Over Pressure

[live2huntmt]

I just started developing a load for a CA Ridgeline 300 RUM with 200gr AccuBonds jumping .020" and Retumbo in 1x fired Norma brass and Fed215 primers. I am way below book charge weights and way over pressure and high velocities. This is a new keg of Retumbo...do you think it's just a really hot lot #? Even 89.2 grains is flattening primers, cratering around firing pin, showing both ejector circles, and clicking at the top of my bolt lift. Is there anything that could be causing this other that really hot powder?

The blue line is an average between the two test rounds at each charge weight.

 

[cohunt]

You change bullets? Copper fouling?
Brass too long (doubt it but possible)
How many rounds through the barrel? Carbon ring?

I'm sure those are just the basics though

 

[live2huntmt]

You change bullets? Copper fouling?
Brass too long (doubt it but possible)
How many rounds through the barrel? Carbon ring?

I'm sure those are just the basics though

I did change bullets and powder. Previous load was RL33 and 230 Bergers. 120 rounds thru the barrel. Around 40 since last cleaning.

 

[sedancowboy]

Not sure it will apply. But I have found it best to strip the copper out before changing bullets.

 

[Shane Lindsey]

I do not know anything about RE33, but I heard it is very notorious for a fast carbon ring build up. May start there. I bought a used RUM. I have cleaned the throat out pretty good (no borescope) and it still pressured early with book loads.

I am new to the RUM and found I had very high pressure/velocities early. All within Nosler min/max. I am not loading to the lands, but still loading a little longer than book OAL. I think the book min/max are listed for their listed OAL to allow for the freebore of the RUM to reduce pressure. Again IDK, still new to the RUM.

I reduced charges down on my last load down to 2gr below book start and got my velocities/pressure to be about what book max velocity was with no pressure signs. Barrel also a Christensen 28". I did not reduce OAL though.

 

[J E Custom]

Just a guess, but the Accubonds have a different O jive than the Berger and act differently with the lead angle, so I would back the Accubond off at least .030 to start with or even .040 on a few to find out if this is the problem.

Retumbo is also one of those powders that can go critical if things are not to it's liking. Also do as suggested and clean the bore and chamber back to white metal and check case length.

J E CUSTOM

 

[Mram10us]

I'd be looking for a carbon ring.

 

[live2huntmt]

I'd be looking for a carbon ring.

How do I look for a carbon ring?

 

[338 dude]

Since you don't own a borescope I would just clean as if you know you have one look for different threads about carbon rings and see the different methods of cleaning for one

 

[fiftybmg]

Did you confirm the 1x fired brass was trimmed to spec the first time you used it ?

Don't assume because it's once fired it had no time to stretch.

The case mouth is prevented from opening when it protrudes into the freebore, raising pressure.

 

[live2huntmt]

Did you confirm the 1x fired brass was trimmed to spec the first time you used it ?

Don't assume because it's once fired it had no time to stretch.

The case mouth is prevented from opening when it protrudes into the freebore, raising pressure.

It is trimmed to min, neck turned, chamfered and de-burred. Also dry lubed to inside of neck. Necks are expanding.006" when fired.

 

[fiftybmg]

If the neck expansion is normal to the case mouth, then there may not be a mechanical problem, just reduce the load till you fall in line with the velocity max.

It happens that every rifle behaves differently, chambers differ slightly, which is why it's always recommended to work the load up.

Federal 215 is the hottest primer available. It was made for the 378 Weatherby. Is that the primer specified in the load manual ? Nosler indicates a WLRM primer. which is slightly cooler.

 

[DUSTY NOGGIN]

i believe it to be something to do with oversizing shoulder or primer choice or lube left on the case ,

i have had same issues , load at 88.8 at pressure with WLRM primers , switched to cci's get to 92.5

i would not use wlrm primers with this bullets / powder combo, possible over bumping shoulder allows headspace clearance ( try for crush fit when closing bolt )

also seating farther away will lower your pressure

 

[live2huntmt]

i believe it to be something to do with oversizing shoulder or primer choice or lube left on the case ,

i have had same issues , load at 88.8 at pressure with WLRM primers , switched to cci's get to 92.5

i would not use wlrm primers with this bullets / powder combo, possible over bumping shoulder allows headspace clearance ( try for crush fit when closing bolt )

also seating farther away will lower your pressure

I am bumping the shoulder back .0015", verified by both my RCBS precision mic and also a Sinclair bump gauge. I have also adjusted neck tension from .003"-.0015" with no noticeable difference. I just stripped the bore down to bare metal and will try again soon. If nothing changes, I will switch primers and seat the bullets .020" deeper.