What happened to my load?!

[25WSM]

I would check how clean your barrel is. New barrels can foul out real fast and need more frequent cleaning. Since you have a chrono try the Satterlee development load test. This will tell you where your node is better than group size to start. Then do groups in that window of the node. Then do a seating test. This will save you time and components. Always follow up with a few 5 shot groups to make sure it is what you think it is. This is how I do my sporters. My benchrest guns start the same way. But have a few additional steps.
Shep

 

[Elkeater]

Did you workup the first load with new brass and the second load with once fired brass.

This very thing has gotten me before.

 

[mpayne]

Tag

 

[John Klingenberg]

That 40 to 50 extreme spread you wont notice in groups at 100yds. As others said I'd send a few more down range. I also wont record an average velocity until I've shot 10 rounds over a standard chrono. The average from ten will more closely follow your ballistic data. On a magneto or lab radar id do at least five to get my average.

 

[brentc]

I just worked up my first loads for my bergara hmr in 300 win mag a week ago. I shot 3 rounds groups going up in .5 grain increments and found a node at 77 grains that gave me <0.4moa groups at 100 yards.

So I went back and loaded up 10 more identical rounds at 77 grains, and 5 each at 77.2 and 76.8. Same exact everything. Seated .02 off the lands.

This time my 77 grain load was 2 moa, the 76.8 was 1 moa and the 77.2 was 1.5 moa.


What happened?? I was so happy. Was it just sheer accident and luck I shot <0.4 moa with a crap load?

Not only was the grouping terrible but my ES was 40-55 FPS. I'm very careful using my beam scale with a powder trickler frequently adding or removing one single granule to get exactly the same each time.


I don't even know where to go from here. Up? Back down to the next lower node that was ok? I really don't want the slower velocity several grains lower. I'd rather stay up near 2950 but now it shoots like garbage.

What brand of brass are you using? If it's anything other than Norma or Nosler, you're probably over pressure at 77 grains with fired brass in a SAAMI chamber. There is a significant case capacity difference between virgin and fired brass in belted mags. On a 300 WM the shoulder will move forward .016"+ from a virgin to fired case due to headspacing off the belt on the first firing. After the first firing with a properly sized case you will headspace off the shoulder just like a non belted case. Over pressure is often masked if you worked up your load with virgin brass.

Back it down to the next node in fired brass, which should be around 75 grains.

 

[SidecarFlip]

I'm chuckling as well and I've been here a long time. I gave up on 100 yards long ago. I sight in at 250 now unless it's my muzzle loader. Heck, I have a handgun that shoots 100 yards....lol

I bet the tube is filthy too and the case necks are getting wokhardened.

 

[TRG65]

I've gone to 3 rounds of testing because I've seen this. I'll do groups of 2-3rd groups at each charge weight .2gr apart. Then on the best narrow to .1 apart. Then if it is still the best shoot a 4 or 5-3rd group set and 10 rd chrono. I've had loads that shot ok on the first two and then go to crap on the last. I've never the 3rd round go to crap with loads that shot really well on the first trials. I always shoot some of a known good load to gauge my shooting for the day also.

 

[Bob Wright]

I now make it a habit to record each velocity for each round fired through all the groups. Then transfer over to your targets and study them. All the input above is helpful as well. When your barrel gets to 100 rounds, then measure jump again, and seat accordingly. Your node will shift until all brass is fire formed and your barrel has been seasoned and settles in.

 

[Mram10us]

I wait 50+ rounds before load workup, but you still can learn from what you've done. Take the load that shot well, and load .1-.2 gr less. Also want to clean the barrel a bit. Not every shot but probably twice in the first 50 rounds

 

[freddiej]

Oh so many questions, so little time to ask them.
as I see it, 3 shot groups get you good prospective loads, 5 shot groups rule out loads that seemed good but aren't, 10 shot groups normally tell you when you have a solidly good load. strings of 3 shot or 5 shot or 10 shot groups are the only way to test out the load to see if it is a good/great load.
I have heard so many ways of choosing a good load, one that I laugh at is one a friend uses and he is a good shooter.

My questions start with: thin barrel or heavier barrel?

Was the sub 0.4" group shot with a hot barrel or was it cool/cold?

I have a rifle that shoots awesome (sub 0.5") with a warm barrel and crappy (1.25") with a cold one. that is my play rifle and it makes some people scratch their heads. the real problem is it is not a varmint/high round gun. it's a M-70, featherweight, carbine (16.5" barreled) 270 Win, light pack rifle.. AKA my go to deer rifle.

did you use a ladder loading method? (I really hate this method- I never can come out with even a mediocre load)

I had a Winchester 70 coyote and Browning something in 223 WSM that hated loads much above starting loads. you might have one of those rifles.

 

[Mram10us]

Ladders work ... if it likes the bullet. Even the worst shooting bullets have nodes

 

[101stCurrahee]

So many answers, so little time...


So this (pictured) was just a sheer statistical coincidence?

Here's the rest of the info

I shot 50 rounds through it new, Shooting once clean once 5x then shoot 5 clean once for rest of the 50. I then shot 30 more (in groups of 3 at different charges) working up my load where I shot the pictured group at 77 grains. At 77.5 grains it widened up, and I stopped at 78 grains even though I still had no signs of pressure.

So at that point I had 80 rounds through. I then loaded up these 20 more that were garbage at the same charge weight. So now I'm at 100 total.




How I started- 100 new brass from gunwerks. I trimmed all to within .001 of each other. I chamfered and deburred and then tumbled. I primed with cci #250s. I checked seating depth with a modified case and got 2.909 with my Berger 215s at the lands. I used a Hornady comparator for measurements. I then meticulously loaded as perfectly as possible with H1000, and seated the bullet at 2.889 for .02 off the lands. I followed this exactly for all the loads I did.

The second test run was once again the new brass. I haven't run through it all yet to mess around and alter after it's fire formed.

I sat at the same bench shooting off a sled for all but a couple that I shot off a bipod to see if it was any better. With my "good load" the first 3 of the 5 were still terrible. It didn't widen up because it was a 5 shot." I also had nearly the same ambient and ammo temps waiting the same amount of time between shots.

The only difference was I had by chrono in closer a bit the second time, maybe that contributed to high FPS a bit too?


My barre is not thin. It's a heavy profile barrel. When working up my 10 3 rounds each loads it kept it as even with temps as possible. Besides the first group or two warning it up(which were 72 grains I had no intention on sticking with) I let it cool to roughly the same temps.


All I did for load testing was the 3 round groups in .5 grain increments, shooting for raw accuracy groups while keeping in mind the vertical dispersion. I wrote down every single shots velocity and saved all targets and information.

 

[mpayne]

101- does 2.889 fit into your clip?

 

[101stCurrahee]

Here is the target from yesterday with the same 77 grain load showing how much different it was. I shot the first five round group of 77 cold and then after I was warmed up shot another one with the same bad results.

The 76.8 looks far better but still meh