28 nosler- extreme pressure with 1x fired brass

[jlvandersnick]

28 nosler , Sammi spec chamber, 26 inch 8.5 twist proof barrel. Clean barrel

I did some preliminary load development while fire forming 105 new (annealed) nosler brass. I hit pressure at about 78.5 grains of retumbo, ..... 3070 fps with the 195 bergers. Shot good groups at 77.8gr (3030 fps)

FL sized brass, bumped shoulder back .002 (.0015) neck tension. Loaded 13 rounds at .1 grain intervals. 77.0 to 78.2 (same can of retumbo, same package of fed 215 primers).

First shot at 77.0 gr showed A LOT of pressure. Thought that was odd.
Loaded a round at 76 grains still a lot of pressure
Loaded a round at 75 grains still some pressure sign
Loaded a round at 74.5….still pressure……..2930 fps

HELP!

 

[odoylerules]

I didn't see where you mentioned your seating depth. Could you be really close to the lands? I've seen that over pressure brass before. Have you verified your trim length? I've also seen big pressure when the neck protrudes just into the bore a bit too much. That can cause a helluva spike. Also, what pressure signs are you seeing exactly?
I've been using Nosler brass in my 300 win and am pretty unhappy with how it's holding up.

 

[Lonewolf74]

Broz had this problem a year ago with a 30 Nosler. I can't remember exactly but I think he had to drop 2 grains of powder going from virgin to once fired brass. In his case though that brought him back into the node whereas the load he found with virgin brass was faster (and pressure signs) when put into once fired.

His theory is virgin brass acts as a buffer sort of absorbing the pressure. He stated he has seen this before just not to the extent that it was with the 30 Nosler. His fix was simply to keep load development to fired brass.

 

[Copperline]

I had the same problem with Retumbo and H-1000, pressure in the middle of book loads. I switched to Vihtavuori 570 and it was magic better velocity with less pressure.

 

[jlvandersnick]

I didn't see where you mentioned your seating depth. Could you be really close to the lands? I've seen that over pressure brass before. Have you verified your trim length? I've also seen big pressure when the neck protrudes just into the bore a bit too much. That can cause a helluva spike. Also, what pressure signs are you seeing exactly?
I've been using Nosler brass in my 300 win and am pretty unhappy with how it's holding up.

The sweet spot was about .012 out with the new brass. That is where I started with the 1x brass....when I was clear down to 74.5 with the powder charge, I moved one round to .002 out and it was a little less pressure for the same powder charge.

Trim length is still about .010 short of the "TRIM TO" length....which has been my experience with nosler brass. Their brass is notoriously short.

The main pressure signs are difficult bolt lift and noticeable circle where the ejector "plunger" is. Can't remember it's exact name right now. Primers are not flattened horribly like you see some times.

 

[jlvandersnick]

I had the same problem with Retumbo and H-1000, pressure in the middle of book loads. I switched to Vihtavuori 570 and it was magic better velocity with less pressure.

Great......another powder. I already have about 4-5 different ones that I'm using for various rifles.

 

[jraulsten]

I have had the same problem before and discovered it was simply from not chamfering the outside of the case mouth on my first reloads. Combined with a chamber cut to exact tolerances, I saw pressure signs at lower charges than that used on the virgin brass. There may have been more to it than that but my issues went away after the second resizing

 

[Prwillard2]

I had the same problem with Retumbo and H-1000, pressure in the middle of book loads. I switched to Vihtavuori 570 and it was magic better velocity with less pressure.

Got any more of that N570? It's harder to find than a unicorn.

 

[jlvandersnick]

I've got an update. I resized two of the 1x fired brass that had showed pressure at 74.5 gr retumbo. Pushed the shoulder back an additional .012 for a total of about .015. I think that is about sammi spec brass. Loaded those two rounds at 77.8 retumbo which was a pretty accurate load in the virgin brass. Virtually no pressure signs and velocity of about 3065. Something about this chamber that doesn't like brass that is sized something other that sammi spec

 

[odoylerules]

Got any more of that N570? It's harder to find than a unicorn.

I emailed vihtavuori about the scarcity of 570. They said they're producing it, but it'll be several months before we see it in large quantities in the States.

 

[jraulsten]

I emailed vihtavuori about the scarcity of 570. They said they're producing it, but it'll be several months before we see it in large quantities in the States.

I was told next year.......Whatever that means

 

[DUSTY NOGGIN]

just thinking out loud ,

maybe the first firing did not fully expand to chamber , you then bumped and additional .002 , totalling ??? then seated your bullets at .012 away from lands/rifling -- if your once fired brass still needed .010 to fully form , if your pin jammed that bullet into the rifling , that could create a spike like you experienced

the seating jump must exceed, the shorter of the sizing bump or the belt gap.

i think seating deeper would have relieved some of that pressure but also think you powder charge was too much for what ever reason,

i have had retumbo lots that are different than others , i will never buy 1 lb bottle of retumbo ever again , having to reverify the new bottle every 70-80 shots gets old ,

even though you measured trim , i would still measure the maximum neck length of your chamber just to check that off the list

 

[Alex Wheeler]

I've got an update. I resized two of the 1x fired brass that had showed pressure at 74.5 gr retumbo. Pushed the shoulder back an additional .012 for a total of about .015. I think that is about sammi spec brass. Loaded those two rounds at 77.8 retumbo which was a pretty accurate load in the virgin brass. Virtually no pressure signs and velocity of about 3065. Something about this chamber that doesn't like brass that is sized something other that sammi spec

What you are doing is take pressure off the boltface. A shorter case is pushed forward in the chamber by the firing pin, the pressure causes the case to expand and grip the chamber. Then the brass will have to stretch to reach the boltface. While this does reduce the signs of pressure, pressure is still there, and your on the fast track to a case head separation and a face full of hot gas. Pushing the shoulder back too far is what causes case head separations. Bump shoulders to a minimum.

 

[dok7mm]

I was thinking "what the heck" also. Definitely, setting shoulder back a total of .015 is inviting trouble, when it probably wasn't fully formed to start with. Alex knows of what he speaks.