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J.Boyette

Adjustable Gas block?

60 posts in this topic

I was thinking about it for the 300BLK upper I recently put together, but when I contacted the manufacturer, he told me that he had not done any testing on the 300BLk, and could not advise what the ideal port size in the plate should be. he offered to sell me an undersize plate that I could test and open up as needed to get the upper to finction as desired, but I don't feel like doing the R&D at this time so I may just throw a Syrac GB on it for now. maybe once I've got the configuration sorted out I'll try one. Like they say "only change one variable at a time in an experiment".

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I final got to go out to the range, I started with the screw all the way in and backed it out 1 1/2 turns, fired one shot and it did not hang open on empty mag, adjusted it out 1/4 turn at a time until it did hang open then went 1/4 turn more, everything seems much smoother and I didn't measure or record anything but my groups are considerably better! I was hitting lime-a-ritas at 200 no problem!

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What troubles me about most of the screw adj. gas blocks is, what if the screw blows out ?

There is a lot of pressure at the point of screw threading, where screw meets gas block . That would be one mean screw to any one or thing was in its path .

 

I reload my own & don't care how the brass looks or where it lands after I shot the round , just as long as it works & functions like it should . 

 

You can go back to the topic of post now .

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Syrac's has a plunger that must be depressed in order to move the setting.  Wilson's has a lock screw that goes in on top of the adjustment.  Both of these are good designs and can be adjusted from the front.

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I used a small set screw from the top to secure the adjustment after it's been made, as far as strength I did not use the drill recommended by the tap drill chart that would only give it 75% thread engagement, I got in the machinery's handbook and found the correct drill for a 95% thread engagement so it really should be no weaker than it was before I drilled the hole. I am sure there is a way to mathematically figure how much the threads will hold depending on the material being tapped and % of thread engagement but that is way over my head.

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As an owner of both a syrac and wilson I'll chime in.

 

I'm using the Low Profile Wilson Combat Adjustable gas block.  It's a 2 set screw design, you loosen the outer hollow set screw, then push the allen wrench down farther to get to the actual adjustment screw, turn to make your adjustment, then set the outer screw to lock the adjustment screw into place.  Not quite as nice as the syrac, but syrac does not make one for my diameter barrel.  I actually time mine for more the 3:00 position so it hits the net and I don't have to go chasing brass :).  I have the Syrac on a 5.56 AR.  Both have extended length handguards so access to the front is key.

 

I don't care for the locktight style, but I'm spoiled by syrac and wilson.

The Syrac was harder to install cause that damn roll pin was a crazy tight fit.  The Wilson came with a straight gas tube already installed.  Of the two I prefer the Syrac.

Edited by Justintoxicated

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I'm starting a build and I'm confused about LR-308 adjustable gas blocks - in looking at Midway's offerings, I see a lot of adjustable gas blocks labeled as being for AR-15.  Is there any difference between a .750 gas block for .308 and one for .223?  I could imagine that a gas block intended for .308 might have a larger inlet hole than one for an AR, to allow a greater amount of gas to move the larger & heavier BCG.  Is that not true?  If not, then I would assume any quality .750 adjustable gas block would work on the LR-308 platform.  True?   thanks

Jeff

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Jeff

Been mulling over the same subject.  To the best of my knowledge, which is not very deep on the subject. It's by journal size.  To simplify the process a bit, been looking at them in sections classified as 308 by companies who sell them.  

A lot of experience here, sure someone can verify. 

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57 minutes ago, JeffPatton00 said:

  Is there any difference between a .750 gas block for .308 and one for .223?

Used to be I would say no, but a recent experience causes me to add a caveat. SLR blocks are good to go on either caliber, lots of long term experience there. I recently tried the Superlative Arms adjustable block on a 308 and ran out of adjustment on the bleed off portion of the setting. They are a bit different with a restrictive mode at one end of the adjustment screw that works like the SLR block in that it restricts the amount of gas allowed into the system. It also has a bleed off portion of the adjustment range that allows gas to bypass the gas tube and exhausts it out the front of the block. On the bleed off portion heavier loads could never be properly adjusted, lighter loads like ZQI and Perfecta 150 grain could be adjusted far enough to cause the bolt travel to be too short but FGMM loads would still fully function at the most open position. The idea was to open up the valve until the rifle stops functioning then turn it back a 1/4 turn to achieve the lowest amount of gas to enter the rifle that it needs to function. If you do a search here you will find threads with links to a video that describes this better than I can.

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The Syrac adjustable is a great piece of equipment, and works on either caliber. Gen2 is the better version.

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