Idaho_Elk_Huntr
Beginner
- Feb 5, 2009
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Can the RCBS Precision Mic be used to determine bullet seating depth? I get so many different readings with my OAL length gauge I dont trust it.
RCBS Precision Mic?
- Thread starter Idaho_Elk_Huntr
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rick smith
Handloader
- Apr 6, 2005
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They can be used for that but they don't work well as you found out. Plus the bullet in the kit is not the one you will be loading. The Hornady comparator and modified case work much better.Rick.
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Idaho_Elk_Huntr
Beginner
- Feb 5, 2009
- 131
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Its the Hornady gauge I dont like. Seems like I get a different reading everytime I try it.
DrMike
Ballistician
- Nov 8, 2006
- 37,186
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The Lock-n-Load gauge reads to the olgive, which varies with each bullet in the average box. The ideal way to obtain a reading is to take the mean of several bullets (theoretically, at least ten). The variation shouldn't be more than a couple of thousandths either side of the mean.
The Hornady can give different readings by a few thousanths. Seems to me it depends upon how you push the bullet to the lands with the gray rod. I have the best results by leaving the bullet back in the case ~1/2"
setting the modified case against the chamber shoulder snugly and then pushing it to the lands with a light consistant continuous movement
The bullet will imbed somewhat into the lands a different amount depending upon the amount of force you use. I just use the Hornady as a tool to hold the bullet on the lands while I use another tool to find the OAL. It is the R-P tool shown here with the Hornady
It is a rod with with a brass tip (removable for smaller calibers)
and 2 locking collets
You insert the rod down to the bolt face (make sure it is cocked and the firing pin retracted) and lock the rear collet
remove the bolt and use the Hornady tool to hold the bullet against the lands, insert the rod to the bullet tip and lock the front collet
and measure between the collets
That is your OAL with that particular bullet. Then I set my seater according to the measurement on that bullet and use a comparator to settle the seater to that length on subsequent bullet seatings.
The Hornady is a great tool but you have to allow for the headspace on the modified case or you will be off by that amount. The R-P is always dead-on and foolproof (which helps me out a lot).
setting the modified case against the chamber shoulder snugly and then pushing it to the lands with a light consistant continuous movement
The bullet will imbed somewhat into the lands a different amount depending upon the amount of force you use. I just use the Hornady as a tool to hold the bullet on the lands while I use another tool to find the OAL. It is the R-P tool shown here with the Hornady
It is a rod with with a brass tip (removable for smaller calibers)
and 2 locking collets
You insert the rod down to the bolt face (make sure it is cocked and the firing pin retracted) and lock the rear collet
remove the bolt and use the Hornady tool to hold the bullet against the lands, insert the rod to the bullet tip and lock the front collet
and measure between the collets
That is your OAL with that particular bullet. Then I set my seater according to the measurement on that bullet and use a comparator to settle the seater to that length on subsequent bullet seatings.
The Hornady is a great tool but you have to allow for the headspace on the modified case or you will be off by that amount. The R-P is always dead-on and foolproof (which helps me out a lot).
rick smith
Handloader
- Apr 6, 2005
- 1,249
- 0
Woods, you are depending on the bullet tip to measure the same, there is more variance in tip length than ogive length. Are the collets from Sinclair? Look like the same ones that they sell.
Idaho, using any new tool requires a learing curve and different folks will have different methods. I make my own modified cases from rounds fired in my rifles. I don't size any part of the case so the bullet will drop out when I aim the case down. When I insert the case into the chamber I aim the rifle down, bullet falls through the neck stopped by the lands. Then let the rod drop to the base of the bullet, lock it in place, remove the case/bullet and measure with a comparator to the ogive. Another way if you happen to have a neck tight modified case, move the rod to the back of the modified case, insert the bullet into the case just enough to hold it, slide that into the chamber letting the lands push the bullet into the case, drop the rod to the base of the bullet, secure and remove for measurement. I don't use the rod to push the bullet into the lands. With just finger pressure you can easily set the bullet 20 thou into the lands.
Now I make a dummy round, try it for function and check for land contact on the bullet.
If you will measure ten or so bullets with your comparator and measure their OAL I think you will find why you may get different readings.Rick.
Idaho, using any new tool requires a learing curve and different folks will have different methods. I make my own modified cases from rounds fired in my rifles. I don't size any part of the case so the bullet will drop out when I aim the case down. When I insert the case into the chamber I aim the rifle down, bullet falls through the neck stopped by the lands. Then let the rod drop to the base of the bullet, lock it in place, remove the case/bullet and measure with a comparator to the ogive. Another way if you happen to have a neck tight modified case, move the rod to the back of the modified case, insert the bullet into the case just enough to hold it, slide that into the chamber letting the lands push the bullet into the case, drop the rod to the base of the bullet, secure and remove for measurement. I don't use the rod to push the bullet into the lands. With just finger pressure you can easily set the bullet 20 thou into the lands.
Now I make a dummy round, try it for function and check for land contact on the bullet.
If you will measure ten or so bullets with your comparator and measure their OAL I think you will find why you may get different readings.Rick.
rick smith":3hcdp1se said:
No, from my post above
I keep that bullet separate and set the seater with a comparator on that one bullet. All the other bullets will be gauged with a comparator that measures to the ogive to match the comparator reading on that one bullet. That takes the bullet tip conformity out of it. Now there can be some variance with the comparator since the hole in it is a few thousandths smaller than caliber diameter and there could be some variation in the linear dimension between where the comparator hits and where the ogive reaches full diameter, but you are reducing the variance by several fold.
Also, the important thing to me is that when we talk about "seating to the lands", that means to the point where the bullet is stopped prior to combustion reaching sufficient pressure to engrave the bullet into the lands. Sometimes there is a very minor constriction that can be bypassed with a minimal amount of finger pressure, such as 2 or 3 pounds worth (trigger pull weight for example).
But it is all relative. For example if I got best results seating .030" off and I was actually .035" off per another method of measurement, it wouldn't matter cause I set the seater to match previous results.
No, the collets were not from Sinclair. They were included in the original purchase of the rod. The Sinclair works from the action end of the barrel and the one I bought
sits in a drawer because it does not work on many of my guns and the little knurl knobs on their collets wear out and are hard to tighten.
One old trick was to split the case neck just so it would hold a bullet then chamber the round use a bullet Comparator to measure from ogive to base of case. I have a set of oversized Expanders for different calibers and I run to into the neck lube inside then start to seat bullet just chamber and that give me ogive to base of case. I also write that measurement down give me an idea as to throat wear.
When I measure a bullet I use a comparator and measure from base of bullet to ogive normally they run + - .002" in the bullets I hunt deer/elk with. I use Wilson or Neil Jones seaters last year I use a 180gr Partition in my 30-06 case base to ogive measure 3.751" to 3.749" that was measure on 40rds that I loaded. In the 280AI with 150gr TSX case base to ogive runs 2.685" to 2.687" measure 60rd.
When I measure a bullet I use a comparator and measure from base of bullet to ogive normally they run + - .002" in the bullets I hunt deer/elk with. I use Wilson or Neil Jones seaters last year I use a 180gr Partition in my 30-06 case base to ogive measure 3.751" to 3.749" that was measure on 40rds that I loaded. In the 280AI with 150gr TSX case base to ogive runs 2.685" to 2.687" measure 60rd.
