Few questions about runout and OCW development

[SJshooter]

Hey all, I've got a few questions about reloading. 

I'm trying to develop OCW loads for my tikka in .223. It's a 16 inch barrel (I cut it down) 1 in 8 twist and I'm trying to get pet loads for Nosler 69gr HPBT with AA2520 and Hornady 55 V-Max with H335. 

Here's where I need help... I did the thing (with both the 69 and 55 bullets) with the sharpie to get an idea where the lands and grooves start, and I backed it off somewhere between .005 and .015. I'm using a RCBS Comp micrometer die with a Hornady LNL Single stage press. I realize that the seating stem seats according to the bullet width at a certain point, and my overall length will vary a bit, but the ogive should be pretty consistent distance from the rifling (right?). I loaded 8 rounds of 25.3 gr AA2520 with the Nosler 69gr and 18 rounds of 55 V-Max at different charge weights. Well, I set the die and just loaded all the rounds, then out of curiosity went back and measured overall length with my micrometer. 

What I found was the Nosler 69gr bullets varied between +/- .003-4, which is acceptable, right? But the 55 V-Max's varies up to  +/- .01 inches! That seems like a lot!
What do you all think? I realize I should isolate one variable at a time when trying to develop loads, so should I go back and even out the overall lengths by adjusting the die? 

Also, when I'm searching for nodes over a large range of powder amounts, should I vary the charge weights by .3 grains, or .5, or more/less? I know to fine tune it, some reloaders vary by .2 or .1 grains, but that's when they find what appears to be a node. What do you all do?

Thanks in advance for your advice.

 

[jlow]

Re: Few questions about runout and OCW development

Your problem may lie in the fact that you cannot seat 55 gr bullets out to the lands in most chambers since they are just too short. For reliable operation, the case neck should grip at least a caliber length of the bullet.

 

[SJshooter]

Re: Few questions about runout and OCW development

But that would be what's affecting accuracy, right? It doesn't explain why the seating depth would differ so much.

 

[SJshooter]

Re: Few questions about runout and OCW development

Ok, so I did find some reading to do on OCW testing. Looks like I have the general idea but I should be increasing in larger amounts ~2% grains. I have been doing a ladder test I think.
I'm used to firing a group (3 or 4 rounds) of different weights and using that as a way to determine the nodes. Appearantly that's not as good as shooting 1 round each of the different weights into different targets and then doing that 3 more times to get a four shot group in each target.

Anyone else test that way?

 

[jlow]

Re: Few questions about runout and OCW development

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SJshooter</div><div class="ubbcode-body">But that would be what's affecting accuracy, right? It doesn't explain why the seating depth would differ so much. </div></div>

If your bullets are only very slightly seated, I doubt they would be able to maintain their position in the case, thus affecting both seating depth and accuracy. Remember, it takes a firm grip to maintain seating depth.

 

[SJshooter]

Re: Few questions about runout and OCW development

True. I'm seating them to 2.345 at the longest, which shouldn't be a problem(?), or is it just a little too long?

 

[SJshooter]

Re: Few questions about runout and OCW development

Can anyone lend advice to my other questions?

I decided I will seat the bullets shorter to ensure that they are being held in place securely enough.
Does anyone else do the marker test and find it accurate?

 

[DCR]

Re: Few questions about runout and OCW development

Ogive to the tip of the bullet can vary between bullets. That's why most measure from the base of the brass to the Ogive. Sinclair and Hornady both make tools for making the measurement.

 

[gvanhyning]

Re: Few questions about runout and OCW development

Here's what I do when I develop a load. I do some homework checking what powder and bullet combinations seem to produce the best accuracy. I start at the max load and work backwards for building test shots and I do this at .2-.3 grain increments. I seat all bullets to magazine length or recommended OAL. I shoot 5 shot groups at each increment beginning with the minimum load I have and work up to the max. I also shoot all test shots through a chronograph so I have an idea of the velocities I'm getting. I look for the best group out of the shots fired and then work up another set of test shots for bullet seating depth. I start with bullet touching lands to jammed .005" and increment the seating depth .003-.005". Once I have the seating depth determined then I shoot 600-1000 yards to test the long range accuracy.

I do use QuickLoad as a way of estimating chamber pressure, case fill, and muzzle velocity. When I'm doing the "homework" on powder/bullet combinations, I usually have a target muzzle velocity. While MV is not the most important factor to me, certainly downrange performance is. This is how I do it and I normally have a good load built up with just two trips to the range and then the long range shots. Hope this helps.

 

[SJshooter]

Re: Few questions about runout and OCW development

Well I kept the lengths the same. They were about 2.335-2.345 overall length instead of the 2.260 recommended. I def found a node though as I had one group all shots touching and another 3 in one hole then I pulled one a quarter inch. I was pretty impressed. I needed to find a light round my tikka likes, and I'm thinkin that this is it! Look out groundhogs!