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View Full Version : SLR Sentry 7 adjustable gas block clamp on vs set screw with Geissele Mk 8


og556
12-25-14, 15:33
I am currently looking into building a new general purpose upper with the following specs:

- Vltor MUR upper
- Noveske 14.5" CL barrel Mid Length gas system
- KAC MAMS pinned/welded
- Geissele Mk 8 M Lok 13" handguard
- BCM FA BCG
- V7 Inconel mid length gas tube
- SLR Rifleworks Sentry 7 gas block

I chose the 14.5" mid length with the SLR sentry 7 gas block to build an upper I can tune to shoot extremely flat but tuned to be reliable with a variety of ammo. I will be pairing this with a lower which uses a Vltor A5 extension and will play with different buffer weights.

The SLR Sentry 7 comes in either a set screw or clamp on configuration and a choice of Melonite CQC or Nitride finish. I have read that the clamp on model ensures the best gas seal but am concerned about clearance with the Geissele Mk8 rail as well as indexing the gas port to ensure it is aligned perfectly.

I wanted to post this to hear feedback and advice about which SLR gas block and what finish gas block I should get. The Noveske barrel comes pre-pinned with a low pro gas block and tube and I haven't been able to find a place to order one that does not come with a pinned gas block. I'm not sure if the clamp on gas block will fit inside the Geissele Mk8.
Onyx Z
12-25-14, 22:07
I have read that the clamp on model ensures the best gas seal..

What you read was wrong IMO. Clamp on gas blocks suck. I don't even know why they still make them.

The best set up is pinned. A dimpled barrel and rocksetted set screw GB comes in a very close second. You will have positive contact with the barrel with both of these option and will seal 100% with zero blow by.
og556
12-25-14, 23:10
Good to know. I posted this mainly because I have zero experience with clamp on or set screw GB's. I would love to have a pinned SLR sentry 7 but as far as I know that's not an option. Would the fact the Noveske barrel comes with a pinned low pro GB be an issue for the set screw GB ?
Iraqgunz
12-26-14, 00:23
Can I ask why you need an adjustable gas block?
Onyx Z
12-26-14, 00:23
Good to know. I posted this mainly because I have zero experience with clamp on or set screw GB's. I would love to have a pinned SLR sentry 7 but as far as I know that's not an option. Would the fact the Noveske barrel comes with a pinned low pro GB be an issue for the set screw GB ?

Not at all. The GB's that come with Noveske's match barrels actually have one set screw along with the pin while their individual component GB's have 2 set screws. The Syrac Gen2 GB's actually have a small flat on the side for an easier start in drilling it for a pin. Might be something to look at if you really want an adjustable GB... I'm not sure if the SLR's can be pinned since they don't have much material to begin with.

FWIW, an adjustable GB is kind of moot on a mid-length as long as the gas port is sized correctly; and being Noveske, it should be. It would probably need to be dang near wide open for 100% reliability. They make a world of difference on a carbine gas though.
BufordTJustice
12-26-14, 09:53
Not at all. The GB's that come with Noveske's match barrels actually have one set screw along with the pin while their individual component GB's have 2 set screws. The Syrac Gen2 GB's actually have a small flat on the side for an easier start in drilling it for a pin. Might be something to look at if you really want an adjustable GB... I'm not sure if the SLR's can be pinned since they don't have much material to begin with.

FWIW, an adjustable GB is kind of moot on a mid-length as long as the gas port is sized correctly; and being Noveske, it should be. It would probably need to be dang near wide open for 100% reliability. They make a world of difference on a carbine gas though.
The SLR has the shelf as well. I pinned my Sentry 7 set screw version with ease.

Also, I disagree why the mid length statement. I use mine on an 18" upper with rifle length gas system and my AGB is closed right at 50%. I also run the Vltor A5 system.
Sumppi
12-26-14, 10:05
Clamp on gas blocks suck.


Can you please clarify why they suck?
I'm also looking for a adjustable gas block for my competition gun.


Sent from my Nexus 5 using Tapatalk
Onyx Z
12-26-14, 10:47
Can you please clarify why they suck?

The clamp on GB's do not have positive contact with the barrel, you are relying solely on friction to hold it in place. With a set screw and rocksett'd GB, you are essentially pinned to the barrel if it's dimpled. Even without the barrel dimpled, I would still trust it over a clamp on.

Plus, depending on the model, the clamping taps hang down and might not fit under certain rails.
colt933
12-30-14, 12:05
I've been running a SLR clamp on with a DD barrel with an undersized gas block journal with zero problems. I chose the clamp on because the Seekins block .752 rattled on the DD .748 barrel.

Also, I ran a YHM clamp on gas block/front sight on an M16 for years and several thousand rounds with no problems.