I am attempting to measure the lands on a RRA 20" Varmint with the sharpie marker black bullet trick. I'm using a Hornady 68 grain BTHP Match bullet. I started at 2.420" COAL and it was setting in the lands quite a bit. I worked a second bullet down to 2.366" after I set one bullet to deep at 2.346" COAL and it was off the lands. I bumped the second bullet down to 2.360" COAL and it looks to be off the lands. So if I'm seeing it righ, with what I have this set up the lands are between 2.366" and 2.360" COAL. Does this sound right? Can I back up to 2.355" COAL and load here? Bullet contacted at 2.420", 2.390", 2.376", 2.366", and it looks like it is off at 2.360".

Not looking for mag length on this load. I'm too broke now to purchase any more gauges at this time. Thanks for any help.

That could very well be right. I believe that RRA uses a Wylde chamber which may have that much freebore. As far as if you can back up to 2.355, it seems you could if you don't mind single loading. I don't think anything much over 2.260 will fit the magazine. If you decide to proceed, I'd suggest starting at beginning loads and working up.

The marker method works fine as does the candle soot method. While some of the newer gadgets are more convenient, some of us old timers used the old methods for a long time with good results.

I used the split case method for along time until I bought the Hornady gage and you can make your own cases if you have a tap & die set

Panther308

Please elaborate on the tap and die method of making a gage.

Thanks
jonblack

You tap the primer pocket area, like Hornady/Stoney Point does, with their modified cases.  The split method uses a cutting wheel to make two slits in the neck in the form of a '+' .  This allows one to insert a bullet and still have the neck grip it, instead of denting in an edge found in the traditional 'dummy' method.

Chris

So if the idea of the method:

1.Push the modified case/bullet combo into the chamber
2. Allow the lands to set the bullet depth
3. Pull the whole thing out
4. Measure it
5. Set up your seating die a few thousandths deeper for a shorter COAL

Is there anything I am missing?

Thanks
jonblack

No, that is it.  Just make sure to use the bullet for the test that you are going to use for your production run.  Ogives vary from brand to brand, style to style.  For example, Widener's .308 168 gn OTM ogive is different from SMK .308 168 gn OTMs. After getting the "touch the land" case and bullet setup, just move the seater stem in an amount that you want to "jump-to-land." and lock it down.  

Will do. I think I'm starting at 23 grains of Varget for my mag length 68 grain HPBT. I'll drop down a bit if I'm going to sit this close to the lands. Also I did pick up the .22 Hornady bullet comparerater (sp?) to get a better measurement.

The problem I ran into with the split case method is if there is to much tension on the neck and you push hard you will actually push it into the lands  several thousands, I actually proved this by taking (2) identical .30 cal cases and after sizing one I split it to the shoulder and inserted a Nosler 168 CC and did 8-10 measurements and was very carful not to push very hard on the bolt then I took the 2nd one that had been sized slightly larger at the mouth with a oversized mandrel and then I drilled and tapped the primer pocket and threaded it onto my Hornady OAL gage and did another 8-10 measurements and found out that the first actually seated it into the lands .005"-.007'

Now don't get wrong I did the first method for along time until I figured out that there is a better way, how much better who knows but I wanted to eliminate all the variables and have a repeatable one of doing it and besides the gage looks cool in my reload box JK

Good point about jamming it into the lands.  That is the reason for the soot or sharpie.  You just tease the OAL until there is practically no bright marks or scratches to the soot or sharpie ink on the bullet.

This is what I did. I was having to point the gun strait down, and lower the sharpied dummy round into the chamber to not get any scratches, marks, dings on the black bullet. I think now that I have the Hornady bullet comparerater, I may retest the set up.