6 UM or 6-7PRC?

[Jimbee]

Typically when a print is made on neck down case, especially 7 to 6, they add neck length in the chamber due to natural neck growth from necking down. Do you have a print to refer to? My other trick, is chamber an empty case, and put my teslong bore scope in from muzzle side, I can typically see if there's room from case neck to end of chamber.

How much clearance should a person try for?

 

[Jimbee]

I’ve had the same thought as well. Going to try the 115s with n570 in fire form brass, and if that doesn’t work I’ll shift over to Berger’s and then hammer bullets. My gun HATES the 108 elem

My FF brass shot the same with N570 and 115dtacs. 106 taps and H1000 wasn't very good in virgin brass.

 

[longrange13]

My FF brass shot the same with N570 and 115dtacs. 106 taps and H1000 wasn't very good in virgin brass.

Have you been cleaning your barrel at all? I was going to try not cleaning on this gun like form and Ryan and shawn carlock were talking about. But I am questioning that choice. Especially since my first 6 shots out of the gun with 115s hammered. Then I quit keeping track while I was fire forming then when I came back to accuracy it sucksd.

 

[khuber84]

How much clearance should a person try for?

I would have added 0.015-0.020 necking down 0.040 bullet diameter. Believe we did 0.020 on my 6 Saum and 6 PRC.

But referring to clearance, man I always use my Henderson and take em back to min spec trim length. Beings chamber is 2.290, I'd say 2.27 or 2.275 would be sufficient.

 

[Jimbee]

Have you been cleaning your barrel at all? I was going to try not cleaning on this gun like form and Ryan and shawn carlock were talking about. But I am questioning that choice. Especially since my first 6 shots out of the gun with 115s hammered. Then I quit keeping track while I was fire forming then when I came back to accuracy it sucksd.

I'm not going to clean it.

 

[longrange13]

I'm not going to clean it.

I need to bore scope mine as well and see if I got a bad barrel that is missing chunks of throat after 100rds. Hopefully not

 

[longrange13]

Got my Henderson trimming head in finally. Case forming and first firing put me right at max case overall length of 2.280” for the um reamer. Re-sizing the brass for the first time put me at 2.282”. I trimmed them back to 2.277”. Hopefully will get to shoot em this week.

 

[longrange13]

Got a few reloads done to test. Once the brass was formed there was no weirdness during the reloading process. No buckled shoulders, etc. Will shoot a few groups this week.

I also ran my bore scope. Barrel looks surprisingly good after 100 rounds. You can see some scratches in the throat, but it looks better than my 6.5 creed currently does after 800rds.

 

[longrange13]

Shot for velocity and pressure today. 20” barrel, Peterson brass, 115 dtacs.
67gr n570 - 3193
68gr n570 - 3242
69gr n570 - 3273.

Probably could push it to 70grns and be fine but I’m calling it at 69.

 

[wind gypsy]

 

[GoatPackr]

View attachment 751200

Any modifications to the case other than neckin it down?

 

[IrkedCitizen]

6.7 cUMmins is better

 

[wind gypsy]

Any modifications to the case other than neckin it down?

Don't know. I've no further intel beyond what was in that post.

 

[Axlrod]

6.7 cUMmins is better

Nah already trademarked it.

 

[longrange13]

Shot for accuracy tonight. First 3 shots grouped well, I stopped and let the barrel and can cool because mirage was so bad I couldn’t see from the can. Once it was about half way cooled down, I shot 3 more shots. The first two grouped well but the 3rd flew way high. After that I let the barrel cool down about 3/4 of the way and then shot 2 shot groups and repeated until I got to 10. Seemed like letting the barrel/can cool helped. I need to get a supressor cover seems like. If it’ll hold similar groups in the future I should be good to go. At 69 grains this time I had clickers on each shot. Not sure if it’s the brass or if I’m higher pressure than I should be. May end up dropping it a half grain. There was a mild ejector mark but the primers weren’t flat. Average velocity over 10 shots was 3285

 

[khuber84]

@longrange13 what dies are you using? Whats the web dimensions of a fired case with clickers VS a sized case? I'm sure UM likely went the with 0.535" chamber spec at the 200 line, or I'd hope they did.

 

[longrange13]

@longrange13 what dies are you using? Whats the web dimensions of a fired case with clickers VS a sized case? I'm sure UM likely went the with 0.535" chamber spec at the 200 line, or I'd hope they did.

The hornady competition 7prc dies with a 6mm insert. I’ll have to check the web dimensions when I get home.

 

[longrange13]

@longrange13 what dies are you using? Whats the web dimensions of a fired case with clickers VS a sized case? I'm sure UM likely went the with 0.535" chamber spec at the 200 line, or I'd hope they did.

Sized case is .532 fired is .534

 

[Jimbee]

Shot for accuracy tonight. First 3 shots grouped well, I stopped and let the barrel and can cool because mirage was so bad I couldn’t see from the can. Once it was about half way cooled down, I shot 3 more shots. The first two grouped well but the 3rd flew way high. After that I let the barrel cool down about 3/4 of the way and then shot 2 shot groups and repeated until I got to 10. Seemed like letting the barrel/can cool helped. I need to get a supressor cover seems like. If it’ll hold similar groups in the future I should be good to go. At 69 grains this time I had clickers on each shot. Not sure if it’s the brass or if I’m higher pressure than I should be. May end up dropping it a half grain. There was a mild ejector mark but the primers weren’t flat. Average velocity over 10 shots was 3285

I shot 10 rds 6/7prc 68gr n570, 115 dtac, Peterson once fired brass. I had ejector marks and about half were clickers. 3206 fps with an 18" barrel. 2" group.