Load Development Weirdness

[Dirt_Nap]

New build. 300prc proof cf barrel on a defiance action

Shooting 199gr hammer hunters

About 110 fired so far. Awesome groups with 80gr of H1000.
Started out consistently at about 3050fps. Hit the jump and I'm at 3100. Very consistent std deviation between shots. About 5fps.

The weirdness is I can only get about 10 shots before the group opens up wildly. I'm talking 1.5" groups. While with a clean barrel I'm getting under 1/2" moa.

Came back and cleaned and more copper fouling. Talked to proof and they said I shouldn't be getting fouling that quick. They said they have guys that don't clean their barrels for a few hundred rounds.

Any ideas on what's going on?

 

[Mikecr]

Is it the bullet type?

 

[Dirt_Nap]

Is it the bullet type?

What do you mean? I'm sorry I don't understand what you're asking

 

[Dmagna]

What do you mean? I'm sorry I don't understand what you're asking

He's asking if the groups open up with different bullets as well

 

[Allen Kitts]

I shoot the exact same load in one of my PRC's and have had no issues like that at all. The rifle is currently on 57 rounds since the last cleaning and the rifle is shooting 1" groups at 300 yards verified on steel last week before my buddy took it to Alaska on a Moose Hunt.

When you say ten shots, is that in a row or overall total over time? If your getting serious copper fouling in ten shots there is either an issue with your barrel/bore or an issue with the Hammers themselves. I know Steve at Hammer Bullets would be happy to talk with you about the copper issue if you gve him a call as they are great people to deal with. He may be able to help.

Please keep us informed on what you figure out.

ADG Brass
Fed 215M Primers
80.0 Grains of H-1000
199 Grain Hammer Bullets
3092 AVG FPS

 

[GLTaylor]

All I've shot for the last few years in several rifles is Hammers. Some old barrels and some new ones. So far, no issue at all with copper fouling in any.
They do recommend you scrub down to clean metal before starting with Hammers if you've shot other bullets.

 

[Mikecr]

What do you mean? I'm sorry I don't understand what you're asking

It sounds like it's copper fouling out, and I don't know anything about Hammer bullets.
GLTaylor pretty much removed the bullet from question, and Proof is suggesting that it shouldn't be a barrel issue.

You're implying a fouling issue, so I wonder what fouling condition the bore has been in during load development?
If fully fouled, then it goes to barrel/action temp and some kind of stress in your build.

 

[Dirt_Nap]

My patches after 10 rounds today

 

[Chadp82]

based on those patches, it doesn't seem like extreme fouling to me.

I have seen more blue than that from jacketed bullets on some of my patches.

Are the 10 shots you took in a single string or is there cooling in between at all?

 

[RockyMtnMT]

Are you using a bronze brush. They will give false positives. Use nylon brushes.

 

[Dirt_Nap]

based on those patches, it doesn't seem like extreme fouling to me.

I have seen more blue than that from jacketed bullets on some of my patches.

Are the 10 shots you took in a single string or is there cooling in between at all?

The 10 shots were over about 2 hours. I never really let the barrel get hot

 

[Dirt_Nap]

Are you using a bronze brush. They will give false positives. Use nylon brushes.

I'm using all bore tech. Proof positive jag and nylon brushes

 

[Mikecr]

For 10 shots, that's more copper than I would accept.
What condition was the barrel during load development (fouling-wise)?

 

[Flintlock shooter]

I have had this happen before. What cured the problem for me was changing to a faster powder. In my case, I went from H1000 to H4831SC. I have never used Hammer Bullets so I don't know if it would be the same as with a cup and core bullet, but might be worth a try.
Also, it's important to get 100% of the copper out when you clean. If any is left in the barrel it will cause more copper fouling.