Mitutoyo micrometers with barrel installed in a vise, the micrometers are forsure calibrated I have a few class zz minus gauges with a tolerance of -0.00020 and it is spot on all of them.
My worries are getting receivers with a .1275-.128 index slot, then the slop would be out of tolerance according to the TDP.
Your tolerance on the measuring tool is -.0002 and your measurement is under by 0.0002 also?
Not colt, I have 3 other barrels from the same manufacturer that measure .12505-.12525 this one is 1.2480 I use the colt TDP for a wide variety part checking.
No I was
no I was referencing that I have a lot of class zz pin gauges that the micrometers read correctly say I want to measure one of my .072 class zz minus gauges my micrometers read .07180 witch is within the .0002 tolerance that the pin gauge has.
Yes correct temperature at room temp, I’m not touching anything that Im measuring with my hands that could potentially expand it, also my Mitutoyo micrometers read my .072 class zz minus pin . At 07180 (random sample gauge I came up with to type this up) and all of my other zz pin gauges fall within the -.0002 spec this is how I know my measuring is accurate.
Why
Absolutely I use minus gauges to check the diameter of most things and use both plus and minus if I want to be as accurate as possible. it’s under sized there is a specific tolerance, and that tolerance is .1255 +0.0 / -.0005 if it was within That minus tolerance even at the bare minimum I wouldn’t care. The reason I do care it is .0002 undersized Can create issues if I get a .1275 through .128 upper receiver index notch, the slop will be over TDP specifications.
May have missed it, but have you considered you’re overthinking this?
Have you considered that it would be easy to buy another index pin? Have you considered that if the pin were “to spec” it might not work with this upper receiver?
Bingo.
If you're in machinist school why don't you make one yourself?
Haven’t gotten to our own projects yet
Fine. Let me teach you something. I was messing with you saying you should make your own. That is the hard and expensive way to go about it. Learn this lesson. Why make it yourself when somebody else can do it much cheaper and better? McMaster Carr is your friend.Haven’t gotten to our own projects yet
www.mcmaster.com www.mcmaster.com Well the mk16 rail specs out with my 1913 picitiany gauge and my Geissele trigger specs out with .155 minus gauges, spring tension checks out, no rust , trigger pull gauge reads constantly great company and customer service from my experience . Don’t have any other parts but that from them. Not sure why you’re so mad but you can go ahead and slap a bunch of out of spec parts together if that’s what you’re into.
Funny you should mention that. I’ve put together 4 ARs with zero “gunsmithing” courses or experience. One was with premium parts and the other three were whatever I could get on sale at various times. What mattered most to me was bolt interface to barrel and that things fit without slop and functioned correctly. Never measured anything to the thousandth or the ten thousandth. Each one shoots great, and by great I mean Moa or better. That includes the 7-1/2” pistol.
Can you let me know how I can filter out this thread for precision machinist only please ?
And you thought gas gun people are crude barbarians; look at the precision instrumentation they’re capable of!
Move it here https://www.practicalmachinist.com/forum/
lmao ok bro
if there’s a tolerance that allows.0005 of leeway, and what I’m measuring is over that actually you know what nvm, I’m rejecting it anyway becuse after further inspection it has pitting/ corrosion In the barrel even after soaking it in wipe out for 24 hours thread is dead by now.
Yep sorry mate I appreciate everyone’s help but didn’t know there was rust in it alreadyWell, who could have predicted that outcome?
Besides everybody that wasted their time trying to help.
