Custom 300 Blackout Barrel

[gvanzeggelaar]

Good Day all.

I am going to get a custom barrel made for an AR and want to shoot 165 - 200gr cast boolits through it. What are your opinions on what would be the best length/twist for this.

[timspawn]

Barrel length is what what ever you are happy with. I have several Blackouts and the twists are 7 in some and 8 in the others. I have shot as low as 115 and as high as the Lee 230. They all seem to shoot very well in either twist. I really like this round.

[Jupiter7]

If your planning to hunt with it and heavy long boolits, go with the slower twist. 1/8 will shoot everything well, I have two 1/8 and one 1/7, I prefer the 1/8 for all around general use. 1/10 if you plan to do some subsonic heavy hunting. I like the 1/7 for the lighter jacketed bullets pushed fast.

[gvanzeggelaar]

I can get a 1:8 12" but it has polygonal rifling. Is polygonal rifling that bad to shoot cast out of or is that mostly myth. I can also get a cut rifled barrel but it is double the price at 400 bucks

[Lever-man]

I have built two of the 300 Blackouts one with a 1/8 and the other with 1/7 barrel in carbine length. While both shoot very well, the 1/8 holds a tighter pattern with the lighter bullets. The 1/7 does better with the heavier bullets, at least that is my observation with the rifles that I have. I have just started to experiment with the Lee 230 gr cast boolit, and I'm having problems getting it to cycle the action. Maybe someone else can answer the question about polygonal rifling as I have no experience with that.

[cutter_spc]

The shorter the bullet the slower the twist, the longer the bullet the faster the twist. In your case, wanting to use the heavier bullets, I would stick with the 1-7, 1-8 twist rate.

[KYShooter73]

I would say 1 in 8 at least. I'm much more satisfied with my 1:8 in pistol port than my 1:7 carbine port. For cast I would like to go 1:10, but I'm not shooting subsonic.

[guywitha3006]

Just an FYI if you want to reliably shoot subsonics and supersonics with or without a can I would recommend a pistol length gas system. I have the Noveske 16" 1/7" for my build and it eats everything both with my can and when I am just plinking.

As far as barrel length goes, I wouldn't look much longer than a normal 16" barrel, as that is what it was designed to use (or shorter if you have a SBR).

For the money for the Lee 300 BLK mold they shoot pretty well for me and you can powder coat them for can use or simply tumble lube them and more then likely shoot as cast.

[Boolseye]

I think I would avoid polygonal rifling if you plan on feeding it a diet of cast, especially in a rifle. I had an H&K USP (polygonal) that shot cast well, but that's only a 3 1/2" barrel. The lead may smear up the bore at rifle velocities, and could even lead to pressure spikes if it gets too badly leaded. If you do go with polygonal, keep it clean.

[gvanzeggelaar]

I ended up ordering the the polygonal rifled barrel. I will let you sll know how it does.

[Artful]

Which molds are you going with in your polygonal barrel?

[gvanzeggelaar]

I have a NOE 311299, & one of there 312 129gr spire points I want to try out. Im leaning more to the 311299