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Thread: SLR Rifleworks Sentry 7 setscrew adjustable gas block review

  1. #1
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    SLR Rifleworks Sentry 7 setscrew adjustable gas block review

    Several weeks ago, I picked up a new Sentry 7 adjustable gas block directly from SLR Rifleworks. They are local to me, in Winter Garden, a Western suburb of Orlando. I called them while about 15 minutes out and spoke with Todd (the owner) on the phone. I explained that I would like to buy a Sentry 7 set screw gas block, and that I would like to pick it up in about 20 minutes. I expected him to provide some type of excuse, but he only replied, "Cool. It'll be ready when you get here."

    I show up in some sordid attire (covered in mud and soaked with rain due to some PT earlier that day on an O-course) and didn't receive as much as a crooked look from anybody there. I then met Todd and he took me for a quick tour of the shop. He is very knowledgeable about AR15's and we spoke for several minutes about my AR, my intended uses, the ammo I would be shooting, gas pressure curves, gas port pressures, my use of the Vltor A5 recoil system, etc. He then handed me my gas block which he had assembled himself so it was ready for my arrival. He gave me some consult on my expected gas settings, a brief history of the design of the Sentry 7, and then sent me on my way with a meaningful LEO discount. The rest of the guys in the shop were just as knowledgeable and just as friendly....a good bunch of gun guys they are.

    Though they were busy, customer service is obviously a priority. I didn't tell them about my participation here on M4C until just before my departure from their shop.


    Inspection:

    The gas block itself is made from 4140 heat treated steel and is coated in a heavy oxide/phosphate finish that appears very rugged and does not scratch easily. The gas block fit perfectly on the gas block journal of my Rainier Arms Mountain Series 18" CHF gov-profile barrel with rifle gas (made by FN). It was a friction fit that required some working by hand to get it on and positioned properly, which is what you want in a gas block (if it slides on and off like a ring pop, that is a recipe for gas leakage IMHO). The adjustment screw, spring capture screw, gas regulator, and the detent spring all appeared to be well machined with no visible flaws or defects. Todd told me that the only change that he has recently made to the Sentry 7 is that he has altered the leaf spring material from 6AL-4V Titanium to 17-5PH spring steel. He explained to me that he has recently had great difficulty in procuring quality batches of the proper grade of titanium due to military and government shipments taking precedent. Absent his sources of quality titanium of the proper grade, he selected a known quantity; 17-5 PH spring steel for the leaf spring. So, rather than delay the production of the Sentry series of gas blocks almost indefinitely, he has switched this (website still needs to be updated). He told me that, due to the dimension of the spring and the low stresses placed on it, 17-5 PH would be more than adequate even for select fire applications and that, technically speaking, the titanium is gilding the lily. Further, the leaf spring is user replaceable if so-desired.


    Installation:

    I have been using a Black River Tactical MicroPin gas block that I continue to recommend VERY highly if you do not desire to have an adjustable gas block. Removing that was easy. This was when I noticed perhaps the only thing that I could call a gripe about the Sentry 7; the screws on the Sentry 7 do not perfectly line up with the BRD barrel dimpling jig (and most Vltor and PRI low pro gas blocks). The rear screw, gas port hole, and the rear of the block are all in-spec and line up perfectly, but the gas block has been made shorter in OAL than a typical low pro and this has required moving the front screw hole rearward a few thousandths. This means that the front dimple, if you have one, will not perfectly align with the screw on the Sentry 7. So, put the rear screw in first (like I did) and it's a non issue. There is enough overlap to allow the McMaster-Carr knurled cup-tip set screw I used to gain purchase inside of the dimple...it was simply not centered within the dimple. No biggie.

    I removed my 13" KMR (which is really more like 13.5"), removed the BRT MicroPin gas block, and installed the gas tube into the Sentry 7. I then positioned the Sentry 7 gas block, applied red high temp Permatex threadlocker (same as Loctite high temp 272, the 450 degree flavor) to both screws, tightened them in the order described and admired my handiwork.

    And this lack of dimple-screw alignment is made up for by the following value-add that I do not see on their website.....a shelf for barrel pinning. YEAH BUDDY! I love pinning as much as Obama loves to read your friggin emails!

    I used the drill bit that came with the BRT MicroPin GB which has a cobalt tip and drilled away (shows how much of a deal the BRT block is, the drill bit can do at least two gas blocks). A few minutes later, having used plenty of lube, I had a clean hole and inserted a spiral roll pin. DONE, SON.

    Prior to firing, I placed a few drops of FireClean on the adjustment screw and the leaf spring as it was partially pushed away from the gas block body (as it is between detent settings).


    Performance:

    My first range trip was uneventful and very satisfying. I started on position 4 (from full-closed....as I will subsequently list all gas settings). This resulted in lock-back using Federal XM193 55gr FMJ and function with .223 pressure PMC 55gr Bronze. From that I went up to setting 5 and I gained lock-back using PMC Bronze. Seeing that I have a .098 gas port, an LMT E-Carrier, and the Vltor A5 system running the A5H4 buffer and a Tubbs Flatwire spring, this amount of restriction from full-open surprised me as most woudl consider my setup already on the border of being under-gassed.

    To describe the recoil (or what was left of it), it felt like a pop gun. Or like a .22LR conversion, but with a slight amount of muzzle dip with the A5H4 buffer as it returned to battery. A phenomenon I did not notice (or, perhaps, did not experience) prior to my use of the gas block on the current settings. After running about 100 rounds through the gun, I cycled the adjustment screw back and forth to settings 4 and 6 and it felt just as smooth as when I first installed it. I placed a drop of FC under the leaf spring after firing and stowed it for the night.


    Summary:

    I am very pleased with both the company (SLR Rifleworks) and the Sentry 7 gas block. It appears to be the most rugged design currently available, with a relatively large and beefy leaf spring in lieu of a small coil spring. It is the same overall profile as my BRT gas block and is actually slightly lighter. The BRT GB weighed 1.3oz on my scale and the Sentry 7 came in at 1.05oz. The cut-outs on the side of the Sentry 7 no doubt contribute to its lack of mass. So far, I am pleased and can tentatively recommend it to the collective. As I pile rounds on the block, I'll keep this thread updated.


    http://slrrifleworks.com/index.php?r...&product_id=84
    Last edited by BufordTJustice; 05-22-14 at 09:32.
    "That thing looks about as enjoyable as a bowl of exploding dicks." - Magic_Salad0892

    "The body cannot go where the mind has not already been."

  2. #2
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    "That thing looks about as enjoyable as a bowl of exploding dicks." - Magic_Salad0892

    "The body cannot go where the mind has not already been."

  3. #3
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    Gas block screw is in position 4 in the pictures as I am currently running an A5H3 buffer and my primary training round is XM193 (and HD/SD round is Federal XM556FBIT3 62gr TBBC). This setting is more than sufficient to grant me 100% function. I appreciate that it does not protrude much from the front face of the block.
    "That thing looks about as enjoyable as a bowl of exploding dicks." - Magic_Salad0892

    "The body cannot go where the mind has not already been."

  4. #4
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    Nice review. Could swear I just replied but its not posted.
    Well designed gas block. Feels like 120 degrees, or 1/3 turn, required to change settings, so not going to happen by chance.
    Which light are you running? Looks like Inforce WML, but cannot be sure.
    Last edited by mpom; 05-21-14 at 19:37.

  5. #5
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    Quote Originally Posted by mpom View Post
    Nice review. Could swear I just replied but its not posted.
    Well designed gas block. Feels like 120 degrees, or 1/3 turn, required to change settings, so not going to happen by chance.
    Which light are you running? Looks like Inforce WML, but cannot be sure.
    It is 1/3rd of a turn and yes, it would have to be intentional absent a complete hardware failure.
    "That thing looks about as enjoyable as a bowl of exploding dicks." - Magic_Salad0892

    "The body cannot go where the mind has not already been."

  6. #6
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    Thank you for this review. I sent the owner an email, but your thread just answered my question. I just wanted to know if it could be pinned. All my gas blocks are pinned, and that was the only thing holding me back.

  7. #7
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    I have one on my SPR upper.
    I was surprised at the difference it made, tuned it to run on PMC bronze and mild reloads.
    That upper shoots like a dream.
    Excellent product and their hand guards are fantastic as well!

  8. #8
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    Want to comment on SLR's customer service.
    Misplaced the long Allen wrench that came with the gas block, so called the company asking for a replacement. No problem, said the man.
    Of course I found the wrench later that day, but 2 days later a package arrives from Todd Gardner, with not only the OE wrench, but a complementary longer one, the one with a screwdriver handle that is an extra cost item. All shipped at SLR's expense, priority mail. So not only a superb product but outstanding custormer service as well! Not sure if Todd visits this forum, but Thank You!

  9. #9
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    Cool... I'll have to view the pics from home... they're filtered at work.
    "You people have too much time on your hands." - scottryan

  10. #10
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    Quote Originally Posted by markm View Post
    Cool... I'll have to view the pics from home... they're filtered at work.
    I'm no stickman, that's the damn truth. Took them with my Galaxy S4.

    Sent from my SPH-L720T using Tapatalk
    "That thing looks about as enjoyable as a bowl of exploding dicks." - Magic_Salad0892

    "The body cannot go where the mind has not already been."

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