Normal micrometers only measure outside diameter, not inside like calipers can. Inside micrometers are for large holes (>1")

To measure a small hole, you'll need a small hole gauge, which you expand until it fits the hole, and then measure it with the micrometer.

https://www.amazon.com/Starrett-829B.../dp/B0006J4Q96
https://i.imgur.com/7WiNSoC.jpg

Thanks much! I figured there was a trick behind it.

Sometimes you can check the hole size with a drill bit.

Or a Roll pin punch. I have one in the gas port now keeping things aligned, if not totally fastened, while I order more pins.

I've done that, and I have a 115 piece drill bit set. But if it's slightly loose the next size up won't fit, and if it's slightly too tight then then the next size down will be way too loose.

Unless it fits perfectly, it just gets you a ballpark.

I had problems replacing a firing pin on a revolver. The firing pin shaft was 1/4" exactly, but the hole was too tight for it to go in and I couldn't figure out what was going on. The drill bits didn't help and I had to take it to a gunsmith and let him deal with it. Turns out the hole was peened ever so slightly making it just barely smaller than the firing pin shaft. I mean it was sooooooo close but the firing pin just would not go in.

Update: I'm going to have to do some re-thinking. I may have to change both the hand guard and/or the gas block. Things are just not fitting properly.


The HG itself is having trouble fitting into the delta ring. I did not have this issue before when I used the Colt LE6920 OEM1. It fit perfectly. Furthermore, I think it's too long, even for the 16.1 " barrel. I'm trying to fit it on and it just isn't fitting into place. We'll see. I took the roll pin from the other gas block that didn't have the set screws and tried it. While it does fit through the block, it doesn't line up with the tube holes.


Earlier, C aleb said (in re: HG and Gas block):



I am wondering now if we could in fact, use a different low profile gas block that could fit underneath the HG front and would allow the HG to seat properly. I'd still have to worry about it fitting on the delta ring but I'll work on that. If it won't, then I may need your guidance on selecting a "free floating" HG because this MOE HG is just not working properly for this build. I'll still stick with it but at some point I'm going ot have to consider some other options.


Anyway, my spare roll pins should arrive in a week or so.

Building Confidence
 

Silly question but, is the HG an actual OEM Magpul and not a copy made for airsoft? The copies are really close to the look but the tolerances and dimensions are sometime off a little.


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Well, put it this way... it comes in a regular MAGPUL MOE box with all the appropriate markings, etc. I believe it's an actual OEM. There are no Airsoft markings anywhere or any other indications therein.


From what I can see/tell, the barrel nut may be a bit larger in diameter for the HG around which to fit. Do std. Milspec barrel nuts come in different sizes. Are some of them "Proprietary" in size? I"ll call Magpul tomorrow and get an answer to that. I might have to change out the barrel nut and delta ring. That's at one end. Then I have to worry about the other end near the gas block. The triangular HG cap does fit. But I don't know if I can get it snug with the back end. We'll see.



Let me see what Magpul has to say about the barrel nut and then we'll plan the next moves.

Post some pics of your problems.

I will. First, let me try to work with Magpul. Then we'll figure it out.