Does anyone know at what pressure sticky bolt lift occurs?

[memtb]

Haha me too. Chemical plant?

High pressure Sour gas plant, here. My last job, near 18 years, the wellhead pressure was 22K psi + with 15 or/so % H2S. High enough to warrant some degree of caution!

Oh, I forgot to mention the plastics plant that I worked in in Baton Rouge……on some products, our reactor pressures exceeded 60 K psi. It was fairly low volume, but you still preferred it to remain contained! memtb

 

[Mike Matteson]

I sure everyone else has chimed in already but sticky bolt lift for me had always happened after I had ejector swipes. So to me sticky bolt lift is way over pressure. I've ran a gun with very very light ejection swipes and it was just slightly over max book charge. I don't do these things anymore. You load can change so fast with temp it's just not reliable. I found the most reliable, accurate charges around it at 75% to 90% of book max. Maybe even lower and about high as 95% book max. There definitely a given sweet spot for every rifle and brass combo. I used to run my 300 RUM maxed out with a 220 ELDX on some RL26. It shot good till I hit about 65 degrees. Now I'm looking at a much milder load that will still have some HP but nothing that recking the brass after a few reloads.

I keep pounding the ground over temp stable powders Some powder change as much as 1.75 & more fps per degree. That turn into pressure increase or decrease per degree. Even if you are using the manual to there powder max load there can be a problem. I hunt in weather from -20 to 110 degrees. I do load above the max powder loads shown in the manual. This what I don't do: I don't use double base powder persently do to their reaction to temp. It's my understanding that there is some double base powders that have reduce their problem with temp. I haven't tried them yet. There been a lot of talk about creatoring primers, and that doesn't really tell the true story. I can go along with that.
I wll set up and do a run up on my powder and pressure by increasing my powder loads by about .5 gr increases until I have flatton primers. I am very carefull about creatoring of primers, and ejector marks. No heavy bolt lift. With creator, ejector marks and heavy bolt lift to me are big problems.
In a great many years ago I stepped into that problem with double base powders and temper change in a late winter into summer and temper changes. I do realize that generally bouble based powder get better velocity, or that's been my experience. If that is where you want to go with double base powders, so be it. Becarefull!

 

[Carey Farmer]

High pressure Sour gas plant, here.

La Barge by any chance?

 

[Frank in the Laurels]

...it would vary from rifle to rifle, depending the reamer specs at the time of the chambering...fresh or well worn reamer...I loaded for a standard .308 awhile back that was sticky well under maximum and other that are well above..

 

[Carey Farmer]

I keep pounding the ground over temp stable powders

Yep. Retumbo, H1000, and N165 are about all I shoot.

 

[VinceMule]

Carey, I think that you are over thinking the issue. Just back down and work up carefully. Brass Rockwell hardness may also vary within the lot and how square the bolt face is maybe another issue.

 

[AussieWriter]

There is a common propensity for handloaders to push too hard. It has become common for owners of .257 Weatherby's to boast their 3700fps loads with 100 garin bullets where Weatherby specs were 3550fps.

Likewise I have seen even the old .30/06 have 180grain handloads well past 2900 fps and pushing into .300 magnum territory.

Brass will fail with fewer reloads and barrel life will shorten whenever factory maximum velocities are exceeded. Sure, there are cases where this is justified such as very old cartridges originating in rifles with actions having less strength than modern rifles made with contemporary steel compositions.

The main factors relating to common sence reloading is that 100fps lower velocities won't be noted as different in most hunting situations and the use of a chronograph is mandatory when building loads to qualify any gains and to maintain repeatability when velocities and accuracy level goals are achieved.

Some of the best maximums are when you stop at an accuracy node, even when the chronograph records a little less velocity than you wanted.

 

[Carey Farmer]

Carey, I think that you are over thinking the issue.

I've been told that a time or two.

 

[cajun]

Mostly oil and gas. Worked in one field that had shut-in wellhead pressures near 10,000 psi. Worked in another that had gas re-injection compression to 5000 psi.

Yes sometimes folks forget the square inch thing. We had a several ton reactor head that was being removed and popped off killing a guy. Turns out there was only a couple psi on the vessel. Of course it should have been zero.

 

[Hugnot]

I prefer long brass life & easy bolt cycling with uniformity & accuracy. My loads probably max out under 64K psi. Some might think my load velocities are pathetic.

Young's modulus applies in any comparison between brass & steel subjected to tension/compression but I don't have any intention of subjecting my relatively soft & weak & pricy brass cartridges to chamber pressures to the extent where differences in steel barrel/chamber design are a bolt operation consideration. I think of my rifle chamber as being sort of rigid/fixed volume space intended to contain rapidly expanding gasses.

I can appreciate various safety features & design over engineering to increase strength & safety for a device that might be subjected to pressures over 70K psi as a result of simple negligence.

Another factor that might be considered is brass head size, like comparisons of cartridge diameters of .473 inch and .532 inch. Assuming chamber pressures are exerted in every direction within the cartridge inside the chamber with loads having equal pressures, the .532 inch head would have .222 sq inches of bolt face surface contact compared to the .473 inch head having .176 sq inches of bolt face contact. Assuming P= F/A, if P remains constant, like 64K psi and A increases from .176 in sq to .222 in sq >> F = A * P, like more bolt thrust force caused by A increase.

"Clickers" can occur even with paltry low pressures - like 1X fired brass from foreign chambers - small base die usually fixes this.

Temperature effects on certain powders are a consideration. My journal of past events showed a bad experience with H414/Win760. The deal was heat - like stepping into a furnace from my nice A/C truck. Hundreds of rodents were lounging about on mounds from 200-600 yards. I had a .22-.250 loaded with 75 AMax (discontinued) & 34.5 gr. H414. I anticipated heat & had about 150, .22-.250 rounds stashed in my cooler with bottled water & Pepsi. After 12-15 rounds sticky bolt lift happened. Everything was hot including chamber, nice cool rounds heated up when cooked in chamber. I switched rifles and resumed ops using a .20P with 25.5 gr. of IMR8205 & the 40 Vmax. .20P hits well over 350 were made but the 600 yard rodents were bullet safe. I now use 36.5 gr. StaBall 6..5 with the 75 ELDM.

To complete my analysis of the problem I need access to an electronic microscope to look at brass crystal growth/structure. Like 2 mil X magnification & $75K-$100K cost. Having that, I could see the brass crystals become smaller and see if any orientation changes occured.

^^ looks like low pressure applied on large area.

 

[cajun]

I keep pounding the ground over temp stable powders Some powder change as much as 1.75 & more fps per degree. That turn into pressure increase or decrease per degree. Even if you are using the manual to there powder max load there can be a problem. I hunt in weather from -20 to 110 degrees. I do load above the max powder loads shown in the manual. This what I don't do: I don't use double base powder persently do to their reaction to temp. It's my understanding that there is some double base powders that have reduce their problem with temp. I haven't tried them yet. There been a lot of talk about creatoring primers, and that doesn't really tell the true story. I can go along with that.
I wll set up and do a run up on my powder and pressure by increasing my powder loads by about .5 gr increases until I have flatton primers. I am very carefull about creatoring of primers, and ejector marks. No heavy bolt lift. With creator, ejector marks and heavy bolt lift to me are big problems.
In a great many years ago I stepped into that problem with double base powders and temper change in a late winter into summer and temper changes. I do realize that generally bouble based powder get better velocity, or that's been my experience. If that is where you want to go with double base powders, so be it. Becarefull!

I do use double based powders but I will work up loads in the summer so temps during season will be lower. The other way around is a recipe for problems. Even with R17 which is not supposed to be very stable I never had issues. Just adjust zero in cooler weather.

 

[RichCoyle]

I live in Oregon but I was loading for a guy with a 22 250 in Arizona. So I put everything in the windshield in direct sunlight. It must have been 140 in there. I don't know it was so hot, anyway, no matter what temperature he encountered, his loads were going to be just fine.

 

[memtb]

La Barge by any chance?

Yep……The LaBarge Project, I actually worked at the plant! However, the high pressure, high SO2 plant was at Lost Cabin! memtb

 

[Mike Matteson]

Yep. Retumbo, H1000, and N165 are about all I shoot.

Varget H4350,H4831,H1000, H4895. I use IMR 4064 in my 220 Swift.