Getting started with the 300blk ...

wquiles

Well-Known Member
I know, I know, freaking "late" to the 300blk party :)

Like most shooters, I do own an ar15 already (223), so I have been for years toying with the idea of just a new upper in 300blk. HOWEVER, once I started making my own F1 suppressors, I could not accept the 16" barrel length + the 8-9" for the suppressor. Yes, I "can" do an SBR - but I don't want the legal issues that come with an SBR, the intra-states potential challenges, etc.. I also had the option of a permanently welded suppressor - but I want to move and re-use my suppressors with various guns, so I didn't want that either (I know, I am weird!). That meant a pistol, which to do all legally and by the book, has to start with a new ar15 receiver never used/sold as a rifle, and using the proper BATF approved rear pistol "thinguie" that goes on the tube (can't call it a stock of course, only rifles have stocks, which makes it into an SBR, etc., etc.). So I then started looking at options - boy are there options today!. I start looking, start mentally adding options in my head, only to get frustrated and put the hold project on hold again.

At any rate, this week I decided to look again, and found a Bear Creek Arsenal complete upper (with charging handle and BCG) with the 10.5" barrel (1 in 7") for about $200 shipped. Wow. I finally pulled the trigger (sorry for the pun):
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Nothing that would win a beauty contest, but I really couldn't care less at this point:
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I will have to cut the handguard, as it will prevent the suppressor from mounting - easy enough to deal with:
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I also ordered a stripped receiver (sent to my FFL, of course), which should arrive some time next week and a complete lower kit with the tube "thingie" that I liked based on reviews (will share once it arrives), and I got both for about $190 shipped - so about $400 for all parts to build me an ar15 300blk pistol. So I guess I am now committed to the 300bkl project, right?

One thing I will change once I get the lower parts, is the grip itself. I hate the angle on it - never has my hand agreed with it. I have an LSS Gen 2 chassis on my Savage, so that is there I tried the new more "straight" grip. This is my Savage/LSS with a stock Hogge AR15 angle:
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and after some fitting, here is the new one installed:
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I already shoot the .308 call bullets (Savage above) so I got a 122gr mold, 2x different 165gr molds, and a 180gr molds to try. For brass, many are very happy using military/LC converted brass. Which of these two suppliers would you buy from:
- never bought from him yet:
http://castboolits.gunloads.com/sho...ed-lake-city-5-56-nato/page6&highlight=300blk

- I have purchased brass from him before - always been pleased:
https://msprocessedbrass.com/produc...ut-fully-processed-converted-military-1000-ct


More to come as I get more "parts" :cool:

Will
 
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Ian

Notorious member
Well, you should have asked first. There's another way, looks like this:

20190607_200620.jpg

There's even a commercial version out there now, 16" barrel with permanent, ventilated shroud and 10.5" rifled version like mine with a quick-attach muzzle brake down inside the shroud. With a 10" removable suppressor the length from breech face to end of the suppressor is about 21". This could be don with a shorter barrel and shorter suppressor if you wanted to get the suppressed "barrel" length down to around 17". Put any buttstock you want on it, it's a Title 1 rifle.
 

Ian

Notorious member
Here's a rifle upper I made in .458 Socom, takes the same 1.5" OD suppressor I use on all my .45 caliber rifles, and is 16.25" long without the suppressor.

20190607_201518.jpg
 

wquiles

Well-Known Member
Those look nice!. I knew about that option, and I did the same "trick" with a Ruger 10/22 where I permanently pined/soldered a barrel extension that goes over the smaller Form 1 22cal suppressor. In fact, it was the commercial version that gave me the idea about the "long" barrel muzzle brake.

That customized 10/22 was the first rifle my daughter shot with a suppressor, and it is the rifle my daughter tells me its 'her' rifle. I could not and did not wanted to argue that one, so I simply bought parts and made another 10/22 rifle instead :)

But like with the permanent welded suppressor, I did not wanted to go that route on this particular gun. My suppressors (save for the 22cal) are 1.625" OD, and I am working on another one which is even wider, and since I wanted the freedom to experiment with barrels, handguards, and suppressors, I wanted total freedom to experiment and still keep it legal, so I compromised in keeping it as an official pistol configuration. Some of these laws are a pain, right?
 

Ian

Notorious member
Gotcha, the pistol does give a lot more options. My thinking was barrels and chrome-moly tubing are cheap and if I wanted to change something it would be plenty feasible both financially and legally. Something rubs me wrong about the whole SBR thing, no way I'm going to spend stamp money on one and have all the travel restrictions etc. that we don't have for silencers.

I've been really tempted to buy one of the KAK blade braces snd build a pistol but so far have resisted.
 

wquiles

Well-Known Member

Ian

Notorious member
I have a question if you don't mind. You're a very talented and very well-equipped hobby machinist, so why don't you make your own lower receivers too? I make most of mine from various 80% blanks just for fun and convenience.
 

wquiles

Well-Known Member
First, thank you for your kind words. I have watched several videos on the 80% process (and even one from a guy who melted rifle brass to make a brass receiver from scratch), and quite honestly, never felt the urge/need to try it out. It is probably due to after 20+ years, I still had the "one" AR15, and I don't even use it much at all, so haven't had the need/want to make more ar15's.

Then when I finally wanted to try the 300blk, the $29 plus transfer fee for a finished receiver made it just too easy to skip finishing an 80% again, and instead use that time and energy to move into working up a couple working loads for this 300blk setup.

Because I have not retired yet (mid 50's) I still don't have "enough" time for all of the things I want to do, and I lave a lot of projects either on hold, or partially completed, and many not started yet (still in my head), so I get more picky as to which projects to attempt, which would be most fun, or where I can learn something I always wanted to learn, etc.. So far, finishing an 80% receiver has not made it to my bucket list :)
 

popper

Well-Known Member
I built a 10" pistol without the brace, not hard to shoot, just cheek the tube and shoot. Thought about the brace but with laws getting trickier, decided against it. Same with SBR & can. Brace does give 3 point support, cheek does almost as good. Did get the single point sling and tube adapter so I can carry over shoulder - otherwise it is heavy to carry very far. If I had a 'truck' I'd definitely use it as a truck gun. I've been converting brass, cheaper and easier than buying. I get free brass from SIL and PP usually go first. Usually shoot 145-185 cast through it, mostly PB.
 

wquiles

Well-Known Member
Cool, thanks.

How about shooting subnonic and supersonic - any particular tips you guys have found work well for the gas system to work with both kinds of ammo? I was going to start with Hodgdon 300 BLK powder based on reviews I have seen so far, although H110 is the other one that is highly recommended.
 

Ian

Notorious member
With a pistol-length gas system (port something like 4.5" from the breech face) you can get away with a lot of things, especially with a suppressor. Carbine-length systems are a lot harder to get to run with subsonics. IMR 4198 works well with the heavy subsonics and some people have even gotten 2400 to work. You'll just have to try some stuff and see. When you get your bullet choices and seating depths worked out, post up some details and I can run some quickload numbers to give you an idea of where to start. Being able to calculate port pressure with a given powder and bullet weight, and knowing what range of port pressure is needed for pistol and carbine systems together with minimum port size requirements makes it a little simpler to figure out where to start.
 

Brad

Benevolent Overlord and site owner
Staff member
Mine is a carbine length system and I have no trouble with I4227 and the 230 gr NOE. Stays subsonic and cycles the action fine. I would have to check but I believe it is around 10 gr of powder.
 

wquiles

Well-Known Member
Ian - that is great news, as I have my own Quickload. How do you use it to calculate the port pressure & target? What is the "standard" port pressure range needed?

My upper has a pistol length port, by the way - 10.5" barrel.
 

Ian

Notorious member
Use the bullet travel vs. chamber pressure graph in QL to see what the pressure will be at the port location. A pistol system with a .090" or larger port should cycle reliably with 6,000 psi at the port. 7K might be better but you'll have to try and see. Once your pistol breaks in after a couple hundred rounds, the pressure required to cycle it will be less. You can use QL to try different powders and charges while keeping an eye on port pressure, muzzle pressure, and predicted muzzle velocity.
 

Brad

Benevolent Overlord and site owner
Staff member
Brad - NOE has a couple of "heavy 30's, is this the one you are using:
311-232-FN-AZ1
Yes, the plain base. It does need to be seated a bit deeper than I like to prevent jamming into the lands. I have some PCd that I need to try. Those may need to be seated even deeper as the PC will have made the nose even fatter. So far the deep seating has no been an issue.
I have never found recoil an issue but will say that when I cranked the 30 sil up to max velocity the rifle got a bit lively. I thin it maxed out in the 1650-1700 FPS range.
 

wquiles

Well-Known Member
Yes, the plain base. It does need to be seated a bit deeper than I like to prevent jamming into the lands. I have some PCd that I need to try. Those may need to be seated even deeper as the PC will have made the nose even fatter. So far the deep seating has no been an issue.
I have never found recoil an issue but will say that when I cranked the 30 sil up to max velocity the rifle got a bit lively. I thin it maxed out in the 1650-1700 FPS range.
I will likely start with the XCB 165gr, and the Lee 165gr bullets that I have first, but I have been meaning to try a heavy 220-230gr in my Savage (1-in-10), but now that I have a 1-in-7 barrel, I guess I have run out of excuses. I PC all of my bullets now, so I will be mindful - thanks for the advice.
 

wquiles

Well-Known Member
Use the bullet travel vs. chamber pressure graph in QL to see what the pressure will be at the port location. A pistol system with a .090" or larger port should cycle reliably with 6,000 psi at the port. 7K might be better but you'll have to try and see. Once your pistol breaks in after a couple hundred rounds, the pressure required to cycle it will be less. You can use QL to try different powders and charges while keeping an eye on port pressure, muzzle pressure, and predicted muzzle velocity.
Excellent. I can "see" how QL would be useful for that type of work. I will try it out when assembling my first loads and use that as a guide. Thanks much for the advice.

You guys are awesome!
 

Brad

Benevolent Overlord and site owner
Staff member
With the 165 gr bullets H110 will do good work but they will not be subsonic, not even close.
Never tried to find a load that was subsonic with that bullet weight much less that would cycle the action.
 

wquiles

Well-Known Member
Thanks Brad. I meant to say that I am starting with the 165gr only for supersonic, to establish a working configuration before moving to subsonics. My heaviest bullet is a Ranch Dog design 180gr. I rather wait until I have the 220+ bullets to try subsonic work :)