7 ELR

[Shadow292]

Hi folks just joined been reading here awhile now.
Looking for advice with carbon ring issues.
Built a Christensen Mesa LR 7 RM to shoot heavy 7s 190 bergers 175 eldx ect.
I fired about 300 rounds with only magpro with no issues. I have alot of it cuz I can find it.
No carbon issues at that point but I seen some have success throating for the longer bullets with powders i cant find like H1000 and N565 so I tryed it with my go to magpro and I'm getting great velocities now but unknown accuracy due to immediate excessive carbon build up at the throat entrance AKA carbon ring. I'm not totally clear what causes this and would like some input before i just off all my magpro and start from scratch.
I'm hoping theres an easy fix like increased neck tension to give the powder more time to burn in the case or deeper seating.
I can experiment with those variables but it costs precious components and another $30-$60 for more neck bushings.
if I back off the charge I'll loose my velocity gains from throating it.
Any advice would be appreciated.
It's a 26in 1:9 416R barrel
Thankyou

 

[NamibHunter]

What speed are you getting with the 190’s? Any soot on the case below the neck? How far away from pressure signs are you?

Have used Magpro 4000 MR in a 6.5 - and it does burn more dirty than H4350. Used a Teslong bore scope and also saw faster carbon buildup in the neck of the chamber and the throat, so cleaned the throat with a bronze brush and Ballistol (there are better carbon solvents too, i just used what i had on hand). Mounted in a drill, set it at low speed, and rotated the oversize bronze brush (carefully), inspecting every 60 seconds or so. Cleaned up the neck fairly quickly. Then used Iosso paste to clean the carbon out of the barrel with a nylon brush and a cleaning rod. Not too difficult, but you have to be real careful with the brush: If any of the twisted steel wire that holds the bristles together come into contact with the chamber walls, it will cause damage. So use a good bore guide like a Dewey and don’t apply too much force.

My conclusion was that the powder works well enough if you are in the upper speed range, but you will need to clean 2x more frequently and clean more thoroughly (until the bore scope says you are done).

Not my favorite powder, but workable, and most important it is available. I use it as a backup in case i run out.

BTW: 4000 MR is somewhat temperature sensitive, but still workable. You might want to reduce your summer load slightly.

 

[Steel head]

I found my magnums especially the more overbore ones need much more frequent cleaning, even more so with double base powders like R26 and N570.

Not aggressive cleaning, just more often.
I just use patches and wipe out about every 50-125 depending on if it’s shooting solids or cup/core.
I can’t say I’ve had any carbon issues since I started cleaning more frequently.

I just can’t get away with the lazy cleaning schedule my 260 allowed without issues with my 7mm or 338

 

[7mmFanBoy]

300rds no accuracy node yet . Clean 60-100rds I would say don't throat the 7mm mag doesn't need it . I did it 338 edge gain alot of capacity also experience accuracy issues with the 338. Try different powder 7828 imr 4350 imr 7977 any reloader 22 or higher. I like expander mandrels for neck tension / Nice about 7mm mag plenty of dies out there to test