Gunsmithing Wildcat Chamber Issue?

[FatBuddah]

Looking for insight / input /solution / advice to my “issue”.
Backstory is I had a 7/300 win improved (PTG 37* bore rider) that was amazing. Shot 180g hybrids out a 26” Benchmark @ over 3200fps with amazing accuracy. Rifle was heavier then desired so I thought ......self, lets build it bigger and better.
Started off contemplating what case to start with and ended up thinking a 7/300 Norma improved should give good brass and push the 195 EOL’s well over 3100. Began collecting parts...... Defiance Deviant, Proof, Terminator T3, Manners T5A Carbon. Had luck with the last PTG reamer so went back to the well and Dave sent me the 7/300 Norma Rogue.
So here’s the issues.......
1- ejector marks- does not matter if it’s Peterson or Norma brass...... 70g To 90g of various powders 7828 SSC, H1000, Retumbo, RL33, US869, Or N570. See 1st pic
2-lack of speed- again running above powders on .5g increments with 195g EOL’s. Looks like it’ll shoot well, but speeds are less then expected.

Had a second rifle with exact components chambered and it as well shows the Sammie issues.... ejector marks and slow speeds.

I do not have my papers I kept on the different powders and respective speeds.

 

[FatBuddah]

Marks

 

[Bradu]

The 300 norma Peterson brass was .0175-.018" thick at the neck. It requires neck turning for that chamber because the neck can't expand. Measure fired brass to confirm or try to push a bullet into a fired case. I ran into this with mine. Norma brass was .015 so it should have been fine, not sure unless you're chamber is a little long. You could try necking up and creating a false shoulder to see if that helps.

 

[FatBuddah]

Would that cause the ejector marks?

 

[Supersubes]

Would that cause the ejector marks?

If the neck isn’t expanding and letting go of the bullets, yes it would.

How fast is it going, ballpark?

Also, have you put a mic on the base of your 195’s? May be bumping into your freebore diameter.

 

[Mr Punisher]

Use different cartridge, you have wrong shoulder angle - it should not be 37°.
Here’s a picture of the right cartridge , after 3-4 shots if you still have the same issue, just do shot after shot untill problem disappears.

 

[Steel head]

Is that the new Creedmoor?

 

[Bradu]

Use different cartridge, you have wrong shoulder angle - it should not be 37°.
Here’s a picture of the right cartridge , after 3-4 shots if you still have the same issue, just do shot after shot untill problem disappears.

View attachment 7064736

He has an improved reamer which changes the taper and shoulder after fireforming.

 

[Steel head]

,,,, kinda interesting Weatherby like shoulder profiles.

 

[DAVETOOLEY]

I think something is too tight somewhere in the neck and throat area. Over the years, at least for me the 7's have behaved like a different animal vs 30's and 338's.

 

[FatBuddah]

Taken what’s been said and trimmed up 5 cases. Will load these and shoot later today. I’ll post up findings

 

[Geno C.]

You didn’t tell us what your loaded neck diameter is. Can you slide a bullet into a fired case?

 

[Bradu]

You didn’t tell us what your loaded neck diameter is. Can you slide a bullet into a fired case?

Going off the reamer print and neck thickness of the Peterson brass I loaded, he could have reloaded without running it through the sizing die. I had to turn my brass because of this.

 

[Mr Punisher]

Hey Big Boy, how was the shooting today?
Anyways keep in mind you can have my rifle to hunt this year.