Finding the lands

[straightshooter1]

You are completely correct. As long as you're not chasing a touch, jam or really short jump, then an accurate measurement is less critical. As I stated in my earlier post, I followed Eric Cortina's recommendation of starting 0.020" off the lands and working down in 0.003" increments. My nodes are 3, 6 or 9 thousandths deeper than 0.020" depending on the powder. (IMR 4350 vs StaBall 6.5 vs H4350)

It's not about the exact dimension off the lands, or the bullet jump dimension itself. It's about finding the seating depth (and COAL) gives you the tightest groups. With a caveat of being at least 0.020" off the lands -- though some people want to shrink that dimension slightly (ex. 0.015") Shooting multiple groups at different seating depths is what allows you to find the node.

I shoot a 5-shot group at each seating depth. At some point I'll probably make a few cartridges that would be 0.017" off the lands -- just in case my original measurement was off. As I type this I'm wondering if I should try some additional seating depths for smaller COALs such as 2.812", 2.809", 2.806" and 2.803". (Factory ammo is 2.800") I punch holes in paper every other weekend, so spending a little bit more time adjusting the seating depth for an evening is no big deal.

Once I get a good idea where the lands is, I'll typically start ~ .015" off, unless I'm looking for mag size cartridges. For the caliber's that I shoot, I also use .003" increments when looking for the right seating depth. But, I only shoot 3-shot groups, sometimes only two shots when the first two shots didn't do well and any subsequent shots aren't going to make it any better. I'll load up a bunch of cartridges at the longest seating depth and adjust the seating depths as the range as I shoot. Sometimes, I'll pull a shot and will need to shoot more than the planned three. Once I get an idea of width of the node, I'll then shoot some 5-shot groups with those seating depths for that node to verify what I saw (or what I think I saw) in my 3 shot groups.

 

[straightshooter1]

I know we discussed stuff in pm’s. But generally I like to start .020” off with any bullet I use. Usually I test a range of powder charges at .020” initially. Testing seating depth is my last step generally if I’m looking for top level of accuracy. Watching for pressures as I approach the lands and seeing what range jump the gun shoots best. Then maybe fine tune powder charge if needed

As you approach the lands, do you find pressure/MV start to spike as you move closer than .010 of the lands?

 

[hafejd30]

As you approach the lands, do you find pressure/MV start to spike as you move closer than .010 of the lands?

Check this from Bryan Litz

https://bergerbullets.com/wp-content/uploads/2013/03/COAL.pdf

 

[CK1.0]

If one is loading to jump their bullets, say .020, .040, or .060", how accurate does one need to be for finding where the lands is?

It's already been stated, but how precise one wants to be depends on use, bullets, and one's own preference.

That said, to answer: if I'm going to go to through the trouble of measuring, I want to be as accurate as I can... but what's more important IMO is to do it in a way that is reliable and repeatable, because I want to learn and get better at this shit as I go on in my own personal journey of lighting money on fire for fun.

In the end, we're all sort of arguing about the same thing... which is how to make the most accurate dummy round we can, and all arguments aside, there are many ways to take a crack at it and get a useable measurement, some are just better methods than others if one wants to be as accurate as can be.

I've been jumping ~0.100" to the lands for the last couple of barrels, so being accurate to a thou probably isn't make or break, but like most things associated with this shit, it can't hurt.

 

[straightshooter1]

Check this from Bryan Litz

https://bergerbullets.com/wp-content/uploads/2013/03/COAL.pdf

He's got his volume 3 of Modern Advancements in Long Range Shooting coming out next month. There's some really cool stuff in it. I'm really looking forward to this addition to either get validation of what I think I know or see where my thinking is off.

 

[Baron23]

I use the Hornady OAL gauge. It took me a few times using it to get consistent results but indeed I do get consistent results now.

I too take multiple measurements and average them but the measurements turned out to be very close with many of them matching exactly. Its is now apparent to me when I get an outlier...a bad measurement due to bad technique...as its just not matching up with the rest of the consistent set of numbers.

Now, is this exactly the objective distance to the lands....dunno...probably not. But just like CBTO using a bullet comparator, I view it as a useful, repeatable, consistent close approximation that I can use for setting seating depth on a relative basis.

As it turns out (if you can't tell I'm not one of the expert reloaders here), my chambers are SAAMI and I want to stay in mag length with MDT mags with binder plates. So, I can't get all that close anyway. I do reload Berger 140 hybrids which I understand are very jump tolerant which seems to be the case from my limited testing (with my very limited precision shooting skills). So, I load to .010 off of max mag length and that seems to be working for now.

The Hornady gauge seems to get a lot of bad press but I've found it to be useable and provide consistent measurements.