My Longest Ladder ever!......7mm Mag & 180 VLD's

[Longtine88]

Been playing around the the Hammer bullets and took a break from them. Decided to try my initial targeted bullet to use in this new rifle. So being new I started 2.8 grains under a max I got. Particulars:

7mm Mag Snow Mountain Rifles
Defiant Action
24" Proof w/ Tit. Brake Sendero
180 VLD's
H1000
Fed 215M
Nosler Virgin Brass
0.030" off Jam Point Seating Depth
All shot's off front rest and bag on back at 200 yards.
Magneto Speed Chrony

You can see they were stacking in there pretty well. Shot 19 was just starting to show slight flattening of primer. Bolt was loose. My thought were to load between shots 14 to 16 and shoot groups. What are y'alls thoughts?

 

[Jud96]

I would go with 16, 17, and 18. I like how 16 and 18 hit in the same hole and 17 was just below them. That shows me that's a good node. Shots 14, 15, and 16 were all horizontal spread. It's hard to nail down at only 200 yards. I would load up 3 rounds each from 70.3 to 71.3 in 0.2gr increments and shoot 3 shot groups. Map out your points of impact and fine tune from there.

 

[GLTaylor]

Pick your best and re-shoot for group. Remember that Bergers frequently like to jump. Once you get your initial load, reshoot at 30 thousandth increments. .030, .060, .090, .120 jump. One of those will shoot noticeably better

 

[GREATSCOTT!]

At this stage in development you're only identifying loads with the least amount of vertical. Far too much vertical in groups 16 - 18 in my opinion at 200 yards. Between 14 - 16 looks real good; least amount of vertical dispersion with little to no change in velocity. Sounds like you're also fire-forming new brass so the following will help get that done too.

You need to shoot your Stage 2 vertical record ladder at 400-500 yards to see what they're doing though. Now I would load 3 rounds from each of the following powder charges 70.0, 70.3, 70.6, 70.9 and see where you end up.

Stage 3 vertical record ladder should be shot at 600-1000 yards, and I'm guessing you'll be refined somewhere between 70.2 - 70.8gr in increments of .2grs to identify your least vertical load. After that, you play with seating depths to tune your best vertical load.

NOTE: Normally for competition load development, I load and shoot 4-5 sighters/foulers and let the barrel cool before shooting record ladders, but you need to shoot cold bore ladders since its a hunting rifle.

 

[Longtine88]

At this stage in development you're only identifying loads with the least amount of vertical. Far too much vertical in groups 16 - 18 in my opinion at 200 yards. Between 14 - 16 looks real good; least amount of vertical dispersion with little to no change in velocity. Sounds like you're also fire-forming new brass so the following will help get that done too.

You need to shoot your Stage 2 vertical record ladder at 400-500 yards to see what they're doing though. Now I would load 3 rounds from each of the following powder charges 70.0, 70.3, 70.6, 70.9 and see where you end up.

Stage 3 vertical record ladder should be shot at 600-1000 yards, and I'm guessing you'll be refined somewhere between 70.2 - 70.8gr in increments of .2grs to identify your least vertical load. After that, you play with seating depths to tune your best vertical load.

NOTE: Normally for competition load development, I load and shoot 4-5 sighters/foulers and let the barrel cool before shooting record ladders, but you need to shoot cold bore ladders since its a hunting rifle.

I totally agree with your assessment. That was the route I was going to take this week with it

 

[GREATSCOTT!]

Awesome, keep updating and documenting this thread as you make progress if you don't mind; this is always great to watch take place.

 

[Longtine88]

Ok, so back to this ladder I've been working on after a week of arctic weather and a few days of rain. I got a break in the weather. 50 degrees no wind or rain. So I am the help of the above decided to go with the 70.1 to 70.7 powder charge range. This is what I did:

1. Loaded 5 at 70.5 as sighters and fowlers.
2. Loaded 5 of each 70.1, 70.3, 70.5, 70.7.
3. Same OAL's as the original ladder firings.

My target was set at 655 yards from the bench. Used 3 fowlers. One to get on target, then 2 at 200 yards to get it dialed in. Then dialed in 11.0 MOA of elevation to shoot.

I used a cold bore type approach since this is a hunting rifle.

I shot one of each group at 4 separate 1.5" targets spaced out around the target which was a piece of sheet metal I had laying around.

1. I shot the first of 70.1 and went through all 4 loads at each of their designated targets letting the barrel cool for 4 mins in between.
2. After the barrel cooled after 20 mins of the first rounds I began the 2nd round and then on to the third round.

After all the shots had been fired I took measurements from center of impacts of each charge weight.

70.1: 1st Left .52" Up .1", 2nd Right .75" Up .22", 3rd Right .2" Up .42". Overall 3 shots 1.24"
70.3: 1st Right 1.05" Up .5", 2nd Left .54" Up .75", 3rd Left .7" Up .32". Overall 3 shots 1.75"
70.5: 1st Right .5" Up 1.3", 2nd Right 2.8" Up 1.8", 3rd Right 2.2" Up 2.5" Overall 3 shots 2.3"
70.7: 1st Right 1.0" Up 2.4", 2nd Right 3.1" Up 3.5", 3rd Right 3.8" Up 2.0" Overall 3 shots 2.8"

Strings 70.1 and 70.3 both had almost identical point of impacts from center and seemed like a stable range between 70.1 and 70.3 because of the very little vertical dispersion and same center of impact point. The 70.5 and 70.7 starting drift up and right from aiming point but still holding a good group. So I still had 2 rounds of each charge weights left and decided to shoot the 70.1 Grains again but this time shoot them one after the other. First shot fell right in the middle of the first 3 shot group. The second went Right .95" Up .6". So this proves my vertical dispersion is really good. It widened the group to 1.46"

At this point I'm thinking of playing around the 70.1 grains and play with seating depths for improved accuracy but then I was like dude this is 1.46" at 650 yards and it's a freaking hunting rifle. The only thing I got to thinking about was maybe dropping down another .2 grains from 70.1 and loading a round of 69.9's and seeing if they held the same point of impact. Thoughts and comments please

 

[Longtine88]

Sorry about no pics, forgot to take them at the target the first trip down and it started raining hard after the last 2 shots I measured and just wanted out of there before rifles got soaked.

 

[GLTaylor]

That is excellent shooting and obviously a very well made rifle. You are shooting competition level groups in your hunting rifle! I would call it good and smile all the way home!!! Any idea of velocities?

 

[Longtine88]

I'm going to load up some more and shoot once more. I'll check the velocities then. They will be around 2940 to 2960