7PRC Load Development: 184 Grain Berger F-Open HT and Ramshot L.R.T

[rockchalk06]

Went out mid afternoon on Friday and ran a couple of ladder tests on this new HMR in 7PRC. Goal was to push this 184 grain F-Open Hybrid Target as close to 3k as I can. I did 2 strings. LRT and Retumbo. Retumbo only got me to 2880, but I have some promising results I'll explore later on. I really wanted to focus on LRT as I have a ton of it on hand and it hasn't worked well in either .300 PRC I have so far. I kind of want to "make it work" in this 7.

Found a good speed node on the slow end around 2970 FPS. I've marked 75.3 grains with .015" jump down in my book to explore later. Not sure what happened with 75.5 as I had the barrel cool and all 4 shots from 75.1 to 75.7 you could cover up with a nickel. I'll come back to it later on possibly.

I ended up choosing 76.3 to run some tests on.



I decided to run with a CBTO of 2.652" which puts me .015" off jam. Plenty of room in the mag, plenty of bearing surface in the neck and I'm not quite into the shoulder junction yet.


When I ran my ladder test, I hit 3017 FPS with 76.3 grains at .015" off jam. My first 5 shot group averaged a little slower (it was 25 degrees cooler) but if I could have a mulligan on whatever happened with that flyer, I'd of been stoked. SD was a tad high at 9, but that flyer was the 4th shot at 3020 FPS. Either way, I was happy with this group, this early. That's 4 shots in the cluster.


Another .005" deeper had a lower SD, but I had a wider spread in the group. Also had more vertical that I prefer. Also had a little drop in velocity.



Another .005" deeper got worse. That wild flyer was the 4th shot.



Another .005" deeper and I get the feeling that I'm wasting some very spensive components. This group looked decent, but my SD went to hell really fast.



Another .005" deeper and I was glad this was the end of this session. Group, SD none of it was acceptable.



All 50 pieces of brass are in the cleaner now, will anneal them later today and load up more this evening. 76.3 grains at .015" off jam looks really promising. I think I am going to load 10 more with this combo and see if I can duplicate this at 100 and see what 200 shows. I want to play with the charge some. Not sure what I will do yet.

This rifle is a blast to shoot. Just enough thump to let you know you are not shooting a .308 and didn't beat your ass like the .300 PRC will.

 

[rockchalk06]

Well, L.R.T. was a soggy shit sandwich this morning. Speeds dropped a good 20 FPS, would not group under an inch. Against my better judgement, I pushed it to 200. Even worse.

Back home cleaning my barrel and loading up some test groups with Retumbo.

 

[JCann]

Why not run H1000? When my 7WSM barrel was new I could achieve a little over 3k with 66.5gr

 

[rockchalk06]

Don't have any on hand

 

[rockchalk06]

Retumbo did pretty good yesterday. The higher charge of 67.7 had the best SD and group. I threw that last shot I think. I mental fucked myself on it. I took extra time and kept telling myself not to screw this up lol



I'm going to roll with this charge and work on seating depth next trip. I'd like to see that FPS a little higher, but I can live this this.

 

[JCann]

Gosh, I get this speed out of a 13 year old barrel with >2,000 rounds and two grains less powder. Looks like the 7PRC is all hat and no cows. I guess hornady is up to their old tricks with a different chambering. Capitalism, you got to love it.

Not busting your balls but this chambering doesn’t do anything the 7WSM already did. Including a 2.67” five shot 1,000 yard UK record.

 

[rockchalk06]

I'm beginning to think that Retumbo likes a lighter for caliber bullet? I got excellent results in both 300 PRC's with 205's vs 230's. Just not getting the speed and accuracy I want in 7PRC with it. I did have a depth at .025" off jam that gave me a sub 4 SD, but lots of vertical and meh. I'll note that and maybe come back later.

I loaded up a ladder test using N570 since I was able to get 12 more pounds. I have two pretty identifiable nodes once I broke 3k. Zero pressure, very promising

 

[rockchalk06]

Ladder test with N570 went well. I found a couple of nodes. Ran 5 at 71.3, 71.5 and 71.9.

71.3 had the best 100 yard group, but had some vertical and the SD was 13.5
71.5 had a really nice group with no vertical and an SD of 14.1. I had one round go 3065 FPS a full 31 FPS over the norm. I exclude that shot, it's a 3.6 SD.
71.9 had 3 in a hole with 2 just outside. SD of 7.1. Tighter group than 71.5. I can work with an SD of 7.

Will run some seating depth tests this afternoon or tomorrow AM. Starting at .015" off jam and ending up .027" off jam. 12 pounds of N570 showed up yesterday, so maybe this was a blessing.

I also picked up a TriggerTech R700 trigger and installed it yesterday. I know this is a cliché, but stock kinda sucks ass.

 

[rockchalk06]

Thanks to Phil over at Berger. I'm kicking around a couple bullets to load for a buddies 7PRC. He sent me their data.

Berger 175 Grain Elite Hunter


Berger 195 Grain Elite Hunter

 

[rockchalk06]

Seating Depth tests went well. Everything was under an inch, but this load at 2.646" stacked. I forgot the target


I'm going to run some distance tests with the above. I'm also going to drop a little off to another node around 2980 I found. I've been looking at data all over the net and I've seen a ton of data under 3k.

 

[rockchalk06]

I forgot to post this. This the Berger data on the 184 LRHT from Phil over at Berger. They don't have Retumbo on it. Said they didn't get the velocity with it they wanted. I'm beginning to think Retumbo just isn't a heavy bullet magnum powder? I didn't get shit for speed in .300 PRC with the 230, but I did with the 205.

This from Hodgdon

 

[rockchalk06]

Not sure if it was the heat (Sunday 06/30 @0645 88°) or what, but in my ladder test, 71.1 Grains of N570 at .020" off jump, chrono'd at 2998. I dropped these seating depth tests to 71.0 even and averaged 3010-3015 all morning. That's only a 10° spike in ambient temp v's my ladder test. I will keep track of that.



This bullet likes a little jump, but not much. I found a nice node between .025" and .030" jump. The other groups had way to much spread and SD's between 9-22.



I loaded up 5 more at .030" jump and .027" jump with .002" neck tension (the above rounds were all .002" neck tension) and will load up the same 5&5 with .003" neck tension when my 21st Century order arrives.