doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com English game loads data 2 1/2" shells.

There was an article on this "Drag" in the American Rifleman many years ago as it related to the Hi-Velocity .22 LR vs the old Standard round. Seems when the new Hi-Vel loads came on the market outdoor target shooters who shot the LR round at comparatively long ranges flocked to them as a means of reducing Wind Drift. Turned out that even though the new round had a shorter Time Of Flight, they actually gave greater wind drift. Seems Wind Drift is based not on actual time of flight, but on lag time, IE difference in actual TOF from a theoretical TOF in a vacuum. The HV round proved to have greater lag time, thus more Wind Drift due to its greater Drag Factor in crossing the Sound Barrier. This phenomenon occurs only with those rounds straddling the SOS. When both rounds start either below or above this velocity increasing MV will reduce Wind drift.

Jones, we all recognize that there's a drop in velocity from the muzzle to 3 feet. We understand why. We're only disagreeing about how great that drop is. The article goes on to explain that Lowry also determined that downrange velocities weren't quite as high as those previously listed. I'm sure Winchester has more sophisticated instruments to measure velocity than do people with a chrono, and what Zutz reported is what Lowry measured.

Zutz goes on to stress that we should not confuse the 3 foot velocities, which are the standard numbers published in this country (and by SAAMI) with actual muzzle velocity. Most people don't realize that.

As for CIP numbers, per the latest information I have--which comes from the British Association for Shooting and Conservation--it now appears that velocity is measured at 2.5 meters. In the case of British velocity figures, that represents a change from both "observed" velocity and true muzzle velocity, both of which have been used in the past. Confusion will arise if you don't pay attention to the date of your source material. Gough Thomas, writing in the 60's in reference to Eley Grand Prix shells, said they had a "designed velocity" of 1070 fps--which seems very slow to us. However, he makes clear that that's the velocity over 20 yards: the old "observed velocity" figure.

If the CIP standard is now 2.5 meters (8.2 ft.) & the English Hull High Pheasant 1 1/16 oz @ 1450 fps that started this thread are measured under CIP standards,they are really fast & depending on your point of view, have all the benefits & negatives of the current speed trend in shotshells.

I'm betting that 1450 figure is true muzzle velocity. That would equate to over 1600 fps at the muzzle if it were 1450 fps at 2.5 meters. Our British cousins like to keep us guessing when it comes to weights and measures.

"As for CIP numbers, per the latest information I have--which comes from the British Association for Shooting and Conservation--it now appears that velocity is measured at 2.5 meters."

"I'm betting that 1450 figure is true muzzle velocity."

This is consistent how? Is not Hull Cartridge actually governed by CIP standards?


"Jones, we all recognize that there's a drop in velocity from the muzzle to 3 feet. We understand why. We're only disagreeing about how great that drop is."

Not exactly. In the case of a velocity decrease totally out of proportion to the second 3 feet, I certainly do not understand the 'why' of a 100 fps deceleration in the first 3 feet at all. That's what I'm trying to 1. verify, 2. understand.

I'm not in denial about not having a laboratory chronograph system, I'm am however stating that I do not observe this dramatic deceleration on what I have.

Has anyone verified Lowry's experiment? That's the essence of science, a repeatable experiment. Data seems to be scarce.

Has anyone seen interior ballistics graphs similar to what Butler published in the 70's that incorporate the new thinking since?

This is all very interesting, and I'd like to learn more.


Miller's post totally baffles me. The theoretical time of flight in a vacuum seems to be dependent on MV and only MV... assuming constant gravity vector. Is Newton wrong too?

[quote=Shotgunjones]"As for CIP numbers, per the latest information I have--which comes from the British Association for Shooting and Conservation--it now appears that velocity is measured at 2.5 meters."

"I'm betting that 1450 figure is true muzzle velocity.

This is consistent how? Is not Hull Cartridge actually governed by CIP standards?"

Good question & it appears to me that there is no consistency or truth in advertising when it comes to manufacturers published velocity figures.

I was impressed by Rottweil's stating 2.5 meters as their measurement point for velocity until I found different & apparently current Rottweil advertising stating velocity as "mouth velocity" and quoting the same exact velocities for the same loads as were published for 2.5 meter velocities. As we have discussed, it can't be the same for both. At least they do state something other than "velocity".

If you care what velocities your loads are providing(& my impression is that very few people do) I'm thinking that Shotgun Jones has the right idea about using chronograph to test the loads yourself. It might not be up to laboratory standards but it seems to me that the info will be of more use than the manufacturers published data in most cases.

I've been using a chronograph for handloading rifle cartridges for years but I never felt the need to chronograph shotgun cartridges until recently.

I don't think accurate velocity figures are as important in shotgun shooting as they are in rifle shooting but I would like to be able to compare & select loads that I can be confident will effectively kill game & will have the least wear & tear on the gun.

No; Newton is not wrong. Yes; the theoretical time of flight in a vacuum is based solely on Muzzle Velocity. It can be calculated by using the muzzle velocity & the range. Thus if a bullet were fired in a vacuum at 1250 FS over a 100 yd (300') range it would arrive in .24 seconds. When the atmosphere is thrown into the mix the the Drag factor comes in. I did not have a time of flight table I could immediately lay hands on but did have a muzzle & 100 yd velocity chart for the standard Velocity vs the a HV round. With both using a standard 40 gr bullet the HV round lost 290 fps over the 100 yds while the SV round lost only 171 Fps. At 1335 FPS the Theoretical TOF for the HV round would have been .225 Sec's while at 1145 FPS the theoretical TOF for the SV round would have been.262 Sec's.
Wind Drift is calculated, not from the actual time of flight in the air, but from the difference from the theoretical TOF to the actual. In this case the standard velocity round has less difference than the HV therefore it had less wind drift. This situation occurs only at this velocity level & occurs because of the greatly increased drag encountered as the sound barrier is broken. "Barrier" here is more than just a figure of speech.

Adhering to CIP standards does not mean all member countries arrive at those standards in the same way. Here's a very good example: Starting in 1989, the British proofhouses started using a proofmark that expressed the proof pressure of the gun in bars. For 12 bores, standard proof was expressed as 850 bar; magnum/superior as 1200 bar. A bar = 14.5 psi (or actually a bit more, but 14.5 is close enough for govt work). However . . . in 1989, the British proofhouses were still measuring pressure by the old crusher methods: lead crusher for lower pressures, like shotguns; copper crushers for higher pressures, like rifles. That confused a lot of folks on this side of the pond, because we thought you could multiply those numbers x 14.5 and get a figure comparable to our own psi figures--which were measured with electronic transducers, not crushers. Then, in the early to mid-90's, the British (and at least some of the other CIP countries) switched from crushers to transducers. However, the British did not change their proofmarks--even though 850 bar crusher = 960 bar transducer. (And once you get to the 960 bar figure, you can then multiply x 14.5 to get the correct psi equivalent.) All of which is a long way of pointing out, via an example, that the CIP does have common standards, but that does not mean that they all express pressure or velocity figures in the same way. And when it comes to velocity, that's not a question of a CIP standard anyhow, except in the case of steel shot loads. As long as the shell in question conforms to CIP PRESSURE standards--which they all do, if they carry the CIP stamp of approval--then you're good to go. For that matter, the same thing applies to American shotgun shells and SAAMI standards: there isn't any velocity standard, only a pressure standard.

But we are far less complicated on velocity than the Brits, because we ALWAYS express velocity measured at 3 feet unless clearly specified otherwise.

Larry,

Thanks for the clarification as to no standard for velocity measurement methods under CIP except for steel loads. I did see a reference on the Eley websight as to steel loads meeting CIP standard but I was not clear as to the meaning of the statement.

From this discussion my take is that an accurate comparison of manufacturer published velocities for loads produced under CIP & SAAMI standards is only possible if the CIP manufacturer clearly states the distance @ which velocity is measured.

With the Rottweil/RWS data listing identical velocity for identical loads @ both 2.5 meter velocity & "mouth velocity" (a translation glitch from muzzle velocity I think))in different publications I'm thinking a rather casual approach is taken with published velocity data by some CIP manufacturers.

Added as an afterthought: I did a search of CIP published info & could not come up with anything relating to velocity test standards so I'm assuming that "no velocity test standard is correct" but that seems strange to me given the stringent specifications on pressure & pressure test methods.

What is the source of your information that changed your previously posted information from conversation with the British Assn. or Shooting & Conservation that indicated 2.5 meters as the CIP standard to "no velocity test standard for CIP" .

Does the statement from the British Assn. for Shooting & Conservation mean that only the UK is establishing 2.5 meters as their own velocity standard for shotshells produced under CIP & is this voluntary or mandatory?

I'm not trying to be confrontational, I'm just trying to get good information on this subject.

Brittany, here's an example from the BASC information sheet I cited: "The mean velocity, measured at a point 2.5 meters from the muzzle . . . " To my knowledge, under CIP rules, steel loads are the ONLY ones that have a velocity limit. And that's how they state velocity will be measured--but only for steel loads. Therefore, ammo makers don't have to adhere to ANY velocity standard on ANY other ammo, as long as those shells meet CIP PRESSURE standards. Which leaves them free to express the velocity of their shotshells (other than steel) in whatever fashion they think buyers are most likely to understand.

It'd be nice if they'd all settle on one standard method of measuring and expressing velocity, as we have on this side of the pond. But I think they like to confuse us.