My new 300blk build

T

TheM4chef

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Southern Gulf Islands, BC
Hi folks, finally got everything I needed and with the barrel nut wrench I was able to do my conversion.

It's a fde Aero upper and lower
Mwi key mod 15" rail. Man this is light compared to the old school 2pc free float I have from them.
Bushmaster 2 stage trigger but I think the trigger tech will replace it
CTR stock
BCM grip and foregrip
BCM mod4 charging handle
DD 16" 300BLK barrel and their A2 style flash hider
Vortex strike eagle in the vortex cantilever mount.

Can't wait to get to the range and try this out.
I've got some factory subs to play with then I have to load up a bunch of 150gr fmj and see how she rips.
 
Nice,
For 150gr pills LiL'gun, A1680, and IMR4227 are your friends. I just loaded some 150's over 4227 a couple days ago. First time with 4227 but most people report good results so I'm hoping for the same.
 
TheM4chef said:
Cr5 I got a few pounds of H110 to play with. For the time being I'm going to use the Hornady info till I get the hang of the 300blk.
Click to expand...

I find H110 is better for 110-130gr projectiles. You'll just have to experiment and see what will cycle your rifle.
I found the Hornady 208gr factory 300 whisper loads wouldn't cycle one of my AR's and haven't tried them on any of my 300BLK rifles since.
You'll find that not all published data was made for semi auto rifles. If you want PM me and I can give you some load data to get you going.
My general rules with 300BLK are that H110 is for lighter projectiles, Lil'Gun and A1680 work well with 150gr and heavier and A1680 is for my 208gr subsonic loads. I'm just starting to use IMR4227 but have heard it works quite well so I just put together some with 150gr FMJ-BT pills and am hoping to do some testing soon.
 
I'm putting together my first 300blk and I've noticed that 16" barrels are available in both pistol and carbine length gas systems.
What are you guys running?
 
thump_rrr said:
I'm putting together my first 300blk and I've noticed that 16" barrels are available in both pistol and carbine length gas systems.
What are you guys running?
Click to expand...

Always go pistol length with 300BLK. Using fast burning pistol powders gives a much different pressure pulse to the gas system, the shorter the gas system the better with this cartridge.
I have my NR ACR conversion running with a carbine length system but the piston system in that rifle is more efficient than the AR gas system. It took a little messing around to get it working and the longer barrel may have helped make it easier.
 
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10/22 it's a possibility
As for the gas system I'm a complete newbie with 300blk but all my research stated with a 16" barrel carbine was the way to go and considering the DD barrel I have is factory take off I'd assume they did that for a reason. Hornady also states in their revised edition that all the loads are tested in a 16" with carbine gas system to be reliable.
Now anything shorter than 16" a pistol gas system is indeed the best bet.

Cr5 it sounds like you have a fair bit of experience with the 300 so I value your advice.
 
cr5 said:
I find H110 is better for 110-130gr projectiles. You'll just have to experiment and see what will cycle your rifle.
I found the Hornady 208gr factory 300 whisper loads wouldn't cycle one of my AR's and haven't tried them on any of my 300BLK rifles since.
You'll find that not all published data was made for semi auto rifles. If you want PM me and I can give you some load data to get you going.
My general rules with 300BLK are that H110 is for lighter projectiles, Lil'Gun and A1680 work well with 150gr and heavier and A1680 is for my 208gr subsonic loads. I'm just starting to use IMR4227 but have heard it works quite well so I just put together some with 150gr FMJ-BT pills and am hoping to do some testing soon.
Click to expand...

Do you have any recommendations for a light weight plinking round? The 150gr amax seems to be most popular? And since I can't hunt with it I just wanted something slightly more economical to plink with
 
I dropped A1680 for Imr 4198 for my 230gr
Cleaner and better accuracy.

150gr I use h110 or w296

I run 9 " pistol length, no issues with cycling rounds.
 
cr5 said:
Nice,
For 150gr pills LiL'gun, A1680, and IMR4227 are your friends. I just loaded some 150's over 4227 a couple days ago. First time with 4227 but most people report good results so I'm hoping for the same.
Click to expand...
I4198, H4198, H335, H110, W296 and R7 will also work and you can make do with I3130. 1680 is the choice for the majority .30 Caliber mid cartridge rounds like the ACC and 7.62's.

The bolded are my preferences that seem to work best for me.
 
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I think you will find that pistol length gas is needed when you want to make sure sub sonic ammo cycles properly.
 
thump_rrr said:
I'm putting together my first 300blk and I've noticed that 16" barrels are available in both pistol and carbine length gas systems.
What are you guys running?
Click to expand...

If you ever want to play with subsonic, go with the pistol length.

My current favourite load is 10.2 to 10.4gr 4227 and a 150gr FMJ bullet. Cycles my 10" BLK nicely and is the quietest combination I have tested yet. Keeping in mind that I am running a custom captive spring system tuned for the rifle.
 
So i'm looking into doing a PDW 300blk Ar piston driven build. I need all the help and advice i can get. I was actually just looking to buy a complete pws but have been pondering a build. Any suggestions.
 
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