Gas tube adjustment and POI Shift

[Dr. Tad Hussein Winslow]

Can anyone tell me off the cuff, the answer to this (before I head to the range to test it myself next chance I get):

I have one of the gas tubes with the adjustment screw installed on my AR10 type (DPMS). Suppose I have it adjusted where it cycles fine, as I do.

Now, if I were to tighten the adjustment screw all the way down, turning it into a single shot / manual repeater:

1. Approximately how much velocity gain would I get (from say, a 120 grain .260 rem full load)?

2. Accordingly, how much POI shift would I experience, do you think, approximately?

3. What portion of that POI shift would be attributable solely to velocity (higher POI), and what portion attributable to changed barrel harmonics (random vector POI shift)? 50% / 50% or what?

4. Would the recoil increase be noticeable from a 10 lb rifle? My guess is yes.

 

[R.W.Dale]

1. Approximately how much velocity gain would I get (from say, a 120 grain .260 rem full load)?

none or at least not enough to measure falling well within day to day ammo and atmospheric variances

2. Accordingly, how much POI shift would I experience, do you think, approximately?

none

3. What portion of that POI shift would be attributable solely to velocity (higher POI), and what portion attributable to changed barrel harmonics (random vector POI shift)? 50% / 50% or what?

see above

4. Would the recoil increase be noticeable from a 10 lb rifle? My guess is yes.

no

Come on you should know good and well at this point that each rifle is it's own individual and trying to quantify such conjecture to a accuracy or velocity loss or gain value through anything other than bullets sent downrange from your particular rifle is pure folly. That any such generalizations coming out of this thread will be by their very nature flawed to the core

 

[Uncle Mike]

I was going to say, it makes no difference on any of my AR-10's.
Tad, sounds like you have been reading too many 'technical' manuals! lol hehehe

 

[rcmodel]

None.
The bullet is out of the barrel and long gone before the pressure from the gas port unlocks the action. By that time, chamber pressure has dropped to near nothing.

If it wasn't, the rifle would blow up.

rc