Gunsmithing Cut and thread questions for 700P

[rrflyer]

Looking to get my 26" barrel chopped down and threaded.

I've searched and searched but haven't found any hard evidence on optimum barrel length for a .308.

I was thinking 21 and threaded. Seems like i should be able to lose some weight and gain mobility without giving up to much velocity.

Right now running 175SMK's at 2700FPS


As far as threading is there a standard thread all brake and suppressor makers tend to use? I was gonna get a VIAS brake but was told it used a special thread that wasn't adaptable to most suppressors.

I don't own a can now but hope to in the future and I didn't see the point in pulling the barrel twice when I can get it done during the chop.

I should ad that this is my only rifle so It gets to do everything from punching paper, competitions, and hunting.

 

[jasonk]

Re: Cut and thread questions for 700P

21 & 3/4" to be exact.

If you've never read this article, there's lots to learn from it.

http://www.angelfire.com/ma3/max357/houston.html

 

[crumpmd]

Re: Cut and thread questions for 700P

18 and threaded.

(That brings it back to 26" with the silencer)

 

[wnroscoe]

Re: Cut and thread questions for 700P

I'd chop, crown and thread at 22", in that order.

 

[x ring accuracy]

Re: Cut and thread questions for 700P

Just an opinion, longer the better. If you need to shorten, easy, if you need to stretch, not so easy.

 

[serpnt]

Re: Cut and thread questions for 700P

The most common thread pattern is 5/8-24 X .625 length. We at Score High Gunsmithing can thread your bbl for a planned suppessor and install one of our Tac Brakes. Give us a call
1-800-326-5632
or drop us a line
www.scorehi.com

Score High Gunsmithing

 

[BlackOps Tech]

Re: Cut and thread questions for 700P

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: rrflyer</div><div class="ubbcode-body">Looking to get my 26" barrel chopped down and threaded.

I've searched and searched but haven't found any hard evidence on optimum barrel length for a .308.

I was thinking 21 and threaded. Seems like i should be able to lose some weight and gain mobility without giving up to much velocity.

Right now running 175SMK's at 2700FPS


As far as threading is there a standard thread all brake and suppressor makers tend to use? I was gonna get a VIAS brake but was told it used a special thread that wasn't adaptable to most suppressors.

I don't own a can now but hope to in the future and I didn't see the point in pulling the barrel twice when I can get it done during the chop.

I should ad that this is my only rifle so It gets to do everything from punching paper, competitions, and hunting. </div></div>

When determining barrel length, there are a few factors involved (or should be) but one of the factors I look at predominately is Ballistic Efficiency, or, does the barrel length I want to use allow full burn of the powder charge. If not, an overbore condition can and will be a result of inadequate barrel length. I agree with WNROSCOE about the 22" barrel for .308 (although I build a lot of 20" barreled .308s). It's a happy medium and will allow full burn of factory loads without having too much barrel to lug around. If you handload, it's possible to design a load for any particular barrel length (within reason of course). I have a 19" barreled .308 with a custom load that I get full powder burn at 18.5". Most factory loads will not burn within 18" barrels so you end up with excessive blast, a big fireball and reduced muzzle velocity. Of course, there are numerous 18" barreled .308s around and videos of ringing steel at 1k yards, but how much energy are you delivering at 1k yards with the reduction in velocity with an 18" barrel and factory loads? I'd say stick to 20 to 22 inch barrels for a .308 when using factory loads and go shorter with handloads....

 

[Boomholzer]

Re: Cut and thread questions for 700P

HateCa custom orders Vias brakes in 5/8-24. He also modifies it internally for allowed increase in barrel thread length for a can. Then the brake is turned with a slighty larger OD at as not to distort the shoulder for can engaugement.

For a 26" 700VS barrel (same as 700P), i had one cut to 22" and lost 40-50fps with 175/178gr BTs without chamber modifications. It shot tighter as a result.

If you ever want to swap the can across rifles you want the same thread length cut. I fight this with two different cans. Some barrels I picked up second-hand where threaded in shorter length so crap fills the forward threads, past the muzzle. This needs to be cleaned and chased to thread back on a different rifle with the proper thread length to the can.

You may want to also consider discussing a recut on the chamber to reduce the throat length.

There really is no optimum barrel length across all utility. The same could be said for picking a barrel profile. If your lucky, the can will add back some velocity. Depends on your expectations at max range and utility with the can on. Given .30 can lengths, anything over 21" isn't proper given my shoulder height.

Put your greed with ballistics at max range and figure 15fps per lost inch and go from there. My take.

 

[sr15match]

Re: Cut and thread questions for 700P

I had my 700P cut to 22"oal then threaded for a brake and really like it. Balance is good and I just bought 500rds of 175gr SMK to start some load development.

Todd