I just bought a low profile gas block and it turned out to be aluminum.  Is that going to present a problem?

Depends on how hard you plan on running it.

PLEASE ELABORATE

what the hell happened there?

Aluminum doesn't have the tensile strength or heat resistance to be appropriate for a gas block.

It also has a significantly larger thermal expansion coefficient than steel - what that means, is that as soon as it starts to get hot, it loosens up on the barrel and gas tube letting gas leak out.

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thats enough info for me sending it back

Different thermal absorption levels in materials.

Aluminum is a more efficient heat sink than steel, it is also less dense and less hard and cannot be treated in the same manner as steel as a result.

what I meant is why did it blow a clean circular hole in the side?  the gas tube is steel also, isn't it?  there's a lot more going on there than just the gas block

JP sells aluminum gas blocks, and say its fine for normal semi auto operation. They do recommend steel for full auto, and SBR's.  You can do the same thing to a barrel if you fire enough rounds fast enough.

im not shooting full auto but I expect this POS to take me through hell and back so I will gto with steel

more info on pic here at bottom of the page

spot on

only caveat is that semi auto fire they are fine but I still prefer steel

The gas block wasn't aligned.

I know what you're thinking: I need to laser-align my gas tube to my gas block?

Well, yes and no.  
You're going to need to get it as close as possible, but it's never going to be absolutely perfect, not even with an alignment hole at the top of the gas block.
The fact that you can even slide a gas tube into a gas block tells you that there's some play between the two parts, there's a gap.  Naturally, high pressure gas will exploit these gaps... it's always trying to equalize pressure, you simply want it to equalize in the manner that's useful to you and the machine you're running.  In this case we're talking about moving as much as you can between two aligned venting holes in a rifle.

Long story short (too late) you're looking at the result of a gas block that wasn't aligned.  

The fact that a hole was worn through the side of the block simply means that the high temperature gas created and exploited a weak point in the material and eventually a means to vent.

High-temperature gas under high pressures will find a place to go.  If you have a material that cools and heats faster than an adjoining material, it will contract and expand at a different rate.  This will change the tolerances of the manner in which they are attached.  
Remember that part about being able to slide a gas tube into a gas block?  Yeah, there's a change there now... it's making a bad situation worse.  In the event of the photo above, it led to catastrophic failure of the gas system.

I know, some of you will convince yourselves that if you fire slow enough and let the barrel cool between shots, that will be enough to keep an aluminum gas block alive for a long period of time... but a few questions in response to that: Is it worth the worry?  Is it worth the cost savings?  Is it worth the weight savings?


My advice:  Get a quality steel block and actually have a gunsmith install it.  If you are reasonably handy with tools and a good set of instructions, you can do it yourself.  
Geissele includes a very good set of instructions with their Super Gas Block... whether you want to use their parts or not, I really don't care.  But their printed installation instructions for a set-screw gas block are the best I've seen in like... ever.

I mention set-screw installation, because I see more gas-related failures due to poorly-installed set-screw blocks than clamp-on blocks or taper pin FSBs.  A lot of DIY builders get excited and rush to put new parts on their gun I think.

I hate them....honestly I do. If you have any plans to stake your screws, don't try it. Also you can easily strip out your set screws. PSA uses that bullshit on their freedom upper iirc. The only part I would replace. Gas block should be steel.

I've never fully understood this. Every gas block I've ever had(PRI, DD, many others) had a significantly larger hole than the gas port. I assume this is to make up for misalignment.

Those holes are plenty big to butt a gas block directly against the shoulder of the barrel and still have full port access, even if the gasblock is designed to be mounted with the hand guard spacer. Is there some benefit to be gained from further alignment, after the port has 100% view of the larger gas block hole?

Doesn't say who made it, how many rounds it had on it, and  how hard it was ran. Its a bunch of complaining with a pic, no real information. The link in that page where it talks about another aluminum gas block failure was said to be a UTG gas bock. I wouldn't run a steel UTG gas bock or any of their parts.

There is no industry standard for location of barrel shoulders, distance from the rear of the gas block to the barrel gas outlet hole, or predicted use for the gas block.  

More importantly, the gas block is an ancillary part that needs to fit the needs of any barrel length, from a pistol-length 7.5" all the way up to a 24" open-class rifle.  The barrels use very different diameter barrel gas outlet holes, if the gas block is built with the largest hole (basically one for a short pistol barrel) then it can be used effectively for any other [longer] barrel.

The gas inlet hole in the gas block doesn't matter too much, it's the barrel gas outlet hole diameter that will limit the amount of gas that feeds the action of the weapon.  It's only going to let x amount of gas into the gas block because of the y diameter-hole in the bore/barrel.
That's why gas outlet hole diameter (in the barrel) is so important to determine correctly in relation to it's length.  

The fact that there is a de-facto industry standard for gas tube diameter is a huge help too.

Unless you're working on a barrel that's super-long or super-short... alignment isn't going to be absolutely super-precise.

ETA: With all that in mind, I'd be really interested in the barrel lengths and ammunition types in these weapons with the gas blocks that experienced destructive failures.  I see photos, but no real details.