Gas port adjustment?

[TACTICAL45]

I am new to the gassers, I bought a used one from a member here on the Hide. I will be testing it out with my hand loads (for my bolt gun I sold here as well) and some FGGM 168's. The rifle is a 16" Ranier Arms Ultra Match, the gas block is a Seekins. My load is as follows, 175 SMK's, 43 gr, Lapua brass, CCI BR primers. I have been doing much reading about what members are shooting though this type of bbl. most seem to be using 168's. I will shoot both to see what it likes best as the gas block is adjusted now. Is there a short cut to tuning the gas block, or is it just shoot, adjust a little each way and see where they hit with each load and the rifle cycles? Is there a starting point on adjustment for the screw? I've never owned a adjustable gas block as you can tell. Thanks.

 

[mtrmn]

I AM NOT AN EXPERT

Now that that's out of the way, there is an ejection pattern chart to be found on the net that will give you an idea which way to adjust according to the angle of ejection. For instance, ejection to 3 0r 4 o'clock is considered ideal. Hotter loads or overgassing will eject more forward to like 1 or 2 o'clock, and weaker loads or undergassing will tend more towards 5 o'clock. Search for "ar15 ejection chart" or similar.Works the same for the larger ARs as well. I hope I understood your question.

 

[wareagle700]

Close your gas flow off completely.

Load 1 round in the mag,
Fire,
Open gas adjustment screw 1/4 turn
Load 1 round in the mag,
fire
Open gas adjustment screw 1/4 turn

Do this until the bolt locks back on the empty mag. Then, open it 1/4-1/2 a turn extra for when the rifle gets dirty or dry. Do this with factory ammo.

The location of the brass on the ground isn't always the best indicator.

 

[TACTICAL45]

Thanks for the input guys.

wareagle700,
Where in S.E. Ga? We are re-deploying in a few day, will be back at FT. Stewart. Maybe do some shooting some time? Also, you say to do it with factory ammo, what will be the difference with hand load? My guess would be the same, but is factory ammo the "catch all" solution?

 

[sandwarrior]

Close your gas flow off completely.

Load 1 round in the mag,
Fire,
Open gas adjustment screw 1/4 turn
Load 1 round in the mag,
fire
Open gas adjustment screw 1/4 turn

Do this until the bolt locks back on the empty mag. Then, open it 1/4-1/2 a turn extra for when the rifle gets dirty or dry. Do this with factory ammo.

The location of the brass on the ground isn't always the best indicator.

+1

There is little telling you how things are working by clock only. Distance from the gun means something as well. A good handload up to a solid operating pressure will best be measured as wareagle has stated. With the gas completely cut off, it's like firing a bolt gun. Work the load up to full pressure at that point. Then tweak to best accuracy. Then begin opening the gas port to described operating parameters.

As for the powder, I recommend using a single base powder. Varget is a very good choice for your load. Your load is somewhere near where you need to be, so I'm assuming it's that. I know the Army has used RE-15 in this instance, but it is dirty. If no Varget find another single base closer to H4895. AA2015 is a very accurate powder, but is limited in velocity. It hits pressure too fast.

 

[TACTICAL45]

sandwarrior,
I just got done doing the Google thing and reading several posts. I am using Varget as you guessed, always had great success with it. I stopped load development at 43 gr because I was overlapping bullet holes and did not want to get too close to my max chamber pressure of my bolt gun. One thing I have noticed during my reading, no one seemed to mention if they have done any upgrades to their weapons, in doing so, that should have effect on ejecting. So, does that come in to play, or do you adjust the gas block to the chart accordingly? I am of the mind that if it shoots correctly, accurately and consistently, let it be, no matter where it ejects to. Or am I wrong?

I will give more information about the rifle to get better feedback, forgot to in prior post.

Black Rain Ordnance matched upper/lower
16" Rainier Arms Ultra-Match Barrel dimpled
Geissele SD-3G trigger
JP complete Low Mass Bolt Carrier Group
JP silent captured spring
Seekins adjustable gas block
Troy TRX-308 handguard with accessory rails
Noveske end plate with flush cup hole
Surefire brake (will be changing out for a YHM Phantom 2)
VLTOR BCM gunfighter medium latch charging handle
Magpul STR
Phase 5 tactical bolt release lever

 

[sandwarrior]

sandwarrior,
I just got done doing the Google thing and reading several posts. I am using Varget as you guessed, always had great success with it. I stopped load development at 43 gr because I was overlapping bullet holes and did not want to get too close to my max chamber pressure of my bolt gun. One thing I have noticed during my reading, no one seemed to mention if they have done any upgrades to their weapons, in doing so, that should have effect on ejecting. So, does that come in to play, or do you adjust the gas block to the chart accordingly? I am of the mind that if it shoots correctly, accurately and consistently, let it be, no matter where it ejects to. Or am I wrong?

I will give more information about the rifle to get better feedback, forgot to in prior post.

Black Rain Ordnance matched upper/lower
16" Rainier Arms Ultra-Match Barrel dimpled
Geissele SD-3G trigger
JP complete Low Mass Bolt Carrier Group
JP silent captured spring
Seekins adjustable gas block
Troy TRX-308 handguard with accessory rails
Noveske end plate with flush cup hole
Surefire brake (will be changing out for a YHM Phantom 2)
VLTOR BCM gunfighter medium latch charging handle
Magpul STR
Phase 5 tactical bolt release lever

You are right on with your assumption. It's up to full pressure and shooting overlapping holes. Leave the load alone and continue to shoot outstanding groups.

As far as upgrades to the weapon, I've not found on either gas or bolt gun, even lever gun that accessories affect performance of load. As long as nothing changes between the basic elements of stock/receiver/barrel. I have seen it where someone put a sling on and the sling stud put pressure on the barrel. Quite a sudden change in POI, along with less accuracy. The "go back and undo what you did, one thing at a time" rule showed what happened. The telltale was a big scratch/wear patch on the underside of the barrel. That was an example. Any accessory that will change how you shoot the weapon may also affect accuracy. But, in general hanging things off the stock or scope (as long as you don't tweak it when installing) aren't going to make differences.

 

[TACTICAL45]

So, follow wareagle's advice and be happy? The reason I listed what I did was to see if the LMOS and buffer should have a effect on anything. What is the top end of chamber pressure of the semi? Thanks for the help.

 

[wareagle700]

Thanks for the input guys.

wareagle700,
Where in S.E. Ga? We are re-deploying in a few day, will be back at FT. Stewart. Maybe do some shooting some time? Also, you say to do it with factory ammo, what will be the difference with hand load? My guess would be the same, but is factory ammo the "catch all" solution?

Im in Bulloch County.
For shooting in the area, it doesn't get much better than this:
http://www.coolacressportingcamp.com

I recommend factory ammo because it will usually be loaded milder than handloads. At least for me it it usually is. You want to set your gas block with the lowesst pressure ammo you plan on using. If you set it while shooting hotter hand loads, factory ammo might not have enough pressure to cycle reliably.

 

[TACTICAL45]

I'll take a look at the range, IIRC, that is a small hike from where I am.
Roger that on the factory ammo, makes sense.

 

[sandwarrior]

I'm familiar with that area. I was at HAAF '81-'85.

 

[TACTICAL45]

Will be home soon, the range looks like it has a lot to offer. Reminds me of a few back home, not much near Ft. Stewart, I've looked around. There is one 100yd range, but from what I have been told it isn't much of one. We usually go to a Army buddies house and shoot, but he ETS'd just before this deployment. After the dust settles when we get back, I'll have to make the trip to see what the range is like.