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Centerfire Rifles - Semiautomatic or Gas Operated Centerfire rifles, carbines and other gas operated rifles.

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  #1  
Old 07-07-2013, 9:37 PM
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Default 300 Blackout - Build Questions

Couldn't see the point of 300 Blackout in CA before, but after further thought, I see the light now. Anyways, I won't build this for a while (or maybe the answers will convince me to not get one until I leave CA), but have a few questions:

Eventual goal is to have a suppressed 300 blackout, ~10" barrel. Plus suppressor for a total length of ~15/16". Will be shooting mostly if not all subsonic, not sure on the exact bullet or load yet. It looks like I'll be going for a 1/8 or 1/7 twist. Not going to concern myself with a suppressor yet in CA.

1. I believe an AR pistol can be converted to a SBR with proper paperwork later on? If so, I believe the only way to buy a pistol AR here is to buy the complete pistol via SSE or can I just buy a lower and register it as a pistol (and will I need to bring an existing upper in for barrel length purposes etc.)? Or would an 80% for an AR pistol be OK with eventual conversion to SBR?

2. I believe I can still swap uppers between lowers freely provided that I don't have a vertical grip?

3. Is it better to buy a complete upper or have one built? I would prefer building via barrel swap on an existing upper but it seems like 300BLK can still be finicky at times. The upper already has an adjustable gas block already on it, so I'm guessing it'd only need a new barrel, gas tube (and w/e peripheral accessories I pick)?

4. Any other suggestions or recommendations? Also I'm guessing spring and buffer weights are something that will have to be experimented with (intend to use carbine length)?

Mods: Move to pistols thread if needed.

Last edited by penguinofsleep; 07-07-2013 at 9:40 PM..
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Old 07-07-2013, 9:42 PM
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Pistol length gas system in a 10" barrel with a standard carbine buffer should function fine with all ammo. You want the gas port hole on the barrel to be .10 for optimum function.
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Old 07-08-2013, 7:05 PM
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sounds good.

should ask now as well:

- Any favorite loads that have worked consistently in many different platforms for anyone?

- Anyone in a free state compared suppressors (and corresponding loads, etc.) for 300 Blackout yet?
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Old 07-08-2013, 7:38 PM
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I haven't shot mine yet but I'm planning to use a Berger or Sierra 125 grain match bullet with the proper load of IMR4227. It should be good for 300 meters or so.
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Old 07-08-2013, 7:44 PM
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I got a LMT 16" 300blk bbl and cut it to 10.5". Put it in my MRP chassis and mated to my Pistol lower. Have tried a few subsonic loads but all have experienced feeding problems...
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  #6  
Old 07-08-2013, 9:51 PM
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Buy H110 or Lil'Gun.
Those 2 powders are viable for supersonic loads of any weight.

Quote:
Originally Posted by skkeeter View Post
I got a LMT 16" 300blk bbl and cut it to 10.5". Put it in my MRP chassis and mated to my Pistol lower. Have tried a few subsonic loads but all have experienced feeding problems...
You made a big mistake by cutting down your barrel, a 10.5" carbine gassed .300 blackout will not function because you do not have enough dwell time past the gas block to cycle your action.

Generally a 16" carbine gassed 300 barrel has barely enough to cycle most loads reliably (this is why you will not find any factory barrels with a carbine gas shorter than 16".

A 10.5" barrel needs to have a pistol gas system in order to function reliably.
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  #7  
Old 07-08-2013, 10:08 PM
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any subsonic loads?

good to know that your super sonics work with imr4227 russ - i would like the ability to fire super sonic if needed.

skeeter - did you buy your pistol lower and just a lower by itself or did you have to buy a complete ar pistol?
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  #8  
Old 07-08-2013, 10:18 PM
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Your options for a pistol in CA are buying a complete AR pistol, dros'd as a pistol or doing an 80% build using a SSE and you can self register if you want though there is no requirement.
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Old 07-08-2013, 10:44 PM
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did you mean:
...complete AR pistol, dros'd as a pistol using a SSE or doing an 80% build and you can self register...
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Old 07-09-2013, 8:04 AM
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There was a mag article out a few months back that did a comprehensive review of multiple 300 platforms from different companies. Essentially all of them experienced malfunctions with subsonic ammo if they were firing unsuppressed. Those using a can and sub ammo seemed to have much better results. If you live in a area that allows use of a suppressor you should be able to put together a reliable set up then with subsonic ammo use. Most of the rifles tested were using a pistol length system with a few using carbine length with the 16' barrels. Pistol length seemed used in anything 14.5 and under. They were also using H2 buffers generally as well.

https://store.intermediaoutdoors.com...2d15-%231-2013

(link to the mag in case you want to check it out)

Last edited by lavey29; 07-09-2013 at 8:06 AM..
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  #11  
Old 07-09-2013, 8:17 AM
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Bottom line. You wanna shoot Sub ammo with no can?
You need a pistol length gas, no matter your barrel length for reliability.
If you want to cycle unsuppressed reliably, if you want your bolt to hold open last round- you need a pistol length gas.
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  #12  
Old 07-09-2013, 8:46 AM
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I just finished a 10.5" pistol build. Haven't made it to the range yet but I've been making ammo and tuning mags in the mean time.

Just after it was all together I started to work the action and hand cycle it. Nothing would feed! Im trying some hornady 150gr fmj, nosler bt, hornady match 225gr...and nothing would work.

So I look at the mag. I haven tried pmags yet but gi mags are no good. The ribs that support the 224 bullet protrude too much for the ogive of the 30cal bullet. So i tried some lancers that i had, also no good. Since the lancer is plastic, I just filed off that internal rib. Feeds perfectly now.

Ballistically speaking, the numbers for the subsonic round are just like a 45acp haaha. But I'm lookong to blast this thing so I got some xtreme bullets. Cheap blaster bullets. They look to be the same shape as berrys. The profile is like a tipped bullet but no tip just a flat point. I loaded up some dummy rounds to 1.9" and 2" to test cycling and all feed by hand! Next is to load some up and then blast away. These will be supersonic but fine for me. Personally I cant afford to load subsonic and definitely not for blasting haaha. Will hit the range soon. Hope any of this helps.
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  #13  
Old 07-09-2013, 9:20 AM
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Quote:
Originally Posted by Intimid8tor View Post
Your options for a pistol in CA are buying a complete AR pistol, dros'd as a pistol or doing an 80% build using a SSE and you can self register if you want though there is no requirement.
Aye, as there is no SSE requirement if you are making the lower as a pistol. But since you can claim you have made it as whatever, I'd keep an 80% for all shorter pistol builds. Just be sure that your AR 80% lower meets all the requirements to be a pistol and not an SSE rifle.
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  #14  
Old 07-09-2013, 9:59 AM
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Quote:
Originally Posted by penguinofsleep View Post
any subsonic loads?

good to know that your super sonics work with imr4227 russ - i would like the ability to fire super sonic if needed.

skeeter - did you buy your pistol lower and just a lower by itself or did you have to buy a complete ar pistol?
I've had a lwrc psd pistol for quite some time. Bought it complete.


Quote:
Originally Posted by Pryde View Post
Buy H110 or Lil'Gun.
Those 2 powders are viable for supersonic loads of any weight.



You made a big mistake by cutting down your barrel, a 10.5" carbine gassed .300 blackout will not function because you do not have enough dwell time past the gas block to cycle your action.

Generally a 16" carbine gassed 300 barrel has barely enough to cycle most loads reliably (this is why you will not find any factory barrels with a carbine gas shorter than 16".

A 10.5" barrel needs to have a pistol gas system in order to function reliably.
Had it covered way before I cut it down. The LMT 300blk 16" barrel comes with a pistol length gas system so no problem there

My issues are possible because I'm using the 220g smk. I might try a different projectile to see if it will feed properly. I have no issues with the gas system. It will run for a few rounds cycling fine and then suffer a feeding failure.
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Last edited by BillyGoatMachine; 07-09-2013 at 10:02 AM..
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  #15  
Old 07-09-2013, 11:42 AM
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I'll just add that I bought a CMMG AR rifle in 300 BLK and I love both the rifle and the 300 BLK round.

I was a little discouraged by the somewhat hard-to-find commercially loaded ammo but I did pickup a couple hundred rounds. I also read a couple articles on making 300 BLK cases from .223/5.56 cases and loading my own. Since I had everything but the dies, I ordered a set from Midway. It's been great. I've not done any subsonic loads because my rifle doesn't have a suppressor but the supersonic loads I've down with 150, 165, and 185 gr. bullets have all been perfect. I'm really happy with the accuracy.

Good luck with your 300 BLK project, I'm sure you'll enjoy it!!
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Old 07-09-2013, 6:37 PM
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In order to have a forward grip the overall length needs to be 26" right? Think I'm going to do a 12" barrel with pistol gas.
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  #17  
Old 07-10-2013, 9:37 PM
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Quote:
Originally Posted by lavey29 View Post
https://store.intermediaoutdoors.com...2d15-%231-2013

(link to the mag in case you want to check it out)
Thanks, I'll check it out when I get the chance.

Quote:
Originally Posted by Dooder View Post

Ballistically speaking, the numbers for the subsonic round are just like a 45acp haaha.
Completely overlooked this but yeah, 220/230 grains going about 1000-1100 fps, only 1 is a 45 cal pistol bullet and 1 is a 30 cal rifle bullet... not sure how much of a difference there is/would be between the different projectiles in terms of effects on target. but i can't imagine rounds that were designed for supersonic performance being great at subsonic vs a round that was designed for subsonic from the get-go. I hate saying this, but after realizing this, that takes a lot of the thrill out of the round for me... maybe I should just get a suppressed 45acp when I can. Or build a pistol/rifle that can handle supersonic loads suppressed... not as quiet, but maybe it won't be as bad as an unsuppressed rifle. Guess this will be for me to decide by experiencing in person (say 223 suppressed vs 300 BLK supersonic loads suppressed vs maybe an AK suppressed).

All the other feedback here keeps me enthusiastic though.

Last edited by penguinofsleep; 07-10-2013 at 9:40 PM..
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Old 07-11-2013, 6:40 AM
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This is what has me a bit worried also. Some companies(y) are coming out with dedicated product though. Check out

http://www.lehighdefense.com/index.p...and-ammunition

in 300BLK
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Old 07-12-2013, 6:41 PM
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interesting. guess its going to be wait and see for now since i have no intention of building a 300blk for long range use (at least for now).
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Old 07-13-2013, 11:33 AM
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Quote:
Originally Posted by penguinofsleep View Post
Thanks, I'll check it out when I get the chance.



Completely overlooked this but yeah, 220/230 grains going about 1000-1100 fps, only 1 is a 45 cal pistol bullet and 1 is a 30 cal rifle bullet... not sure how much of a difference there is/would be between the different projectiles in terms of effects on target. but i can't imagine rounds that were designed for supersonic performance being great at subsonic vs a round that was designed for subsonic from the get-go. I hate saying this, but after realizing this, that takes a lot of the thrill out of the round for me... maybe I should just get a suppressed 45acp when I can. Or build a pistol/rifle that can handle supersonic loads suppressed... not as quiet, but maybe it won't be as bad as an unsuppressed rifle. Guess this will be for me to decide by experiencing in person (say 223 suppressed vs 300 BLK supersonic loads suppressed vs maybe an AK suppressed).

All the other feedback here keeps me enthusiastic though.
You need to take a step back. The 300blk was designed to run both supersonic and subsonic. the .45 was designed only to do subsonic. When you say you are not sure about the performance of a round that was designed for subsonic from the get go vs a rounds designed for supersonic going subsonic you have to remember the subsonic version of 300 is designed to go subsonic. You use a different projectile and different load. Picking the right projectile is important. Case in point, I am owed a bunch of projectiles by hornady. I could chose their 150 grain .308 which would "work" for 300blk. But, it is in the middle of the range so it is going to be neither good at supersonic or subsonic. Pick the right bullet.

The 300blk was designed to be able to effectively operate supersonic and then with a mag change go subsonic effectively. It is not a long range rifle. A suppressed 300blk is super quiet. I am guessing, quieter than a 45 suppressed, but I have no basis for that guess. You can shoot supersonic through a suppressor. It makes a big difference, but you still have the sonic crack of the bullet as it goes over the speed of sound.

I guess I am just rambling at this point. 300blk is not the end all of rounds, but I think it is a good way to go if you have the option of going suppressed at some point.
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Old 07-15-2013, 1:44 PM
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intimidator - i thought that most projectiles for the 300black were just heavy 30 bullets originally meant for stuff like 300 lapua or the like (aka fast, not slow).

but think you are saying 300blk is a good suppressed close quarters round that can do, but is not optimized for, longer range or supersonic, if you need it to. if so, then yes, i agree on that front. i guess this one will go on the back burner as it will probably come down to how loud/quiet all of the different loads (maybe with different suppressors) are at this point, which i can't experience here.

also, i too can imagine that a 30 cal bullet would be quieter than a 45 cal bullet simply b/c given the same velocity, weights, etc. one is smaller than the other (smaller hole), so less sound "leaks" out, although i do know that even suppressed, short of suppressed 22lr rifles with subsonic ammo, guns are still going to be pretty loud regardless, just not at ear splitting and immediate hearing loss levels.
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Old 07-15-2013, 1:57 PM
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The ballistics tables will tell you what you need to know about it. Personally I do not feel like this round is to substitute an existing caliber. Its just something different. But its a capable round. Lots of people are using it for hog hunting. It won multigun nationals, its not a one trick pony.

Supersonic with 125gr or sub to 240gr bullets, its the variety and case forming that is really interesting. I've seen it said hete before but someone labelled 300blk as the "handloaders dream" haaha. And we'll I fell for it haaha.
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Old 07-15-2013, 9:33 PM
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Ballistic is very different between 45ACP and 300blk. If they were similar, 300blk would not have been developed.
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Old 07-18-2013, 4:58 AM
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16" carbine barrel, 17 grains H110 pushing a Sierra 125 grain out of Lancer or p-mags has worked flawlessly for over 2000 rounds. Looking for a substitute powder because of the lack of availability of H110 currently.
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Old 07-18-2013, 9:41 AM
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Quote:
Originally Posted by jimhart69 View Post
16" carbine barrel, 17 grains H110 pushing a Sierra 125 grain out of Lancer or p-mags has worked flawlessly for over 2000 rounds. Looking for a substitute powder because of the lack of availability of H110 currently.
W296 is considered the same as H110. Look at the load data for both and they're almost the same.
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Old 07-18-2013, 10:18 AM
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Compare the BC of a 240SMK vs some round ball 230 45acp ammo. Punch those numbers into a ballistics calculator and you will see that the 300 blk holds its velocity/energy and bucks the wind far better than your 1911 will.

In short the 300 AAC Blackout DOES NOT have the same ballistics as a 45acp......
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Old 07-18-2013, 12:17 PM
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Yes you are correct. My point was more on the lines of cq blasting.

Im trying to say in a subsonic load of a 225gr @ 900fps vs a 230gr ball at 850fps in close range (which is basically how its going to be used) its basically the same.

Cq blasting is what im talking about. Just my logic but when I think of 10.5" pistol build shooting subsonic, the thought of how its going to buck the wind and print at 100yds doesn't even cross my mind since its going to have a red dot and all the cq garbage mounted on it.

Last edited by Dooder; 07-18-2013 at 12:21 PM..
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Old 07-18-2013, 12:45 PM
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Quote:
Originally Posted by Psychbiker View Post
In order to have a forward grip the overall length needs to be 26" right? Think I'm going to do a 12" barrel with pistol gas.
No CA it is 30"

Also you cannot have a rifle with a barrel shorter than 16" federally without NFA paperwork and that's not even an option in CA.
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Old 07-18-2013, 2:25 PM
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^ He is talking about a pistol / long gun other
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Old 07-18-2013, 4:44 PM
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Quote:
Originally Posted by klewan View Post
W296 is considered the same as H110. Look at the load data for both and they're almost the same.
W296 is nowhere either, was looking at 300-MP as I have found some of that.
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