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I've milled my first AR15 lower. I'll be building a 300 blackout pistol out of it and need some advice on the build. I'd like to buy a kit to finish the build rather than piece meal it together. Or build out based on components that are tested together and proven reliable. I do intend to put a lot of rounds through this build.

I'm going to go with 10" barrel length, or slightly shorter. I do want to be able to shoot suppressed as well. I don't have enough knowledge or experience yet to say what kind of loads I'd be using.

I'd love to hear what you all would recommend to complete this build. I've got the cash to spend what I want on this, so budget is not a major issue.

If you recommend something you've already built please include pics.
 
Check out Rainer Arms. They have some quality components and decent prices.
They are very helpful and I'm pleased with the 10.5" barrel I bought from them.
 
You will want to go with a 10.5 probably it's going to be a bit more reliable. You gas tube length makes all the difference. You get into pistol tubes and you have more to deal with. Your going to want to do some investigating into the correct buffer weight. 300 are great you can have a large choice of bullet weights but the better are subs ranging from about 208 to 220 grain. With a suppressor you will love it. They can get dirty quickly so cleaning the chamber in necessary to keep it feeding smooth but shooting suppressed will cause most of those issues. Mine prefers higher quality ammo to be reliable. Fun as hell to shoot no hearing protection required.
 
I basically did the same thing last winter and used ground zero precision diy kit. I got the 9" ballistic advantage barrel in the kit and I am very pleased with the choice. Moa accurate at 100yds and cycles subs and supers with and without suppressor. If you go this route, do your self a favor and spring for the BA barrel. You won't regret it. If I were to do it over again I probably would piece the build together around the BA barrel as I have changed out several components from the kit at this point. Btw my gas system on the 9" BA barrel is pistol and it works great.
 
I would vote for building from the ground up unless you can find the exact setup you want. I love building just because you can add the exact parts you want without changing stuff out that you already paid for. Here is my build, 9" Grim Reaper Tactical barrel and I've had zero issues feeding Rem. 220gr subsonic both suppressed through a Specwar or just ran unsuppressed.
 
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My 300 I built, With some 220 grain this thing brings a smile to everybody's face that shoots it. I also put a jp silent spring in it so no more twang in the jaw. Smooth as butter but I do have to keep the chamber clean compared to my 5.56. It's a 10.5 barrel all Noveske, Geissele trigger. I should add the dirty part is only because I shoot this with a silencer. If you don't have a can your not going to have to deal with as much crud. Sometimes you want to try a heavier or lighter buffer weight. For example my set up I want it to cycle a little slower. But it nothing you would notice when shooting really just reliability. Hope that gets you thinking about what to look into.
 
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Here's a pic of my very first AR build.
.300 Blackout SBR with a 10.5" Rainer barrel, Spike's nickle boron BCG , AAC 7.62 SDN 6 suppressor with a very stout Ace M4 Socom butt stock to balance the weight of the suppressor.
Everything worked perfectly, which was a real surprise to me, being it was my first build.

300 blk sbr 002.JPG
 
Ive got several 300 BO guns. Only one I ever had any trouble with was a Daniel Defense 10.2" upper. Probably too small of a gas port. Otherwise Ive had outstanding service out of my el cheapo 7.5" Anderson barrel with pistol length tube of course. It has never failed to cycle on anything Ive put in it subs or super.

FWIW the side charger upper REALLY keeps the gas out of my face when the silencer is mounted. How? There is no charging handle in back. Just a plug.

PTXTZv.jpg
 
I bought one of those special charging handles that shunt the gases off to the side.
Works great. Some folks just use black silicon sealant around the back of the upper where the handle rests.
 
Yea that side charge make a big difference. Not all pistol barrels have issues and sometimes you just get lucky. I have had more issues with my 10.5, 5.56 with a adjustable gas block than any gun I have owned. To be honest it's been a bit of a pain I fix one issue and another pops up! both while shooting suppressed and unsuppressed.
 
I also got one of those SNATCH gas ported handles and a gas ported forward assist its on my 5.56. I found both not to be very helpful. I'd just buy a gas buster charging handle and call it good. And just went with the AXTS only on my 300 no blowback issues at all.
 
Not sure if you have a suppressor already.

If you do, you may want to double check with the manufacturer on minimum barrel length that they recommend for the caliber. Too short a barrel may invalidate your warranty. My 5.56 pistol has an 11.5" barrel due to the warranty for my AAC M4-2000.

My 300blk sbr has an 11" Seekins Precision barrel.
Aero Precision Enhanced upper & lower.
No real issues of any sort, and good groups with subsonic/suppressed out to 100yds.
 
Surplus Ammo sells many choices of both Uppers & Lowers 5.56 & 300 BO. I was told get the 8.5 in if going 300 BO as it's reliable and that's the minimum they recommend to suppress also for reliable feeds. I've talked to two separate guys their and both said the same thing. Hope that helps.
 
Sure it makes sense on paper but it really all has to do with how big the manufacturer made the gas port. The length seems to make no difference at all. I couldnt get subs to cycle worth a damn in my 16" SIG 300 BLK barrel and my 10.2 Daniel defense was maybe 60% with subs. My 8.5 is 90%+ with subs and my 7.5" is 100%.
 
Interesting... I'm going with the one they make themselves there. It's a local maker so if there's any issue's they said they'd help get it squared away.
 

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