doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Patterning, high pressure vs low pressure

There is a body of thought backed up with a fair amount of tests by trap shooters and articles that says that Green Dot [comparitively slow] gives slightly higher percentage pattern yeilds than does Red Dot [comapratively faster] when using the same shot in similar velocity loads. I never did that particualr comparison as I never much used Red Dot powder. I have found that slightly lower velocity loads will generally yeild tighter patterns and that the claimed amount of Antimony matters little once the shot size reaches #5 in uncoated lead shot. I generally use published data w/some primer switching at times [at my own risk] & I had/have no means of measuring pressures aside from sending some few rounds off to be tested, but that was to insure their safety & not for pattern comparison purposes. Shot hardness does matter in smaller sizes, and that is essentially irrefutable. The rest is a matter of what the plate or paper shows you and your confidence in its truth. Reality is subject to exceptions .. the 'golden pellet'!

Logic & some patterning as confirmation both would indicate that a less abrupt ignition should slightly improve the patterns; logic = less pellet deformation; patterning = slight % improvements. However, it is hard to prove as any absolute. I think in large part because of today's plastic wads that compress a great deal [expand the combustion chamber size, reduce pressure and blow to shot column] before the shot column even begins to move, and even then the shot is protected by the plastic cup from being forced into direct contact w/the bbl. With older card/felt wads I would think the comparison may be more readily seen or distinct.

Going back to published data, I generally use the lower published pressure loads for any given velocity within the 1050~1220 fps range, but have to admit that really only applies to the 12ga., finding reliable 'low pressure' loads for the smaller gauges is often quite hard to do.

Hope you find something here from an old & ever curious shooter of use;-)

Montana - I don't think shot bounces around within the shot charge. What is the mechanism of shot deformation? I'd say it is the pellet to pellet contact pressure due to acceleration. Other opinions?

t1958 - Interesting that you found little actual difference. Did you find enough to say it is directionally true, or only enough to say the patterns changed (perhaps within statistical limits only)?

JM - this is not intended to be a smart a$$ question. Would you describe what attributes make patters "better" or "pattern beautifully?" I often hear such subjective descriptions and I always wonder what the author bases his opinion on. How does one achieve this "equilibrium?"

Rocket, Given my test work on that particular shotgun I would say the pattern change was only within statistical limits. Looking back I would have to say that the major flaw in my pattern work has to be that I only changed (increased and decreased) the powder charged in 10 grain by volume increments.
All the best

Jag,
Last time I looked there were many different Fed Gold Medal loads. Some were: 7/8 oz @ 1325 fps, 1 oz @ 1350 fps, 1 oz @ 1240 fps, 1 1/8 oz @ 1300 fps, 1 1/8 oz @ 1100 fps, 1 oz @ 1180 fps, etc.

Is there only one of these loads that patterns well? I have only tried the T175 1 oz @ 1180 fps load and it seemed to pattern very well although I did not pattern statistically.

tw - good thinking and nicely written. Hope you will engage in some discussion of some of your points.

"Shot hardness does matter in smaller sizes, and that is essentially irrefutable." I have often seen hardness and sphericity cited as critical to pattern "goodness." Do we really know this?

I'm not keen on accepting tighter (higher pellet count in a given circle at a given distance) as "better." This, IMO, is one of the prime reasons for statistical analysis. Until someone shows me something different, I'm going to believe patterns are basically Rayleigh distributions (never, never, "even" ala pegboard). I'm also going to believe that the "patchiness" (for lack of a better word) is more important than tightness; we can tighten it up with choke (within the limits of full choke).

Sooooo, has anyone ever put some small shot between two steel plates and fetched the top plate a healthy smack with a largish hammer - sufficient to deform all/most of the shot, then loaded and patterned said deformed shot in comparison to undeformed shot? That experiment is in my retirement folio - and it will be done subject to Dr. Jones's program. But, I'd love to hear results for someone else.

Can I once again ask that people consider recording patterning experiments with a digital camera? It allows sharing of visual images at a minimum!!

tw, I surely don't intend to be picking on you. I just hope we can get this discussion going sufficient to flush out what we really know about patterning. "Flush" may the appropriate word, too.

I once subcribed to idea that velocity of powder gases exiting behind wad was important to pattern density. The basic idea is that at low gas velocities, gas expanding laterally on release from muzzle would disturb wad and overlying shot less than at high gas velocities.

I did then see some agreement with this in my handloads. With high velocity loads with slow burning powders generally giving less dense patterns than those with medium burn rate powders. However, these were not well controlled tests.

My tightest patterning hand load in 12X76 (Browning Citori full choke) was with 76 mm hulls Winchester CF hulls, 1 3/8 oz of shot, IMR SR7625, one-peice wads with long cushining section and Cu-plated #4 magnum shot. Muzzle velocity was about 1200-1250 fps. Patterns were 85-90% with tight centers from full choke barrel and 70-75% and uniform from half choke barrel, all at 40 yds.

Once I went to heavier shot loads, 1,5 to 1,75 oz of #5 and #4 hard shot, I could only get consistantly decently dense patterns (60-70% and even) by going to classical heavy loads of large shot at low velocities (1000 to 1100 fps). I always suspected that this was partly, at least, because this gun was not designed to give dense patterns with such large shot loads.

I did consistantly find that hard (so called "magnum") shot gave denser (and much more even) patterns than soft (so called "chilled") shot, with Cu plating giving maybe 5% denser patterns. Actually, I could improve patterns of Remington factory 76 mm loads with 1 5/8 oz of shot from 45-55% to 70+% just by replacing factory shot with Lawrance magnum, Cu-plated shot -- shot size in both cases was #4. At least in one barrel, that is, the more open choked one, not in the full choked barrel, for which patterns remained in the 50% range.

Rocketman, I do know that I have never missed a target or bird because the pattern was at fault! And I can prove that rigorously for anyone who wants to take me hunting.

After about a century or more of various experimenters endeavoring to mathmatically define performance of shotguns, chokes and their various shapes, shot sizes and composition plus duplexing, pressures, velocities, rates of acceleration,shot stringing, wadding with all it's variables, forcing cones with lengths and shapes, chamber dimension variation, weight to bore ratios, buffers, burn rates, priming compound brisance, bore condition, rifling straight or twisted, phases of the moon, northern or southern hemisphere vortex influence and sundry other real or imagined variables; the national budget could be fully consumed without resolve. So my flippant response above may actually be mankind's best shot at ever fully grasping effective shotgun performance. The answer is to be found in Mona Lisa's smile. It is what you believe it to be.

Post deleted by treblig1958

JVL - good answer! OK, and thank you very much for some variables I'd not thought of. More work. Actually, I'd be happy to nail down even one more variable that influences patterns in a predictable way.

Lots of interesting comments above. I can easily accept that a significant change in velocity might affect patterns some but seriously doubt that different pressures would make much, if any difference. I also very much agree with Rocket's question as to what is usually meant by "beautiful", "perfect" or "greatly improved" patterns.
My strong suspicion is that it usually means about the same as when some obvious newbie(or even many oldies) mount a new shotgun in a store and eloquently proclaim it to be "nice and light" or "has excellent balance". Most of the time it is the same material as the pile found under a peddler's wagon horse's tail, after he's been parked too long and just about as useful.
The clerk, who likely knows even less about the subject will say, "absolutely".