Gas block pinning, and effects on accuracy, looking for IRL experiences

[danieljmaunder]

So, as the title says, I'm looking for people experiences with barrels, starting out with non pinned gas blocks, and after pinning the gas block was there a notable degredation in accuracy? In my personal experience I have never had a properly dimpled and installed gas block come loose, but coming from the .mil side, if the gas block is exposed I usually prefer to have them pinned for security and robustness of install. I have a WOA 18" spr barrel thats installed on an upper that has a geissele 13" mk 4 rail leaving the gas block mostly exposed. I have a triarc easy pin gas block installed, and want to pin the gas block, however if its going to turn the barrel into something that doesn't shoot any better than a standard CL barrel, i'll probably skip the pin. Let me know what your guys experiences have been!

[opngrnd]

I've had a gas block come loose that was installed with Red loctiteand covered by a handguard. I've had two barrels pinned that I have notes from before and after. Both barrels were shot for a while prior to being pinned, and both of them retained accuracy.

Lightweight barrel shot 2MOAish with 55gr handloads, and 1.5MOA or under with match ammo before being pinned. Pinning with roll pin installed didn't change accuracy.

Medium weight fluted SPR barrel shot approx 1MOA prior to and shoots approx 1MOA after being pinned in traditional manner.

[danieljmaunder]

I've had a gas block come loose that was installed with Red loctiteand covered by a handguard. I've had two barrels pinned that I have notes from before and after. Both barrels were shot for a while prior to being pinned, and both of them retained accuracy.

Lightweight barrel shot 2MOAish with 55gr handloads, and 1.5MOA or under with match ammo before being pinned. Pinning with roll pin installed didn't change accuracy.

Medium weight fluted SPR barrel shot approx 1MOA prior to and shoots approx 1MOA after being pinned in traditional manner.

I wonder if using roll pins / coil pins makes a difference vs taper pins.

[opngrnd]

I wonder if using roll pins / coil pins makes a difference vs taper pins.

According to smarter people than me, it does. Pounding a taper pin puts stress into the barrel and can affect the bore. Last I heard, the Marine Corps upcoming contracts that specify not using taper pins to fasten the gas block. That's off the top of my head, so it's worth what you paid for it.

[danieljmaunder]

According to smarter people than me, it does. Pounding a taper pin puts stress into the barrel and can affect the bore. Last I heard, the Marine Corps upcoming contracts that specify not using taper pins to fasten the gas block. That's off the top of my head, so it's worth what you paid for it.

From a mechanical standpoint I can definitely see it, roll pins, straight pins, and coil pins will provide more even pressure versus a taper pin.

[markm]

I have to imagine the taper pin is massively stronger than roll pin. There's no way I'd buy an FSB barrel with roll pins holding it together... lo pro blocks, you can get away with that. (just my unquantified opinion)

[opngrnd]

I have to imagine the taper pin is massively stronger than roll pin. There's no way I'd buy an FSB barrel with roll pins holding it together... lo pro blocks, you can get away with that. (just my unquantified opinion)

Absolutely. The blocks I was referring to earlier are lo-pro covered by a rail.

According to a conversation I had with one barrel manufacturer, the change in bore from taper pins can actually be measured with the right tools. In some cases, such as FSBs, that's a fair trade. I would not expect the same deformation from coil pins, etc.

[markm]

Absolutely. The blocks I was referring to earlier are lo-pro covered by a rail.

According to a conversation I had with one barrel manufacturer, the change in bore from taper pins can actually be measured with the right tools. In some cases, such as FSBs, that's a fair trade. I would not expect the same deformation from coil pins, etc.

Agreed. But I've seen some effed up taper reams that come unnecessarily close to the bore... to the point that the ream hole is completely into the outer surface of the barrel. (good old American Mediocrity/stupidity/laziness) When done right to where the taper ream into the barrel's outer diameter is only 50 percent +/- of the pin diameter, there's way less possibility for bore deformation.

It's almost like the old carbine Gas port problem. Imbeciles over spec'd the ports, and other imbeciles bought into Piston guns to correct the first incompetence. Do shit wrong and then blame the design?

[AndyLate]

I had a local machinist drill my BRT gas block and barrel for BRT's coil pin and had no noticeable change in accuracy, but I don't shoot that rifle for groups much.

The low profile gas block pins are not as tight an tapered FSB pins so pinning the gas block really should not affect accuracy.

Andy

[danieljmaunder]

So last night my triarc easy pin gas block was delivered, installed the gas block, and went ahead and pinned it. Game out very clean and was very easy to install. There was not a whole lot of material removed from the barrel compared to a standard pin job I've seen on other barrels, leading me to believe there won't be much of a change if at all. And I have a lot more piece of mind now that its pinned.

Attached pic of the pinned GB

https://imgur.com/a/jVnYI4L