9mm AR SBR subsonic ammo

[brobin10]

hey guys,

i am going to start the lengthy process of building a SBR 9mm AR-15 and had a question about subsonic ammo.....

im seeing mixed reviews on what stays subsonic and what doesnt....some places say most 147gr loads stay subsonic regardless of barrel length

others are saying 147gr loads in only a 5" barrel stay subsonic

based on your experiences....which is true??

id rather not drop money on a can and have that annoying CRACK....

 

[jmorris]

The load I use mostly in mine is 3.1 of VV N310 with a berrys 147 @ 1.160". If you don't load just buy 50 rounds of what you want and test it, before you buy a case or more.

 

[brobin10]

but i dont wanna build something with a barrel too long and find out that nothing in it is subsonic

 

[dprice3844444]

buy a chronograph

 

[ironhead7544]

Most of the 147 gr ammo is subsonic. If you handload a subsonic load will be easy to make.

 

[jmorris]

Barrel length matters less with fast powders. The gain over a 4.25" vs a 16" with the load I posted above is very little. Swap out the N310 with HS-7 and you have different results.

 

[brobin10]

thanks for the info guys

looks like if i went with a 7" barrel i could maintain subsonic ammo if i did the loads myself. might be hard to maintain subsonic ammo off the shelves with the 7" barrel