https://imgur.com/a/6IvPjEM

Gun worked fine after building it & during subsequent fun. I took it out today for the first time in some time, shot it twice, and after the second shot it started short stroking. I figured I was a moron, but turns out the screw heads SHEARED OFF when I shot my second shot.

I used a feeler gauge to space the gas block & it was torqued to spec. Crazy. Never using clamp on titanium blocks for anything I’d want to be “reliable”

I don't think clamp on gas blocks are bad.  I think the expansion coefficients of different metals was at play here.

IMO gas blocks should always be steel.

Theres no problem with clamp on gas blocks.  Yours is an anonoly .


Out of curiosity, what the end of the gas tube look like?  The end that feeds the BCg.

Where did you get the bolts, what were they rated, and did you torque them wet or dry?

Gas block size bolts have a very fine margin between properly torqued and going righty-loosey.

I also don’t see how they could have possibly failed in shear. They are a tension bolt.

Agree,
Not a fan of mixing different materials

That is 100% an example of torsional failure as can clearly be seen in the top picture screw on the right with those textbook opposing sharp perpendicular peaks. The bolt on the left is less obvious but on the bottom of the fracture face I can still see a telltale peak. That means either the screws were of poor quality, or you over torqued them. Also, titanium can and will pretty readily gall so I'm wondering was anything applied to the threads when you torqued them or were they clean and dry?

Tension failures look much different, those screws exhibit no sign of the cup and cone with a granular look associated with a tension failure mode. Also 'shear' isn't quite accurate either, as someone else said there is virtually no shear load in a clamping application like this.

What is the brand of gas block? Looks to me that the screws were not as strong as they should be, installation torque was higher than it should have been, or threads not treated per installation instructions.

Bad threads on the block is also a possibility, but easy to check.

As stated above, they likely were torsionally yielded during installation.

SLR GB7 - Titanium Gas Block - screws were torqued dry to spec (25 in/lbs)

And I definitely used shear colloquially. Regardless - everything was done to spec

What torque wrench/screwdriver did you use to apply the torque?

Were the screws marked YFS by chance?

I actually don't remember the screw markings unfortunately, I didn't find the parts that popped off to tell you better :(

https://www.amazon.com/gp/product/B000RZ1D86/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

I used that Torque Wrench

This was the Gas Block: https://slrrifleworks.com/gb7-titanium-micro-gas-block-set-screw/

Hmmm, hard to say on that screwdriver. But it looks like it might be similar in quality to the Wheeler FAT wrench. Of course, without knowing where the screws came from it's hard to say about their quality.

I didn’t look at the pics the first time.

25in/lb seems like a lot of torque for a (excuse me, not a machinist or ME, just going off SLR sells 2mm hex keys) 2.5mm or so thread. Even being the socket cap screw type, which AFAIK are all supposed to be 12.9 grade or so, those poor little threads were tuggin hard. Obviously it wasn’t a thread failure specifically.

Much in agreement with another poster, my guess is that they galled/seized, and the final bit of torque wasn’t causing the bolt to stretch and apply tension, but actually snap the head off by twisting.

If you can get the broken bolts to spin using some pliers, the threads didn’t seize. I doubt they will.

Maybe SLR will fix it by tapping the next size, or a local machinist/gunsmith might do it for you.

Next time, don’t put threads together dry. In my experience and opinion, you should never put threads together dry. The only time I let it slide is with grade 2 or 307A zinc coated bolts, for inside use in low stress applications. If you’re mixing metals, or using any high strength stuff, they need antiseize. Even loctite acts as a lubricant before it dries, if needed, like I’d recommend on optics mounting hardware.

Jacking off the tin man only costs you a couple bucks, breaking stuff is priceless.