RCBS precision MIC

[barthowes]

Question???
I browse other reloading forums regularly. One thread I saw was about measuring from a bullet ogive's to find the best seating depth. their prefered method was with a caliper and scribing a line in the ogive..ect...I recomended the PREC MIC and was shot down. HE said that if I changed bullets the data wasn't comparable but their way was. Isn't the whole point of MIC is to measure ogive that will contact lands first and finding precisly the distance off lands.

HERE IS THE ORIGINAL THREAD
Rocky Raab
You need nothing more than a steel caliper - and this article: http://www.reloadingroom.com/index_files/Off Lands.htm

HERE IS MY POST & HIS REPLY

Maybe I'm miss understanding you guys, but it sounds like the RCBS Precision MIC is exactly what you want. It come with a "collet" to the right size as your cartridge and is micrometer graduations for measuring. I use this in conjuction with the RCBS competition seater die (also Micrometer graduations) to perfectly seat bullet X amount off my lands. all Measured from the ogive

Rocky Raab

The RCBS Precision Mic is fine, but it only comes with one given bullet shape (ogive). You can set an identical bullet perfectly, but none other.

The thing I have against all such methods and devices is simple: your groups can be mediocre, but by jiminy, you can brag about being exactly 0.023473" off the lands.

 

[rick smith]

While I like RCBS products their measuring device with the plastic bullet leaves a lot to be desired. I have tried it and was disappointed with the concept. Their plastic bullet doesn't match the ogive of many bullets and finding the distance to the lands must be done with the bullet you are using not a plastic substitute. If you find the exact distance to the lands with a NBT, you can't substitute a Hornady or Sierra to the distance and be correct. Also Rocky's method of marking the bullet and then measuring the hypotneuse of a right triangle to a curved surface would be difficult at best. I have responded to his method on one of the sites and requested he post a picture which he did. That is where I saw his measuring to a curved surface. Bottom line is that I start a known distance off the lands and if I remember he starts somewhere else. I use the Stoney Point, Hornady, method with a modified case which I make from a case fired in the rifle. Once I find the length I make a dummy round and verify the length. There are several methods which work for many loaders, use the one which satisfies your loading and is repeatable.Rick.

 

[sithlord6512]

I have both the RCBS prescison mic kit and the Hornady OAL guage. I personally preferr the Hornady product for determining seating depth.

However, I have often wondered if the common criticism of the RCBS precision mike is valid (i.e., different bullets have different ogive lengths). If the ogive is defined as where the bearing surface ends and the curved part of the bullet begins, would the distance from the OGIVE to the CASE HEAD really vary depeding on bulet shape? I can see why the distance from the OGIVE to the MEPLAT WOULD vary based on different bullet shapes, but I am finding it hard to see why distance between the head of the case to the ogive would vary (the distance that seems to be the most important when considering bullet-seating depth). A Tanget ogive might contact the lands earlier than a Secant ogive (or vise versa) in relation to their curved surfaces (i.e., distances between the ogive and meplat for secant ogive versus tangent ogives would be different), but the distance between the case head and ogive would be indential regardless of bullet shape, would it not? I don't know the answer - I would be certainly be interested in learning.

 

[sithlord6512]

Measured the various Barnes Bullets I do have - answered my own question. Bullet shapes do make a difference - sometimes a big difference in distance from case head to ogive

Examples of various 180 and 165 grain Barnes Bullets (OAL to ogive at a distance of .050" off the lands

180 Barnes MRX = 2.259, TTSX=2.260, TSX=2.251 to Ogive and .050 off lands, 165 TSX = 2.254.

All measurments made with Hornady OAL guage and all are averages obtained from samples sizes of 10.

 

[RiverRider]

If the collar of the Precision Mic was machined to be exactly the same dimensions as the throat and leade of a particular rifle, then the results obtained from it might be useful as an absolute measurement. But it is not so. At best, the Precision Mic can be used for relative measurements in a limited way for setting up seating depth and watching headspace. I agree with Rick on the point that the simulated cartridge that comes with the tool is totally useless. Gadgets are not necessary at all for setting up seating depth.

 

[Oldtrader3]

For that matter, you could lower whatever bullet (with it's ogive) which you want to measure into the lead of the barrel and use a depth micrometer, a dial indicator mounted through a tooling bar, or even a caliper to measure the distance to the base of the bullet from the face of the action ring. A dial indicator would be ideal.

Then just compare measurements and it will tell you the difference between seating depths of various bullets and therefore, where to seat the a fixed distance from the lands. Plot it out and think about it. Then save yourself the money for a gage.

You may need to put Dykem on one bullet loosely seated in a case to establish an overall dimension but the rest is easy. Right BigBoreDan?