Load Gone Bad

[trout004]

This has happened to some extent on almost every new barrel I have tired regardless of cartridge/caliber. This is why I usually just have fun fireforming the first 50-100 pieces of brass without too much serious worry about load work up. Potential can be recognized though at tis time, and it always seems that a barrel has a sweet spot in the velocity where it shoots better. I try to get back to those numbers after the magical speed up happens.

I would recommend a good cleaning especially in the throat area to remove carbon and then drop your powder charge a bit to try and hit the previous velocity again. By the velocity numbers you listed, I would guess that your load isn't smoking hot, but I do kind of have a hard time believing that throat/distance to the lands hasn't changed after 7900 grains of retumbo was forced through it either. Maybe the change is negligible??

 

[K.E.C. Darkside]

Normal- barrel broke in and a Hot Rod.
Usually this is the time to dial your load.

 

[Ben Keller]

This has happened to some extent on almost every new barrel I have tired regardless of cartridge/caliber. This is why I usually just have fun fireforming the first 50-100 pieces of brass without too much serious worry about load work up. Potential can be recognized though at tis time, and it always seems that a barrel has a sweet spot in the velocity where it shoots better. I try to get back to those numbers after the magical speed up happens.

I would recommend a good cleaning especially in the throat area to remove carbon and then drop your powder charge a bit to try and hit the previous velocity again. By the velocity numbers you listed, I would guess that your load isn't smoking hot, but I do kind of have a hard time believing that throat/distance to the lands hasn't changed after 7900 grains of retumbo was forced through it either. Maybe the change is negligible??

Zero change throat. I measured it when brand new and just did again two days ago. Literally wasn't even off by 0.001 when I averaged five measurements.

 

[lancetkenyon]

2877, even with a 22" 28 Nosler is like putting 87 octane in a top fuel dragster and running a governor to limit RPMs to 3500.

Step on the gas and get to the next node. A 180 should be 3000-3080 in a 22" 28 Nosler. I see 3000fps w. 195s and 3100 w. 184s in 24" 28 Noslers. And 3080-3150 w. 195s and nearly 3200 w. 180s in 26"ers.

Looking at my notes, with ADG brass, Fed GM215M, 184 Hyb and Retumbo, I START at 79.0gr. I find max around 84.0gr +/-. For 195s, I start @ 78.8 and max is usually around 83.4gr in several rifles.

 

[Mike Matteson]

Following!

 

[waveslayer]

Who made the barrel? 2 options, poor barrel quality that finally got somewhat polished and severely caked with copper and carbon and has caused more pressure...

Or it is a quality barrle and needs to be polished because you have fouled it up, causing more pressure.

This is why an OCW test works over a ladder, test different variables for pressure and nodes

 

[BSPPC]

Atmospheric conditions will cause a load to go out of tune, but this is assuming you have an incredibly accurate gun and load to start with.

 

[Phil Rizzo]

This is why I've never gotten serious about load development until I've fired my brass at least once, and that's normally 150 rounds. 2 firings is better.
Brass capacity is changing, and your barrel is changing at the same time.
Fire cracking and hard carbon start to appear. Assuming the copper has been kept out. Some smoothing has taken place, where tiny imperfections are left from the reamer. Or in some cases a lack of lapping.
I never run full power loads on the first firing for obvious reasons. Your gun is fine, it just took a while to settle in I'm betting.
Retumbo is reported to be on the cooler side of powders for overbore cases. I haven't used it in 15 years but I'm betting some amount of erosion has taken place.

If the seating depth worked previously, leave it as is and adjust powder first.
People will give you different opinions on chasing lands, my opinion is do whatever it takes. One thing at a time.

 

[Ben Keller]

Sound advice from a lot of people. The consensus is to adjust the powder amount first and later seating depth if necessary.

I knew I was going to get some hate for the lower velocities in my 22" barrel. I agree that the speed of the 28 is the real benefit so why go so slow? 2850 fps with a 180 eldm is still a 1000 yard gun on any animal in North America. To be honest, I search for accuracy over speed. I am going to step up the powder until I find another sweet spot, but speed doesn't drive me. The gun is 8lbs and 15 ounces. It's short and packs well. How much more speed do I need?

I will update with my results when I have them. Should be back out there with new loads in the next couple days. Thanks to everyone for the info.