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Joined: 11 Feb 2012 Posts: 68 Location: Olympia WA

I know this probably seems like a silly question. But for someone who doesnt know, I dont mind asking. So please give me all the crap you want for a silly question but please then answer it. I am trying to figure all this out with less guess work.

So how do you select the right pressure for each type of shotgun. Or does it matter. Vintage guns aside. Pump, Over Under, SXS, Semi

How does Pressure effect shot gun patterns.

How does Speed effect shot gun patterns.

Are they advantages to low pressure vs. high pressure.

Does Size of shot effect the pattern?

I know there is no substitute for shooting paper. But knowing more about the variables will help me pick the direction I need to go.

Anyways I can and will read some more on the subject and educated myself. But I thought this would be a good subject of conversation. I have been reloading for about 3 years now and ready to move beyond my understanding how to load and into how loads are effected by the variables. I got into reloading because of the limited 16ga ammo and cost, but have found that I really enjoy it and ready to take the plunge. I know I am over complicating it but I am such a terrible shot, so if I can blame the velocity for something then great.

Joined: 15 Jun 2010 Posts: 1358 Location: Twin Cities, MN

Joe,
There are stupid questions, but yours are not. These are excellent questions. Some of these topics are fairly straight forward and others are not. You are going to hear a variety of answers on several of these topics, especially pressure. I am trained in science and prefer controlled experiments with real data, but there is very little of this with shotgun ballistics. Here is what I know, and I may well be wrong on some points.
Pattern size MAY be affected by velocity, shot size, forcing cone length, wad, crimp, shot hardness, primer, pressure, bore size, amount of choke, choke configuration, ambient temperature, the temperature of the ammunition, altitude, wind and humidity. The shape of any pattern is due to the interplay of all of the above. Some of these things we can control and others we can not.
Larger shot, harder shot, more choke constriction and slower velocities cause patterns to tighten. These are pretty indisputable. When it's really cold patterns open up - this is due to air density. Some folks claim lower pressure in and of itself can tighten patterns, but I don't believe this has ever been shown conclusively and would be almost impossible to test. Green Dot is claimed by many trapshooters to throw tighter patterns at handicap yardages than faster powders, given that all loads have the same velocity. It is argued that this is due to the lower pressures generated by GD vs, say, 700X. This lower pressure is purported to cause less shot deformation. If that is the case then loads with slower powders at even lower pressures should pattern even tighter. However, when you change powders you have different burn characteristics, pressure being only one of them, so this may be a generalization and not a rule. I would like to see some one actually test this rigorously.
So, as you can see this is not as simple as we would like it to be.
Pressure is a volatile topic. All modern guns, no matter which configuration, should be able to stand a steady diet of ammo that is within SAAMI spec. It makes sense to shoot less than max pressure loads in old guns, especially SxS guns, but what exactly constitutes low and friendly pressure? No one has a definitive answer. And remember, pressure is required for consistent and reliable ignition. I shoot in Minnesota in winter and 5,000 psi loads just don't work well. Some powders such as Longshot and PB work well at lower pressures in the cold, but it's also going to depend a lot on the primer, wad and crimp. I try not to shoot loads above 10,000 psi in MY older guns, but you'll have to choose your own comfort level.
We all like to think we load fabulous ammunition that is maximizing our ability to hit birds and clays, and that's okay. However, a fabulous shot with low quality ammunition thrown down a barrel with less than ideal internal dimensions will always outshoot the poor shot with top notch equipment. Choose a standard load that lots of other people have found to work and learn to shoot better. In 16 gauge I shoot targets with mostly 7/8 oz loads going just over 1200 fps. I shoot birds with 1 oz or 1 1/8 oz going the same velocity.
Now let's see what all of the other folks have to say. So what makes me an expert? I had business cards made!
Regards,
Jeff

Joined: 28 Aug 2014 Posts: 924 Location: Eastern Tennessee

Many questions, I'll touch on just a couple I have researched.

Shot size and speed (fps) both have an impact on pattern.

I have heard time and time again that #4 is the largest size you will get consistent patterns with 16ga. I have no need to test that theory but others have and I see no reason to challenge them.

I have personally seen the impact of speed, but this must be weighed against the distance desired. I found there is a happy place between speed, distance, size, and shot weight. A test of mine showed patterns for 1 1/8 oz of lead gave a better pattern at 30 yards in the 1200 range, but the penatration was lacking for that desired range. I played with increasing my shot size and found going to 1300 fps made me more happy. I have read enough to conclude that choosing the slowest, smallest shot size and weight you feel right about will result in the best patterns.

It could also be suggested that the same rule applies in chokes, choose the most open choke that gives you a good pattern at the distance you want.

Member Joined: 06 Oct 2007 Posts: 2349 Location: West MI

Along with the info you're going to get from this thread, my 2cents, if you haven't already I'd suggest picking up a copy of Lymans 4th or 5th edition and reading it cover to cover.

Best of luck with the new hobby

Joined: 15 Jun 2010 Posts: 1358 Location: Twin Cities, MN

The best way to improve penetration is to use larger shot. Remember - the faster a pellet starts out the faster it slows down. Two loads starting 100 fps apart will be going the same velocity at somewhere around 35 to 45 yards, and after that the load with the slower initial velocity will be going faster. Physics. Of course, if you are shooting birds at 20 yards then the faster load has higher velocity, but at 20 yards a 3/4 oz load is all anyone needs. Lots of loads work well in all applications. Nick Hammack will tell you that light payloads of small shot at high velocity is the ultimate bird load. It works for him and that is all that matters.
Regards,
Jeff

Joe wrote, "I am over complicating it but I am such a terrible shot, so if I can blame the velocity for something then great."

More often than not, it is the indian and not the arrow.
Having been where you are, I understand your frustration. Many years go a friend and mentor too me under his wing and taught me to shoot. Because I'm primarily a bird hunter he taught me the "Swing Through Method" using a low gun and I shot at a skeet field.
He first taught me the correct way to mount my gun and after lots of practice in front of a mirror with my wife watching to verify smoothness, I was ready to actually begin to shoot low gun skeet. I say all this not to discourage your quest for knowledge, but to encourage you to find an instructor to help you shoot.

Joined: 28 Aug 2014 Posts: 924 Location: Eastern Tennessee

Jeff,

To your point about speed and size I failed to clearly explain that not only did I change the mix to add 100 FPS but I also changed the shot size from #6 to #5. I started with #6 mag lead at 1200 fps and ended up going to #5 mag lead at 1300 fps. I was almost as happy with the pattern, but was much more happy with the penetration.

I personally am still 'working' to accept that shooting less than 7/8 of an oz at anything is ideal. I'll get there in time. Along that line I did recently change my cereal purchasing habits to support reloading. I am beginning to wonder if it is a more versatile product - part food, part vitamin, part reloading fill. Did I mention the box is a wonderful source of over shot cards? God what have you people done to me Shocked

Joined: 21 May 2010 Posts: 603 Location: Victoria BC Canada

Charlie16; Cereal boxes work well as O/S cards, but I prefer waxed card milk containers. Scrap from picture frame shops do well as O/P wads.

P.S; And milk is good for us! Smile

*Last edited by 16gaugeguy on Wed Jan 21, 2015 3:04 pm; edited 4 times in total*

Here are four rules of thumb which may help guide you in understanding shot shell ballistics.

A) Every shotgun barrel is a law unto itself. No two barrels, even seemingly identical ones, will perform and pattern identically with the same load design. There are always too many variables at work to be able to predict exactly what will happen. So pattern testing is mandatory. Otherwise, we are simply guessing. Period.

B) [b]All else being equal, projectiles with higher ballistic co-efficients always lose their velocities slower than projectiles with lower ballistic co-efficients. Two projectiles which have identical ballistic co-efficients and masses and are fired at identical initial trajectories and velocities will always fly at the same speed and to the same distance. If one of these two identical projectiles has a higher initial velocity, then it will always be flying faster than the slower one at any given distance down range until both come to a complete rest. The faster one will always have travelled further down range after coming to a complete rest.

C) The only way to improve the ballistic co-efficient of a sphere with a given specific gravity is to increase it's mass (make it heavier by making it bigger). Of two lead spheres, the bigger heavier one will always have the higher ballistic co-efficient and will always hold onto it's velocity better than a smaller lead sphere.

If two identical lead spheres are fired at the same initial trajectory, then the one with a higher initial velocity will always be going faster at any given distance down range until it comes to a complete rest. The initially faster pellet will also always have travelled farther before coming to rest than the one with the lower initial velocity.

Simply remember that speed is always a measurement of both time and distance.

D) All else being equal, the only way to improve a given shotgun barrel's ballistic performance is to increase it's bore diameter. This is why overboring improves a shotgun barrel's performance with any given load. This also explains why any shotgun barrel with a larger bore diameter will always perform better with larger pellets than a shotgun barrel with a smaller bore diameter if all else is equal.

Joined: 28 Aug 2014 Posts: 924 Location: Eastern Tennessee

Carlos,

When ever did cereal ever have a better friend than milk! They are a natural partner in breakfast and in reloading. Laughing

Joined: 15 Jun 2010 Posts: 1358 Location: Twin Cities, MN

In theory back boring improves patterns, but I believe that if there is a measurable improvement it is very, very small. I'm actually going to put this to the test this year.
Jeff

Joined: 21 May 2010 Posts: 603 Location: Victoria BC Canada

Joined: 15 Jun 2010 Posts: 1358 Location: Twin Cities, MN

Thanks 16gg - I remembered the velocity thing incorrectly. It is true that the faster a projectile starts, the faster it loses velocity so that as distance increases the difference in velocity between two equivalent projectiles fired at different initial velocities becomes smaller.
Jeff

as GG said , every barrel is a different thing . Also , you have to have an idea what distance you want to shoot (very rarely be at that distance when hunting !). The closer , the less velocity you REALLY need . I like to know where the gun shoots and idea if it is tight or light , but that's it . Pellets don't fly true for the most part , so what looks good here , may be totally diff there .... If you want to see an anomoly to physics , go hunting with Nick . Cyl bores , fast speeds , hits them up front every time as far as 60 yds . Would you trust your 5/8 oz pattern out of a cyl at that range !? The pattern should be open enough at that range to be lucky to even hit the bird , much less in the beak ! Yet it happens time after time . Any target load today is way better than yesteryear - put your faith in learning to point and not so much in a lot of patterning !

Joined: 11 Feb 2012 Posts: 68 Location: Olympia WA

JNW you had me in a tailspin with the velocity and physics. I actual felt sick, my whole idea of how the world worked was up side down. I starting thinking about how the air must create some kind of back draft that caused the load to slow down. How the impact of the high pressure caused the load to become deformed or the speed that it left the barrel made it go haywire. Then 16gaugeguy came to the rescue and turn the worl rightside up again. Thanks 16gaugeguy!

About fixing my shooting. That why I shoot sporting clay is to improve my shot for bird hunting. I work on my muscle memory and instint shot from low gun just like I shoot from in the field, well all most I dont have the gun learning up against some bush while pretending to take a leak. But I try to come as close to that since that is when I get most of my shooting opportunities in the field. Believe me I get lots of instruction. In fact my first time I went sporting clays I shot a 68 then I got educated about shooting and watch a bunch a videos and asked the experts at the range and shot a 25. My best is 68 I average around 50 now. I will get there and I enjoy the process.

I am bad shot, Fat, out of shape and I got a boot licker of a dog seems to attract more hunting buddies then the truth. Which is my dog is not a boot licker.

So can one of you walk me through the process of patterning a shot gun and load. All the details I should be looking for to get consistent data.