New 7mm Rem Mag Load Development

[lancetkenyon]

So I had a member and a friend ask me to do some load development for him on his brand new rifle. I thought I would start a thread about the steps I took for his load development and some results.

 

A little rifle info:

Rem 700 LA DBM action trued

Krieger #5 fluted 1 in 9" twist @ 26" plus Vias brake

Jewell HVR trigger @ about 1.5#

McMillan stock

Swaro X5 3.5-18x50

 

The components he brought me were as follows:

100 New matching lot # Nosler brass

Nosler 160 gr. Accubond

IMR 7828 powder

Federal GM215M primers

 

The good thing about Nosler brass is a lot of the prep work is done or not needed. Flash holes are drilled, not punched, so no need to debur flash holes. Primer pockets seeded no uniforming at all. Weight sorting was easy with the lots I had, because they weigh them and package them by weight in lot numbers. All the brass was within .002" for case length, so I didn't trim any of them. Neck thickness was spot on across 25 I checked randomly, with no variation at all.

 

Brass weights ranged from 254.7 to 255.7 across all 100 pieces. That is as good as my Lapua brass.

 

 

 

 

Checking the shoulder datum with a comparator, I got only .001" of difference across all 100 as well in the new brass. 2.1045" to 2.1055".

 

 

Checked overall brass length on about 50 of them, and all were within .001" too, and at .015" shorter than max SAAMI case length of 2.500".

 

 

The only thing I had to do for prep was to neck size them, as some were a bit dented around the necks. Plus, I wanted the same neck tension.

 

 

Next, I weight sorted the 160 Accubonds and checked BTO lengths and recorded the info down along with everything else done so far for repeatability on future loadings.

 

Across 200 Accubonds, I think weight ranged from 159.6 to 160.3 grains. OAL was an average of 1.403" w. a .0010" +/- and BTO was .822" +/- .0015".

 

Next was annealing the brass.

 

 

I measured max magazine length to ensure the cartridges would fit in the magazine. 3.685" if I remember correctly.

 

I then checked seating depth to lands using an unsized neck case that I stretched out a bit by seating and pulling a bullet so it had neck tension enough to hold a bullet, but loose enough to let it moved with a little pressure.

 

I measured jammed .0015" and just touching the lands lengths. I was also going to try the 175 NABLR, but have never gotten around to working on those yet.

 

 

Easily fits in the magazine

 

 

Plenty of bullet purchase

 

 

Keeping accurate records is key to being able to recreate loads and tweak what is needed.

 

 

Loaded up for break in, sight in, and ladder test.

Bottom row is for break in and sight in. Then a ladder test of 13 rounds from 60.0 to 66.0 (above book max) in .5 gr. increments.

 

 

After sight in during break in, I shot a 3 shot group to verify POI. Not bad for a brand new rifle with no load development. About 1" @ 100.

 

 

Then I shot a ladder test @ 300 since I was by myself and walking down range after every shot gets tiresome. Results were a little different than what I was used to. But shows good potential from a rifle shooting 13 different charge weights at 300 yards.

 

 

The cases fired in this chamber grew fro virgin brass as expected, to 2.115" to shoulder datum using the same comparator. o they grew about .010" after being fired in the new chamber.

 

 

I set the die to bump the shoulder back .002" and resized the fired cases.

 

 

After looking at the ladder test, I opted to try the node for charge weights 5/6/7 (62.0 to 63.0 of IMR 7828 & speeds from 2980 to 3070fps).

 

I loaded up 3 rounds of each starting at 61.5 and going up in .5gr. increments to 63.5 and then went and shot for groups. Everything was under .75", but best was 62.5gr. @ .397"

 

 

Then I started seating depth testing. Started out @ 2.783" CBTO, and went down on .0300" increments seating them deeper off the lands.

 

 

 

 

 

 

 

After testing, I brought group sizes down to sub 1/4".

 

 

To finish testing an verification, I chose a lousy day to test at long range. But I made the best of it. 15-25+mph winds made shooting at 892 yards interesting. But the results were pretty good for the conditions. I went up to 7W, and out in the flats hung a 12" x 18" steel. I had Taylor spotting for me.

 

I dialed 16.5 MOA and held 5 MOA right. First shot was just left of target as called by Taylor. I held another .5 MOA right and hit left side of target. Held 6 MOA right and put the next 5 in a 6.5" group. Not the best, but I was very happy given the conditions.

 

 

I was shooting from the bald hill I am pointing at.

 

 

Came back and loaded up 100 with the recipe.

 

 

Load development took my about 55 rounds total with verification. So 45 virgin brass loads, which I told him to practice with, and 55 once fired loads. All information is in the small notebook, from gun info, scope info, velocities, lengths, shot count, etc.

 

 

Now all he has to do is practice with it, verify drops, and go kill something!

[firstcoueswas80]

Lance, will you send me a link to the case comparator?I've been looking for one of those for the brass but don't know exactly which one to get to measure the shoulder.

[lancetkenyon]

Lance, will you send me a link to the case comparator?I've been looking for one of those for the brass but don't know exactly which one to get to measure the shoulder.

There are 5 different sizes, depending on what cartridge you are shooting. The most common that cover probably 80% are the C375, C400, & C425. Technically called a Headspace gauge.

 

http://www.sportsmanswarehouse.com/sportsmans/Hornady-Lock-N-Load-Headspace-Bushing/productDetail/Reloading-Accessories/prod9999002234/cat100166

[firstcoueswas80]

Which one for 257 wby and 28 nosler?

[Hoss50]

Very nice Lance. I am going to start working on my 7mm Rem Mag load this weekend. I doubt I will get that kind of accuracy out of my box stock rifle, but if I can get to the .75-1" range like your stock test loads I will be super happy.

 

Now I need to save up to build a nice rifle and get some super sick accuracy like you do.

[MULEPACKHUNTER]

Great work. Funny I just started working up a new batch of 50 for edge. I have them in the tumbler now all prepped. I spent some time sorting my pistol brass from recent shoots and man what a pile we shot. Lol

[lancetkenyon]

Detachable mag, McMillan stock, not factory.

[trphyhntr]

Detachable mag, McMillan stock, not factory.

i read that at the top and deleted my comments lol. rarely ever see the 700 DM.

[apache12]

That was so good I read it twice. Excellent post

[apache12]

Could you explain your ladder test? I thought a ladder test was setting five or so targets with five different loads and then shooting One round from each load at a its own target so 1,2,3,4,5 and then start over

[Mike S]

Lots of good info there... do you typically anneal virgin brass?

[lancetkenyon]

I anneal all brass. Virgin, and after every firing. Only virgin brass I don't anneal is Lapua, as it is already annealed from Lapua.

 

As for my ladder test, I load one round ln each charge weight, bullets always seated touching the lands, and shoot them, from lowest to highest charge weights and marking target after each shot. If you get signs of pressure, stop.

When you shoot, your barrel flexes. You should get a node high and low, meaning where the bullet is exiting at either the bottom or top of the barrel whip. The barrel pauses for a millisecond, andbyou will get 2 to 4 together that group well, meaning your barrel likes that range of charge qeight and velocity span. It gives you a bit of wiggle room for velocity differences to still leave the varrel at the right time. Enhancing accuracy potetial.

[WampusCat]

Which one for 257 wby and 28 nosler?

You just need one that will fit over the neck of the case but is smaller than the outside diameter of the shoulder. That way it will land in the middle of the tapered portion. Exactly where isn't super important, only that it's repeatable. The important measurement is the difference between the sized / unfired case and the case after firing.

 

The numbers on the gauge are the size of the hole. 375 = .375" and 420 = .420". Measure your case to find the one that fits the specific shoulder best. Or when you have several you can just drop them on one at a time to see which fits the the best.

[Mike S]

I anneal all brass. Virgin, and after every firing. Only virgin brass I don't anneal is Lapua, as it is already annealed from Lapua.

 

 

Please elaborate on your annealing process if you don't mind. Do you use a machine or just a torch? I've been spinning necks in a propane flame with the case sitting a deep well socket in a drill... but always looking for a better way.

Thanks,

Mike

[lancetkenyon]

 

I anneal all brass. Virgin, and after every firing. Only virgin brass I don't anneal is Lapua, as it is already annealed from Lapua.

 

Please elaborate on your annealing process if you don't mind. Do you use a machine or just a torch? I've been spinning necks in a propane flame with the case sitting a deep well socket in a drill... but always looking for a better way.

Thanks,

Mike

If it ain't broke, don't fix it. I do the same thing, except I use MAP gas. About twice as hot, so it heats the necks faster and you don't get as much transfer down the body. Even though the deep socket acts as a heat sink.