Measuring chamber

[MuleyFever]

So now I am watching different videos on measuring the chamber to get the seating depth. From what I gather measuring for the ogive is where it's at and not over all length.

I did order the hornady gage and a modified case but after watching one of Sam's videos it appears this won't give me the best data. I should be using a case I'll be loading as the measurement will probably be different from the hornady case.

Any thoughts on this? I have seen videos where they use a fired case and just chamber it to push the bullet to the lands and measure it.

 

[Wrench]

Pushing it to the lands is near impossible to get repeatable results....as it is, the mod case should be used several times and measured each time. The mod case is the right tool as it'll measure from the ogive to the case head and it really does not matter where the shoulder is as the point of measurement is the bolt face, which is not going to change.

It takes a gentle touch to get the bullet to just kiss.....you'll see.

 

[Wrench]

If you're running an Ackley or custom, things are different, but the amount of variations in chambers and cases from shoulder to case head are at best a couple thou and you'll be lucky if you can hit within a couple thou with the tool.....especially if it has any throat erosion.

 

[muddydogs]

Listen to Wrench, he's spot one.

Your measuring from bottom of case to bullet ojive so the case shoulder/head space really has no bearing on the measurement. Even if the head space is way shorter on the mod case it's not going to matter since your going for length of bullet and case, once you start loading the bullet into a correctly sized case your just going to have more bullet in the longer case then was in the mod case.

 

[doc88]

Videos | wheeleraccuracy

www.wheeleraccuracy.com

Couple of good videos here if you haven't seen them. Do the brass sizing first before finding length to lands.
The Hornady modified cases and measuring with the comparators are a "good enough" rough measurement for most of my measuring except when I don't have a modified case for a certain cartridge.

 

[rayporter]

dont get hung up on the exact measurement or exactly where the lands start. even if it is off or not repeatable means little--it is only a starting point. you are going to test from there. it wont matter if you start testing 3 thou different than some other measurement or 4 thou different from what i use. it is just a place to start testing your set up. and you dont know where you will end up.

 

[MuleyFever]

Great, thanks.

 

[Montana Slim]

Listen to Wrench, he's spot one.

Your measuring from bottom of case to bullet ojive so the case shoulder/head space really has no bearing on the measurement. Even if the head space is way shorter on the mod case it's not going to matter since your going for length of bullet and case, once you start loading the bullet into a correctly sized case your just going to have more bullet in the longer case then was in the mod case.

^^this.
COAL isn't that useful except making sure of magazine fit. You can send a fired case in to hornady to get a 'custom' case for you rifle to use with the comparator - I think it's like 15 bucks. But why? With the reasoning above, I don't see that it's necessary... Ogive to case bottom is the "length to lands" and that will change with each (style) bullet.

 

[muddydogs]

While knowing the OAL to the lands can be helpful your mag length will probably be the determining factor for oal anyway.

What I do is measure base of case to lands, make a dummy round just under this length, start at what ever jump to the lands that you want, then test mag fit.
If the round fits in the mag then I calculate how much bullet is in the case, I like to have a caliber of bullet in the case for good neck tension so for a 308 I like to have .308 or so of the bullet in the case. If I don't have a caliber in the case then I will seat the bullet deeper until I do and start my load testing there.
If the dummy round doesn't fit in the mag I keep seating the bullet into the case until it just does, if its not obvious that I have a caliber in the case then I will calculate it here also and adjust until I do and then start testing the load at this length.
One last thing I check is after I have loaded up enough test rounds to fit in the mag I will load the mag completely making sure the bottom round isn't contacting the mag still. I have a couple mags that are just a tad smaller at the bottom then the top which can mess things up.

 

[Muley Buck]

Videos | wheeleraccuracy

www.wheeleraccuracy.com

Couple of good videos here if you haven't seen them. Do the brass sizing first before finding length to lands.
The Hornady modified cases and measuring with the comparators are a "good enough" rough measurement for most of my measuring except when I don't have a modified case for a certain cartridge.

I do like his "finding your lands" video. Good way to do it, probably the best.

Another way that is also super cheap is the Frankford Arsenal kit used in this video. It works easy. I don't neccesarily agree on the suggested "hunting rounds measurement" but it's a good display of how it works. Also he fails to mention that the measurement taken is only good for that one particular bullet used. So you need to use that bullet first when starting the seating process. When you reach the desired seating depth with that bullet, stop and measure the base to ogive (BTO). Now that BTO number will and should be accurate for the rest of the bullets to be seated. Make sure you use good consistent strokes with your press and measure often.