AR15.Com Archives
 Adjustable gas block options.
Greyknight  [Member]
3/30/2008 4:22:13 PM
Okay, after some POS bastard stole my information, I have finally got my bank account back in order and am prgoggressing with my .300 whisper build. For my build an adjustable gas system is mandatory, unfortuneately, an adjustable tube isn't an option (port is at the pistol position) so I am wondering what my block options are. I know Noveske is working on one, but who knows when it will be ready. Right now, I am leaning towards the JP because I have heard nothing but praise about their products. PRI also has one, but I have no experience with them, and have heard little about anything but their gas buster charging handle. So does anyone have any other options? I have designed my own in Solidworks, but I'm guessing prototyping costs will be rediculous.
Southern_Raider  [Member]
3/30/2008 8:27:03 PM

Originally Posted By Greyknight:
an adjustable tube isn't an option (port is at the pistol position)


In the past, I have purchased the MGI adjustable gas tube and transferred the gas block portion of it to other tubes. Other than a hand drill and a roll pin punch all you need is a little mechanical aptitude.

If you're interested, drop me a line and I'll post tips.


I am leaning towards the JP because I have heard nothing but praise about their products.

I can't say anything bad about the JP adjustable gas block, but all it seems to be is a a hole tapped for a 6-32 screw. I want to add this to my DPMS LR-308 and will probably just do it myself on a drill press.
STEEL1212  [Member]
3/30/2008 10:12:38 PM
I had a JP adjustable but locktite is REQUIRED! I since have switched to the PRI unit that MSTN sells and I like it 100 times better. No locktite required as it has enough threads to hold its position, you could use it if you want though I guess. JP is good but I shoot 3 gun and the barrel tends to heat up and if you use blue locktite the screw can come loose. If you use red you can't adjust for diffrent loads.
cav_scout_tj  [Member]
3/30/2008 10:42:34 PM
I have the PRI, it does have a lot more threads. The only minus is that that makes the top of the block wide. Like too wide to go under a LaRue rail, or any of the thinner rail systems. I have a YHM rail which fits most anything.

I am still waiting on the barrel, so I cant say how it works, but I have held it in my hand.

Greyknight  [Member]
3/31/2008 1:46:36 AM
Southern_raider, that would be great, I may give it a shot if I can make it work.

The rail I plan to use is in fact a YHM ultra-light (mostly so I can be sure the can will be able to get partially under the foregrip).

Thanks for the advice on the JP, frequent changes will be likely as I switch between super and subsonics.
Southern_Raider  [Member]
3/31/2008 1:57:47 PM
To Transfer the MGI Valve Block

When you get the MGI tube, you need to remove the valve block. Remove the roll pin that secures it to the tube, then unscrew the gas adjustment until the valve block can be slid off.

Slide the valve block onto the new tube and get it into the position you want. Since you are drilling the holes, you get to pick the position/angle. Once you find the place, tighten the adjustment screw to lock the block in place. You actually want to force the tip of the screw to dimple the tube for later drilling, but for now we want it to stay still.

Chase the roll pin hole with a drill, then reinstall the roll pin.

Remove the adjustment screw altogether, and drill out a spot in the tube for it. There should be a dimple from the tightening step to guide you. It may be beneficial to start with a smaller pilot hole, but the ending size should be just a tad bigger than the diameter of the screw. Be careful not to overdrill through the other size of the tube!

Replace the adjustment screw and strart shooting.

Bearbait1  [Team Member]
3/31/2008 2:53:02 PM
One thing that you did not specifically address is whether you goal is to get the rifle functioning with one load, or full and subsonic. I have both the MGI tube and the JP block and both work well, although I would not consider them to be a solution for going back and forth between load types. It can be done, but the allen type screw head is really not indexable, easily. Plus, the small head screw hole is a bugger waiting to happen.

This has come up before and Marty at Teppo Jutsu does have a truely user friendly adjustable block or two that might be worth talking to him about, if you desire to switch back and forth.

Craig
Greyknight  [Member]
4/1/2008 12:21:46 AM

Originally Posted By Bearbait1:
One thing that you did not specifically address is whether you goal is to get the rifle functioning with one load, or full and subsonic. I have both the MGI tube and the JP block and both work well, although I would not consider them to be a solution for going back and forth between load types. It can be done, but the allen type screw head is really not indexable, easily. Plus, the small head screw hole is a bugger waiting to happen.

This has come up before and Marty at Teppo Jutsu does have a truely user friendly adjustable block or two that might be worth talking to him about, if you desire to switch back and forth.

Craig


Spot on. Want to switch back and forth and didn't realize Teppo had other options available. I figured I would close the valve all the way and just back it out to the predetermined value for various loads. Why is it that every time I look for something unique and cool, Marty's name comes up?

Also, thanks southern_raider, I am going to try the procedure if I can't get a better option from Teppo.
JFA  [Member]
4/1/2008 12:41:27 AM

Originally Posted By Southern_Raider:
To Transfer the MGI Valve Block

When you get the MGI tube, you need to remove the valve block. Remove the roll pin that secures it to the tube, then unscrew the gas adjustment until the valve block can be slid off.

Slide the valve block onto the new tube and get it into the position you want. Since you are drilling the holes, you get to pick the position/angle. Once you find the place, tighten the adjustment screw to lock the block in place. You actually want to force the tip of the screw to dimple the tube for later drilling, but for now we want it to stay still.

Chase the roll pin hole with a drill, then reinstall the roll pin.

Remove the adjustment screw altogether, and drill out a spot in the tube for it. There should be a dimple from the tightening step to guide you. It may be beneficial to start with a smaller pilot hole, but the ending size should be just a tad bigger than the diameter of the screw. Be careful not to overdrill through the other size of the tube!

Replace the adjustment screw and strart shooting.



Raider.....on the roll pin that hold the valve body on the tube, when you chase the roll pin hole does this merely just cut a slight round notch in the gas tube? I didn't realize the gas tube wall was thick enough to do that, but apparently it is. Thanks...Joe
Southern_Raider  [Member]
4/1/2008 9:20:36 AM

Originally Posted By JFA:
Raider.....on the roll pin that hold the valve body on the tube, when you chase the roll pin hole does this merely just cut a slight round notch in the gas tube? I didn't realize the gas tube wall was thick enough to do that, but apparently it is. Thanks...Joe

It's been a while since I last did this, but yes, I seem to recall that the roll pin barely nicks the outside of the gas tube and doesn't break through.
Cold  [Moderator]
4/1/2008 9:40:07 AM

Originally Posted By STEEL1212:
I had a JP adjustable but locktite is REQUIRED! I since have switched to the PRI unit that MSTN sells and I like it 100 times better. No locktite required as it has enough threads to hold its position, you could use it if you want though I guess. JP is good but I shoot 3 gun and the barrel tends to heat up and if you use blue locktite the screw can come loose. If you use red you can't adjust for diffrent loads.


I use a JP rifles adj gas block on my 3 gun rig. I echo what the quoted poster says, LOCKTITE it down as it uses set screws, its not pinned, least mine is not.
Now the Switchblock that Noveske is working on is geared toward suppressors last I heard.

I am working on 2 different 300 Whisper builds, I think I will try a JP adj gb on one and then either the MSTN or Switchblock (when out) on the other.
STEEL1212  [Member]
4/1/2008 9:52:00 AM

Originally Posted By cav_scout_tj:
I have the PRI, it does have a lot more threads. The only minus is that that makes the top of the block wide. Like too wide to go under a LaRue rail, or any of the thinner rail systems. I have a YHM rail which fits most anything.

I am still waiting on the barrel, so I cant say how it works, but I have held it in my hand.



I got mine from MSTN and its not wide at the top like the one they have pictured on their website. Mine fits fine under a Troy rail.
Banzai  [Member]
4/1/2008 9:56:07 AM

Originally Posted By Cold:

Now the Switchblock that Noveske is working on is geared toward suppressors last I heard.



It is. Word is that there will be a different block for each barrel location/gas port size. The block uses a straight gas tube, which is fixed to the rotating part of the block. As the lever is rotated between full, supressed, and off, the opening in the tube is what actually gets obscured.

Hopefully, he'll have one for the Whisper set up. That would be ultra cool and uber useful, depending on wether he picks carbine, or pistol length to develop (hopefully both?). The only issue would be accessibility when hidden under a FF rail, but I think we could all figure that out, too!

Tom
JFA  [Member]
4/1/2008 12:46:45 PM
Well you fellows sure opened my eyes about the MGI gas valve. I was under the assumption that it was one solid unit which included the gas tube. Here, according to you all, it comes apart. I tell you what, for the price of it I do believe I'll be making myself one on the lathe. That's a pretty simple item to make if you have the fine thread gunsmith taps, which I do.
Southern_Raider  [Member]
4/1/2008 3:15:47 PM

Originally Posted By JFA:
Well you fellows sure opened my eyes about the MGI gas valve. I was under the assumption that it was one solid unit which included the gas tube. Here, according to you all, it comes apart. I tell you what, for the price of it I do believe I'll be making myself one on the lathe. That's a pretty simple item to make if you have the fine thread gunsmith taps, which I do.

MGI doesn't sell the blocks alone, from what I've heard. If you want to do several, you might find some buyers. Let me know what you're up to and I may pick up one or two. It would be a very simple part to make and I'd be there if I had a mill.

The only other thing to consider about the MGI is the adjustment screw is a conventional set screw (10-32?) that has has the point turned down to a smooth surface (about 0.1" dia).
JFA  [Member]
4/1/2008 5:28:16 PM

Originally Posted By Southern_Raider:

Originally Posted By JFA:
Well you fellows sure opened my eyes about the MGI gas valve. I was under the assumption that it was one solid unit which included the gas tube. Here, according to you all, it comes apart. I tell you what, for the price of it I do believe I'll be making myself one on the lathe. That's a pretty simple item to make if you have the fine thread gunsmith taps, which I do.

MGI doesn't sell the blocks alone, from what I've heard. If you want to do several, you might find some buyers. Let me know what you're up to and I may pick up one or two. It would be a very simple part to make and I'd be there if I had a mill.

The only other thing to consider about the MGI is the adjustment screw is a conventional set screw (10-32?) that has has the point turned down to a smooth surface (about 0.1" dia).


No problem to make any of that gas valve, but the thing is I'm not doing it and selling them because that isn't fair to MGI. They may even have a patent on it and to make it would be legally and morally wrong. For myself, np.
Mad5757  [Member]
4/1/2008 7:26:29 PM
I have the JP adjustable on my LR .260. I had problems with loctite just like others here. I now use a heavy amount of teflon tape. It doesn't freeze up, it won't strip the threads, it stays in place, and it turns easily.
jrainw  [Member]
4/2/2008 9:04:06 AM
Check out quarterbore.com's whisper forums. In the classified section a member is selling custom gas blocks for $60 each shipped. I just ordered one for my Noveske 10.5. He has two position push button (off and on), three position (off, subsonic, supersonic) and you have the option of a lever for adjustment or a slotted adjustment. I'll post how it works when it gets here.
comp1911  [Team Member]
4/2/2008 9:10:51 AM

Originally Posted By Greyknight:
I have designed my own in Solidworks, but I'm guessing prototyping costs will be rediculous.


I had a hard time finding a 0.875" bore block so I drew one up in Microstation and sent it out to bid to a couple job shops for a quantity of one.

Bid 1 - $205
Bid 2 - $257



I found a PRi with 0.875 bore for $53.
JFA  [Member]
4/2/2008 10:49:07 AM

Originally Posted By jrainw:
Check out quarterbore.com's whisper forums. In the classified section a member is selling custom gas blocks for $60 each shipped. I just ordered one for my Noveske 10.5. He has two position push button (off and on), three position (off, subsonic, supersonic) and you have the option of a lever for adjustment or a slotted adjustment. I'll post how it works when it gets here.


How about a direct link, I went there...first quarter bore, then 300 whisper page, then whisper forum, then classified, I saw nothing of the such.
JFA  [Member]
4/2/2008 10:59:03 AM

Originally Posted By comp1911:

Originally Posted By Greyknight:
I have designed my own in Solidworks, but I'm guessing prototyping costs will be rediculous.


I had a hard time finding a 0.875" bore block so I drew one up in Microstation and sent it out to bid to a couple job shops for a quantity of one.

Bid 1 - $205
Bid 2 - $257



I found a PRi with 0.875 bore for $53.


Where did you fine your PRI with a .875 bore? This is the size that CSS 6.5 barrels use and they have PRI make the gas blocks for them, but dang if I could find them on PRI's site.
comp1911  [Team Member]
4/2/2008 12:29:35 PM

Originally Posted By JFA:

Originally Posted By comp1911:

Originally Posted By Greyknight:
I have designed my own in Solidworks, but I'm guessing prototyping costs will be rediculous.


I had a hard time finding a 0.875" bore block so I drew one up in Microstation and sent it out to bid to a couple job shops for a quantity of one.

Bid 1 - $205
Bid 2 - $257



I found a PRi with 0.875 bore for $53.


Where did you fine your PRI with a .875 bore? This is the size that CSS 6.5 barrels use and they have PRI make the gas blocks for them, but dang if I could find them on PRI's site.


It's in the PRi catalog. It's not on their site.

I found one here: dynamicarmament.com/items/ar-15-gas-blocks/pri-low-profile-gas-block-875-steel-ar-10-05-875-01-detail.htm

They have 10% off web orders until April 15th.
jrainw  [Member]
4/2/2008 9:04:15 PM
Try this,

http://www.quarterbore.net/forums/showthread.php?t=1533

I haven't recieved mine yet but I just ordered it this week.
I don't know how to make the link hot but it will get you there.
JFA  [Member]
4/2/2008 9:14:15 PM

Originally Posted By jrainw:
Try this,

http://www.quarterbore.net/forums/showthread.php?t=1533

I haven't recieved mine yet but I just ordered it this week.
I don't know how to make the link hot but it will get you there.


That's worked thanks. That's an interesting idea. Funny, a friend asked about making a similar gas block that would have three positions: one a .085 orifice, the other a .040 orifice, and the last position "off".
rover15  [Member]
4/2/2008 9:59:27 PM
I have one of the lever actuated 3 position gas blocks made by tp555 on quarterbore. Mine is the stainless steel model and I use it on my 10" 300 Fireball pistol. I run a .102" pistol port so I can cycle the really light subsonics but it would be a mess if I shot supersonics with that kind of porting so I just switch it to low and it works fine.
OMP1973  [Member]
4/2/2008 11:11:36 PM
I have one of TP55 3 pos blocks. Nice work, even made by hand. Tamed my 300 whisper. Little bit of grinding and fits under my YHM handguards. (Pistol length gas tube makes it kind of tricky. Works great in sub , super, and off settings. Cant say enough good about him or the product. Migh have him make one to fit my 50B.


OMP
MartytW  [Team Member]
4/2/2008 11:20:05 PM
Tom designed these after working with us on our Gen 1 blocks and are considered the Gen 3 blocks

Gen 1 adjusted from the front and used non-modified gas tube


Gen 2a adjusted from the side and vented, but would not fully shut off, used our block body



Gen 2b was similar but used Tom's body style

Gen 3 used the new body but had high, medium and off settings


Gen 4 is the quick switch low profile on/off version

I still have one or two of the Gen 2b and one or two of the Gen 3 in stock, 0.936 and 0.75 size. If you need a custom version, get with Tom or else check with me ...