Long range load development at 100 yards.

[DarrellA]

And another question for Erik. I'm working my OCW and shot ten 5 shot groups with 0.4 grain increments between each. My first reaction was to work smaller increments around group 7. Because group 7 looks really good. But then I read your take on vertical separation of the groups, not the individual shots. I ran the freebie On Target calculator and graphed the results. Now I'm thinking that I should be working smaller increments (0.2 grains) between groups 4, 5 and 6. The line between those groups seems to be the flattest and shows the least amount of change from one group to the next.

I have already run through the Berget VLD test and will tweak seating depth some more after I figure out the powder.

Am I understanding this correctly or just chasing my tail?

Weatherby 7mm-08 sporter, 24" barrel
Berger 140 grain VLD
Varget
100 yards

Thanks

 

[Erik Cortina]

Load up load #5 and work on seating depth in .003" increments. After you bring the groups in, you can work powder in smaller increments to find your accuracy node bounds.

 

[DarrellA]

Thanks, Erik. I'm doing a reset on where I was headed and will try your recommendations.

 

[105gr]

Have a look Erik? The top numbers are the charge (38.7gr of 4064) and the numbers under are seating depths. These two seating depths have done well with every charge I have tried but they tell different stories. The thing that scares me is the muzzle velocities. The only time I got consistent muzzle velocities was at 38.5ish grains. In target 2 there ARE 5 holes.....one went through the same hole just above the dime. I forgot to write down the MV reading before I shot the next one

 

[savageshooter86]

how far were those shot at?

Looks to me(I hope) that it is a chrony error causing that much variance in velocities

 

[105gr]

they were shot @ 100yds....you think that big of a variance would have opened those groups up farther than that?

 

[Erik Cortina]

Groups kind of big for 100 yards and ES is not great either. :-\

Have you tried Varget or H4350?

 

[105gr]

yea 4350 was terrible...it shot 7 moa with 4350

 

[PMA3]

Erik,

This has been one of the most informative threads ever...thank you for taking so much personal time to answer the ton of questions directed your way. My question is this...can any useful information be obtained regarding this thread while fire forming new brass (6.5x47 to 6x47)? My understanding is that to fire form these cases correctly, you need to jam at least .010" and use a near max load to fully form the new case. Or do you just put 80 rounds down the barrel and then start the load development with fire formed cases?

 

[Erik Cortina]

For fireforming, I like jamming the bullets like you suggested and then work up a powder charge that gives me acceptable accuracy to get some good practice or even shoot a midrange match. After it's fireformed, you can tweak powder and seating depth to obtain best results.

 

[stinnett1981]

Great thread Eric. I been reading it since you first created it. May it be my turn now! I just got back from the range with these 100 yard groups out of my new .308 Win. Im shooting 175g SMK's, Varget, Winchester brass and primers. All loads are .018" off lands. Here is the details if you cant read the writing in the pics.

Top page
- 1st row right group is a clean barrel and cold bore 3 shot group with 43g Varget
- 1st row left group and 2nd row left group is 5 shot groups with 43g Varget
- 2nd row right group and 3rd row right group is 5 shot groups with 43.5g Varget
- 3rd row left group is a 2 shot group with 43.5g Varget

Bottom page (shot 15 min after top page)
- both 1st row groups are 5 shot groups of 44g Varget (the right group was cold bore)
- both 2nd row groups are 5 shot groups of 44.5g Varget
- both 3rd row groups are 5 shot groups of 44.7g Varget
- 4th row left groups is a 5 shot groups of 45g Varget
- 4th row right group is a 10 shot group of 45g Varget. I also did 1 click down and 1 click right to ZERO on bullseye.

I like the 44.7 grains of Varget!

 

[Erik Cortina]

44.7 looks good. Load up from 44.2 to 45.0 in 0.1 gr increments to see exactly where your window starts and ends so you can load to the middle of the load.

Have you done seating depth testing?

 

[stinnett1981]

Will do. Thanks.
No I have not done seating depth test yet. I simply picked .018" jump because lots of people say .01" to .025" jump is where you wanna be with a .308 and 175 SMK's. I will load some more from 44.2 to 45 grains of Varget. After that I will do some seating depth testing.

 

[Erik Cortina]

Did you feel like you pulled any shots? You have a nice group surrounded by bad ones. Any chronograph numbers?

 

[johnnyi]

I did notice after I had a poor setup with my front rest where my swivel stud was contacting my rest bag. The first few I felt like I was double checking my from and rear rest to return to battery. I did end up tearing a hole in my front rest. I may have to redo the test on the upper end of the charge string...?

No chrono on this day.

 

[Erik Cortina]

Yes, that would give you inconsistent results. Take the swivel studs off, front and back. The gun must recoil freely.

 

[johnnyi]

Ok I have removed those POI/bag killers from the stock and have a rerun tomorrow.

 

[stinnett1981]

Ok I have removed those POI/bag killers from the stock and have a rerun tomorrow.

Did u get back out there and re-test your loads? Let's see em! Love this thread!

 

[johnnyi]

Ok here is a redo same string as above with the swivel studs removed!
Ignore target "F" as that was from a previous outing. Bottom targets G I and J the bolt seemed to start getting a little harder to open. No pressure signs on the head stamp.

 

[Erik Cortina]

Between 46.6 and 47.0 looks best. I would try 48.8 gr and work on seating depth. Did you shoot over a chronograph by any chance?