Article on pressure testing shotguns.

[BigBore45]

The link below is an article in shotgun life written by a ballistic tech about testing shotgun barrels and pressure. I find it interesting because everyone is scared to deviate a tiny bit from the book, this article seems as if they might have some room before catastrophe strikes. At the very least you would see pressure signs way before a gun came apart.

http://www.shotgunlife.com/shotguns/tom-roster/important-information-about-shotshell-pressures.html

 

[Grumulkin]

For some reason there is, among handloaders, a lot of angst about changing ANYTHING in a shotgun load that isn't printed in some manual. If they read their metallic reloading manuals carefully, they would find that the publisher also says not to change ANYTHING. If one writes anything on a forum about deviating from a load in a manual, there will promptly be pundits elaborating on the dangers of using certain wads in tapered hulls, etc. which they probably have never had any experience in doing. I would agree; you probably shouldn't use a heaver shot load than called for but not use a different primer? Really?



Everything in the above loads was the same except the hull and they all shot fine.

I did meet a guy once with a scarred up arm. He had been shooting a shotgun with his grandson, if I remember correctly. His grandson had taken a few shots after which he gave it a try and the gun blew up. They weren't handloads either.

 

[Stumper]

The fears are fostered by factual reporting.....for example numerous tests have shown a 3000psi change from primer substitution in SOME shotshell loads. Given the relatively low pressures of shotshell loadings that could mean a change of over 25% and push pressures over nominal maximum. As the linked article points out it is unlikely to result in catastrophe. A careful review of shotshell loading data will review a number of powder charge and shot charge combos that worked with just about every hull wad or primer combo possible. More data allows for certain substitutions with little worry and reveals wher likely problems might arise........but follow the recipe exactly is the fallback position.

 

[BigBore45]

The fears are fostered by factual reporting.....for example numerous tests have shown a 3000psi change from primer substitution in SOME shotshell loads. Given the relatively low pressures of shotshell loadings that could mean a change of over 25% and push pressures over nominal maximum. As the linked article points out it is unlikely to result in catastrophe. A careful review of shotshell loading data will review a number of powder charge and shot charge combos that worked with just about every hull wad or primer combo possible. More data allows for certain substitutions with little worry and reveals wher likely problems might arise........but follow the recipe exactly is the fallback position.

I agree, but say I have a cheddite or rio primer. I know for a fact i can use those in place of federal primers because the ferderals are hotter and winchester primers because they are known to be very close to the euro primers in terms of power.

Or if you look at buckshot data, very little combos out there, suppose to not interchange that data with shot data but there is no real difference as long as payload is the Same weight and payload is the Same material.

 

[Stumper]

I concur. Comparing large amounts of data shows us that some primers are very close in performance across a broad spectrum of loads while others(such as Federals) tend to yield higher average pressures. Research seems fairly conclusive that larger shot actually tends to flow through bores more easily than small shot and slugs(if not hard AND oversized) will yield lower pressures than an equal weight of shot assuming the same wad column. Some substitutions are not rash nor foolish but we have to take responsibility for our choices.

 

[splattergun]

Where there is only 1 powder charge given for a specific set of components, I will use that charge. If won't pattern, I won't use it any more. But where there is a higher power load and a lower power load option given, I will tune the charge between the high and low charges to pattern best in my shotgun.

I always use the specified wads, or the charted equivalent. I won't use a Federal primer if a Winchester primer is specified, but I will use a Winchester or CCI primer where a Federal is specified. I don't care for Rio primers.

I haven't blown up any of my splatterguns yet.

 

[hdwhit]

BigBore45 wrote:
I find it interesting because everyone is scared to deviate a tiny bit from the book,

I don't think for a minute that "everyone" is "scared" to deviate from the book; but I do think the majority of reloaders are content to follow the book and load shells they can be confident will both perform well and be safe.

this article seems as if they might have some room before catastrophe strikes.

For some finite number of rounds, perhaps.

The problem for the casual reloader is they don't have pressure instrumentation for testing their loads so they have no idea of the effect of substitutions or changes in load have on the resulting chamber pressure once they go outside the range of published data. Going 1,000 or 2,000 psi above designed chamber pressure may not be catastrophic now; but the fatigue caused to the structure from repeatedly overloading it is cumulative and could one day result in catastrophic failure.

At the very least you would see pressure signs way before a gun came apart.

Not necessarily.

On a new gun where you were just barely flirting with changes that nominally raised pressures, you might have come considerable time, but in a 50 or 70 year old gun of uncertain provenance that unbeknownst to you was subjected to 15% overloads for years, the next overloaded round could be all that was needed to make things "come apart".

 

[BigBore45]

I don't think for a minute that "everyone" is "scared" to deviate from the book; but I do think the majority of reloaders are content to follow the book and load shells they can be confident will both perform well and be safe.

As many people that ask about wad substitutions and shot type substitutions I don't thing they are content about following the book per se. I mean it seems on a couple shotgun forums that one of those questions is asked every day.

For some finite number of rounds, perhaps.

The problem for the casual reloader is they don't have pressure instrumentation for testing their loads so they have no idea of the effect of substitutions or changes in load have on the resulting chamber pressure once they go outside the range of published data. Going 1,000 or 2,000 psi above designed chamber pressure may not be catastrophic now; but the fatigue caused to the structure from repeatedly overloading it is cumulative and could one day result in catastrophic failure.

1k to 2k. Psi over max will not affect a gun in 100 years to the point of catastrophic failure. Period. I doubt anything would ever be noticed at all.

Not necessarily.

On a new gun where you were just barely flirting with changes that nominally raised pressures, you might have come considerable time, but in a 50 or 70 year old gun of uncertain provenance that unbeknownst to you was subjected to 15% overloads for years, the next overloaded round could be all that was needed to make things "come apart".

Like the article stats, it's not going to cause a gun to blow up even that high over. I personally use a Remington model 11 that is from 1924 that I rebuilt in 2000, I know for a fact that it will take several thousand rounds of 1 to 2k over pressure rounds. I would say that firing a factory hunting load on the light setting would be much more catastrophic than over pressure rounds on the heavy setting.