doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Pressure and Velocity

You're both correct. Probably shouldn't have gotten my feet wet or even waded in. Left out the direct correlation between velocity to Max pressure part didn't I. There isn't one that will stand alone.

Only point that I was trying to make & did a poor job of is that velocities from the low noise/low-recoil levels in the 900+fps range can and do break clay targets as well as suitable sized pellets traveling at 1200fps & more and that Max pressures running from as little as 5K to industry Max levels can and have been measured in some published recipes and they all will work at skeet ranges.

Wonk's saying the cartridge, shooter & target would not know the dif. is an accurate assessment when applied to the OP's Q regarding worn hulls & ugly mouths.

Will also acknowledge that most powder companies avoid publishing low Max pressure loads and I have been told by more than one ballistician employed in the industry it is because reliability is frequently compromised at low temps w/many loads below 7K even though they may be fine in our triple digit summer temps here. Little point in publishing a recipe that might lead to their product being spoken ill of.

OTOH, using PB in 12ga. rounds, if you are fortunate enough to have any, can produce adequate velocity w/quite low Max pressures even in cold temps, not that it was asked.

Best I stop digging, eh? This hole is deep enough. Y'all have a great day. I'm going to the club and shoot [or shoot at may be the better descriptor] some clays.. w/ugly reloads;-)

As Chuck mentions, peak acceleration is correlated with peak pressure. The peak occurs in the chamber, and overcomes the payload inertia 'right smartly'.

It's not just accelerating, it's accelerating to beat hell.

Butler's data from Winchester shows a 3 dram one ounce load attains 1,000 FPS after 7" of payload movement. 7" !

It's been common wisdom for some time that all that force can't help but mash the poor pellets out of round traversing the chamber cone and being shoved into a narrower tube, so over boring has become almost universal to 'improve patterns'.

Then Winston comes along and says it makes no difference. With test data and pronouncements from the oracle of Jones, he claims it's all smoke and mirrors and does nothing at all.

Yet, in a another of his articles in Drew's reference he extols the virtues of 'extra hard' shot as being an essential contributor to throwing winning trap patterns.

Anyone care to reconcile those two conclusions?

This seems to point to acceleration deformation as being the primary, indeed the only, cause of out of round pellets.

If so, would not a more gentle acceleration such as provided by a slower powder result in tighter patterns?

Were this true, Unique should outshoot Red Dot every time.

The pronouncements and denials of Mr. Winston's contentions is no surprise. Faith conquers all. Belief systems are incontestable. Simple facts are easily ignored when such overwhelming evidence of experience is available. Not to mention the superiority of Hogwarts Physics. And we all know that anyone else's data is prima facie inferior to our own regardless of derivation.

Shot deformation in the choke is generally considered to be the origin of the squashed hence the usual superiority of harder shot pattern-wise. I think I recall some patterning studies of plastic wad vs fiber that lent credence to that contention as well.

Rather an interesting post from one whom we know from the 'one pellet break' discussions does not worship at the altar of Jones.

Do tell how a choke functions while imparting the claimed deformation. Note that choke works with soft or hard shot, and that even patterns with no choke are improved by hard shot.

Ever pick up a fired wad? We are launching a lot of little dodecahedrons. Is it likely they originate where the pressure is 10K PSI and the acceleration is at max or in the choke where the pressure is 500 PSI (tops) and the load is accelerating at 20 fps?

That's a joke, right?

Keep trolling tho, you might find someone who wants to play

I'll play, in the interest of science

Why does Hevi-Shot fly true/pattern better than round shot? The shuttlecock effect?



and what about Winchester Hex shot?
https://www.americanhunter.org/articles/2011/9/9/winchester-blind-side/

and Federal Black Cloud FliteStopper spaceships
https://www.federalpremium.com/products/brands/blackcloud.aspx

The peak rate of acceleration is necessarily higher in the rifle example because we know the ejecta separates from the gun at a significantly higher velocity. But, the peak force at the moment of highest acceleration is no more than it takes for the smaller bore and lighter ejecta mass to overcome its resistance.

In identical guns in every way, including the total force of the ejecta clearing the muzzle, the rifle will have some higher peak force. But, only to the extent that the area under the graph for total force can be identical to a slower, heavier shotgun load over a shorter period of time.

Doc Drew's article by Hall took pains to assure constants in the devise he used to record the measurements, but he also wanted to document that the ammo he used was a constant. His conclusion was that he could test a different gun and predict differences in how recoil would be perceived.

I never realized that type of recoil study was available, but all else being equal, what did it reveal about differences in felt recoil between heavier/slower and lighter/faster equal energy loads? If peaks and totals happen over very short periods of time, how discriminating could the human be. It seems like Hall measured a vertical rise component, that may be interesting in the longer duration of a slower shotgun load.

Maybe, more pop in the cheek would be perceived as more felt recoil than accelerating the gun at a higher rate directed more inline with the shoulder. But, the conclusion was that the magnum rifle would necessarily generate more felt recoil due to a higher peak contained within the total duration of firing the ejecta. Only in light hearted fun Chuck, and I remain open to understanding what I'm missing in those recoil charts.

Drew, maybe Winston could shed some light on that.

Me too.

Another little tidbit here, related to some of the posts, but not the original.
Pure lead has a Brinell Hardness of about 5. Lead will begin to deform at a pressure of around 1400 PSI Per BH #. Thus the pure lead with BH # of 5 would deform at about 7K psi. Another thing of note is in measuring the hardness the load is applied to the ball ( for BH) & held for a prescribed interval. Full deformation is not absolutely Immediate. This is why LUP differs from true PSI, the time interval. If loading to the same ballistics with Red Dot & Unique as mentioned Red Dot would produce the higher pressure, but Unique would have a longer time interval. Assuming that both were producing a pressure above the yield point of the alloy being used the pressure vs time would to some extent at least be off-setting elements.
Unfortunately most of us do not have the ways & means of truly doing the Exhaustive Testing which would be required for Absolutely Conclusive data so we just struggle along as best we can. We thus apply what seems reasonable to our conditions.