First off, yes i read the FAQs and did a site specific search on google and didnt get much info.. maybe im not using the correct terms? In the process of building my first black rifle. I understand most of the standard mil spec parts/standards and such, but know next to nothing about ammo and have lots of questions..

so, ive decided to build my first rifle in 300blk.. i know its a popular reload caliber, but i dont know shit about reloading or the basics of 300blk. i just want to shoot the thing at paper targets and have some piece of mind for personal defense. maybe one day when i know more, i will get into reloading. here are my questions, i would appreciate it if someone could explain this to me:



the higher the grain weight, the slower, but more powerful the bullet, correct? vice versa?

i found this link (http://www.ar15.com/content/page.html?id=186), but what caliber is it for? .223/5.56? can i use that link as a guide for 300 blk?

since were on the subject of twist rate, i see 1x7 and 1x8 for 300 blk barrels (im sure there are others as well). i understand the difference in barrel, but i do not know what it does to bullets. does one handle heavier bullets better? better at longer ranges? more velocity/fps?

ive read that 300 blk burns all of the power around 9", im looking to get a 14.5" bbl with a pinned flash hider. i asked at my local gun store what this means for my (future) rifle and the guy just shrugged it off like it was no big deal and said the only difference i would get would be better grouping with the longer barrel. why is this? more time for the bullet to stabilize in the bbl?

if all the powder is burnt by 9" in, does that mean i lose velocity with a 14.5/16" barrel?

what about accuracy at longer ranges with different bullet weights? do i want a lighter or heavier bullet?

subsonic vs supersonic. i really only know 2 things: one goes slower than the other and that you want subsonic if youre running a suppressed setup to keep the noise down.. i wont be running a suppressor, but can i still use subsonic? would supersonic be the better choice for non suppressed setups?




im in the process of building (what i think is) a fairly nice rifle.. i want to make sure i get it right the first time and not just start buying random ammo.
thanks in advance for any help. i am completely in the dark about ammo and really could use some help.

Some answers.  As usual...nothing is black and white though.

Grain weight. Heavier = slower but more momentum, typically  more penetration. Lighter - faster, more Kinetic energy and expansion. May have less penetration than heavy but still could be perfectly adequate.

Longer barrel = faster round. You GAIN velocity by going from a 9 to 14.5 inch barrel. Even if all the powder is burned (not sure where you got your 9 inch number), the gas is still expanding and accelerating the bullet.

Subsonic - less than ~1080 fps depending on temp, elevation, and other things. Supersonic is above that. When you shoot a round,  there are two sound contributors: the explosion of the gunpowder and the sonic boom of the supersonic round.

If you are shooting supressed, subsonic is recommended, as the suppressor only reduces the noise of the gunpowder. You CAN shoot supersonic out of a supressor, but it won't be as quiet. Likewise, you can shoot subsonic without a suppressor.

For 300 blk, the subsonic round is about the same weight and velocity as a 45acp round. This means you are not getting the benefit of rifle level energy. If you shoot subsonic ammo out if the 300 blk it should be supressed, as the only real benefit  is that it is so quite. No supressor, shoot supersonic ammo.

thank you both very much for the help. seems to be fairly straight forward, maybe i am just over thinking it all?!

i cant wait to finish my build and start shooting at longer ranges. something i have yet to do.

If you want to shoot a lot, Ide stick with 5.56 before diving into 300blk, factory ammo is 3x what .223/5.56 will be. 300blk would make an excellent second rifle. Yes, you will.

918- I am aware of the added costs of 300 blk. I dont go shooting anywhere near as much as i would like to.. im still looking for an outdoor range that isnt an 1+ away from my house. It is possible that i might start going more when i find one closer.

802- thanks for the tip, I know I should get into reloading to save monies, but I need to get the rifle done first.

looks like ive got plenty of reading to do! thanks again everyone for the help!