RCBS Precision Mic Gauge

[SquirrelNuts]

I picked up a RCBS Precision Mic Gauge. I fully understand the headspace "half" of the tool, but I do not fully understand the seating depth "half" of the tool.

According to the instructions, you (1) set the freebore tool to a specified length (done). Then you (2) chamber the freebore tool (done). Then you (3) measure the freebore tool and record the new length (done). How does that then translate to a seating depth? The best I can figure is that you make a dummy round and then measure it in the gauge and make adjustments to your seater die until you get the desired depth - something like whatever your measurement is in step 3 minus 0.010" as measured in the gauge. Is that correct? You basically keep adjusting your seater die, seat your dummy round, and then put it in the gauge?

The directions are not very clear on the last part.

Thanks!

 

[Doug b]

SquirrelNuts never used one I like the stoney point set up but I found this http://www.centerfirecentral.com/productreviews/precisionmic.htm Maybe it will help.

 

[emb]

It's been a while since I used any of mine. I prefer the stoney point. But here goes.

You chamber the "freebore tool" or whatever it is called and carefully close the bolt. This is tricky on some controlled feed actions.

Take it out and use the mic gauge to measure the COAL of the tool. Be careful not to collapse the freebore tool. Note the COAL of the freebore tool. Assuming that the ogive portion of the tool matches the ogive on the bullet you plan to load, seating a bullet to this COAL will seat the bullet on the rifle lands.

If you want to seat your bullet 5, 10, 20 or whatevever 1000s off of the lands, just keep seating the bullet deeper until you get to the desired COAL.

Good luck.

 

[SquirrelNuts]

emb,

That is what confuses me. The reading from the mic gauge does not correspond to anything other than a reference point on the gauge itself from what I can tell. For example, if I read 0.176 (no units attached to this number), how does that correspond to COAL? I know that it does not mean 3.176" for sure. I load most of my .30-06 ammo to 3.250" and that does not touch the lands.

There is also a short discussion in the instructions in that the COAL length for different bullets can vary so long as the ogive is at the proper place (this makes sense). Does the mic gauge simulate a rifle throat and start of the lands in the barrel such that even though the freebore tool does not really have a realistic bullet design, but at least you will find the sweet spot to compare to?

 

[SquirrelNuts]

Doug b,

Thanks. It looks like I do insert a dummy round in to the mic gauge and keep adjusting my seater plug in the seater die. The RCBS instructions and that tutorial never explicitly tell you to do that, it is just implied. I hate making assumptions on things.

 

[Borg]

You should get an ogive checker from Sinclair, that fits on your calipers.
That way you take the reading off the freebore gage, and use that reading to seat ALL bullets.
Ken S

 

[dirtman]

squirrel,

I really like my RCBS Precision Mic for doing head space for sizing brass its really great for that.. but for finding the lands i really like my stoney point... its very repeatable... easy to use....

 

[SquirrelNuts]

dirtman,

I seem to be finding out that half of the RCBS mic gauge is good and the other half....uhhhhhh. I will check out the stoney point.

 

[USSR]

I seem to be finding out that half of the RCBS mic gauge is good and the other half....uhhhhhh. I will check out the stoney point.

Good move. The Stoney Point O.A.L. tool is now made by Hornady.

Don

 

[emb]

Squirrel. I just use the mic gauge to insure consistency. I pay no attention to the measurements on the tool except to size the round to the same place on the tool.

The tool is great to size the brass etc. I initially started with mic dies for all calibers that I shoot. But I found that the stoney point was faster and cheaper to use in the long run. Since you size the round using the bullet you intend to load, it's a lot more accurate in trying to size off the lands.

 

[ranger335v]

"You basically keep adjusting your seater die, seat your dummy round, and then put it in the gauge?"

Well...not real sure what you're saying. If you mean to first seat the "dummy round" or "freebore tool", you do that in the rifle, not the seater.

The Mic has to have something to measure and the dummy round is its standard for later comparision as you ajust your seater to match the dummy.

I slightly prefer to use my Mics over the Stoney Point but that's a personal thing, no reflection on the superiority of either tool IF used correctly. But I ignore that silly "freebore" tool for finding the lands as not being worth the hassle of using it.

 

[Bullet]

I picked up a RCBS Precision Mic Gauge. I fully understand the headspace "half" of the tool, but I do not fully understand the seating depth "half" of the tool.

I like the mic to measure cases but use a magic marker to find the lands.

 

[SquirrelNuts]

I think I am going to use the my Lee Collet Die to neck size a cartridge with a little neck tension and insert the bullet and chanber it and measure OAL from that, and try the stoney point gauge.

 

[Bullet]

When trying to determine the length to the lands you can use the mic part of the precision mic as a comparator. Just measure your own cartridge using your own bullets. The mic will take a measurement from somewhere on the ogive and you can us this measurement to set up your seating die. You don’t measure the cartridge OAL to determine the distance to the lands because the bullet tips will vary.
I use the Sinclair comparator but the mic will work too.

http://www.sinclairintl.com/product/5582/Bullet-Comparators

 

[SquirrelNuts]

Bullet,

I figured it could be used as a comparator, but the instructions are vague.