case forming newbie has screwed up somewhere- pls help

[Ogre6br]

What have I done wrong???
This is my first rifle that requires this level of case prep, never done necking up and turning etc


Have been forming brass for my 30 BR and have run into a problem

I sent of 4 dummies with the barrel when it was getting built
Necked up using Redding tapered 6mm-.30cal expander
2 Lapua and 2 Norma brand cases – 1 each with 125 TNT and 1 each with 168 sierra HPBT

G-smith under instructions to make chamber usable with both brands of cases

Neck is to be .334 for a turned loaded size of .330- I like a little extra clearance as this will be a hunting as well as a play comp gun

Talking to the G-smith when he is ready to do the job-- he says his .336 neck reamer better matches the cases and my dies.
No problems make it a .336 neck chamber.

Get rifle back for G-smith- in the middle of chemo cycle at the time so it just went into the safe.
Setup to form brass
Using same tapered expander
Same press
Same lube
Same shell holder
Same die to shell holder clearance +- a thou or 2 either way- die ring still locked from previous and screwed in hard to press
Using the Norma brass as I have 200 of them- Keep the Lapua for my 6mm BR.

Neck up the brass
Run a few of the brass through the neck turning expander mandrel for the neck turner
Turn the brass to give a .330 loaded neck dia,125 TNT)

-Go to test chamber new dummy-
-Case jambs in chamber
-Check neck dia stamped on barrel .336
-Re-check neck diameter with MITAtoy dial calipers .3295 .330 loaded- same box of TNT’s a previous dummies
-Dissasemble new dummy- random check dias of projectiles all ok and as best I can tell all the same.
-Remeasure case necks ---fine
-Reassemble dummy
-Jambs
-Disassemble
-Try case by itself
-Jambs
-Neck turn another case as donuts measures .339-.340 so cases need turning to fit anyway.
-New case loaded TNT dummy .330 loaded
-Jamb

-Go make a coffee and try calm down

-Turn a neck paper thin to make sure it’s not the neck
-Still sticks at same spot as before

Am neither equipped or skilled enough to make a chamber cast with liquid metal- don’t know it’s name

-Put case into drill chuck and polish the case mirror bright with 00 steel wool and chamber with some force
-Jambs tight
-Ring line mark on the case around circumference 75-80 thou down case body from first shoulder
-No marks on neck
-Measured diameter of bright ring mark .4615-.462
-Checked 10 other necked up cases- all within the .4610-.4620 range

Grabbed a new Lapua unfired un necked up 6mm BR case, NO un necked up Norma left)
-Polished it mirror bright
-Measures same area as where bright ring was on necked up cases- .4565-.4570
-Chambered with some force
-Jambs tight
-No bright circumfrential ring
-Skuff marks in case body on one side ranging from single -20 thou wide score mark from shoulder to almost rim
-Additional contact patch about 40 thou to left of score mark in a pear shape approx 120 wide to almost 300 starting 40 thou below where ring mark was to 250 thou above base of case.


-Grabbed the biggest bronze brush I have,.338) and run on high speed in cordless drill covered with patch material inside chamber- tight fit
-Patch material comes out clean except top tip near rifling
-Clean barrel
-Redo tight patch on .338 brush- material comes out clean

Do 338 brush by itself --rotation to get all of chamber neck and beginning of rifling

-Spray out with PC compressed air and then INOX lube
-Redo tight patch on 338 Brush till patch material is clean once again
-Re-polish unfired Lapua case mirror bright again and chamber with force again
-Same score line- same contact patch some jamb and non closing of bolt


What am I missing??

What have I done wrong

Please help

Oh yes- tried dummies that went to G-smith- chmbered smooth as melted butter

P

 

[fdshuster]

Ogre6BR: Very detailed, well written & described post. I've read it over several times: reads like a murder mystery. Have you verified that the mouth of the case is not stopping on the forward end of the chamber? Example: Overall case length of 2.340" for a chamber length of 2.328", just using numbers for example). I would look at this area, but that would not explain the rub markings on the case body. If it were me, and the g'smith were within driving distance, I'd be at his shop demonstrating the problem to him in person, and let him figure it out. Try setting back the shoulder further than would be "normal"? Could his chambering reamer have a smaller than standard base diameter? Hope others, more experienced chime in with some answers: very interesting: keep us informed.

 

[fdshuster]

Ogre6BR: Another thought: Will the bolt close on an out-of-the-box Lapua 6BR brass case? If there is a problem with chamber body dimensions, too small?) it should show up here. What about closing the bolt on a BR "Go-Gage"? If a chambering reamer was used that had cut many chambers, it will be worn to the point of cutting undersized chambers. Chamber cast material is "Cerrosafe", and after reading the directions, I did not want to get involved with it. I take my chamber dimensions from a fired case, minus the allowance for "spring-back". Somewhere there is an answer, and don't be so quick to think you "screwed-up".