What barrel? 300 blk
- Thread starter Sniper338
- Start date
For 300BO - 1:8 twist for shooting heavy subsonic bullets (190gr-230gr) and work fine with lighter supersonic bullets (110gr - 147gr). There is marginal benefit for 300BO with barrel longer than 16", especially if you plan to shoot subsonic ammo.
There are plenty of barrels available from top manufacturers +$350 down to run of the mill barrels $150.
There are plenty of barrels available from top manufacturers +$350 down to run of the mill barrels $150.
I ordered a 300 BO barrel earlier this year and had the exact same questions rolling through my mind. I didn't want to spend a ton since it is mostly an experiment for me and the blackouts claim to fame isn't long range accuracy. I had a hard time deciding 14.5 inch or 16 and didn't want a real heavy barrel but I finally went with the 16" 1 in 7. I went with the pistol gas system to make it run for my project. I haven't shot it yet as the adjustable gas block I want seems to be on back order all the time. Thats ok I'll save it for one of my winter projects.
Here is what I got. They are 147.00 from AIM with free shipping. The thing might be a total piece of crap once I start testing it but we'll see.
https://www.ballisticadvantage.com/16-inch-300-blackout-pistol-length-barrel-modern-series.html
Here is what I got. They are 147.00 from AIM with free shipping. The thing might be a total piece of crap once I start testing it but we'll see.
https://www.ballisticadvantage.com/16-inch-300-blackout-pistol-length-barrel-modern-series.html
dellet
Gold $$ Contributor
If you hand load options are limitless, if you depend on off the shelf ammo, it might change my thoughts some.
It really depends on what your use will be, the argument over twist rates are almost pointless unless you have a very specific use in mind. I shoot everything from 1/5-1/10, both sub and super. The only thing more pointless than twist arguments is gas length.
Carbine gas works fine from 10.5” to 20”, if you are shooting suppressed, but you will be limited in choice to about 8 or 10 different powders for subs with barrels under 12”, maybe a couple less for barrels longer than 16”.
Pistol gas really is a poor choice for supers in longer barrels unless you can cut off the gas.
My long barrel AR is 18” carbine gas, 1/10. It’s consistent 1/2-3/4 MOA with supers to 300 yards. Subs are a challenge because of vertical but 208 Amax or ELD are basically sub MOA under 100 yards and 1 1/2 MOA out to about 300.
Add about 1/8 MOA if it’s a 8” 1/5 twist with pistol gas. That’s why I just don’t care what twist I shoot unless I have a specific bullet or purpose.
I shoot bullets from 80-265 grains, you just have to pay attention with longer bullets in the slower twists and the varmint or some expanding type bullets in the faster twists. The long subs will tumble at distance, the light supers will spin apart.
Xcaliber makes a very good barrel for the price, and will make it how you want it for around $200 or so with the discount they run on the forum. They made the ones I spoke of.
The cartridge has out grown the original intent, so it’s worth a purpose built upper or two. An 18” barrel will allow 3000 fps with bullets under 90 grains, there are a few out there. It will also shoot something like a 175 SMK from 1-2000 fps and hold MOA or better to 300 yards through the velocity range.
It’s an interesting cartridge that can take you down a rabbit hole or two if you let it.
It really depends on what your use will be, the argument over twist rates are almost pointless unless you have a very specific use in mind. I shoot everything from 1/5-1/10, both sub and super. The only thing more pointless than twist arguments is gas length.
Carbine gas works fine from 10.5” to 20”, if you are shooting suppressed, but you will be limited in choice to about 8 or 10 different powders for subs with barrels under 12”, maybe a couple less for barrels longer than 16”.
Pistol gas really is a poor choice for supers in longer barrels unless you can cut off the gas.
My long barrel AR is 18” carbine gas, 1/10. It’s consistent 1/2-3/4 MOA with supers to 300 yards. Subs are a challenge because of vertical but 208 Amax or ELD are basically sub MOA under 100 yards and 1 1/2 MOA out to about 300.
Add about 1/8 MOA if it’s a 8” 1/5 twist with pistol gas. That’s why I just don’t care what twist I shoot unless I have a specific bullet or purpose.
I shoot bullets from 80-265 grains, you just have to pay attention with longer bullets in the slower twists and the varmint or some expanding type bullets in the faster twists. The long subs will tumble at distance, the light supers will spin apart.
Xcaliber makes a very good barrel for the price, and will make it how you want it for around $200 or so with the discount they run on the forum. They made the ones I spoke of.
The cartridge has out grown the original intent, so it’s worth a purpose built upper or two. An 18” barrel will allow 3000 fps with bullets under 90 grains, there are a few out there. It will also shoot something like a 175 SMK from 1-2000 fps and hold MOA or better to 300 yards through the velocity range.
It’s an interesting cartridge that can take you down a rabbit hole or two if you let it.
I am running a Noveske 8.5" barrel and a Daniel Defense 16" barrel in my AR15. I am very impressed by performance of both. These are $300-$400 barrels and shoot great.
Supersonic:
110gr Barnes TAC-TX bullets for hunting.
120gr-130gr SMK for target.
120gr Speers TNT bullets for cheap plinking or 3gun.
Subsonic:
194gr ELD
194gr Lehigh Defense Max Expansion for hunting (prefer to use supersonic rounds to hunt)
S&B subsonic ammo for plinking (buddy buys this...I shoot it for him)
Keep in mind that 300BO is somewhere between a pistol and rifle round. It is a Warthog... more power than a pistol, but slower and less accurate then standard rifle. 1MOA is an respectful performance for this round. Don't get me wrong with the right gun and ammo it can shoot 1/2MOA, but this is the exception.
I'm glad that Dellet chimed in. $200 is great price for barrel that performs. I wouldn't hesitate to take his recommendation.
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So thats my intent, 100 yard subsonic 100% 16 to 18 inch barrel, 208 eld or something similar. I just want the twist and gas set up right for 100% subsonic. My lower is set up, tricked out, jp silent capture buffer.
dellet
Gold $$ Contributor
If I knew for sure that was my bullet and distance, I would probably go with a 8 or 8 twist.
100% sub-sonic creates some issues with an 18" barrel. Unless you have a truly integrated suppressor, you have an extra 1-1.5 pounds hanging out there at 25", for no practical reason.
The main reason for more barrel is higher velocity. You're limiting that artificially to 1050 fps. Unless you just want to shoot from the bench, it's a tougher package to haul around.
The plus side is that 18", carbine gas can be extremely quiet.
To take advantage of the quietest powders, pistol gas works best, BUT in that length of barrel, you have a difficult time keeping them at subsonic velocities. It's a bit of a trade off and can be argued pretty well either way.
Twist rate really depends on the bullet and doing some reverse engineering if you want best accuracy. Most of the calculators work on velocity. These do a bit more and are extremely valuable for sub sonic bullet choice.
http://www.geoffrey-kolbe.com/drag.htm
http://www.geoffrey-kolbe.com/barrel_twist.htm
Stability changes dramatically at lower velocity and these programs put it on a graph that might change your thinking some.
Other bullets create other issues.
That's a 250 Atip loaded at magazine length 2.260" and where it hits the lands at 2.580". Not much room for powder, but that bullet is extremely jump tolerant.
100% sub-sonic creates some issues with an 18" barrel. Unless you have a truly integrated suppressor, you have an extra 1-1.5 pounds hanging out there at 25", for no practical reason.
The main reason for more barrel is higher velocity. You're limiting that artificially to 1050 fps. Unless you just want to shoot from the bench, it's a tougher package to haul around.
The plus side is that 18", carbine gas can be extremely quiet.
To take advantage of the quietest powders, pistol gas works best, BUT in that length of barrel, you have a difficult time keeping them at subsonic velocities. It's a bit of a trade off and can be argued pretty well either way.
Twist rate really depends on the bullet and doing some reverse engineering if you want best accuracy. Most of the calculators work on velocity. These do a bit more and are extremely valuable for sub sonic bullet choice.
http://www.geoffrey-kolbe.com/drag.htm
http://www.geoffrey-kolbe.com/barrel_twist.htm
Stability changes dramatically at lower velocity and these programs put it on a graph that might change your thinking some.
Other bullets create other issues.
That's a 250 Atip loaded at magazine length 2.260" and where it hits the lands at 2.580". Not much room for powder, but that bullet is extremely jump tolerant.
My first 300BLK build was with a 1-8 twist, carbine gas ported, CMMG barrel. And it will still put all of them in MOA or better when I try. I believe it was under $99 at the time. It's so accurate I made it my designated night vision rig several years ago.
Thats future pans for this upper. I have a TBAC 30 cal 9 inch direct thread to hook up on it.
X-Caveman
Gold $$ Contributor
I have a KAK 9" "Mr Blonde" that I like quite well. They also make a 16" BBL that's $150. I started with a 16" 300BLK shooting suppressed. Got tired of all that weight way out there. Ordered the MR Blonde and welded on a stainless HVT can to bring it to legal length. I love it.
7 or 8 twist for suppressed. I shoot a Hornady 208 A-Max over Accurate 1680.
Have fun with it!
I have had great success with Odin Works on several builds, albeit all short barrels. They come with an adjustable gas block.
https://www.odinworks.com/300_Blackout_Barrel_16_1_Pistol_p/b-300-16-p-tg.htm
https://www.odinworks.com/300_Blackout_Barrel_16_1_Pistol_p/b-300-16-p-tg.htm
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