbs before I add anything to it. The deal breaker there will be finding a gas block I like that has a picatinny rail. I want to run Magpul flip-up sights as the primary sights.

[0ne5hot]

Nice! I like it. I was wondering how those monolithic rails opened. That is a sharp design.

I am fairly certain that I am going to use a poly cover to keep weight down to 5 lbs or less (without a mag and can). With a quad rail, it will be over 5 lbs before I add anything to it. The deal breaker there will be finding a gas block I like that has a picatinny rail. I want to run Magpul flip-up sights as the primary sights.

I hope you are talking about the "iron" Magpul flip-up sights cause the polymer one on a gas block can melt...

Yeah when you drop about ~$600 on a upper it had better be sharp...dang I just burned myself...

[MarcSpaz]

Billet aluminum front and rears. The only way to fly. Not putting "backup" sighta on it. LoL

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[MarcSpaz]

.
So, I have a lower ready to go. I put the Sig tube and brace on a Bravo Company lower. Also has a BCM Gunfighter Mod 1 Grip and a Daniel Defense lower receiver parts kit.

The only specialty tool I needed was a spanner wrench for the locking nut on the buffer tube. I bought the TAPCO armorers tool for $25. I bought it about 2 years ago to do a barrel swap. Money well spent.



I was going to do a step-by-step lower build instruction... but good grief, I have done 3D puzzles made for kids 8+ that were harder than putting a lower together. I have to say though... not sure I can get the front pin out without breaking something. Glad that sucker does need to come out. LOL

Anyway... I am starting to think the hardest thing with be setting the bolt head clearance. I am letting a skilled armorer do that.

[Snakester]

Even if it is not finished by The Meet and Greet , you could bring it for show and tell. I would really like to see it !

[MarcSpaz]

For sure! That's a good idea. I can slap a 16" upper in it to test fire it too.

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