My first custom chamber: 300 Ultra X! (Creedmoor was taken)

[Mram10us]

Here is a pic of a cutoff piece of brass. The walls are .0365" thick. From base to interior flash hole surface is .202". Expansion will definitely stretch the case walls, but with a .0365" wall, it seems there is more than enough to make up for it. I'll find out during the pressure tests today

 

[Rum Man]

Here is a pic of a cutoff piece of brass. The walls are .0365" thick. From base to interior flash hole surface is .202". Expansion will definitely stretch the case walls, but with a .0365" wall, it seems there is more than enough to make up for it. I'll find out during the pressure tests today
View attachment 165746

I can build the heck out of a House ..but you have me puzzled with your endeavor on this Rum !! Lol
Rum Man

 

[Mram10us]

I think what he meant is the rum brass is only about .550 while the .7 of flat is around .560. The cup section (.220) should not blow out much, but ahead of that it will probably swell to .554-.557 maybe not quite that much with spring back but the "swell" probably will be noticeable.
My question is how did the straight section finish after the reamer quit cutting?

No issues on finish that I could see. I always polish my chambers after. I'll take some pics of the chamber with the borescope after shooting today. Also, get some pics of the inside of some fireformed pieces of brass to see the interior differences

 

[Mram10us]

I can build the heck out of a House ..but you have me puzzled with your endeavor on this Rum !! Lol
Rum Man

I like fiddling . That lathe has made more work for me. I've made comparators for my cartridges, headspace making tools, jigs, jags, etc. Crazy what is possible

 

[Rum Man]

I like fiddling . That lathe has made more work for me. I've made comparators for my cartridges, headspace making tools, jigs, jags, etc. Crazy what is possible

Send over the info on your lathe sometime ! I like a little trouble too !! Ha ha
Rum Man

 

[bigngreen]

Im baffled by what you have going!! I've done this but never had this straight section your talking about.

 

[Mram10us]

Im baffled by what you have going!! I've done this but never had this straight section your talking about.

So the end of the 300wsm reamer is inside the chamber when finished by x amount. The x amount is all the same diameter. I know you understand this stuff, so I must not be clearly explaining it. The diagram on the first page shows two arrows from .5563. That shows the flat from base to the ~.7 mark.

 

[Mram10us]

Send over the info on your lathe sometime ! I like a little trouble too !! Ha ha
Rum Man

I'll text it to ya. Best tool I've ever had. Pays for itself in a couple rifle builds.

 

[bigngreen]

So are you driving the reamer .740 past the end of the cutting flutes creating an actual straight section in the chamber?

 

[Mram10us]

So are you driving the reamer .740 past the end of the cutting flutes creating an actual straight section in the chamber?

Can't remember the exact amount on the reamer since I was going off of headspace measurements. I can check later

 

[Mram10us]

Update:
Did the pressure test today at 300yards. The starting charge of 86gr h1000 with 230otm showed high pressure. I shot these:
86.0 3011
86.3 3011
86.6 3004
86.9. 3015
Pretty tight bolt lift on the 86.9 so I stopped. Back to the drawing board.

Bad: definitely need to fireform with light loads and make sure the bullet is in the lands or the case had a bit of crush. Had one case head separation on a loose fitting round.

So far, the cartridge isn't worth it if I can only get 3011 with a hot shootable load. Too early to tell though.

 

[can1010]

I always thought that H-1000 was to fast for the 230s. had better luck with retumbo when it was available now rl-33 has been working with the heavies. are the primers showing any pressure or is it case design? any pics of brass?

 

[Mram10us]

I always thought that H-1000 was to fast for the 230s. had better luck with retumbo when it was available now rl-33 has been working with the heavies. are the primers showing any pressure or is it case design? any pics of brass?

I'll try r33 next. Also, get you guys some pics of brass when I get back home

 

[can1010]

playing with wildcats is expensive but a lot of fun and more failures then successes. I know I changed my 30-338 rum imp reamer a couple times and about to make another change for all the new bullets and brass that is now available
keep us informed and have fun.