Precision Rifle Load Development/ Part II: Bullet Choices & Initial Seating Depth 

Thanks brother I knew someone would know!

copper creek cartridge co. makes these from your fired brass

I found a local machinist to do the job. Bought the tap on Amazon. He charged me $20. Hornady will do it for you also with a fired case....

Gregory Stramat Thanks for bringing this up. I did a follow-up in the next video pointing that out. I have noticed, though, that some inserts will give consistent CBTO measurements across several brands/weights of bullets. I suppose if the diameter of the insert matches the bore/lands at the point of bullet contact, it should match perfectly on all bullets. If not, the shape of the ogive determines the variation. Anyway, it’s easier to just use the bullet you want to shoot when measuring. Thanks again for the comment.

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I used it long ago in a 300 Wthby. It shot good, and lasted the life of the barrel ( nine cycles), with minimal sizing and shoulder bump.

762gunr The next episode will cover primers, but my experience is like yours. I’ll be starting with the same primer I’ve been using in everything for the last few years. I might do a comparison of different primers once I settle on a load.

No. That's dependant on the size of your chamber, so without having previously measured the chamber, you can't make a custom gauge for measuring the chamber: a bit of a catch 22. I'd be confident using a hand drill and a hand tap since you are not measuring the tooling, only the case to the bullet (the tool just keeps the bullet from moving so it doesn't matter how cockeyed you get, it'll still do that). Also, Hornady has a custom service: you can mail in a fire formed case and they will cut the threads for you, I read it's $15 (probably about the price of the specialised tools if you intend this to be a one time deal...)

I have a 2700-B in hand for a review right now.

Panhandle Precision right on can't wait

I usually keep the bullet with the modified case, if only because it gets dinged up and scratched from checking measurements. I used to check CBTO with every style/brand bullet I might use in the barrel. I don't do that anymore. I found that in the long run, the consistency of my technique was more important when it comes to getting a consistent reading. I do note which bullet I used when I record the initial throat measurement.

Yes it will. Each manufacturer has different standards. Each bullet from each and every manufacturer will vary in weight per its class by around point (.)9 to 1.2 grains, but all need to match SAMI Specs.

I have found the same to be true. When using the Hornady comparator on my AR Krieger "223 Match" marked barrel, I was stopping at the first "gentle" hump (sign of resistance) and finding the results were around .06" or so shorter than if I pushed through the first hump to the more solid resistance just behind it. At first my measurements were very inconsistent and I was confused. Later I discovered a chart at AR15barrels that showed that the reamer used to cut 223 Match barrels had .068" of Freebore between the end of the case mouth and the beginning of the lands (vs .025" of standard 223 chambers, .050-.056" for 5.56 NATO chambers). I used Cerrosafe to cast my chamber, and discovered that was exactly what I had. It was the bullet entering the tight freebore area that I was sensing through the comparator at first, but pushing through resulted in finally touching the lands, and my measurements suddenly became more consistent, usually within 3-4 thousandths or so. Another clue that doing this was the correct way to go about it was that there were no significant marks, scratches, dings, etc on the ogive of the bullet after being pushed all the way through, and the bullets (68gr Hornady HPBT or 69gr SMK's) weren't even being pushed in hard enough to get them stuck in the lands, suggesting I was on to something. On my Rem 700 5R, the comparator showed I have a .160" jump to overcome between max spec COAL and the lands, measured using a 168gr SMK. Apparently this is common with Remington rifles. Fortunately, 168 SMK's are pretty jump-tolerant. The issue with overly long jumps is one of the reasons people eventually go with a custom action and build around it, to avoid that problem (among many other issues with Remington factory rifles). At the very least one might want to have their barrel set back to "fix" the issue.

When you fire. The firing pin and or ejector push the shoulder up against the front of the chamber. So if you dont use brass exactly as you load it. Your measurements to the lands will be off

There are too many variables involved to determine that. Pressure is affected more by overall chamber size (including the throat/bullet jump) than the space inside the case from different seating depths.

Doug Anderson That’s the one. Thanks!

I have similar problem with my rem700 308win. Mag length is like 2.80in but bullet jam measured 2.92in. I come to some possible choices; load to mag length, it should still shoot well. Dont use the mag and load to fit the chamber. Have the barrel rechambered. Change from short action to long action receiver.

@@r0nb0h0ju pretty much what I have gleaned from my research. A factory rifle is a compromise, but a good place to start until you know what you really need/want.

It doesn't hurt to try! Maybe a drill press or even hand drilling. It'll work as long as the case seats on the OAL gauge straight enough to be sure the caliper's blade is measuring off the case head. I sure wouldn't buy a lathe just to do this kind of work! Hornady will tap your case for a fee. Scroll to the bottom of this page: www.hornady.com/reloading/precision-measuring/precision-tools-and-gauges/oal-gauges-modified-cases#!/

@@PanhandlePrecision Thanks for this info. I was already tripping out since I don't have a lathe. You're ahead of the game sir!

It mostly adds the convenience of an accurate reference for seating depth. If you use the same case throughout the whole process, though, and base everything you do on that case, you should get the same results.

Sounds good, keeping bullet and case in die box should work.Thanks

I work in .010" increments. I would start an ELD at .020" off the lands.

Mr NiceKnife You would get really close by doing that. Once you measure the max CBTO for a baseline number, it becomes a relative number to adjust seating depth anyway, so as long as you use the same tools and techniques, it doesn’t matter.

Mr NiceKnife you beat me to it with this question, I was thinking the same. We would be using a once fired case and using the Hornady headspace comparator bit to measure the case length from base of cartridge to the neck datum line wouldn't we? We wouldn't be using the smaller ogive type comparator like the one Sam is showing in this video.

Not everyone has a lathe at their disposal to make a custom modified case. Measuring a fired/sized & shoulder bumped case, comparing it to the Hornady modified case with a headspace gauge, and adding/subtracting the difference is the best most of us can do.

Vaughn Precision They’re all over the place around here. That match is back on, but with a different format/sponsor. Check Sportsman’s Challenge for details. If you’re on Facebook, join Northwest Precision Rifle Shooters to get info on local matches.

Vaughn Precision I have heard about a range up near Colville wa , I'm still researching what or how many shoots they have a year.

Kirk Goddard I’ve always heard it the other way around. Lapua is pretty thick, so if the chamber is cut for thinner brass, you could have an issue with bullet release due to neck dimensions. My reamer cuts the neck for a fired case neck O.D. of .298” That dimension is also what the chambers had in other 260s I’ve owned. That works for Lapua, Alpha, and Remington at least. There aren’t any other chamber dimensions that should matter. .298 is .005” more than loaded neck O.D. of Lapua brass.

odd766 I wouldn’t touch it; it already has a light chamfer. It does take some practice, but your readings should be repeatable.