First Post - Could use some help interpreting OCW test results.

[Apollo19408]

I've been lurking on here for awhile absorbing information and I now have some targets I need help interpreting. All of these were shot in the OCW round robin fashion at 100 yards.

Firearm:

Howa 1500, 22" sporter barrel, 6.5x55 Swede.

Load info:

No velocity data at this point.

Bullets tested - Hornady 143gn ELD-x, Sierra 140gn Gameking, Hornady 140gn ELD-M

Powder - H4350

Powder Charges indicated on target. Book indicated max is 43.7-44.0gn for this powder, however none of the 44.4gn charges had any pressure signs and the listed max charges are for safety in Mil-Surp rifles. I am comfortable venturing beyond them in a controlled and methodical manner.

Seating depth - All are loaded as long as I'm comfortable loading them. The chamber is really long, which is typical for this caliber. They all have between .050 and .070 jump.

Brass - Fire formed PPU brass

Primer - Win LRP

Targets and My Thoughts:

143gn ELD-X

This will be my primary hunting bullet until California goes to all lead free in a couple years. Based on the results, I think I should look into the 43.2 - 43.6 range with tighter increments, but I'm also intrigued by the tight vertical grouping at 44.4 and I want to look into testing 44.2-44.6. Does that sound reasonable?




140gn Gameking

This will be a "backup" hunting load in case I can't find ELD-X's at some point, since Gamekings seem to be readily available to me locally. I like how 43.6 -44.4 group in a very similar location. I might test in that range in .2gn increments, or I might just pick 44.0 and run with it given my intentions for this load.




140gn ELD-M

This load will be the primary paper punching load for my wife and I. I want it to be capable at 600-1k yards. I am really happy with how 42.8 and 43.2 grouped and they grouped in similar locations. I will definitely be exploring this range with tighter increments and to see if I can repeat these .25" groups. But I don't think that range will give me the velocity I want for longer range shooting. I think that 44.0 and 44.4 would have grouped similarly if I hadn't pulled a shot. I might explore that and add in 44.6 as well. Am I being silly here considering how the rifle seems to really like this load in the 42.8-43.2 range?



Thank you for any advice and guidance you can provide.

 

[Orcon]

Oh goody, I love reading tea leaves!

This will be my primary hunting bullet until California goes to all lead free in a couple years. Based on the results, I think I should look into the 43.2 - 43.6 range with tighter increments, but I'm also intrigued by the tight vertical grouping at 44.4 and I want to look into testing 44.2-44.6. Does that sound reasonable?

Yup, I would do the same.

140gn Gameking

This will be a "backup" hunting load in case I can't find ELD-X's at some point, since Gamekings seem to be readily available to me locally. I like how 43.6 -44.4 group in a very similar location. I might test in that range in .2gn increments, or I might just pick 44.0 and run with it given my intentions for this load.

Not a bad idea, try fussing with the seating depth maybe things will tighten up.

140gn ELD-M

This load will be the primary paper punching load for my wife and I. I want it to be capable at 600-1k yards. I am really happy with how 42.8 and 43.2 grouped and they grouped in similar locations. I will definitely be exploring this range with tighter increments and to see if I can repeat these .25" groups. But I don't think that range will give me the velocity I want for longer range shooting. I think that 44.0 and 44.4 would have grouped similarly if I hadn't pulled a shot. I might explore that and add in 44.6 as well. Am I being silly here considering how the rifle seems to really like this load in the 42.8-43.2 range?

Meh, I'd toy with the lower end load. No harm in retrying the high end either though, three rounds may give you and indicator but it's hardly definitive. Some people will show up soon and tell you you have to shoot 20 rounds per load or it doesn't count. Try downloading the free On Target software and measure group centers and compare the relationship to the orientation of the point of aim. http://www.ontargetshooting.com/

Oh, and welcome to The High Road!

 

[Bart B.]

You've shown the ELD M 140 gr. bullet with charge weights from 42.8 to 44.4 grains of powder will, statistically, shoot under an inch. Statistically, 3-shot groups typically go from half the size of the first one fired to two and a half times bigger. There a good chance any charge weight in that range will put 20 shots in about an inch. Therefore, I'd use the 44.4 grain load to test at 600 and 1000 yards. Your own variables can easily increase the rifle and ammo's real accuracy half an inch at 100 yards.

Keep in mind group size in MOA at 100 yards opens up about 10% each 100 yards further down range. Velocity and bullet BC spread plus subtle atmosphere changes make that happen.

Accuracy you can count on all the time is the largest group shot. All rifles and their ammo shoot groups between zero and some value; most average and the rest larger and smaller.

 

[Gtscotty]

OP,
I agree with your reasoning on the ELD-X, on the other two bullets I believe that I would explore seating depths with the 44gr charge.

 

[wally]

I'd split the difference and go with 43.0 and shoot some groups of at least 10 shots to see if you've really got a consistent and accurate load.

I'd go with the lightest load that produces the tightest groups.

 

[Apollo19408]

Thanks for the advice. I think I will focus on the 44.0 range with all bullets and shoot more rounds per charge for better data.

I can't ignore the 43.0 area with the EL-M's and will do some exploring there too, but I plugged in the data of the velocities I THINK I would get from that charge and it's a significant difference in drop at long ranges over the velocity range I want to be in. Obviously this is just a guess on velocities at this point. The only chrono data I have with this rifle right now is 42.0gn of H4350 under 140gn Hornady BTHP's gave me a 5 round average of 2454fps. I want to be in the 2650-2750fps range.

 

[wally]

IMHO you need to go with the smallest groups and take whatever velocity you get. Gravity is very predictable so the vertical component is easy to compensate for, and the extra velocity will never make up for the larger group size with a reduction from wind drift since your uncertainty in "doping the wind" will almost certainly be larger than the reduced drift from a few hundred fps at the muzzle -- if your wind dope is perfect, your ballistics calculator will compensate for it same as for drop if your velocity is accurate and consistent.

 

[Chuck R.]

The way I've read and used the OCW process is different........

My understanding is at this point, you're looking for groups/loads with a similar POI and not being too concerned with actual group size at this point. IAW Dan's sight:

http://optimalchargeweight.embarqspace.com/#/ocw-instructions/4529817134

"
14. Triangulate the groups. This means to connect all three shots in a triangular form, and determine the center of the group, and plot that point on the target. Measure this point's distance and direction from the bullseye, and record the information somewhere on the target. Do this for all of the targets. If you have a called flyer, you should discount that shot, or replace it in the group if you have an additional round loaded with that charge.

15. You will now look for the three groups which come the closest to hitting the same POI (point of impact) on the targets. The trend of the groups should be obvious, normally going from low and favoring one side, to high and favoring the other side. But along the progression, there should be a string of at least three groups that all hit the target in the same relative point.

16. After you have carefully measured group sizes and distances and directions from the bullseye, you will know which three groups come the closest to hitting the target in the same POI. You now choose the powder charge which represents the center of this string. For example, if 34.7, 35.0, and 35.3 grains all grouped about 1.5 inches high, and about 3/4 of an inch right of the bullseye, you would choose the 35.0 grain charge as your OCW (optimal charge weight). This charge will allow 34.7 and 35.3 grain charges to group right with it. This will be a very "pressure tolerant" or "resilient" load.

17. Remember, don't get "bowled over" by a tiny group which falls outside the OCW zone. You can tune any of the groups to be tiny with bullet seating depth changes. After you have determined the OCW, you may want to try seating the bullets deeper or longer in .010" increments to see where your particular rifle does its best. I have often found that OCW recipes are so reliable that seating depth alterations--especially for hunting cartridges--often don't seem necessary.

18. Your next step would be to confirm your load recipe at the maximum range you will expect to use it. Load one round about 1% below, and another round about 1% above the OCW charge, and fire a three shot group with these two charges plus the standard charge at the maximum range you will require the load to be accurate at. You should note MOA, or very close to MOA grouping..."

When I've done OCW process I could literally cut out my targets, lay them on top of each other and some would overlap a POI very, very close to other charge weight groups. It was kind of amazing to see, but so far it's worked in a couple of rifles of mine.

Based on what I see on your targets I'd re-look the Gameking 140 with 44.0 grains and the ELD-M with 43.2 IF you want to stick with the OCW process. On my next set of test I shoot 2 5 shot groups per load in a single string (Unlike the round-robbin cycle the OCW calls for). This veryfies the groups weren't a fluke and I chronograph to see IF I'nm getting good stats.

Before I start the OCW process I shoot some individual loads over a chrono to verify I'm in the velocity range I want to be in.

Chuck

 

[murf]

have you eliminated parallax?

murf

 

[Apollo19408]

Chuck R. - Thanks. I had read his website and I thought I was following his method pretty closely. My understanding is that the 43.6-44.4 range with the Gameking bullet is textbook what I should be looking for. I will choose the 44.0 load with that bullet and tweak the seating depth to see if I can get any improvements.

I will test the ELD-M in the 42.8 - 43.4 range in .2gn increments with 5 shot groups and see how they group and choose the group that fits the OCW criteria. Then I'll chrono and see what the velocity numbers are before I decide if I want to explore the higher charge weight range with that bullet. I'll try to heed wally's advice and not get hung up on velocity, but I won't make any promises.

With the ELD-X I'm going to shoot 44.0-44.6 in .2gn increments, 5 shot groups and see what happens.

murf - I'm not experienced enough with scoped rifles to know if it's been eliminated, but the scope I'm using has a side focus adjustment that was set for the correct distance.

 

[murf]

to check parallax:

set rifle on bench and put scope cross hairs on target center. without touching rifle, look through scope and move your head around and up and down while looking at the cross hairs on the target. if the cross hairs move around the target, move your adjustment knob until they stop moving.

the hash marks on parallax adjustment knobs (or rings) seldom match the parallax-free distance.

luck,

murf

 

[Apollo19408]

to check parallax:

set rifle on bench and put scope cross hairs on target center. without touching rifle, look through scope and move your head around and up and down while looking at the cross hairs on the target. if the cross hairs move around the target, move your adjustment knob until they stop moving.

the hash marks on parallax adjustment knobs (or rings) seldom match the parallax-free distance.

luck,

murf

I didn't do that. What I did do was put the hash mark at the 100 yard mark and then while looking through the scope I adjusted it until the target and reticle were both in perfect focus. It ended with the dial at what would be a the 90 yard location. I will try what you suggested the next time I shoot.