Hi all.

I bought myself a Chrony earlier this year, and now it seems that "the more I know, the less I know".

For example, I was testing some 180 grain .30-06 loads over the weekend. Firing groups of 3 cartridges for each load increment, using S365 (+/- IMR4350) and CCI 250 magnum primers.

The results (velocity is average of 3-shot group):

c v (ft/s)
================
53 2771
54 2813
55 2672


Notice the anticipated increase in velocity from 53 to 54 grains, and then the sharp decrease in muzzle velocity when moving to 55 gr.

Is this at all possible?

My only thought is that this may be possible if the charge is excessive and some powder remains unburnt, hence reduction in pressure and muzzle velocity?

Or is my Chrony screwy?

Cheers

While the results you show is indeed, possible, I am surprised to see it with this combination of components in a 30-06.

IMR 4350 is a classic powder for the 30-06 and your loads do not seem excessive. I would be tempted to try the same set of loads with a standard primer, though. Maybe the CCI 250 is just too much fire for this combo. I have loaded LOTS of 30-06 ammo with IMR 4350 and have always used standard primers.

It is not that uncommon to see a step up in powder make no difference at all, not often a decrease like you show. In testing a couple of 300 WSM rifles when approaching maximum I saw little or no increase in velocity with one more grain of powder (but at least no decrease).

Years ago in an attempt to get more velocity out of a 25-06 we just kept adding more and more IMR 7828 behind a 100 grain bullet. When we got to a certain point we saw no more gain in velocity even after several more grains of powder. But this is more of a case of mismatching components, IMR 7828 works much better with heavy bullets.

It might well be worth trying the test again with standard large rifle powders, but I would double check the Chrony while you are at it.

I have seen this happen too. I started over just to see what would happen. Sometimes things went as expected, sometimes not. I do not think it is your chronograph.

Consider the distance from your muzzle to the sky screens. If they aren't far enough away from the rifle, you can get eroneous readings from the blast, powder residue and/or smoke.

This makes some sense in this case because you are experiencing it as charges increase. You have more ejecta to interfere with the reading. I like 15' most of the time. I'll shorten it up for rimfires, 223 and pistol rounds.

i believe your chrono isn't accurate in these readings -- however, to answer your question, NO, more powder doesn't always mean an increase in velocity .. i look for these sags, flat spots, and jumps in vel to tell me what is going on.. but loosing OR GAINING 100 FPS for 2 grains is disturbing ..

umshiniwam: This is the kind of thing that I look for along with extream spread (difference between highest and lowest shots in a group) when working up loads. If you did a 54.5gr load you would most likey find it in the mid 2700's. Even without a drop in speed the extream spread can some time show a sweet spot. As you load up the ES will usualy go down and then start to go back up. At that point I start doing small changes in grs up and down and then changes in seating depths. PS: jeffeosso I am still waiting for the loads for a 30Mag and the 35cal.

For whatever reason you are getting erroneous chronograph readings.

This old myth falls into the same category of physics as perpetual motion machines.

What say You HC?

Those velocities seem a bit high to me. I'd redo the test. With the chrony a bit further from the muzzle.
As several have posted, with some powders there seems to be a maximum effeciency for a given case and if you go above that, you are merely burning more powder for no results. Often in load books you will see max loads that are well below the pressure max. This is because the case is full at that point or a reasonable gain in velocity was lacking with the increase in powder.

First of all, I don't load for the .30-06 but I too don't like your last number. In my .270 Win., I load 57 grs. of Rldr-22 with a 150 gr. bullet and only use a standard primer with no problem.
I'd also agree with the others that something might be wrong with your last Chrony reading. I too have a chrony and always locate it a measured 5 yds. (15 ft.) from the muzzle. Never had a problem. I also look at the "efficiency" of the load - AKA Vel./grain. and find it rather interesting. BTW, I put a piece of clear tape over both of my chrony sensors to help keep dust, moisture, etc, out. It's always worked fine.
Bear in Fairbanks

My first thought on seeing the numbers was to wonder if the groups of three were somehow fired in the wrong order. Could it be that it was the
53gn gave 2672
54gn gave 2771
55gn gave 2813

Von Gruff.

quote:

Originally posted by rcamuglia:
What say You HC?

There is always a relatively simple explaination to this kind of result. Just has to be figured out.

Looks like there are plenty of ideas available.

quote:

Originally posted by umshiniwam:
Hi all.

I bought myself a Chrony earlier this year, and now it seems that "the more I know, the less I know".

For example, I was testing some 180 grain .30-06 loads over the weekend. Firing groups of 3 cartridges for each load increment, using S365 (+/- IMR4350) and CCI 250 magnum primers.

The results (velocity is average of 3-shot group):

c v (ft/s)
================
53 2771
54 2813
55 2672


Notice the anticipated increase in velocity from 53 to 54 grains, and then the sharp decrease in muzzle velocity when moving to 55 gr.

Is this at all possible?

My only thought is that this may be possible if the charge is excessive and some powder remains unburnt, hence reduction in pressure and muzzle velocity?

Or is my Chrony screwy?

Cheers

Something is not right. You need to retest your loads, that should not have happened. Somchem S 365 should be stepping up in velocity (and pressure) at 55 grains, not down.

Other then the screwy velocity of your last test load of 55 grains, they seem reasonable.

There is a point of diminishing returns, where you add more powder, and the velocity drops off. This is very common, but usually only rears it's head at top loads or above. Is this the same lot of powder you are using in your 270? If it is maybe you have found the problem, and as I mentioned earlier, if you could get some IMR4350, and try that maybe all this will go away. Just a thought.

Regards

Jerry

There maybe a point of “diminishing returns” in velocity but I have a feeling that there is no point that pressure stops increasing.

quote:

Originally posted by umshiniwam:
Hi all.

I bought myself a Chrony earlier this year, and now it seems that "the more I know, the less I know".

For example, I was testing some 180 grain .30-06 loads over the weekend. Firing groups of 3 cartridges for each load increment, using S365 (+/- IMR4350) and CCI 250 magnum primers.

The results (velocity is average of 3-shot group):

c v (ft/s)
================
53 2771
54 2813
55 2672


Notice the anticipated increase in velocity from 53 to 54 grains, and then the sharp decrease in muzzle velocity when moving to 55 gr.

Is this at all possible?

My only thought is that this may be possible if the charge is excessive and some powder remains unburnt, hence reduction in pressure and muzzle velocity?

Or is my Chrony screwy?

Cheers

Yes it does happen. Not often, but once in a great while.

The last time I personally saw it was in trying to find maximum loads for the .300 Weatherby using TCI 5050 (spherical) powder behind 200 gr. Nosler Partitions.

In that instance we got good velocity progressions up through about 92 grains of powder and 3300+ fps velocity with the 200 grain bullets noted above. The next two 1 grain increases showed almost no change in velocity, up or down. The final increase (to 95 grains of powder) showed a velocity decrease of over 50 fps.

At that point we decided that we were probably above a useable max charge, and/or that TCI-5050 wasn't suited to that use in that cartridge.

Anyway, we called 91 grains our workable max with 5050, and eventually went to another powder altogether....something we thought had a more predictable performance in that application.

Still, it could also have been your chrony, but I can't tell yea or nay from here.

Sometimes highly compressed loads will give atypical results, such as less velocity than expected, even reduced velocity than less compressed loads. AIU

Gentlemen;

Thanks for your response.

quote:

Originally posted by Von Gruff:
My first thought on seeing the numbers was to wonder if the groups of three were somehow fired in the wrong order. Could it be that it was the
53gn gave 2672
54gn gave 2771
55gn gave 2813

Von Gruff.

This would make sense, and is not out of the question. I was pretty careful about the order in which I fired the loads.

This may however be the simplest explanation, and hence the right one.

What is clear is that I should re-test the loads.

I have a Chrony F1 Master, which has a remote LCD connected to the skyscreen unit via a 16 ft cable.

So I am sure that the Chrony was at least 15 ft away from teh muzzle, as I had the LCD lying on the ground in front of the shooting bench, cable fully extended.

The procedure of shooting through under the the screens seems fairly simple, not sure what I could be doing wrong.

Cheers,
Scott.

I have had comparable results when trying magnum primers in 30-40K. They gave a lot more velocity variation as the loads increased.

I think the same happened here and since you only shot three of each load you managed to get three varying on the slow side. Test again using standard primers and more shots of each load.

quote:

There maybe a point of “diminishing returns” in velocity but I have a feeling that there is no point that pressure stops increasing

Mick: You are absolutly right. In this case velocity may drop, but the pressure continues to increase.

Jerry

quote:

Originally posted by Jerry Eden:

quote:

There maybe a point of “diminishing returns” in velocity but I have a feeling that there is no point that pressure stops increasing

Mick: You are absolutly right. In this case velocity may drop, but the pressure continues to increase.

Jerry

VERY likely --- as pressure does not equal velocity -- (ever) .. WORK equals velocity.

I've seen this in the .270 Win with H4831. with 130gr bullets, my 22" barrel stops gaining velocity at 59.5 grain, but the other longer barreled one's I have access to continue to increase in velocity. It's another reason I like longer barrels.

Three shot groups? Not a very big sample size.

While it is highly unusual, averages of small sample sizes can be deceiving. Assuming that velocities follow the Normal Distribution, is it entirely possible that your three shots were all on the lower three sigma side of the curve. They would still be within the distribution, but you just happened to roll snake eyes three times.
The larger the sample size the closer to the true population you will be.

I usually shoot 10 rounds with a rifle, with a handgun I shoot up to the limit of the machine which is 32 shots. I wish it would average 50 rounds as that is the number that comes in a typical box of pistol ammunition, but who ever set up the program decided 32 was the number.

But there is another easier explanation: Instrumentation error. My chrony is very sensitive to shot location and plumb. I spend a lot of time lining my chrony up with a bubble level and I try my best to shoot directly over the sensors. I shoot a “reference” load to see that my numbers are ball park. Even so, there have been plenty of times that off axis shots register abnormal values. If shots are not perfectly perpendicular to the sensors you can get some weird, low values. If powder is crossing over the sensors you will get abnormally high shots.

I had to move the Chrony out about 15 yards to chronograph 58 caliber Musket loads. There was so much powder residue over the screens that values were crazy.

quote:

Originally posted by SlamFire:

I like this idea. And thanks for the great advice.

Well,Alf, there arev several anecdotal references to that right here in this thread.

As far as published ones, maybe they aren't published because the companies involved believe them to be indicative of unsafe loads, or in an "region" of loads that is unsafe, and therefore are careful to NOT publish any such info...for fear someone may try it out and come to harm. So far as I have seen, loading manuals, for instance, usually list only loads they feel safe recommending to others for use.

Seems to me I have actually seen reference to this phenomenon back in the writings of the '40s or '50s , but it is not often. Quite frankly, I have other things to do, so I am not going to waste my time going back searching for it.

I HAVE seen it with my own eyes, so that is good enough for me.

I've always found it a good practice to try to learn things to be cautions about, from other's experiences, so I don't ignore their reports of what they have encountered, whether published in reference tomes or not.


Best wishes,

AC

quote:

Originally posted by ALF:
Can Someone point me to any load book, manual, electronic load manual in fact any reference where the increase in load mass actually gives a reversal or decrease in velocity ( within the minimum and maximum loads cited and given that the correct propellant is chosen for a particular cartridge) ?

ie a load to velocity curve that reverses ?

And I'm not referring to a demished return but a actual reversal in velocity when charge mass is increased !

Please point me to that reference I would be most interested to see it.

go look them up yourself, alf ..

fill a rifle case 1/2 full of pistol powder, and you will likely get a reading.. fill it all the way, and no bullet will cross, now, will it?

as AC says, and I've seen repeatedly

"I HAVE seen it with my own eyes, so that is good enough for me"

now, when you sober up, you can't delete all history of your threads

again^64

ALF
BUY A CHRONO and find out for yourself. I've seen this frequently in rel22 and h335.

since its outside your experience.. (googling old mags) you might experience it for yourself.
just for once

quote:

Originally posted by SlamFire:


I had to move the Chrony out about 15 yards to chronograph 58 caliber Musket loads. There was so much powder residue over the screens that values were crazy.

Where did you get the long cord. When I ran into the same problem with large capacity smokeless cartridges, the voice from India told me I'd have to ""make"" a 15 ft. cord to eliminate smoke and powder residue. That was shortly before I bought the Oehler. roger

quote:

Originally posted by ALF:
Alberta Canuck:

Thank you for your answer However I will ask again?

If you are using the correct propellant in terms of vivacity for a specific cartridge and within the what is seen as functional expansion volume and you are not exceding the maximum allowable safe pressure as detrmined my case strength or you go below what is deemed the mimimum load density for that cartridge there is not a single manual, load recipe electronic or otherwise where a incremental increase in charge mass does not lead to an incremental increase in velocity.

I have just about every load manual ever produced in the USA, including almost complete sets of most of the popoular magazines, annuals and books published on the subject of "american Shooting" including many from other countries mostly German and in not in a single one is there a reversal of velocity cited for a published load ! Not one !

If you wander outside the parameters, such a low density loads or extemely long barrels for powder type etc I agree or you are playing with propellants that are usually to slow for the expansion volume. Yes then I agree.

Alf- I too have a geat many publications on firearms and loading ammo...over 3,000 volumes as a matter of fact (not counting periodicals). I don't have them all, but have a significant number. I did have a lot more on the periodical side, but when my wife recently retired and we downsized our lifestyle, I had to give away a great many to facilitate the move here.

Anyway, I agree wth you when you restrict tested loads to powders intended for the pressures, volumes, and bullet weights being used, at proper temperatures and with proper ignitors.

BUT, such phenomena DO occur when the conditions listed above are not met. Matter of fact, that is one of the signals I pay great heed to when testing. If I see it, I am almost certain one of the conditions listed is NOT being met, or the powder is a wrong one for that use.

BTW, the more I think it over, the more certain I am I have seen published references to this phenomenon in question. I am also certain they indicated the same things I list above regarding why it is a warning to handloaders when it occurs.

Anyway...best wishes again. Glad to be able to discuss things with you.

AC

quote:

Where did you get the long cord. When I ran into the same problem with large capacity smokeless cartridges, the voice from India told me I'd have to ""make"" a 15 ft. cord to eliminate smoke and powder residue. That was shortly before I bought the Oehler. roger

I set the display on my shooting stool which was nearer to the line than my chronograph.

In so far as adding powder and decreasing velocity, maybe funny things like that happen. But I am 100% certain that regardless of what the velocity is doing, the pressures are increasing with increasing powder charges.

The more nitrocellulose you have burning, the more pressure you are producing. It is not like packing the stuff in there somehow reduces the burn rate or the pressure curve. It will always increase.

More means more.

we aren't burning nitrocellulose, my friend.. americans haven't for a long time. i know what you meant, but what you SAID was wrong

pressure and velocity are NOT directly related .. doesnt matter how much you stuff your fingers in your ears and try to ignore it.

a 308 and a 300 rum, loaded to the same pressure and same length barrel-- which one goes faster? if you answered anything other than "they go the same" then you know pressure isn't magic

if you had a 65K blue dot load in a 3006, does it go as fast as the same rifle with rel22, at the same pressure? (assumes 165 gr bullet)

OF COURSE NOT

pick up ANY reloading manual... each max load, ina bullet/caliber chart, is about the same pressure.. but right there is "10" different powders with different results.

quote:

Originally posted by jeffeosso:


a 308 and a 300 rum, loaded to the same pressure and same length barrel-- which one goes faster? if you answered anything other than "they go the same" then you know pressure isn't magic

Would you mind explaining this to me? The old grey matter just isn't registering it. roger

quote:

Originally posted by bartsche:

quote:

Originally posted by jeffeosso:


a 308 and a 300 rum, loaded to the same pressure and same length barrel-- which one goes faster? if you answered anything other than "they go the same" then you know pressure isn't magic

Would you mind explaining this to me? The old grey matter just isn't registering it. roger

no, its registering perfectly .. and that it does register as nonsense revokes all the "thought" that pressure means velocity

Even though the thread is slightly off track I think this is pertinent.
I was wringing out some loads for my .338 Win Mag you can see the results below. More powder was slightly less accurate and slightly slower.

quote:

revokes all the "thought" that pressure means velocity

Jeffe,

You sure don't mean that pressure and velocity are totally unrelated?

Nobody is saying it is a pure linear relationship, where y = mx + c.
However, between minimum and maximum published loads, we can fit a straight line if we do curve-fitting.
Or from a statistical point of view, we expect a high correlation coefficient.
That is generally good enough for hobbyist reloaders.

And at some point we reach diminishing returns, where there is no velocity gain, but only more pressure.
So there comes a point where the relationship breaks down.
But that is outside recommended operating parameters as advised by reloading manuals.

We should not get too technical about it, as then we can also start to debate why the very same load yield 2 different pressures at a testing laboratory from the same case, same test barrel, same room and temperature, etc. In fact, we can shoot 10 rounds and log 10 different pressures, all of which is marginally oscillating around the mean value, with little significance and consequence.

Warrior