Hello, I have found a 1/12 twist Rem. 700 take off barrel that is in mint condition. I want to use this as a dedicated cast boolit barrel as my current AR top end is 1/7 twist. The take off is 26 inches so I have the luxury of length choice for my new top end. I was thinking of between 12.5 and 14.5 inches. Just wondering if at that length what my best gas system length should be or does it really matter?
Thanks!
You don't say what caliber and it depends on what you want to do with it.
On every question of construction let us carry ourselves back to the time when the Constitution was adopted, recollect the spirit manifested in the debates, and instead of trying what meaning may be squeezed out of the text or invented against it, conform to the probable one in which it was passed.
Thomas Jefferson, letter to William Johnson, June 12, 1823
Im guessing 223 bc of the 1:7 & 1:12. I prefer mid length bc its smoother, but idk how short the barrel can be with a midlength gas tube. Are you going to sbr the rifle?
Sorry folks,need another cup of coffee. Yes it is .223 and as I`m in Canada, unfortunately I can`t hunt with it. It will be a plinker.
Will 223 shorter than 12 inches may become obnoxious. At 12 inches you may be stuck with using a carbine length gas system as a Mid may be hard to do.
Realistically the cost to repurpose a Rem 700 barrel and install and head space a barrel extension along with the machine work to re profile may be more than just buying a proven barrel from a dealer.
On every question of construction let us carry ourselves back to the time when the Constitution was adopted, recollect the spirit manifested in the debates, and instead of trying what meaning may be squeezed out of the text or invented against it, conform to the probable one in which it was passed.
Thomas Jefferson, letter to William Johnson, June 12, 1823
I'd go with one of the newer gas tube lengths that are longer than pistol, but shorter than carbine. Reason being is that I suspect you'll be wanting to use lower pressure loads for your cast boolits. The longer dwell time and higher port pressure (compared to further out the tube) should allow you to tune the action easier. I've repurposed takeoff bolt action barrels as well. $15-20 for an extension and a little shop time and you have an inexpensive barrel as long as you got the takeoff barrel cheap enough. They used to be all over ebay or at gunshows for $25 but like everything else have been going for more around here lately.
On my AR match rifles we moved the gas ports out 4" from standard tube. this help keep the "timing" closer to what was needed they function and feed reliably and fired brass dosnt have a fuzzy look to it. I also use a adjustable gas block on my rifles. I believe I read some where the gas ports and timing are actually from the muzzle to the port. Once the bullet passes the port the distance to the muzzle is what controls the actual impulse of the gas.
Port pressure, volume and duration. Think of it as a triangle and the surface area of the triangle is what is needed to run the gas system. If you make one of the legs longer or shorter you'll have to make changes to one or both of the other legs to maintain the same volume or you'll be under or over gassed. I've got 9x19 uppers with the port around 1.5" from the case mouth step on the chamber for a 16" barrel. Basically the same barrel in 357AR which has much more case capacity and you can use a carbine length tube on a 16" barrel.
Last edited by Moleman-; 09-26-2017 at 12:23 PM.
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