Hidden Pressure Reading: A Method

nksmfamjp said:
I find bolt lift to be a pretty consistent pressure indicator….better than primers. The only real issue is it is more of a ~70000 psi indicator, it seems so I find I need to back off about 1gr on a 60gr load.

I do also find pre-bolt lift are ejector marks under 10-20x magnification.

I would warn you straight walls like 458 Lott don't really exhibit bolt lift IME.

Are any of you not seeing bolt lift?

I have only once had a primer pocket issue. That was clearly a brass issue.
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I think if you get to bolt lift stiffness you're beyond primer pocket longevity. Having a sacrificial case to "load to pressure" is what I've done. Then back off a grain, then reduced .3gr till I found accuracy.

I think if I monitor my Lapua brass from the start and keep the primer pockets to no growth to under .210 I won't need to hit the bolt lift sign.
 
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I had same issue with Nosler brass with it first came out. I bought some in 300 RUM. After 3 firings the primers were almost falling out. Never bought any for any caliber again. Back then with my Rem. bralss I could get 7 hot loads before primer pockets started getting loose. I use ADG, Norma and Rem. now depending on cartridge .
 
If I get heavy bolt lift. I am overpressure. I generally don't get there. I am watching my case all the time. Proven or unproven. In my Belted Mags I lose primer pockets in about 12 rounds. That being Winchester Brass. I have just switch or switching to Peterson or Lapua brass now. Other cases I generally don't lose to primer pockets.
 
Gingerman said:
I think if you get to bolt lift stiffness you're beyond primer pocket longevity.
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I must be more sensitive to bolt lift or something…

I agree heavy bolt lift is past good pressure. That is why it is only used to define max,,, then I back off until it shoots. No need to find heavy lift with more than 1-2 rounds. There is no accuracy there.

I've never lost a case from a loose primer pocket except Winchester 350 leg brass that was crap!

Everything else fails from neck cracks or too much sizing causing thin case heads.
 
nksmfamjp said:
I agree heavy bolt lift is past good pressure. That is why it is only used to define max,,, then I back off until it shoots. No need to find heavy lift with more than 1-2 rounds. There is no accuracy there.
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Sage advise. I have seen loads shoot their best where there is the ever slightest increase in bolt lift, very slight, which went away in cold hunting weather. Remember, in a single lot# of brass, there will be cases that have the very slightest amount of Rockwell softness, maybe 2-3 out of a hundred of which would be Rem, Win, or Federal, brass. I do not know about other brands, but be aware of this issue.
 
Mark37082 said:
Oh great. Another tool I need. My latest rifle seems to show pressure by those shiny ejector marks. Once I hit heavy bolt lift the brass is usually trashed with ejector marks. Chasing velocity has a down side.
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I have save problem with my C.A. Ridgeline 6.5 PRC. Drives me nuts. I have an MGM TC Encore full bull barrel in 6.5 PRC that I can't even get pressure signs in with 4 grains hotter than C.A.. 🙄
 
You guys are free to do whatever you want, but I really can't believe how many times this has to be repeated. If you are getting hard bolt lift you are WAY WAY past pressure limits. You are north of 90,000 PSI and past even proof test loads. If you are losing primer pockets after 1 or 2 firings, even on soft bras, you are Way past pressure limits. All of the traditional pressure signs, flat primers, ejector marks etc are well over the proper pressure.

Hodgdon publishes the pressure for all their loads, and these are all 100% tested. Different guns, powder, brass will give slightly different results but if you think you can significantly exceed their velocity or loads you are just fooling yourself. If you think loads have been lawyered, call Hodgdon. They will confirm that better testing equipment and current powder profiles is what has lead to current loads.

Like I said at the start, guys are going to do whatever they want, but I am glad I don't have to share a range with guys shooting 100,000 PSI loads.
 
dogz said:
What kinds of speeds are you running?

Pressure equals speed and speed equals pressure
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This grand experiment has so many variables. Following a manual or others' experience must be approached with great care especially when trying unpublished load combinations. Some barrels, bullets, powders, and brass seem to hide pressure more than others. Combine that with AI or wildcat chambers and things can get complicated. Running pressure ladders looking for signs of pressure is the only way I know to find the sweet spot. Speed is only one indicator, but is not absolute IMO.
 

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