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98Z5V

300 BLK MINIMUM gas port sizes...

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I know that I've remembered, for some reason, that we had to be around "100" on the 16" carbine-gas configs - 0.100" gas port diameter.

I know I'm not completely crazy now...  :lmao:

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^^^  Again, 300BLK, 16" barrel, carbine-gas... we need to be around a hundred on the port size.  90 from some manufacturers just won't cut it.

We need this pinned in this section. 

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3 hours ago, 98Z5V said:

^^^  Again, 300BLK, 16" barrel, carbine-gas... we need to be around a hundred on the port size.  90 from some manufacturers just won't cut it.

We need this pinned in this section. 

Done

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On 1/4/2017 at 3:57 PM, 98Z5V said:

We, collectively, have been down this road before, especially on the 16" 300BLK barrels.  This article sums it up nicely, and it's a very worthy read.

http://micromoa.com/300-blk-port-size-testing/

 I posted that link in the "Start Tweaking or what" thread in this section & its a good article to be pined .

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Bummer. My 300 BO barrel has a port size of 0.097". I don't want to start drilling unless I really have to. It perfectly feeds the supers but I'm trying to get 150 gr FMJ subs to work. It doesn't like the 150 FMJ-BT. I can only barely move the bolt. I know the 'why' question will pop up. The 150 FMJ-BT allows me to shoot more since they are more affordable and it seems to be a very challenging load.

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12 hours ago, Steve L said:

Bummer. My 300 BO barrel has a port size of 0.097". I don't want to start drilling unless I really have to. It perfectly feeds the supers but I'm trying to get 150 gr FMJ subs to work. It doesn't like the 150 FMJ-BT. I can only barely move the bolt. I know the 'why' question will pop up. The 150 FMJ-BT allows me to shoot more since they are more affordable and it seems to be a very challenging load.

  Check this Thread out 

 

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On 9/6/2017 at 4:04 PM, Steve L said:

Bummer. My 300 BO barrel has a port size of 0.097". I don't want to start drilling unless I really have to. It perfectly feeds the supers but I'm trying to get 150 gr FMJ subs to work. It doesn't like the 150 FMJ-BT. I can only barely move the bolt. I know the 'why' question will pop up. The 150 FMJ-BT allows me to shoot more since they are more affordable and it seems to be a very challenging load.

I only load Hornady 150gr FMJBTs for this caliber, and they're going between 1800~1900 fps.  They're far from subsonic.  I don't know how far down you'd have to load to get those projos under 1100 fps, but that would have to be a pretty low charge.  I'd look at the load your making before I'd try to make that load work by drilling your gas port. 

a 150 grain projectile is not the ideal item to try to make subsonic in this caliber.  Go for a 200~220gr projectile, if subsonic is your thing.  You'll have ALOT better luck.

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It is not too difficult to get the 150 gr FMJBT to fire subsonic. The challenge is generating enough gas pressure to completely cycle the action. Last monday I shot a few of my subs using Trail Boss to test for basic functionality. The load is well known to be subsonic and it is also well known to not cycle an AR. I did not chrono it so I cannot confirm it was truly subsonic but the recoil was greatly reduced and it sounded much quieter than then my supers (my perception/no suppressors with ear pro). My calculations on felt recoil show my supers (1620 fps) at 5.6 ft lbs and my subs (if under 1100 fps) should have a felt recoil of 2.0 ft lbs. Now the fun part is getting the subs to cycle. Likely looking at some new powders before I start drilling out gas ports and playing with buffers/spring rates. I have a few ideas! [Insert Dr Evil laugh here]

As you can see, like most of us here, I know getting 150 subs is a bit of a challenge which is what motivates me! The heavy subs have been proven to work well and is my fallback position.

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On 9/7/2017 at 6:14 AM, survivalshop said:

  Check this Thread out 

 

I have an 8" 300 AAC barrel with a gas port of 0.097". Unfortunately, I received the barrel cheap and the previous owner did not know who the manufacturer is. I figured if it sucked then I'll buy a new one. It shoots very well so far!

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Here's the data from the MicroMOA site, which is down now:

(BIG KUDOS to @survivalshop for grabbing this info before it went down!!!  :hail:)

 

AR-15 Platform 300 BLK Conversion Subsonic Ammo
16" car 300 BLK UNSUPRESSED 0.12
16" car 300 BLK UNSUPRESSED 0.125
16"  car 300 BLK SUPRESSED 0.106
16"  car 300 BLK SUPRESSED 0.11
16" pistol 300 BLK UNSUPRESSED 0.067
16" pistol 300 BLK SUPPRESSED 0.086
9.5" pistol 300 BLK UNSUPRESSED 0.093
9.5" pistol 300 BLK SUPPRESSED 0.093
8.1" pistol 300 BLK UNSUPRESSED 0.104
8.1" pistol 300 BLK UNSUPRESSED 0.12
8.1" pistol 300 BLK SUPRESSED 0.086
8.1" pistol 300 BLK SUPRESSED 0.093
         
         
AR-15 Platform 300 BLK Conversion Supersonic Ammo
16" pistol 300 BLK UNSUPRESSED 0.0625
16" pistol 300 BLK SUPPRESSED 0.059
16" car 300 BLK UNSUPRESSED 0.099
16" car 300 BLK SUPPRESSED 0.093
9.5" pistol 300 BLK UNSUPRESSED 0.073
9.5" pistol 300 BLK SUPPRESSED 0.067
8.1" pistol 300 BLK UNSUPRESSED 0.076
8.1"  pistol 300 BLK SUPPRESSED

0.067

The 300 Blackout data has been compiled from Micro MOA

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@Gopher this is the graphic I talked to you about, on the barrel length versus gas system, depending if you want to run subsonic, supersonic, or both.  FOr the hogs your after, I wouldn't even worry about the subsonic stuff, unless you're running a suppressor in the future, brother. Down the road, if you do that, just change out to an adjustable gas block...  :thumbup: In a nutshell, 16" with a Carbine Gas System does it all, unless ALL you do is subsonic shooting, without the suppressor on... 

image.png.b5c6c22570da1109539f3b54b8851681.png

Edited by 98Z5V

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