Horrible run out. 6/284

[Jimbee]

Just a theory, and I don't have any first hand experience with finding data or loading for Wildcat-284 (yet..), but I have read about excessive headspace and too low of a charge allowing the case head to slap the bolt face and produce ejector marks that are actually false pressure signs.

Were you testing with fireformed brass?
Any bolt lift, or just ejector mark?
Where did you get your data?

I started with some new Norma 6.5/284 brass necked down in 3 steps with a Redding 6/284 bushing die. Somewhere on this forum another member said he was using 55gr H1000 with a 108eldm. I started a 53 iirc and it was too hot. I think my chamber is on the loose side, but was told within spec. I decided to throw money at the problem and bought some Lapua 6.5/284 brass and tried again with the same result. Backed down to 49 grains and it shoots good, but slow. I tried once fired brass at 50gr and get ejector marks and can sometimes feel sticky bolt lift.
I resized the brass with a full length 6/284 Redding die. I measured headspace growth and am just bumping back shoulder until the bolt closes easily, a few thousandths. It requires a bit of effort to resize. It's been a problem child. It's strengthening my resolve to move towards having only 223 and 6cm.

 

[Harvey_NW]

I started with some new Norma 6.5/284 brass necked down in 3 steps with a Redding 6/284 bushing die. Somewhere on this forum another member said he was using 55gr H1000 with a 108eldm. I started a 53 iirc and it was too hot. I think my chamber is on the loose side, but was told within spec. I decided to throw money at the problem and bought some Lapua 6.5/284 brass and tried again with the same result. Backed down to 49 grains and it shoots good, but slow. I tried once fired brass at 50gr and get ejector marks and can sometimes feel sticky bolt lift.
I resized the brass with a full length 6/284 Redding die. I measured headspace growth and am just bumping back shoulder until the bolt closes easily, a few thousandths. It requires a bit of effort to resize. It's been a problem child. It's strengthening my resolve to move towards having only 223 and 6cm.

Loose chamber typically won't be the reason for pressure with fireformed brass, being tight somewhere will though. FWIW the only resizing die I've ever struggled with was a Redding. I would assume all 6-284 reamers would be no turn (depending), but it sounds to me like you might have too much material in the neck from sizing down, which I've read can also cause pressure.

Does a bullet drop into a fired case easily?

 

[Jimbee]

Loose chamber typically won't be the reason for pressure with fireformed brass, being tight somewhere will though. FWIW the only resizing die I've ever struggled with was a Redding. I would assume all 6-284 reamers would be no turn (depending), but it sounds to me like you might have too much material in the neck from sizing down, which I've read can also cause pressure.

Does a bullet drop into a fired case easily?

Yes, I checked that.

 

[Harvey_NW]

Yes, I checked that.

Damn. Okay last thing I can think of, measure the fired case diameter at .200" above case head the best you can, and make sure it's not under SAAMI min.

I have a 284 Win originally chambered by a well known smith and his reamer was under spec. It pressured out (nearly locked the bolt up and stuck a case first shot with a mild load), and basically all he told me was "it closed on my gauge". Sent to another smith and he cleaned it up and had it running smooth as silk.

 

[eLightfoot]

have you checked for donuts formed inside the neck?

 

[HighUintas]

Damn. Okay last thing I can think of, measure the fired case diameter at .200" above case head the best you can, and make sure it's not under SAAMI min.

I have a 284 Win originally chambered by a well known smith and his reamer was under spec. It pressured out (nearly locked the bolt up and stuck a case first shot with a mild load), and basically all he told me was "it closed on my gauge". Sent to another smith and he cleaned it up and had it running smooth as silk.

I second the idea to check the 0.200 line. I also had a smith that cut a 284 chamber for me, but he used a 30-40 year old reamer that was specd for the old win brass that has a smaller 0.200 dimension. The Peterson brass I used barely fit. This caused me to have early pressure signs and sticky extractions. Lapua and Peterson 284 both have a fatter 0.200 dimension than Winchester.

if you have a minimum amount of clearance in the chamber I think it's possible that the brass just can't expand enough to absorb some of that pressure.

H However, I'm not a gunsmith.

 

[Jimbee]

Damn. Okay last thing I can think of, measure the fired case diameter at .200" above case head the best you can, and make sure it's not under SAAMI min.

I have a 284 Win originally chambered by a well known smith and his reamer was under spec. It pressured out (nearly locked the bolt up and stuck a case first shot with a mild load), and basically all he told me was "it closed on my gauge". Sent to another smith and he cleaned it up and had it running smooth as silk.

I did measure the .2" and the cases grew quite a bit. I'll have to see if I can find where I wrote it down. I thought that's why I couldn't resize with a full length non bushing die, but turns out the inside of the die was really dirty. I did spray it out with carb cleaner because that's all I've ever done with new dies previously, but my GS said he put it on a lathe and polished it.

 

[Jimbee]

have you checked for donuts formed inside the neck?

I have not.

 

[AZ_Hunter]

Any updates?

 

[Jimbee]

I did figure out why I was getting pressure with low charge weights of H1000. I found out that I was using an old partial 1lb jug of H1000 that had some varget mixed in.
I'm hoping to get time to play with it again soon.