intermittent pressure signs 6.5 cm

[rockwind1]

so had a load worked up for my 6.5 cm ruger rpr gen1. might have 1700+ rds thru it. i posted something about it before but running 1x norma with 42.3 gr h4350, br2's and berger 140's at about 2740ish. usually no problems. i am going to try to describe as well as possible

but the other day i loaded up 4 different test groups of the same 1x brass, one group had uncleaned primer pockets, another group had cleaned pockets, i i used a mandrel to set neck tension, another i used a bushing.

one group had 10 rds and i used 5 fed 210m primers and 5 of my usual br2 to see if i had any difference in es.

i wound up with 4 sighter rounds out of the loading session.

so i go out, with no previous pressure issues, and i fire the 4 sighter rounds, no problems. then i fire the 5 rounds with fed 210 primers with no issues.

i then fire one of the rounds with the br2 primers, super heavy bolt lift. really shine ejector. weird mv same as always per labradar. maybe i screwed up a case somehow, says i. i shoot another,,,,same thing, heavy bolt, super shiny ejector mark. now i do something stupid and shoot one more after looking at it and comparing it to other loaded rounds. same thing so now 3 in row from that group have serious pressure marks, so i finally give up on that group. i go to another group and i fire one, same thing again. i put gun away to check out at home.

i borescoped it and other than being dirty, i don't see anything too crazy.

i go out today with some factory fedggm 130 gr hybrids

i shoot 3 at 550 yds in a nice tight group that i am very impressed with, i send one more, out of the blue, super heavy bolt lift, shiny ejector! i shoot one more, same thing. mv very close on all 5. the last 2 did not seem to shoot as well on target but i may have been nervous.


so question, why would it shoot 3 with no problem and then 2 with pressure? with the factory ammo.

obviously i am going to clean the crap out of it and try again

 

[shoot4fun]

Carbon ring in the chamber?
Maybe even a double ring; carbon in chamber and carbon/copper in throat.

 

[rockwind1]

Carbon ring in the chamber?
Maybe even a double ring; carbon in chamber and carbon/copper in throat.

figured i would see it with my scope but maybe not,,, there are very very few pictures out in the internet of real carbon rings. for some reason. anyone got a good picture?

 

[varget204]

Look for a dark,blackish ring at back of throat,easy way to tell,with over size brush[brass works the best or stiff nylon] ,take about 20-30 stokes in throat w/cleaner on it,then run a wet patch down barrel,if there is a carbon/copper ring patch will be dirty

 

[Webster]

My Berger reload manual has 40.7 gr 4350 max load for a 140 gr bullet 2685 fps. Your making an assumption that a border line hot load would show pressure on every shot. I am sure other manuals will give different max loads. Decision time. Maybe your barrel bore is on the small end of diameter spec.?

 

[golong]

You are running a lot of powder for a 140 (your charge is more suited for a 123 grain). What I am wondering is why are your velocities so slow? Something does not add up. At 42.30 you should be pushing 2900's.

 

[T-shooter]

Possible variations in componets. How close are your powder charges? There can be variations in bullet lengths, weight, and diameter. I've seen Berger and Sierra as much as .0003" out of round which is withing their tolerances. Case volume can vary. I've seen the same part number in different lots (in .308) vary by as much as 7%. Also if you are pushing zero jump, a few 1/000ths can make a difference. And the temper of the cases can cause more or less neck tension regardless of the expansion when the bullet is seated. I would think that different pressures would show up on the chrono but possibly not. Are your barrel temperatures staying close to the same?

 

[ballisticdaddy]

I run almost the same load 42.2 grains of H4350 pushing a 140 hybrid around 2,780 fps with no pressure signs of any kind. What did you shoot for 1700 rounds and what did you change for these loads?

 

[rockwind1]

I run almost the same load 42.2 grains of H4350 pushing a 140 hybrid around 2,780 fps with no pressure signs of any kind. What did you shoot for 1700 rounds and what did you change for these loads?

Sorry for late reply

I shot almost exclusively prime Ammo but maybe a 100 rds of asst hornady. I started reloading and had lots of 140 hybrids. Update. I scoped the muzzle end of the gun and believe I found some lands missing so I think it is a barrel issue. Have new barrel in hand will put on asap.