Sudden pressure signs

[Grizz1148]

There is one possible. Oil or cleaner left in the chamber will cause a case to slam into the boltface and give signs of high pressure. Dry the chamber thoroughly before firing loads

Pretty sure it was dry but thanks for the input.

 

[Grizz1148]

Thanks for all the input guys. I'll be testing this weekend, I'll post what I find. I'm guessing powder lot as that is the only change.

 

[Calhntr]

30 yrs ago, Had the same thing happen after firing. 270 Winchester cases 4-5 times, case length grew too long, closing the bolt got increasingly harder , and after firing much worse, could barely open the bolt, just had to trim the cases back to recommended C.O.A.L, problem solved.

 

[Grizz1148]

30 yrs ago, Had the same thing happen after firing. 270 Winchester cases 4-5 times, case length grew too long, closing the bolt got increasingly harder , and after firing much worse, could barely open the bolt, just had to trim the cases back to recommended C.O.A.L, problem solved.

I would've checked for that but this is once fired lapua brass that didn't do it before changing lots of powder.

 

[TwoMore]

I am on the powder lot wagon, retumbo is famous for spiking. Please forgive me if you have already answered it but how many rounds has the rifle shot.

 

[mfk]

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?

was the day you were shooting much hotter than the other days? did your ammo have a chance to get a lot warmer?

 

[Grizz1148]

No. About the same

 

[Grizz1148]

I am on the powder lot wagon, retumbo is famous for spiking. Please forgive me if you have already answered it but how many rounds has the rifle shot.

I've only shot it 50 rds, bought it used on LRH and it's supposed to have 75 from the original owner

 

[Locknload]

You might want to read the following reaserch article which may document a similar incident to your change of powder lots.
https://arxiv.org/pdf/1501.07163.pdf

Ed

 

[MarkA]

You might want to read the following reaserch article which may document a similar incident to your change of powder lots.
https://arxiv.org/pdf/1501.07163.pdf

Ed

+1 This!

 

[SilverbulletMAG]

Didn't read the entire thread but if it hasn't already been mentioned, possible carbon ring causing pressure spike?

 

[TwoMore]

I've only shot it 50 rds, bought it used on LRH and it's supposed to have 75 from the original owner

I know with my rifles I see a jump in pressure around the 100 to 150 round mark and I usually have to drop a a bit on my load to keep the same pressure and chrono speeds. one rifle I was hunting with this year picked up 100 fps and had some bolt stiffness,surprisingly it was the dept of winter go figure lol. just dropped my charge 2 grains and it settled right in there. I think if you get some speed readings and adjust the load you will be Good to go

 

[skipglo]

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?

Go with the bullet length absolutely....measure each bullet in the box. I recently encountered this problem with 208 great MATCH BULLETS with a variance of .05 top to bottom. Couldn't close the bolt on every other round. Had to individually seat and caliper 20 rounds I had loaded to get them out of the lands .Subsequently they are back at the manufacturer

 

[HTJ]

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?

After you clean well you should place some good anti seize grease behind the bolt lugs where they make contact with the bolt face to help prevent gauling. Just a thought to try.