Sudden pressure signs

[Grizz1148]

why would a load suddenly have bolt lift issues? Same load that I have shot the last several days, built on the same equipment, same dies, same brass, same bullets, primers, powder same type (retumbo) but new bottle. Double checked scale to be sure it was calibrated, pulled a bullet and weighed charge to be sure and it actually came out 2/10 under for some reason but less anyway. Any ideas?

 

[RockyMtnMT]

Is the new powder the same lot as the last?

 

[DUSTY NOGGIN]

if charge didn't weigh exactly what you expected then id say scale issues

there are other possibilities , but since you know you have at lease one issue ... fix that first

 

[lancetkenyon]

Same bullet lot? I have seen bullets of the same weight by the same maker change in BTO length between lots. Some as much as .020". Which could put you into the lands depending on you previous jump distance. That would definitely cause pressure changes.

Powder lots can easily change pressures, but Retumbo should not be too far off.

Barrel need cleaning? How many rounds? Carbon ring or badly fouled barrel will cause pressure.

Primers from the same lot?

 

[Grizz1148]

diff lot of powder but same load previous owner shot as well. Will a diff lot of powder go from zero signs to sticky bolt?

 

[Grizz1148]

Same bullet lot? I have seen bullets of the same weight by the same maker change in BTO length between lots. Some as much as .020". Which could put you into the lands depending on you previous jump distance. That would definitely cause pressure changes.

Powder lots can easily change pressures, but Retumbo should not be too far off.

Barrel need cleaning? How many rounds? Carbon ring or badly fouled barrel will cause pressure.

Primers from the same lot?

Just cleaned night before firing, shot it yesterday and the day before with no issues

 

[lancetkenyon]

Did you shoot it over a chrono to check to see if velocity climbed as well?

Powder lots can definitely run hotter lot to lot.

 

[lancetkenyon]

Just cleaned night before firing, shot it yesterday and the day before with no issues

Did you make sure you got all the solvent/oil out of the chamber? Chambers needs to be clean and dry for brass to "stick" to the walls when fired and not slip/slam back against the bolt face.

 

[Grizz1148]

Did you make sure you got all the solvent/oil out of the chamber? Chambers needs to be clean and dry for brass to "stick" to the walls when fired and not slip/slam back against the bolt face.

I guess I didn't "make sure" but I cleaned as always.

 

[Grizz1148]

Did you shoot it over a chrono to check to see if velocity climbed as well?

Powder lots can definitely run hotter lot to lot.

I did not. Stopped shooting due to the signs.

 

[Grizz1148]

I knew powder can change lot to lot but didn't know it could vary this much. Hmm

 

[Gregg C]

Is your load close to max ? I found same thing with Retumbo but I am running close to max load. Big cartridge. If your charge is 100grs then 1 or 2 percent is not alot of powder. I myself am recommending backing off 5 percent or more with new lot powder at close too max load. New to me.

 

[Grizz1148]

It is near max and it is a big caliber. 338 lapua. I was obviously going to back it down anyway but thanks for the info. Didn't know lot to lot could vary enough to cause this much extra pressure.

 

[Gregg C]

In fact next time I open a new lot, I'm going to back off to Hogdgon start weight to see whats what. Better burning components than hurting myself my rifle or others. 2 cents worth.