Stepping up charge weight....how much per step?

[txfireguy2003]

I'm about to start working up a load for my newest addition, a Remington 700 in .308 Win. I know start at the lowest recommended charge and work your way up until you see pressure signs and back off, but how much difference do you use in charge weights? Let's say I'm looking at load data that says from 40.0gr to 44.0 gr Varget (about a 10% difference between min and max). I'll start at 40.0, obviously, and load a 5 round batch, then move to a higher charge weight. What should that weight be? 41.0 (2.5% increase)? 40.5 (1.25%)? 40.4 (1%)? In the past, I've always loaded in 0.5gr steps, but that was with .223, which only had about a 2.0gr difference between min and max loads, so 0.5gr steps gave me 5 batches and a total of 25 rounds to test. If I used 0.5gr steps for .308, I'm looking at 8-10 batches of 5 rounds. Nearly a whole box of bullets just to find the load it likes? On the other hand, I don't want to use too big of steps, and end up going from a safe load to a massively overpressure load in one step, I like my hands and my life, rather not lose them.

 

[txfireguy2003]

Okay, so since nobody has answered, I went with advice from another forum this morning. (I know, I didn't give you guys very long, my fault) Here's what I did, tell me if you think I'm on the right track. I didn't mess with finding the lands, I went with the length recommended on the Hodgdon load data sheet, which was 2.750, it works in the magazine, so I went with it, all rounds are loaded to the same COAL. The load data suggests charges from 42.0gr up to 46.0gr of Varget for a 165gr SPBT (Sierra Gameking), which is what I'm shooting. I started at 42.0 and worked up in 0.5gr increments up to 46.0gr. That gave me 9 groups to shoot, but instead of loading 5 for each combination, I loaded only 3 to save a few components. Once I find the general vicinity of the sweet spot, and what is safe in my gun, I'll go back and load 5 shot strings around that area, then play with seating depth if I feel it's needed. This is going to be a hunting load, and I'll work on a target/pure accuracy load later, but I really want a hunting load that is deadnutz accurate too. I've been able to get 5 rounds of .223 Gamekings to touch at 100 yards consistently with this meathod and a pure factory rifle, so hopefully I'll do okay with the .308 as well. I was also able to get sub 1/2moa groupings from a .270WSM with this meathod in a factory rifle, so I think I'll be okay, I was just trying to save a few bullets and some powder by stretching the increments a bit. I did stretch the .270WSM increments a bit, not so much to save powder and bullets, but rather to save the shooter's shoulder, but I was still right around 1% increase in powder charge with each load on the .270WSM because I figured if one load was safe, 1% higher wouldn't likely be so overpressure that it would be dangerous for one shot to find out it was too high. I also never exceed recommended maximums, no matter what, so if what I've read is true, and the manuals are conservative, I think I should be safe. What do you all think?

 

[TexasRedneck]

You should be fine - the manuals ARE conservative, so you should have no problems - have fun!

 

[Charlie]

You're doing basically what I have done but you're doing it a little more in depth that I have. That method worked pretty good for me. A year or so ago I loaded my .223 with a 55 gr. SP (can't remember which one) and Varget (I love Varget!). I started with 25 gr. then 25.3 gr, 25.5 gr., 25.7 gr. 26 gr.,and 26.3 gr. Groups started at about 1.25 inch (with the 25 gr load) and decreased in size until I got over 26 gr. The 26 grain load shot a 7/16" group and going to the 26.3 gr. opened it up a little so I stopped. I'm limited on COAL by the AR magazine. I do have them a tad longer than the 2.260 but they don't fee right if I go longer.

 

[Charlie]

You should be fine - the manuals ARE conservative, so you should have no problems - have fun!

Well said!

 

[woolleyworm]

For a new load, I am a big fan of the Audette Ladder tests, 20 total rounds and you'll pin-point your sweetspot 99% of the time. PM sent

 

[txfireguy2003]

Well, things didn't work out as well as I had hoped, but all loads were safe. I didn't get any really great groups, except one from black hills factory match loads that came in around 3/4" outside to outside, so when you subtract the bullet diameter, probably getting around .5" or less center to center. Part of my problem is a heavy trigger, and I think the non-free floating stock the rifle has, those will both be remedied in the future. My other problem was that it was HOT out there and my hands were sweating, so I couldn't get a good grip on the rifle, and when you combine that with the smooth face and heavy pull of the X-mark trigger, I couldn't get a good trigger squeeze. I'll try again early one morning or late one evening so it won't be so dang hot and see what I come up with.

 

[noylj]

2% for rifles, 0.3gn for most handgun rounds.

 

[Texas1911]

You're doing what's called a ladder test ... start wide and go small once you ID a node.

40.0
40.5
41.0
41.5
Etc.

Then once you see what works best out of that, vary it by a tenth and go from there. Off the top of my head most of the Varget loads that do well are around 43 - 45 grains with lighter bullets.

 

[medalguy]

Texas1911 did what I do, increment each load by 0.5 gr but I always run them through a chrono to see where I am in regards to velocity. When I get to the best grouping, start +/- from there by 0.2 gr and see where it takes me. I generally do 5 rounds at each trial load.

 

[txfireguy2003]

I'm going to have to try this test again. At some point during the shooting, my rear scope ring apparently became loose. I didn't notice until I took the rifle out to clean it. The ring is still clamped on the scope well, but the ring was not clamped to the mount tightly at all. I'm not sure why it came loose, but it did. It was tight when I started shooting, I know it was tight and the fact that I was able to get a 1/2" or better group with Black Hills ammo is evidence of it as well. I'm using the Vortex Tactical rings, 30mm, with 6 screws on top of each ring, but the ring to mount clamp is a large hex nut (1/2" IIRC). I don't really see how I can loctite it, but any suggestions on how to keep if from loosening up again would be appreciated.

 

[Bearbacker]

If I were you, I would make sure the threads on the screw and nut that came loose are completely free of oil, and then I might use a drop of Loctite. NOT the permanent bond stuff, but the stuff you can get loose when you need to. I usually don't have to do the Loctite on ring screws, though.

When doing an initial load workup, I usually go up .5 grain at a time on powder charge, and shoot a series of three shot groups. After all, if 3 shots go into a group of 4 inches, two more shots won't shrink the group any. If one group shows some promise, then I load a few 5-shot strings with that load to see how it does. If it still looks consistent, I then vary seating depth to see if I can shrink the groups more. I have been known to cheat by trying to match the seating depth of a factory load that shoots well, and then go from there.