AR Sponsor
Posted: 1/5/2015 10:44:02 PM EDT
|
I bought a 20" AR barrel off EE last year, but I forgot to write down the twist.
Stamped on the barrel is FNMI MP CHROME BORE It's 20" long, straight contoured, and about 9/16" diameter. If that's not enough, is there a way to determine the twist of a barrel? |
|
If you have a Dewey cleaning rod, a jag, and patch, you ought to be able to figure out the twist by pushing the rod in and measuring how far the rod has to travel to make one revolution,
Push the jag/patch into the bore just past the chamber, and then wrap a piece of tape on the rod, even with the back of the upper receiver. That is your "begin" mark.. Put a piece of tape further back by the handle and mark it on top, at the 12 o'clock position. That's the index mark which you watch revolve until it gives you one revolution. Push the jag slowly into the bore, and note the timing mark--as the jag moves down the bore, your timing mark will start to revolve in a clockwise fashion. When the timing mark revolves all the way around back to 12 o'clock, stop pushing the jag. Put another piece of tape flush with the back of the receiver, to mark "END" and remove the cleaning rod from the bore, and measure from the front of the start position to the front of the stop position. However many inches you get between start mark and end mark is the number of inches it takes for the bullet to make one revolution. Seven inches would be a 1/7 barrel. Nine inches would be a 1/9 barrel. Twelve inches would be a 1/12. You Capisce? ETA: LOL. I should've just Googled and posted a link. 
|
AR Sponsor