XM-18 Standoffs

B

brianml

Joined
Sep 7, 2004
Messages
197
Do the latest generation of 3" XM-18s come with titanium standoffs on a standard configuration?

Thanks,
Brian
 
Not to poach this thread too much, but...I received some standoffs(blue, bronze and plain) in a trade, all said to be Ti. How can I tell if the plain ones actually are Ti? I used the magnet test and they were not magnetic, but now I'm skeptical. Thanks
 
UK_CATS_FAN said:
Not to poach this thread too much, but...I received some standoffs(blue, bronze and plain) in a trade, all said to be Ti. How can I tell if the plain ones actually are Ti? I used the magnet test and they were not magnetic, but now I'm skeptical. Thanks
Click to expand...

If you can be sure that you can eliminate any air pockets do this:

Weigh them, then submerge in water of a known volume. Measure the increase in volume. That is the volume of metal. Ti is 4507 kilograms per cubic meter, or 4.507 grams per cubic centimeter. 1 cubic centimeter is equal to a milliliter.

Anyone wanna check my math?
 
Whoa look at the brain on Brandog......your like the dude in the bathtub, you know the eureka guy....what was his name? Once again the forums amaze me.....that's AWSOME!
 
Or weigh them compared to stainless that's what I did to at least be able to determine they weren't SS.
 
brandog said:
If you can be sure that you can eliminate any air pockets do this:

Weigh them, then submerge in water of a known volume. Measure the increase in volume. That is the volume of metal. Ti is 4507 kilograms per cubic meter, or 4.507 grams per cubic centimeter. 1 cubic centimeter is equal to a milliliter.

Anyone wanna check my math?
Click to expand...

The standoffs are made to the same overall dimensions irrespective of material, the steel and titanium standoffs will displace the same volume of water and therefore are the same volume.

Only the weight will differentiate the two and being the same volume the titanium will have a lower density.

Visually the stainless standoffs are more white and bright metal, the titanium standoffs should appear more grey and less bright.
 
The 17-4PH stainless standoffs are slightly magnetic, that is how I check every new Hinderer I get. Any standard neodymium magnet will attempt to pick it up. Focus on ATTEMPT. The amount of pull on the standoff is very small but it's there. Titanium has zero attraction to the magnet.
I've never gotten a new XM-18 with Ti standoffs but have gotten a few with titanium LBS's.
You could also weigh the standoffs with a gram scale. If anyone has their XM apart & a scale we could chip in & get the exact weights.
 
Jaytaylor said:
The standoffs are made to the same overall dimensions irrespective of material, the steel and titanium standoffs will displace the same volume of water and therefore are the same volume.

Only the weight will differentiate the two and being the same volume the titanium will have a lower density.

Visually the stainless standoffs are more white and bright metal, the titanium standoffs should appear more grey and less bright.
Click to expand...

I guess i assumed that people would understand that im getting at density. You need to weigh them then figure out their volume to get the density. Once this is done you can determine if their ti/steel. d=m/v
 
I believe that if you want to "prove" an item is a specific element Brandog is right, the easiest scientific way is to determain total mass, and weight, then use the formula above to find its density. Then compare the density found with the elements listed scientific density and hope they match..... But seeing as we would expect these to both be from hinderer, and knowing they are the same mass etc... And steel is heavier then Titainium... And most steel is ferris (i.e. magnetic due to iron content. Note: some stainless is not) and all ti is not... I dunno I think everyone is right!

And... The dude with the bath tub was... Archimedes
 
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As a mechanical engineer I completely got what you were saying, it just seemed like nerdy overkill :p

The water idea would be difficult without really good instruments, if I needed the volume of something so simple I would just measure it with calipers and figure it out or model it and have ProE figure it out. The main thing is weighing them, and yes assuming they are all genuine and most everyone has a set of ss ones around a simple weighing would generally suffice.

brandog said:
I guess i assumed that people would understand that im getting at density. You need to weigh them then figure out their volume to get the density. Once this is done you can determine if their ti/steel. d=m/v
Click to expand...
 
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