Measuring distance to lands and chamber distance, obtaining the actual numbers?

[RickyRodney]

I watched the videos posted by Sheldon N about finds the length to your lands, but seating a bullet and putting it deeper and deeper by the .001 until the bolt handle closes freely. Or measuring brass by sizing it down and until you reach the same result. Then how to you measure your results so they can be repeatable. Do you need micrometer dies? It sounds like the Hornady gauges that go on calipers are not accurate? So if they aren't accurate how to you know how to set up your dies next time, if you can establish the proper length of the brass but van't use the caliper? I have a heap of federal brass I want to begin to reload. How should I proceed. I'm shooting .308 out of a DTA SRS.

 

[JoeBUtah]

I'm not familiar with the video you mention, but I can tell you what works for me: I use the Hornady tool with the threaded case to check where my lands are. Typically I take 10 measurements, add them up and find the average. Then its a simple subtraction problem to establish the amount of jump. With that as my target, I set up my die: I've recently purchased a micrometer seating die and it's pretty cool to work with. I set the die really high and then work my way down to the target ogive length from the measurement obtained, measuring as I go with the Hornady bullet comparator on my calipers. Once I hit the target I'm good to go; I check every 8 to 10 rounds just to be sure. I then record the setting shown on the micrometer die for next time. As mentioned, this process works for me; your mileage may vary...

 

[RickyRodney]

I'm not shooting benchrest here. Your approach sounds effective and practical. Thanks for the input.

 

[OzTRG]

What joe said - that’s the same process that I use. IMHO if you use the anvil that is purchased separately from the gauges it improves the repeatability of measuring the seating depth

 

[trob_205]

 

[PAYDIRT]

Another vote for the Hornady tool.

 

[RickyRodney]

Trob, I don't know how to remove the ejector out of my DTA bolt? I saw this video and was excited. Also in video how does the guy as he says "continues to seat the bullet," how does he know where he is with the seating? Off the micrometer seating indicator? I didn't think the horned comparator was accurate?

 

[trob_205]

Not sure on how to removed your ejector. Yea he is using his die seating indicator guage it. I cannot comment on the Hornady tool other than if you want an exact measurement, I don’t know how you are going to tell how much pressure causes the bullet to kiss the lands and if that’s even repeatable. It just depends on how exact you want to take the measurement. I got lost on threads from this guy on accurateshooter.com and he even claims that the sharpie method still isn’t perfect and you can still be touching a thou or two and not get the sharpie mark to be removed. I’m not sure I care that much always lol. The bullet shoots where the bullet wants to shoot no matter where that measure happens to be. But if this method is easily achieved then why not. I’d look into how easily you can removed whatever parts necessary.

 

[Rerun7]

I used the method shown in the video and it worked great. I just measured to the ogive of the bullet and used that to set up my die.

It consistently shoots .5moa so that method seems to work pretty well. And I use the Hornady comparator so if it’s not accurate then I haven’t noticed any effect down range.

 

[Sheldon N]

Hornady comparator insert on calipers to measure ogive may not be "accurate" in the sense that it's not an absolute measurement or comparable with another person's tool, but it's a very repeatable number that you can use for your own reference. If you load ammo to 1.925 to ogive, then do it again a month from now, they will both be the same.

The Hornady comparator modified case where you push a bullet in with the rod by feel then tighten the set screw is less precise. I've found that there's about a 15-30 thou window where the bullet starts to encounter the lands and you can keep pushing until eventually it stops completely. The only way to get a really repeatable number with this method is to jam the bullet all the way hard into the lands. Otherwise your number depends on how far or how hard you pushed the bullet from where it first touched the lands.

The method in the video is more precise in that it gives you an exact point where the lands first touch the bullet. The bench rest guys use this because they really closely watch throat erosion as the barrel wears and the lands move. They might try to keep the bullet seated at exactly 10 thou off "touch" or 10 thou "into" the lands. I'm personally not that picky and I'm not shooting benchrest. I just use this method when I don't have a custom modified case.

Bigger thing to remember is that there's nothing magic about where the lands are, as long as you're not jamming and causing overpressure. It's just a reference point and the number that really matters is what base to ogive measurement shoots the best in your gun, and being able to repeat that at the loading bench.

 

[Danrobberg]

Would this method work with a bighorn action? The floating bolt head I would think would give you problems.

 

[Sheldon N]

Would this method work with a bighorn action? The floating bolt head I would think would give you problems.

No problems with the floating bolt head at all. I've got a pair of TL3's and do this all the time for both brass sizing and finding lands. I actually think the TL3 is the best action for this because you can pull the firing pin in 1 second and there's no ejector plunger in the way either. Just clip the brass under the extractor and you're ready to rock.