Biggest factor in shotshell pressure?

[Tripplebeards]

I agree! I’m just not a fan of #5’s past 40 yards. Kind of defeats the purpose of owning a 10 gauge. I do use one and 5/8 ounce load of number six along with a 100 grains of FG in my old Damascus 10 gauge with real black powder. I think they probably pattern better.lol

It was just a fun experiment. That’s why only loaded two. Obviously, it sucks for patterns. My guess is a big wide modified choke tube would probably pattern way better with a 3 ounce load. Still a complete waste of shot I agree.

I used to use factory Remington 2 1/4 ounce number six loads for turkey hunting out of my 10 gauge and a gobble stopper choke tube. It look like my target was a screen at 40 yards. If I shot a bird out to 50 plus yards (which there was plenty of pellet count) it would hit the ground and then get up and run. I normally wait till they’re 20 or 25 yards now which doesn’t make any difference what I use for that. The old factory roll crimp federal grand slams and Winchesters with number fives pattern way better at 50 yards than the gun does with 3 ounce hand loads of #5 at 40 yards. I might have to buy a box of longbeard 3” #5’s and see how they pattern in my 12 gauges with the code black turkey choke. My guess is they will put the 10 gauge to shame. I have enough ammo laying around that I figured a half way decent pattern is acceptable at most of the ranges I shoot. I always used to chase a nice tight pattern with tons of pellets over the decades, but I realize it’s not really needed. I sure would like to get a little tighter patterns in both guns though.

I agree though… I wasted a lot of pellets just in 6 ounces of testing shot!… even if they all went into the 10 inch circle because it’s not needed for a turkey. Maybe if I was trying to knock 30 crow out of the sky at once.lol.

[megasupermagnum]

I wouldn't be surprised your blackpowder loads are better. In my muzzleloader with improved cylinder chokes, 1 5/8 oz of #6 puts 100 hits in a 10" circle at 35 yards. I'm not sure I can agree that #5 is a waste in 10 gauge. It does not take a whole lot to break a turkeys head, but it does take a lot to hit it. Plenty of people used #7.5 out to 40 yards, and I've never heard of a failure. I personally wouldn't, but in something like a 20 gauge, I absolutely would consider #7.5 as one of the best shot sizes for inside 35 yards. I know #6 is perfectly adequate to 45 yards, and it's my most used size for turkeys. Based on KYP ballistics, #5 will perform the same at about 55 yards. I've never got any 12 or 10 gauge to pattern well enough for a 55 yard shot. I think #5 is about ideal for 10 gauge turkey loads, but I understand if someone doesn't feel the same way.

I found a mean old 10 gauge load in a BPI buckshot and slug manual from the 80's. It's 2 1/2 oz of buffered shot with bluedot, surely meant for geese. I've got some loaded with #5, and at some point I'll try them out at 50 yards to see how they do. Maybe I'll do that tomorrow. I still maintain that #1 shot hardness, and #2 buffer are absolute keys to maximizing patterns. I'm not even convinced plastic wads help much if at all. If you aren't using the hardest shot you can get, and aren't buffering, you are wasting time. I too don't worry about maximum range as much as I used to. It's even less important now when hunting in SD, we can use handguns here. If I ever hang up a bird at 40-75 yards, it's getting a 327 federal sent through it.

[Coopaloop86]

I've worked in a ballistics lab for many years. After having seen 10s of thousands of combinations tested I can tell you that everything can have an impact, that being said 1. Wads are the biggest and most radical factor. A wad change can affect pressures several thousand PSI. 2. Modern shotguns can withstand a significant amount of force but the issue is there are no indicators in shotshell of high pressure before you reach the fail point. Just last week, was experimenting with a light slug load. Began hitting high pressures before reaching intended velocities. By simply switching to a more cushioned wad it allowed 4kpsi to be shaved off which allowed target velocity to be reached.

[megasupermagnum]

I've worked in a ballistics lab for many years. After having seen 10s of thousands of combinations tested I can tell you that everything can have an impact, that being said 1. Wads are the biggest and most radical factor. A wad change can affect pressures several thousand PSI. 2. Modern shotguns can withstand a significant amount of force but the issue is there are no indicators in shotshell of high pressure before you reach the fail point. Just last week, was experimenting with a light slug load. Began hitting high pressures before reaching intended velocities. By simply switching to a more cushioned wad it allowed 4kpsi to be shaved off which allowed target velocity to be reached.

I think you are right, but if people were at least half intelligent it wouldn't really be an issue. The problem is it seems a lot of people aren't very good at making deductions if you don't teach them. I completely believe that if you took a 1 1/8oz load meant for a Winchester AA wad, and instead used a steel shot wad like a TPS, added shot, and filled over the top with fillers to take up space, I can definitely see pressure going up thousands of PSI. If we take a much more reasonable look at it, I don't think it's as big of an issue. A reasonable person would not do that, they would be looking at something like a Remington figure 8 wad. I really find it hard to believe you are going to measure any significant pressure change when you make a wad substitution like that. I never worked in a lab, I just do this for fun. I've not seen these huge pressure swings from reasonable wad swaps. Reasonable being the key word.

Primers I think are the most significant of the components you can swap easily. A person who doesn't know much about reloading could easily make the mistake of putting a CCI 209M in place of a load that calls for a CCI 209. A reasonable person could make that mistake. Tom Armbrust had done some of that testing and research. Some loads showed no appreciable difference. Hodgdon testing found some more significant difference with International Clays powder. With a CCI 209 it was only 8,400 psi, with a CCI 209M it went to 10,400 psi.

I doubt you are ever going to get hurt swapping one thing, but it wouldn't take much to stack problems. Put a CCI 209M primer in there, set crimp a little too deep say .090", and get a slightly fast lot of powder, and you could be looking at a 15,000+ PSI load which still probably wont hurt anything with the extreme safety margin most shotguns have. Take it a step farther, say you are loading 3 1/2" 12 gauge which is normally operating north of 13,000 psi, it wouldn't take huge mistakes to get you up to that range you can start to see case failures.

I still maintain that going forward we should be educating reloaders on what they can and cant do, what does and does not make big differences. The current reloading manuals no tolerance "don't make substitutions or you will die" is fine to CYA, but it is no longer a practical solution in todays reloading market, and hasn't been for at least 10 years. Shotgun reloaders HAVE to be able to make certain reasonable substitutions. Some manuals have done this. A good example is Tom Rosters newest manual allows you to swap Winchester 209 and Cheddite 209 primers. He also lists hull substitutions you can do. Lyman needs to step up in their 6th manual.

[Coopaloop86]

I totally agree with you. I routinely substitute components in my personal reloading. Common sense goes a really long way, unfortunately common sense isn't real common nowadays. Again, you are totally correct in that it would take a substantial error or series of to cause issues in modern firearms. I have shot loads where everything seemed fine other than some punishing recoil to later find out it was rather over SAAMI spec. Shotshell has few if any indicators of problems without a specialized equipment. Maybe you'll get a sticky extraction? You hit the nail on the head. If you're going to make substitutions to published data, find similar items. Don't try to compare apples to asparagus.

[Graybeard96]

As Cap’N Morgan stated, seating pressure is the most overlooked and the most important factor that can affect chamber pressure. It’s the equivalent of seating a bullet’s OAL too deep.

However, I know I’m gonna get some backlash from this, but here goes:

You will never blow a shotgun up by subbing primers. You will never blow a shotgun up by subbing wads or hulls. I’m talking modern shotguns in good working order.

As many of you know I do a lot of pressure testing. Highest pressure I’ve purposely recorded was 28.7k psi with a double charge of a certain powder with a 1 oz shot payload.

Wanna know what happened to that Mossberg? Nothing. Absolutely nothing. I still use it.

Shotguns can take a lot more pressure than people think. Tom Roster hit over 55k psi. Wrote he was able to an 870 barre up and while strong, they aren’t the strongest in the market.

So what exactly am I saying?

I’m saying to still be smart and pay attention when reloading. Don’t venture off the unpublished data path if you don’t have the knowledge or experience to do so.

The main jest of this is don’t tear down your loads because you mistakenly used a magnum primer when data called for a standard primer or you used a FED 12S4 when you should of used a WAA12. You’ll be just fine.


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I agree 100% and I am also a follower of Tom Roster (Shotgun Professor). Up here in Canada its hard or better actually almost impossible to get all the published ingrediency for a certain published Load using the Lyman Books. The more adventurous of us make do with what we have in this almost SHTF scenario.
I am currently loading 16 Ga. with # 4 Buckshot for which I don't have published Data. Would like to load # 1 Buckshot too but cant even get a Mold.

Cheers