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Discussion Starter · #1 ·
I was checking out some load data on the Alliant website. Prior to entering the page with the load data, a precautionary page comes up that says , a person should always reduce his starting loads by 10% of the load listed. Now, as I do rifle reloading too, this is something worth knowing about. Does anybody actually bother to reduce starting loads on a shotshell by 10%? I have never bothered myself, but was curious. :lol:
 

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My Alliant guide states that shotshell loading info should be followed exactly. The only mention of reducing powder charge is in the metallic cartridge section which comes after the shotshell section. My Lyman manuals say the same thing, follow exactly. Saying that, I have strayed from the listed loads but not by much.
 

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12ga.

Yup, I noticed that too! No I don't reduce my shotgun loads 10% to start. I typicaly don't work powder charges with shotgun loads like I do with rifle and handgun loads. I use what the book says, or as close as I can get my loader to drop the powder and run them over my chronograph to see what is happening.. Some will surprise you!! Not even close to what they say you should be getting! Sure wouldn't want to decrease THOSE by another 10%!

BP
 

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Discussion Starter · #4 ·
I thought it was unlikely that one would reduce loads for shotshells. I do load one recipe from the Alliant on-line data for the AA 12ga, 18gr Green Dot, AAwad, CCI209, 1-1/8oz, that appears to be about 10% lower than what my Lyman load data suggests. It is a nice soft load, easy on recoil, but still breaks the clays. (I have used the W209 primer with this load as well.)

I would be interested in doing some chrony comparisons, but was afraid of blowing away the chrony. How far in font of the muzzle do you usually set it up?
 

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when i am using a faster powder for the gauge, i will often download a little. if a load calls for 18 gr of red dot in a 12 ga., i will load down to 16-16.5 gr. if i were loading a high speed load of 1 1/4oz shot with, say blue dot or herco, i would stay pretty close to recipe because slower powders do not download well. some 410 powders, such as alliant's 410 do not download well. ask the old heads at your gun club or on this forum.
 

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That's what the "experts" say using the coil type professional chronographs, is it get's the average, but i don't really buy it.
How could any portion of a shot string be going 35 fps different than the rest of the shot string? The wad with the shot still in the cup as it exits the muzzle is all traveling the same speed, how do you all of the sudden get some mysterious 35 fps difference at 8 feet,i chrono at 6 feet BTW.
Sure, some of the shot starts to slow faster than others, but 25 at 6 feet, i'm skeptical.The ballistic tech at Ballistic Products was trying to tell me how inaccurate over the counter chrono's are for measuring shotgun velocities, and gave me all this professional chrono, avg vel., song and dance, I told him the velocities i was getting with some of his steel recipes were not even close! he claimed 1500 fps , i was getting 1320 fps, i test my chrono with "known" factory shotshells at 6 feet, i shot a PMC dove load 1 oz that claimed 1290 fps, and darned if those things don't clock over my chrono at exactly 1290 fps, also shot Win AA loads over my chrono, the box said 1255 fps,
what did they go over my chrono at, 1255 fps , actually the velocity loss at 6-8 feet is probably the 35 fps your talking about anyway, so shoot at 6-8 feet and the LCD will light up your muzzle velocity.
 

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100% agreement with UltraMag on this. I been using a Pact Model 1 for something like 10 years or so with outstanding results with rifle, handgun, and pistol. You do as much loading and chronographing as I have past some years, you know when it's lying to you or not. Projectile speed is just that, projectile speed, that's all the chronograph times. It couldn't care less if it is a pellet, wad, bug, you name it. First thing over the eye gets timed! I doubt you will see a 35' difference in 4' difference in distance from the muzzle.

BP
 

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Shot can slow down as much as 50 fps between the muzzle and three feet depending on the initial velocity. Under 1200 fps and the amount is up to 20 fps, above that and the fall off increases greatly. This is according to E.D. Lowry's "Shotshell Ballistics for Windows" program. The 35 fps "rule" I recently saw in a 1984 reloading manual, "The Handbook of Shotshell Reloading" by Kenneth Couger comparing actual velocities to SAAMI nominals. Screen chronos can be fooled by various means, the main one I have been told is that they measure from when the first screen reaquires the light after the shot column passes to when the light is first blocked on the second screen. With the shot column beginning to elongate at this point, velocities can get to be rather quick in some loads. I have a 20 ga load that registers 1400 fps at 8' on my screen and 1200 fps on an industry coil at the muzzle. Other loads it is reasonably close. It likely has to do with how soon the shot column begins to shed the wad and that can differ depending on components. I have also found the same loads to have differing velocities in different guns. It is common for shells in my .742" Invector Plus barrel to be 35-70 fps faster on average than the same loads in my .725" Miroku barrel. Tighter chokes can also raise velocities as much as 40 fps. That is one reason test barrels often have full chokes. Reloading manuals used to put a disclaimer that listed velocities and pressures were for the test barrel only, results may differ in other barrels. I use my chronograph to measure consistancy, if anything appears greatly out of line then I try to get a second opinion from a different source.
 

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The "normal" industry standard in the USA for measuring shotshell velocity is three (3) feet from the muzzle. This is not true of import shells that are typically measured at the muzzle.

If you ever get the chance to use a high quality chronograph such as an Ohler 35 you could test any of your shells at various distances and you will indeed find that shot can and does slow down radically in the first six (6) feet out of the muzzle. :eek:

You can also discover that the same shell fired in different guns with different barrel features, such as over boring, porting, differnt amounts of choke, length, and different actions will have widely varing results.

All consumer chronographs use leading pellet technology, which simply stated means they measure the first pellet in the shot string.
Industrial chronographs use the coil method which employs complex measurement calculations to measure the middle of the shot string. A shell with a published velocity of 1200 fps will normally read about 20 fps faster in a 30 inch barrel, standard bore, full choke.

Remember also that each one second of time is divided into one million parts by the chronograph's computer using the speed of light as a reference point, so the tinyest little itty bitty change in distance from the muzzle to the sensor can and does translate into quite a few fps (feet per second) differance.

GCB
 

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Discussion Starter · #12 ·
GCBluerock said:
If you ever get the chance to use a high quality chronograph such as an Ohler 35 you could test any of your shells at various distances and you will indeed find that shot can and does slow down radically in the first six (6) feet out of the muzzle. :eek: GCB
Wonder if this Ohler 35 will measure the velocity at 35yds? :D Now that would be real interesting, and a great way to compare loads!
 

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:) I asked the tech rep. at pact about this several weeks ago and was told that you can measure the velocity at 1 1/2 feet from the muzzle (with shotgun). I had been using the recommended 10 feet that came with the instructions (Model 1).

In my comparisons the same load from the same gun on the same day the loads at 10' were on the ave. 35-40 fps slower.
I have chronographed factory Federals, Winchester, and Remington shells at 1 1/2 feet and they are with-in 5 to 10 fps plus or minus published velocity. ^o^
 

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The distance to the first screen depends upon the distances between screens. The reading given by chronographs is essentially an average velocity between the two screens. If, for example, you are using screens with a 2' separation and want the velocity recorded at 3', one would want the first screen at 2' from the muzzle. If one is using a 4' screen separation, then one would want the first screen 1 foot from the muzzle.

In my case, whether I'm using the M43 or the M35P, I use three sky screens on a 4' rail. Setting the screens up so that the first one is 2 feet from the muzzle gives me a velocity at 3 feet and another velocity at 5 feet.
 

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Dear guys,

You are all correct for the methods that you use to measure. There are a lot of facts in this thread from beginning to end. You must remember however that oath we take on testifying about the "truth, the whole truth, and nothing but the truth." A few independent facts maybe true but are not the whole truth.

When I got into shotgun reloading, I surveyed all of the people who supply the data for theose books we rely on so well for load data. All of them (Hodgdon, Alliant, IMR, AA, Winchester) had SAAMI pressure guns but ALL of them used different methods for calculating velocity! Not one single book tells us exactly what method they used to determine the velocity and most do not tell us exactly what distance they used to determine it! SAAMI does not have a standard for velocity for shotshells only pressure.

A lot of the e-mails back from their technical departments revealed the wide disparity in methodology and distance from the muzzle. Here the exact e-mail question and response from Hodgdon as an example:

The loads are shot across and Oheler system 30 chronograph. The fist screen is 10' from the muzzle and the second screen is 10' beyond that. The barrel is a 30" full choke.

Thank you for your inquiry.

Phil Hodgdon

-----Original Message-----
From: Dave Tarasevich [mailto:[email protected]]
Sent: Thursday, October 31, 2002 11:30 AM
To: Help Account
Subject: Published shotshell velocities

To whom it may concern,

Can you please tell me what is the basis for your published shotgun shell velocities? Are they measured at the muzzle or are they measured at the 3-foot level? What method do you use to measure these velocities? Is it induction coil or sky screen method? May I suggest you please include this data in your future manuals?

Thank you for the excellent powder, data, and service. You are the best by far at taking care of the customer.
Cordially,
D.J.Tarasevich

A subsequent phone conversation with them indicated that published data is adjusted to a 3 foot velocity using a ballistic formula from the 10 foot spacing at 10 feet! They said that they used industion coils for the triggers. They also said that they would include the methodology in future data and that they were going to a different system closer to the muzzle. Their most recent manual still does not indicate this data.

Other producers were even more cryptic and confusing about methods.

The fact is the sky screen for over the counter triggers leaves a lot to be desired with shotshells. The detectors look for shadows to trip the logic. The shadows cast by a single pellet or even a group of pellets may or may not trip the sensor for a given test shot depending on the light source variability and contrast required. The shot stringing effect and the nature of the ejecta in essence defeats the sensor. Wads and unburned powder and stuff screw standardization. The shorter the distance between screens the worse the error.

Do not get me wrong, the formulas are accurate and sacrosanct proven physics and all chronos use the same very accurate formulas. To a large extent the internal timers may also be very similar. However the data from the sensors that is fed into them is always suspect and not always repeatable.

This is true even with an induction coil device for the triggers which I use at the muzzle and also at three feet. My data correlates very closely with that found in the Ballistic Calculator program but, not every shot series run does not have some unexplained anomalies and variability that cannot be traced.

What does this all say? That accurate velocity is an emphermeral goal and that as long as your setup for measuring it is repeatable within your requirments and statistical significance continue to use it. The goal should be to have accurate comparative data for your needs. The velocities quoted for your setup are not comparable to mine. If you get a correlation to factory data it is simply luck not the "whole truth."

As long as your load meets pressure standards you should care about the end results not the velocity number. If you've killed 100 quail with a given load or a hundred pheasants or 100 clay pigeons were turned to dust who really cares about the velocity?

OK Shotgunner's setup is as good as it gets with a realistic budget along with his experience both professionally and hobbyist. Burnt's long and hard acquired experience and meticulous nature are proven. The same goes for the rest of the gang. If you provide the data and load I try it not because of the velocity data but because of your experience in its end use.
 

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Dave makes very valid points. Velocity and pressure are neither as easily measured nor as universal as, say, weighing out a pound of butter. Velocity and pressure data from any source is only an indication of what it could be from your shotgun -- or rifle or handgun for that matter.

Ballistic labs use SAAMI spec test firearms, and these will usually -- not always but usually -- give higher peak pressures for a given load than what one will obtain from a production firearm. Higher peak pressures will also usually result in a higher velocity.

Peak pressure, however, is not the whole story. Velocities are really a product of the area under the pressure curve, so it is entirely possible to obtain a higher or equal velocity with less peak pressure. This is especially noticeable in rifles and handguns, but anyone can see this by examining published load data. For example, using the same components other than the propellant we see a Hodgon published load using 16.9 grs. Titewad producing 1250 fps @ 8,200 psi. Hodgdon obtained the same 1250 fps using 18 grs. of Clays but did it at 7,300 psi. Moreover, they obtained the same velocity using 20.5 grs. International at 6,900 psi.

There is also some potentially bad generic advice floating around about reducing the propellant charge by 10%. There is a "little" thing referred to as secondary explosion effect. It is not well understood and the various explanations have been subject to some professional controversy, but that it exits is a fact beyond dispute. We oftentimes refer to propellants as being fast or slow, which refers to its burn rate. "Fast" or "slow" is, however, relative to context. For example, a "slow" propellant in a 12 gauge might be perfect in a 20 gauge and too fast in a 28 gauge. The point here is that every now and then a "slow" propellant can detonate if loaded too lightly for the payload. Winchester, for example, cautions not to reduce their published loads using their 296 propellant for that very reason. In truth, though, I've never seen, nor know of any verified instances, where secondary explosion was the cause of a shotgun's destruction.

Anyway, these are just some points to consider and is one more reason why one should balance the burn rate of a propellant (i.e., propellant type) to the gauge/bore and payload.
 
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