new build - SLR sentry 7 adj GB issue

[Potshot]

Do you feel like this block was worth the extra cost over the other options? I love my sentry 6 so far!

[tb-av]

I think so. In the grand scheme of parts cost and finding things you like personally. I have since bought another one ( S7 ).

I did run into one other minor issue. Because this gas port is so far out towards the muzzle, when I installed the Griffin taper mount muzzle device I can no longer adjust the gas with a typical Allen wrench. I will need to grind one down so the short L part is about 1/2 normal length. Then it will fit between the shoulder on the muzzle device and the head of the adjustment screw.

Now that's really not anyone's fault, it simply needs a special tool. I could grab the screw with needle nose pliers I'm sure, but don't want to do that. So I just need to make one and toss it in the grip.

Either that or I need a super tiny universal joint adapter. Which ironically I could probably find off one of those RC cars.

We shot it last week suppressed and it's fine but it's blowing gas up my nose. I'm hoping to be ale to tone it down a bit.

So yeah, now that I have it working I like it.

[Potshot]

I have mine on a barrel with permd device so I sincerely hope it works long term lol. Would a pri gas buster help at all?

[ScottsBad]

Yes, simple. A standard gas block is simpler mechanically, but more difficult to tune and almost impossible to fine tune. With a standard gas block, the tuner can change spring rate and reciprocating mass, but can only make gross changes and can only hope the changes will put the carrier speed in that sweet spot between ejecting but not locking back and locking back but buffer slams into the rear of the receiver extension. The SLR also makes it easier to tune the AR to run reliably suppressed while minimizing gas-to-face.

Reciprocating mass, spring rate and gas flow are the three legs of the tuning triangle. Using a standard gas block limits tuning to spring rate and reciprocating mass and if gas flow (port diameter) is wrong, then mass and/or spring rate will by necessity be less than ideal to compensate, a situation which complicates matters. Not simple. Using an adjustable gas block makes it simple to set gas flow correctly.

tb-av, the factors that will make the gas block mushy are spring tension, detent length being short and detent radius not matching the grooves in the adjustment screw. From your description, I think the likely culprit is the leaf spring.

I'm using an SLR 7 on my AR pistol and now that I think about it, it feels a bit mushy too and I have to pay close attention to feel the "clicks". Also, the set screw needs to be turned one third of a turn to go from one "click" to the next. It helps to watch how far you turn the Allen key.

If the adjustment is too mushy, contact SLR and explain your problem and see if you can get them to send you a new leaf spring, detent and set screw.

You other options are to try a standard gas block and hope the gas port in the barrel is the right size, or try the gas block inserts Jerry has been experimenting with. Gas block inserts will work well, but you have to remove the gas block from the barrel to change the insert during tuning

Couple of things. First, if reliability is the most important factor, then a Adjustable Gas Block is not the way to go. I would never run one in a self defense rifle. Second, the spring rate has very little to do with tuning. The most important factor is buffer weight. Spring rate is much more important in stripping the next round and chambering it.

Tuning with buffer weights is a much more robust way to tune your rifle for the broadest range of ammunition in the worst environments without concern for problems introduced by AGBs. IMHO

However, if the rifle is not for self defense and will primarily be used for sport, I think an adjustable GB is a great alternative. JMHO

[tb-av]

I have mine on a barrel with permd device so I sincerely hope it works long term lol. Would a pri gas buster help at all?

You mean for me? I can turn the gas down, I just didn't have an Allen wrench with me. Didn't have time to grind one down before we went shooting. So the dial is set for non-suppressed. I think people say they can dial back 2 to 3 steps once suppressed.

[BufordTJustice]

Couple of things. First, if reliability is the most important factor, then a Adjustable Gas Block is not the way to go. I would never run one in a self defense rifle. Second, the spring rate has very little to do with tuning. The most important factor is buffer weight. Spring rate is much more important in stripping the next round and chambering it.

Tuning with buffer weights is a much more robust way to tune your rifle for the broadest range of ammunition in the worst environments without concern for problems introduced by AGBs. IMHO

However, if the rifle is not for self defense and will primarily be used for sport, I think an adjustable GB is a great alternative. JMHO

I've been using an SLR adjustable Sentry block on my duty rifle for the last 4 years, without issue. Have another on my suppressed SBR and another on my wife's 18" with rifle gas.

Not less than 3k rounds through any of them except my current BRT 16" Optimized based upper; and the BRT upper has over 1500 rounds on it.

When properly installed, on an in-spec gas block journal, using knurled-cup-tip set screws, on a dimpled barrel, with rocksett or loctite red, and properly torqued...... You're just not going to have an issue.

I have a buddy on a metro SWAT team with a select fire Colt lower and the 18" and suppressed SBR have both seen a few hundred rounds of select fire.

Literally, not a single issue.

Haven't cleaned a single gun yet aside from an occasional dry pull-through of the bore with a boresnake.

I'm going to have to respectfully disagree.

Sent from my SPH-L720T using Tapatalk

[MistWolf]

Second, the spring rate has very little to do with tuning. The most important factor is buffer weight. Spring rate is much more important in stripping the next round and chambering it

Because the spring has to return the carrier to battery and strip the next round from the magazine and chamber it, spring rate is a large part of AR tuning. The spring stores the energy imparted to it from the momentum of the BCG & buffer and the momentum comes from the energy in the gas. It's a balancing act of gas flow, reciprocating mass and spring rate

[ScottsBad]

Because the spring has to return the carrier to battery and strip the next round from the magazine and chamber it, spring rate is a large part of AR tuning. The spring stores the energy imparted to it from the momentum of the BCG & buffer and the momentum comes from the energy in the gas. It's a balancing act of gas flow, reciprocating mass and spring rate

We can argue about it all day, but we are just talking past each other. When I refer to tuning I always mean using buffers to slow the cyclic rate to the point where the rifle will operate with the weakest ammo I use, with a little margin for cold weather or dirty rifle. I just assume that I will be using a strong enough spring to strip the next round and put the round into battery.

You on the other hand consider the power of the spring to put the round into battery as a major aspect of tuning, not just the cyclic rate adjustments.

If I've recounted your position correctly, we are both right. I would always consider getting the next round into battery as a crucial step. But I take it for granted because I always use the same spring in 8 rifles (Sprinco Blue...well I have one white and one green too to make 10). And I assume that if the system will lock back on the last round, it is strong enough, with inertia, to strip the next round and put it in battery.

I can see that it is possible to have too much reciprocating weight with a weak spring to get the round into battery. Or too little reciprocating weight. In my opinion, those are extremes.

So, you are correct. I just don't see springs as a major factor if they are at least quality standard springs in good shape. Usually, the magazines are the problem.

EDIT: Let me expand on one last point. A dirty gun is one reason that a round might not go into battery. You are correct to be concerned about that.

[ScottsBad]

I've been using an SLR adjustable Sentry block on my duty rifle for the last 4 years, without issue. Have another on my suppressed SBR and another on my wife's 18" with rifle gas.

Not less than 3k rounds through any of them except my current BRT 16" Optimized based upper; and the BRT upper has over 1500 rounds on it.

When properly installed, on an in-spec gas block journal, using knurled-cup-tip set screws, on a dimpled barrel, with rocksett or loctite red, and properly torqued...... You're just not going to have an issue.

I have a buddy on a metro SWAT team with a select fire Colt lower and the 18" and suppressed SBR have both seen a few hundred rounds of select fire.

Literally, not a single issue.

Haven't cleaned a single gun yet aside from an occasional dry pull-through of the bore with a boresnake.

I'm going to have to respectfully disagree.

Sent from my SPH-L720T using Tapatalk

BufordTJustice,

Thank you for that. I'm glad to hear that I won't have any problems. I appreciate your experience. Allow me to remain cautious until I've done my own shooting however. You can understand my position I have several ARs, none of which have an adjustable GB. I am interested to try the SLR out.

I did a meticulous installation, with a good quality dimple jig, a quality torque wrench, fresh 272 (high temp) Red. I only drilled one dimple on this one however, because I may at some point want to change the GB.

EDIT: I continue to believe that adding another component, like an adjustable GB, is adding another potential problem point whether it be user error or component induced problems. Therefore, I cannot see myself ever using an Adj. GB in a go-to rifle.

Again, thanks for you input.

[ScottsBad]

This. OP, get new parts for free, no reason not too.

SLR adjustable gas block for bomb proof go-to-war gun? I am tending toward gas-port inserts if not barrel porting. But for defense in Urban CONUS/ LEO patrol capacity. SLR adjustable seems just fine.

The reason not to is because it is unethical?