Long range load development at 100 yards.

[dmoran]

My only concern is "chasing" the lands if I go much smaller.

Can't help but feel your chasing a myth.....
For throat erosion will change your seating distance to the lands the same if your 015-IN or 100-OFF.
More times then not, I find the best seating position in close proximity of the rifling, and 2nd best at jumps (of say 015 to 030-Off).
I also strongly feel many do not ever find the very best seating position, and settle on a lesser that produces good accuracy, but not best.
Good Luck
Donovan

 

[minnesotamulisha]

Ok. Would I be better to test closer to the lands, or farther away such as .015-.030" like you suggest? Or should I try both?

 

['Freak]

First try seating incrementing further out, moving the ogive closer to and then possibly into the lands, watch for pressure signs. Mr. Cortina’s “jam” point has the ogive well into the lands, found by closing the bolt on one seated way out to put the ogive in hard contact with the lands whilst the bolt shoving on the case seats the projectile.

 

[minnesotamulisha]

Thanks OleFreak.

 

[dmoran]

Ok. Would I be better to test closer to the lands, or farther away such as .015-.030" like you suggest? Or should I try both?

By your data (2.218" at the lands) you tested from 010-Off to .027-Off already, from which I see the least amount of vertical was at the first tested increment of 010-Off. And is why I suggested to test IN from 2.208"/010-Off to at least the lands (and/or into the rifling as well).

My 2-Cents
Donovan

 

[minnesotamulisha]

When testing seating depth, is it more important to select a group with the least amount of vertical or the group that is the smallest?

 

[Erik Cortina]

When testing seating depth, is it more important to select a group with the least amount of vertical or the group that is the smallest?

It is more important to have 2 or 3 groups in a row that print small and in same point in reference to point of aim. So what you are looking for is consistency.

 

[minnesotamulisha]

Thanks Erik.

 

[Barrys]

Call me shallow minded, but I just don't see it. It's driving me crazy. It appears to be the 38.5 is strung closest together vertically and on the same horizontal plane. What am I missing? I understand windage is not in this equation but the 3 shots are on the same horizontal plane and with no windage would be in same hole. Can somebody PLEASE explain this in depth as simple as possible?

 

[Erik Cortina]

Call me shallow minded, but I just don't see it. It's driving me crazy. It appears to be the 38.5 is strung closest together vertically and on the same horizontal plane. What am I missing? I understand windage is not in this equation but the 3 shots are on the same horizontal plane and with no windage would be in same hole. Can somebody PLEASE explain this in depth as simple as possible?

Please post a picture of the target you are referring to.

 

[bsumoba]

Alright, here we go...my first 6 Dasher.

Bottom row is false shoulder fireforming.

Middle row is Hydroformed brass, which seem to be blown out almost near 95%. After the first firing, they had sharp corners already.

Lapua 6BR brass turned to 0.0125.
105gr hybrids
Varget powder
Loaded 10K out
2K neck tension

So, I decided to do some charge weights with the hydroformed brass to see what kind of groups I can get. This is the row I am most interested in. Rightmost target on the middle row...ignore this as this was the target I used for chrono with a magneto. I plan on running up to 33.3 grains with once fired brass next weekend.

Hydroformed brass velocities (only did two rounds just to get an idea of where the velocities were in this barrel):
32.2 - 2894, 2905
32.4 - 2908, 2900
32.6 - 2918, 2918
32.8 - 2936, 2943

32.2-32.4 seems to be a nice with velocities that seem to be similar. 32.4 has a flier in it I think.
32.4-32.6 seems to be nice because of vertical similarities. Group for 32.6 is not too shabby either
33.8 grain has decent ES and is right in the velocity window I was looking for and I can't complain about the group. Only concern here is the POI shift in lower than 32.2-32.6. Could be me though as mirage was killer today, even at 100 yards.

I will extend this out to 33.3 grains on the next range trip.

Any other input would be greatly appreciated.

 

[Barrys]

The target is the 1st one you posted on the very 1st page, very 1st post.

 

[BradY]

Call me shallow minded, but I just don't see it. It's driving me crazy. It appears to be the 38.5 is strung closest together vertically and on the same horizontal plane. What am I missing? I understand windage is not in this equation but the 3 shots are on the same horizontal plane and with no windage would be in same hole. Can somebody PLEASE explain this in depth as simple as possible?

Your looking at the individual shots, not the entire groups. Look at each group as a whole. Sure at 38.5 its nice and tight. But is there anything either side that shows that its within an accuracy node? No. I would call this a scatter node. They look promising but take one to 1000yds then you will see why its no good. Possibly at 37.5 you might get a trend of a lower velocity node around 38gr- but theres no shooting done that low to prove it.

Now if you look at all the groups as a whole, you will see the average point of impact in each group isnt lining up with 38, 38.5 and 39gr. Therefore saying 38.5 is the load is wrong. You want 3 successive loads to shoot the same vertical average point of impact in a row. This suggests a node worth trying. 39.5, 40 and 40.5 all line up with the same average POI in each group. Remembering that a scoring circle is widest near across the middle, you want shots to hit as uniformly in the vertical plane as possible. With 3 loads in a row that do this at 100yds you know that your at least in with a chance in that regard. Because if it wont work like that at 100yds then how is it going to work at 1000yds?

The other thing to think about when choosing a group is not just its shape, or vertical position- is also the weather conditions when shooting. Having 3 consecutive charges that shoot same average vertical position will give you a range you can work in. Say your shooting test loads and its 65 degrees. You get 3 charges in a row that shoot well. After you have tuned the seating depth and the load is performing well, you go to a match and find that its 105. If you know the range your load worked in at 65 you can adjust to suit the warmer temperatures. Ie in this case Erik might go down to 39.5gr powder because of the hotter day. Oppositely if shooting in colder climate, he might go above 40gr. Remember all powder is temperature sensitive, just some more than others. Knowing you have a wide node to work in is great for the long range competitive shooter.

 

[jimbo88mm]

Call me shallow minded, but I just don't see it. It's driving me crazy. It appears to be the 38.5 is strung closest together vertically and on the same horizontal plane. What am I missing? I understand windage is not in this equation but the 3 shots are on the same horizontal plane and with no windage would be in same hole. Can somebody PLEASE explain this in depth as simple as possible?

I think what you are missing is that the accuracy node for the photo in that first post is 39.5 to 40.5. While 38.5 printed the tightest group look at 38 and 39 in relation to the center of the target. If you look at all three you have a significant veriticle string there.

Looking at 39.5, 40, and 40.5, all three loads hit relativly close to the center. That means a load anywhere between 39.5 to 40.5 should be pretty consistent on the target.

To me that means other variables like how well your scale worked that day to the ambient temp when your shooting will have less of an impact since you are in the middle of a nice fat accuracy node.

(Erik, pls correct me if my analysis is wrong, I'm still learning myself )

 

[Barrys]

I see what youre saying now Jimbo, but accuracy goes both ways- horizontal and vertical. So if this was correct and all shots were made in the same environmental conditions, are we to assume that the other factors that keep it on the same horizontal plane are to be made with neck tension, powder charge and jump/jam when now trying to achieve the same elevation?

 

[Erik Cortina]

I see what youre saying now Jimbo, but accuracy goes both ways- horizontal and vertical. So if this was correct and all shots were made in the same environmental conditions, are we to assume that the other factors that keep it on the same horizontal plane are to be made with neck tension, powder charge and jump/jam when now trying to achieve the same elevation?

Jimbo and BY1983 have it right.
What we are looking for during the initial powder test is consistency. Even if groups are not small, consistency is key because we can shrink groups with seating depth. The 38.5 gr. group is small, but groups on each side do not show a pattern.

 

[Barrys]

I understand now thanks.

 

[akajiggs]

Eric,I have a question.I understand the process and like it.If you were developing a load for a hunting rifle,would you clean the barrel between groups so each group would be shot on a clean barrel?I do not shoot competition but like my hunting rifles to shoot as well as possible.Most of the time,before opening deer season,I will shoot one round and dirty the barrel just a little.
What is your thoughts?
Thank you.
Jim Gregory

 

[Erik Cortina]

Eric,I have a question.I understand the process and like it.If you were developing a load for a hunting rifle,would you clean the barrel between groups so each group would be shot on a clean barrel?I do not shoot competition but like my hunting rifles to shoot as well as possible.Most of the time,before opening deer season,I will shoot one round and dirty the barrel just a little.
What is your thoughts?
Thank you.
Jim Gregory

I would not clean between groups unless your barrel is fouling real bad. If so, you must take a couple of fouling shots before you resume group shooting.

 

[savageshooter86]

Seating depth test