RCBS precision mic
- Thread starter BC_Guy
- Start date
+ .00495 ....I "think"... (not allowing for parallax of course) ...I have a couple of these that haven't been out of the box for a while and will double check as soon as I can get to the instructions ... there were a pretty good set of instructions in the "little green box" ..along with the bullet seater guide... what calibre btw..
if you like I can scan the directions and send a copy...might as well have them and be sure..
if you like I can scan the directions and send a copy...might as well have them and be sure..
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It's for .223rem. I've got the directions, it's just that after reading them about 10 times, I still can't believe the reading it's giving (way out of spec), so I'm assuming I'm reading it wrong.
It says each line on the body equals .050" and each line on the headspace nut equals .001". Minimum headspace equals zero on the body.
It's about 1/4 of the way from "0" to the notch numbered "1" on the body, and the "0" on the headspace nut is just past the body line.
.223 dimensions are given as 1.4636/1.4736.
To me, this looks about .0124" (1/4 of one line @.050" per line, minus .001"), which would mean... well bad things. It's a fairly new chamber to my knowledge, so that doesn't make sense.
It says each line on the body equals .050" and each line on the headspace nut equals .001". Minimum headspace equals zero on the body.
It's about 1/4 of the way from "0" to the notch numbered "1" on the body, and the "0" on the headspace nut is just past the body line.
.223 dimensions are given as 1.4636/1.4736.
To me, this looks about .0124" (1/4 of one line @.050" per line, minus .001"), which would mean... well bad things. It's a fairly new chamber to my knowledge, so that doesn't make sense.
You don't read the line on the body until you have passed 0 on the nut. The lines on the body are placeholders for the number of times you have passed 0.
In your picture, if you were a little further and just past the 0 to the first line, then you would read the first line on the body as .050 and add the line on the nut to get .051
In your picture, if you were a little further and just past the 0 to the first line, then you would read the first line on the body as .050 and add the line on the nut to get .051
I though so too, but if that were the case, wouldn't that give me a chamber size of around 1.5246", which is massively out of spec (zero being 1.4636", and the max chamber size being listed as 1.4736")? Would not any of your answers apart from the first one be a sign of danger?
Just pulled out my instructions and Stewie333 is correct from how I read them as well...+.0495 (I clearly was wrong by a decimal point..).
However zero (as you point out is 1.4636) adding .0495 results in 1.5131 I think ... not 1.5246...leaving you still over max by .0395 (assuming my math is right)...
I presume you mic'd this after firing but Before resizing...the expander ball can stretch the case back over max. Also you might want to check a new factory round to see how close to zero your mic. comes ..it will likely be a few thou over zero. If it is much more it is possible that the mic got twisted (apparently the spool is epoxied on to the body) . Also check to see that there is no crud in the base or neck of the mic. giving a longer reading...
the other question is what rifle are you firing the cartridge in?
And yes...if that ends up being the length of your chamber...it is excessive for factory ammo
and ps..thanks for getting me to pull out my mic's ... they were dry and needed a litle oil... best regards
However zero (as you point out is 1.4636) adding .0495 results in 1.5131 I think ... not 1.5246...leaving you still over max by .0395 (assuming my math is right)...
I presume you mic'd this after firing but Before resizing...the expander ball can stretch the case back over max. Also you might want to check a new factory round to see how close to zero your mic. comes ..it will likely be a few thou over zero. If it is much more it is possible that the mic got twisted (apparently the spool is epoxied on to the body) . Also check to see that there is no crud in the base or neck of the mic. giving a longer reading...
the other question is what rifle are you firing the cartridge in?
And yes...if that ends up being the length of your chamber...it is excessive for factory ammo
and ps..thanks for getting me to pull out my mic's ... they were dry and needed a litle oil... best regards
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I added Slash5's guess to arrive at 1.5246", but as you said, they're all over spec. This is once fired pre-resized brass, yes. The rifle is an ar.
I'm glad you suggested I try it out on a factory round. The factory round closes to either the exact same place or .001" less. Does this mean that zero is not zero, but at around .0495-6" on this mic? Thanks a lot for your troubles.
I'm glad you suggested I try it out on a factory round. The factory round closes to either the exact same place or .001" less. Does this mean that zero is not zero, but at around .0495-6" on this mic? Thanks a lot for your troubles.
The reading is -.0005" from minimum.
The gauge is not set very well from the factory. Unfortunately you can't reset it, it is bonded in place. If you resize your brass or use a new factory round it would read the same.
I would say your chamber on your AR is tight, zero head space.
The gauge is not set very well from the factory. Unfortunately you can't reset it, it is bonded in place. If you resize your brass or use a new factory round it would read the same.
I would say your chamber on your AR is tight, zero head space.
BC Guy... I am not sure I completely agree with 2 Katz...it may be that your case is almost bang on as he suggests...but the mic illustration you provide - even allowing for some parallax from the photo angle - shows that it is almost backed off to the first line on the body and that is 50 thou. (we seem to agree that in it is actually a hair under that or .0495)...so that is weird.
The fact that a new factory round shows the same (or pretty close) reading suggests that your rifle is "good to go" ... it is just that the mic is not telling you that.
I am suspicious of the Mic...in any event as comparative tool it is probably still ok and again...this would suggest your chamber is fine. BTW I am aware of some dimensional differences in 5.56 and .223 chambers/cartridges...but as far as I know.. their headspace measurements are the same....
I think I would poke a "Q" tip in the base and thimble units and see if there isn't any crud stuck there....then I would call RCBS ... they have great customer service...they may suggest sending the unit back or may explain we are all crazy and reading it incorrectly.....
best regards
btw...last night when I was screwing around (literally) with one of my mic's (a 7/08 Rem) ...it showed a new factory round was a few thou over zero... fwiw
The fact that a new factory round shows the same (or pretty close) reading suggests that your rifle is "good to go" ... it is just that the mic is not telling you that.
I am suspicious of the Mic...in any event as comparative tool it is probably still ok and again...this would suggest your chamber is fine. BTW I am aware of some dimensional differences in 5.56 and .223 chambers/cartridges...but as far as I know.. their headspace measurements are the same....
I think I would poke a "Q" tip in the base and thimble units and see if there isn't any crud stuck there....then I would call RCBS ... they have great customer service...they may suggest sending the unit back or may explain we are all crazy and reading it incorrectly.....
best regards
btw...last night when I was screwing around (literally) with one of my mic's (a 7/08 Rem) ...it showed a new factory round was a few thou over zero... fwiw
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A properly set mic should have the edge of the thimble right on the zero line. Do this test, try to zero it with no case. You will find that you can't, it will overshoot the zero line and be at the same distance but on the other side of the zero line.
Not to be rude Katz... but more curious - do you own one of these RCBS case mic's and does it behave as you point out (eg .. does it overshoot the zero line)....I understand your point regarding standard Mic's .. I have a Starret and several 10 thou Mitutoyo mics and you can "set" up the Starret to rezero when changing the anvil...but the on all of my RCBS units (I checked 4 this morning) the thimble "zero's" as it meets the line on the body. I am under the impression they are meant to do this in order to get an actual reading rather than just a comparative reading...
Or is your point that there is something wrong with this unit?? cause I think I agree with you
regards
Or is your point that there is something wrong with this unit?? cause I think I agree with you
regards
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Yes I do have those mic's for all of my rifle ammo. The 308 and .223 were fine just slightly past the zero line but the 30-06 was way out almost to the next division. It was showing plus .0450", sent it back and RCBS set me a better one.
Not so good of a picture, still trying to figure it out.
Not so good of a picture, still trying to figure it out.
Katz... that's very interesting. Perhaps BC-Guy might consider returning his unit for a replacement as you did. I am a little surprised by the varying QA here. Although I did once get a die from RCBS (for an 8x68s) that had a poor expander ball - it had a sharp ridge that actually shaved brass from the inside of the neck...but that has been pretty much all the issues I can remember with RCBS after quite a few years of collecting their stuff...anyway they seem pretty responsive when I have called them...I would be interested in hearing what RCBS have to say if it happens that they are called about this..
best regards..
and good luck BC-Guy - hope it all works out fine
best regards..
and good luck BC-Guy - hope it all works out fine
Definitely going to send it back for another one. In a way it was good news though, because it meant that my $50 dollar mic was messed up, rather than my couple thousand dollar ar. Thanks again for the replies.
Just got off the phone with them. The whole conversation lasted about 15 seconds. "Doesn't zero correctly? Just send it back, we'll send you a brand new one." That's that.
Just got off the phone with them. The whole conversation lasted about 15 seconds. "Doesn't zero correctly? Just send it back, we'll send you a brand new one." That's that.
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beretta boy
CGN Ultra frequent flyer
- Location
- Orillia, Ontario
RCBS Customer Service is exceptional in my experiance.
Not the first instance I've heard of that they were very
cooperative in resolving issues, and I'm sure, not the last.
Not the first instance I've heard of that they were very
cooperative in resolving issues, and I'm sure, not the last.
Haha. All I can do is laugh. What a hunk of junk. Precision mic.... off by .010"....... need I say more 2Katz. I can #### out more precision #### than that with the gibs loose. What I am trying to say it quality control????/Ground thread form or at least Major diameter.
mouse said:
Well, I have four of them and I would not call them junk, they do have a issue with the line not lining up but once you realize it and work around it, they are a excellent tool to measure headspace of the firearm, Setting up your reloading dies for perfect brass to chamber fit and lastly measuring overall length of loaded cartridge to the rifling.
Hardly what I would call a hunk of junk.......
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