what are good high pressure signs to look for

[Lloyd Smale]

in shotgun shells. Do the primers flatten like a rifle primer when your getting up there in pressure?

[lavenatti]

I suspect the shotgun would be in pieces long before that type of pressure sign showed up.

[turbo1889]

You cannot count on pressure signs on the primer.



Do not look at the primer.



Primer means nothing.






















What you do want to look for is head expansion and/or sticky extraction. A single shot break action gun, especially those with a spring activated unsupported extractor finger in the bottom of the chamber is of considerable help in working up shotgun loads. Even if you are loading for another gun that is a pump gun or such having a break action gun preferably a good sturdily built one with an extractor that is driven by a spring not a mechanical cam and even better yet the extractor is not directly mechanically supported at the bottom of the chamber is a very good thing to have to use as a test gun.

In such a gun with high pressure loads the shell will stick in the chamber and when you open the action the spring will not be strong enough to eject the shell and it will not eject and you will have to use a cleaning rod to push the empty out of the chamber from the muzzle end. That is a very good thing and is the final pressure sign that tells you that you have exceeded maximum pressure levels by nearly 20% or so and need to stop what you are doing and back off.

Before that happens at lower but still quite hot pressure levels you will usually get extraction that is sticky and hesitates.

Before that happens you will usually get shells that eject fine but if you try to re-chamber the empty you can feel the resistance because the head has been fully expanded to the chamber. If the shells you are using are weaker head two or three piece separate base wad hulls you will be at about a maximum load that is at or slightly below maximum pressure levels when that happens. If on the other hand the shells you are using are strong head single piece compression formed hulls such as Remington STS or the old single piece compression formed Winchester AA hulls then you will be just a little over max.

If the extractor is unsupported you will also see a visible bulge formed in the bottom of the hull head brass right over the extractor where the shell is not fully supported. A phenomenon very similar to what happens with unsupported chambers in Glock handguns with metallic pistol cartridges. You can measure the extent of that bulge with a micro-meter, or a set of calipers, and even see the difference in how much it bulges with the naked eye with progressively hotter loads. Comparison with known maximum but not over pressure loads followed exactly from published load data in the same set of hulls from the same box (either once fired only or better yet brand new unloaded hulls purchased as such from the same bag) will tell you what you need to know at least as best as it gets without actual pressure test equipment.

YMMV but that is what I know and have learned about pressure signs in shotgun loads. As always no guarantees can be made and you proceed at your own risk.

[375RUGER]

:goodpost:

[357maximum]

Read post #3 real well. Awesome post.:p

I would add that with shotguns it is Best/Ideal to follow atrusted loadbook recipe 100% to the letter. Real world that is not always gonna happen due to available components ...... so read post #3 for them occassions.

[hubel458]

Post # 3 is the way. In our 12ga FH work my ole NEF
gets workout. Plus I mike the base cups after setting the bases
new or second loaded cases all the same on a MEC Super sizer.
After a while with experience I can take mike reading and can
get the top load without going all the way to sticking case level.
and also with lab testing we did I measure so i can relate expansion
to a certain tested level.ED

[405]

To my knowledge there is no reliable way to tell- short of a pressure gauge. I think of the internal ballistics of a modern shotshell this way- small quantity of very fast powder under a bunch of stuff that does complex, dynamic things and weighs a lot. Or- given the above parameters, very fast powder means a very sharp pressure curve that is just short of being too hot when loaded correctly. BUT, foul one thing up and that very sharp pressure curve quickly exceeds the capability of the firearm and kaboom. Not much margin for error, so the details of components and recipes in the reloading manuals are a friend indeed.

[Lloyd Smale]

thanks guys I saw a post online somewhere where a guy was reading primers for pressure it it just didnt seem possible to me.

[turbo1889]

thanks guys I saw a post online somewhere where a guy was reading primers for pressure it it just didnt seem possible to me.

Unfortionatly, that is a common amateur mistake when "loading off book" with shotguns and is potentially a very dangerous one.

I've even heard of someone posting that they blew out the shell base and destroyed the extractor claw on a bolt action shotgun with only a normal load that couldn't be high pressure because the primers didn't show pressure signs and was trying to understand how it could be that the shell head got blown out with only a normal pressure load even to the point of blaming the bolt design for not fully supporting the case head. :veryconfu :shock:

That kind of crazy stuff makes the hair on the back of my neck stand on edge. It is theoretically possible to get a shotgun shell casing that is faulty manufacture and that fails at normal pressure levels usually in the form of the brass case head separating from the plastic tube but it is by far the exception not the norm and when you start blowing out the side of the hull where the extractor is and blowing a hole clean through the metal of the case head and you refuse to consider even the possibility that you are over pressure because the primers look fine I seriously question your knowledge and in some more extreme cases potentially even your "minimum base line intelligence". ("Minimum base line intelligence" has to do with being just barely smart enough to have the ability to learn and thus become smarter if you don't have enough to meet the base line then you are hopeless because you aren't even smart enough to learn well enough to potentially become smarter and thus you are stuck on the bottom of the barrel and nothing can be done about it.)

Think about it; in a high pressure rifle cartridge primers may look just fine with no pressure signs when operating at 50,000 PSI. Many handgun cartridges using the thinner pistol type primer cups that are probably about the same as shotgun primer cups operate at 30,000 PSI with no pressure signs. The "proof test" pressure testing level of shotguns is 20,000 PSI and the maximum normal pressure load is anywhere between 8,000 and 14,000 depending on the exact shell gauge and chamber length in question. By the time you do get pressure signs showing reliably and repeatably on a shotgun primer you are probably going to be at pressure levels that exceed 30,000 PSI which is 150% that of a proof charge and about 200-300% of normal operating pressures. The definition of a proof test load is that if a shotgun is randomly selected off the assembly line brand new a single proof test load won't blow it up. So even operating at proof test load pressure levels isn't necessarily safe since high pressure loads can have a cumulative effect leading to failure over time.

Long story short, unless you have a shotgun that is built like a tank and has earned a reputation for taking higher pressure loads without issues because they are over-built you are never going to get into high enough pressure levels that pressure signs on the primers can be relied upon. There are a few shotguns like that that do exist some of which are quite popular for building double rifles on their actions but don't go there unless you have done your research first.

[Chicken Thief]

Here's a pressure sign for you.
Unfired at the bottom and then overloads in 10gr increments from red through green until way over max in blue.
http://i295.photobucket.com/albums/mm153/Chickenthief/Skydning/Til%20andre/R0010972.jpg
http://i295.photobucket.com/albums/mm153/Chickenthief/Skydning/Til%20andre/R0010975.jpg
http://i295.photobucket.com/albums/mm153/Chickenthief/Skydning/Til%20andre/R0010974.jpg
http://i295.photobucket.com/albums/mm153/Chickenthief/Skydning/Til%20andre/R0010973.jpg
Note flattend primers and bottom metal floating into the ejector groove (all at 12 oclock).
It's funny how the left red primer "reformed" and almost deleted the firing pin indent.

[Chicken Thief]

Oh by the way, the exact same loads in another type of shell will show absolutly no pressure signs.

[turbo1889]

Oh by the way, the exact same loads in another type of shell will show absolutly no pressure signs.

My point exactly, you can't count on the primers. With some primers in some shells they may show signs but not with other combinations when the pressures are just as high. Expansion in the forward part of the head that isn't supported by the base wad (which varies in strength) thus effecting pressure signs on the base of the head is your best bet.