OCW Interpretation

[famebyassociatn]

I tried out my first string of loads today and would like some help interpreting the results. This is my first time doing this and my first time reloading. Any suggestions/comments would help. I have no idea what happened on 44.7. I think the hole on the bottom of the picture is a stray bullet (shared range). Thanks.

remington 700 aac sd 308
178amax
lapua brass
IMR 4064
win primers
2.81

[ar15barrels]

Re-do your tests at 300yds and they will be MUCH easier to read.
Specifically, look at the dispersion along the vertical axis.
Don't worry so much about horizontal dispersion as that's just the wind.

When you find a load that leaves a "flat line" across the target, that's the one you want to be using.

100yd testing tells you very little as differences between different charges will often fall within the intrinisic accuracy of the rifle.

[CobraRed]

300+

[bsumoba]

if you cannot get to 300 yard or even a 200 yard range, i will attempt to answer your question.

Looks like you have a node around 42.3-42.6gr as well as something possible around the 43.4gr range. The shot dispersion is okay, but more importantly as AR15barrels mentioned, the groups are in the same relative area (high right of center or high of center). It looks like your shot group goes to hell after 44.0 grains, and you're probably starting to come out of a node around 44.0 How did you feel on these shots? Was it you or did you feel go on your shot?

A few questions also:
* what scope are you using?
* what length barrel are you shooting?
* what position are you shooting?
* did you hand weigh each charge?
* did you notice any pressure signs? do you know how to look for pressure signs?
* are you crimping?

Max listed for 175gr is 45.6gr and thats a compressed load. You might want to get access to a chronograph to see what velocities you're spitting out around the 43.5 as well as 42.5 grain range. If you're getting around 2500-2600, your're in the range you should expect to be in and probably do not need to try above 44 grains, or at least i would not.

The goal in ladder or OCW testing is to find a range (node) that yields good vertical stability, meaning over a range, for example, 0.5-1.0 grains, you will get a similar point of impact vertically, which is called an accuracy node. Once you find this range, choose a charge weight in the middle of this range and then play with seating depth to tighten your groups. Not to complicate it more, but you could also determine your length to ogive and load either jammed on the lands, off the lands, etc. This is more of an advanced reloading thing, but do some research.

The more info you give us, the more we can help

[famebyassociatn]

Thanks for the replies. Next time I am out, I will try it at 300 yards. I will also try to gain access to a chronograph. As far as how I felt on some of these shots, there was definitely some shooter error involved. This is my first bolt action.

* what scope are you using?
SWFA 5-20x50, the rings and bases (seekins) are torqued per mfg.

* what length barrel are you shooting?
20" 1:10 twist

* what position are you shooting?
benchrest with sand bags front and rear

* did you hand weigh each charge?
yes, used a rcbs 505 beam scale

* did you notice any pressure signs? do you know how to look for pressure signs?
I didn't notice any pressure signs. No sticky bolt, primers look fine, etc.

* are you crimping?
no, just a seating die (lee)

[bsumoba]

you got all the right answers. scope is good, position is good, etc. some trigger time will obviously help. .308 has some kick so if this is an issue, you could try putting on a brake, which helps reduce felt recoil. sometimes the recoil, especially when throwing that many rounds downrange in a 308 bolt could cause flinching or bad shooting habits.

I would say the next step is to load 3+ rounds at 42.2, 42.4, 42.6 and 42.8, 43.0, 43.2, 43.4 and 43.6. If you care about velocity, work the higher numbers if you dont want to load that many rounds. Shoot in a round robin fashion as well and dont go too crazy heating the barrel up.

If you want, try different powders. 178gr will/should work well with Varget and RE15. Same OCW rules apply.

When you find a range of charge weights that keep the POI relatively the same, then work that range and play with seating depths. That would be your next step.

You'll get there.

[famebyassociatn]

I took your suggestions and performed a second string of OCW shots for the higher powder charges at 200 yards to see if I can determine the higher node. I was aiming for the highlighted circles per each grain charge. The grain charges are listed on the target. There was a 10 mph crosswind left to right while shooting. The second shot for the 43.2 charge was off once I pulled the trigger (I flinched). I am assuming that round would be closer to the other two if it was shot properly.

Judging by the results, it looks like I may have a node around 43.3/43.4. Would this be a correct interpretation? It seems it would match my first round assessment made by bsumoba. I will probably stick with this charge for loading so I can practice my fundamentals. Once I feel like I have those down I may do more load testing. Thanks for the suggestions and comments.

[bsumoba]

Looks like you validated that 43.2-43.4 works well. I would say, do some more work load ups around 43.3. Now, the next step IMO is to play with seat depth at this charge to tighten up the groups.

The groups at 200 yards seem really dispersed, which could be wind, but could also indicate that your reloading needs work. Would you care to briefly go through your reloading process?

Are you doing any kind of measurement of your ogive?
What COAL are you loading to?

[famebyassociatn]

Looks like you validated that 43.2-43.4 works well. I would say, do some more work load ups around 43.3. Now, the next step IMO is to play with seat depth at this charge to tighten up the groups.

The groups at 200 yards seem really dispersed, which could be wind, but could also indicate that your reloading needs work. Would you care to briefly go through your reloading process?

Are you doing any kind of measurement of your ogive?
What COAL are you loading to?

All of these loads were made with virgin lapua brass. First I ran a lee collet die. Then put in the primers. Weighed each charge using a beam scale. Then used a bullet seater. I measured the COAL with calipers. I did notice the tips on the amax are not always uniform, thus I was getting COAL from 2.81 to 2.82. This could be a factor. I need a tool to measure the length by ogive. Do you have any suggestion for an ogive measurement tool?

I also did a drop test using the 43.4 charge from 200 yds to 480 and 545. Based on JBM ballistics using 178amax (litz), I am pushing around 2580 fps. This is a rough estimate and I did not factor in the angle to target. I will measure it next time. For a 10mph crosswind with that velocity, JBM states a 3 inch shift at 200 yards.

[bsumoba]

i noticed this with a-max's as well and for my loads with certain dies and went with a redding vld seating die w/micrometer (i noticed this with my 6.5 creed dies). Right now, im using 175gr SMKs in my 308 gasser. This is what Im using:

http://www.brownells.com/reloading/measuring-tools/bullet-comparator-inserts/xl-comparator-bump-gage-body-sku749011959-34014-74727.aspx

sounds like you did your homework with the reloading process. 2580fps is a good velocity. Im getting 2642 on a chrono with a 20" barrel in my gasser. keep working the load and good luck!

[killshot44]

I measured the COAL with calipers. I did notice the tips on the amax are not always uniform, thus I was getting COAL from 2.81 to 2.82. This could be a factor. I need a tool to measure the length by ogive. Do you have any suggestion for an ogive measurement tool?

Stop. Don't waste any more components until you can accurately measure the BTO (base-to-ogive). Your actual seating depth (where the bullet's bearing surface is) could be varying as much as .010" with your measuring method.

Hit Midway and order the Hornady bullet comparator and comparator body. If you don't already have them, also order a case comparator to meaure shoulder set-back (sizing) and a OAL gauge and Modified case to measure the distance to the lands. I prefer the Hornady bullet comparator to the Sinclair as the latter has a funky chamfer that doesn't work with every bullet profile.

Then do the tests again.

[vliberatore]

Stop. Don't waste any more components until you can accurately measure the BTO (base-to-ogive). Your actual seating depth (where the bullet's bearing surface is) could be varying as much as .010" with your measuring method.

Hit Midway and order the Hornady bullet comparator and comparator body. If you don't already have them, also order a case comparator to meaure shoulder set-back (sizing) and a OAL gauge and Modified case to measure the distance to the lands. I prefer the Hornady bullet comparator to the Sinclair as the latter has a funky chamfer that doesn't work with every bullet profile.

Then do the tests again.

This what you're talking about?

http://www.midwayusa.com/product/231904/hornady-lock-n-load-bullet-comparator-basic-set-with-6-inserts