Strange Velocity

shootist · Posted: Tue Jun 13, 2006 5:52 pm Post subject: Re: Strange Velocity

Hi Squirrelbait....I think PaulS has a handle on it...watch your [b]crimping.
Take a close look. Check flaring and the residual crimp.

Regards,

Shootist

kbis · Posted: Tue Jun 13, 2006 11:01 pm Post subject: Re: Strange Velocity

I agree that the condition of the barrel will have some affect, but to clean the barrel after every shot seems a little extreme. The 44 shot 5 of 6 rounds with only a total of 16 FPS between all of them. Isn't that pretty close or should I expect to get 1 or 2 FPS difference with cleaning the barrel between shots ?

I just looked at the cases again and from looking at the pimers I could not tell you which one was hot or slow, they all look the same.

I am using a "Chrony Master" and I had the shades in place. I don't know how much good they did since the sun was over my shoulder and shining right on the lenses.

As far as point of impact on the target some of that may be my fault. Yes I am shooting at a target, but my main concern is not shooting the chronograph.

There were a few clouds that day, but they were high and fluffy. You could not tell when the sun went behind a cloud, I wish they were dark so we could get some rain and break this hot spell.

I weigh each charge and will add or delete until I get a 0 on the scales. My scales are mechanical but old, but are supposed to be accurate to 1/10 of a grain. They were made for Lyman by Ohaus and still have the Gemco (if you remember them Smile

) price tag of $20.99

I don't remember if any brass was trimed with the 44, but it is a straight wall case like the 357 and they don't tend to grow like the bottle neck cases do. I do remember removing brass when I trimed the cases on the 30/30, but did not measure them as this has never been a problem in the past.

I sure appreciate all the inputs, When I get off these weird hours at work I will load up some more and try it along with a some factory loads to see what happens.

guncollector · Posted: Wed Jun 14, 2006 5:19 pm Post subject: Re: Strange Velocity

Extreme spread of 16 fps is very good even with a 4 shot sample. You could introduce more error than that if you cleaned after every shot and left slightly varying amounts of cleaning fluid in the barrel. I'm sure you've noticed that the first shot after a cleaning is usually a bit slower than following shots. That's why it is called a fouling shot.

Flattened primers are a indication of increasing pressure but, as Bushie points out, not necessarily overpressure. You can see this yourself if you load some moderate loads and some max loads and look at the primers. The higher pressure, max loads will typically flatten the primers more than a moderate load.

Perhaps a better high pressure indication is an extractor mark on the base of the cartridge. This is where the cartridge is shoved back against the extractor at greater than typical force. It looks like a shiny spot.

kbis · Posted: Wed Jun 14, 2006 10:53 pm Post subject: Re: Strange Velocity

Guncollector- I hate to ask dumb questions ( but seem to do so alot on this forum Smile

) but where will the "bright" spot be??

In a perfect world all the bullets will come out of the barrel at the same speed, but in the real world what range of spread is good? I seem to remember (old age is setting in Smile

)reading some where that the SAMMI (or what ever the letters were) standard was 90 PFS.

squirrelbait · Posted: Thu Jun 15, 2006 5:41 am Post subject: Re: Strange Velocity

Pauls, you raise an interesting thought.......not to get off topic but I have been wondering how my faster "varmit" loads in my 243 shoot lower impact from same point of aim at 100yds as my "deer" loads. Is this the answer? Varmit loads= 4000fps, deer loads= 2900fps.
Always confused and looking for answers!

Bushmaster · Posted: Thu Jun 15, 2006 5:47 am Post subject: Re: Strange Velocity

Squirrelbait...Pauls has it. Due to barrel recoil and recoil muzzle rise the slower bullet gets to the muzzle during that rise. Whereas the faster bullet gets to the muzzle sooner, hence less muzzle rise.

guncollector · Posted: Fri Jun 16, 2006 11:50 am Post subject: Re: Strange Velocity

kbis -

You asked where the bright spot will be - a picture is worth a thousand words so go to

stevespages.com/table3.html and select "diagnosing problems" under the case section.

Steve's website is a treasure trove of information on reloading if you haven't found it before.

WRT "a good range of spread" I think the way to look at it is to find the load that gives you the lowest extreme spread. In one rifle, it might be 10 fps and in another it might be 50 fps. Consistent velocity is a key component of repeatable accuracy but not of accuracy in and of itself so you also have to find an accurate load.

PaulS · Posted: Sat Jun 17, 2006 1:14 am Post subject: Re: Strange Velocity

I never discover anything about velocity, extreme spread or Standard deviation until after I have selected and fine tuned my load.
I find the most consistantly accurate load and then run forty rounds over the chronograph to find out about all the "good stuff".
I load first and foremost for accuracy - so I find the one that hits the smallest spce on the target most often, under the widest range of conditions and then I find out how fast it goes, the standard and mean average deviation and the extreme spread. Then I test it in the fackler box for penetration and expansion. I compare that to my data base for past performance of that bullet to find out what I can expect on game. I record everything because I am working on an terminal ballistics formula that will approximate what I am recording in real life in the fackler box and in game. I should be able to come up with a formula that will tell me how much penetration and expansion I can expect for a given bullet at a given velocity - and whether it will explode on impact with a hummingbirds tail feathers or expand 10% as it breaks through the shoulder of a bull elephant. Ok - a slight exageration but I should be able to put some math together to cover the results of what I prove in the box and link it to "real world" hits.

kbis · Posted: Sat Jun 17, 2006 2:02 pm Post subject: Re: Strange Velocity

PaulS
I have a dumb question, what is a "fackler box" ?

Guncollector
Great link, thanks.

st_albert · Member Joined: May 31, 2006 Posts: 38

I'm not PaulS, but a Fackler box is basically a wooden trough that holds a bunch of ziploc sandwich bags filled with water in a line, with an open end. You shoot through the open end, through the line of baggies, and note the distance the bullet penetrated through the water-filled bags, and the expansion of the bullet. It's a "poor man's" substitute for ballistic geletin. Correlations exist to let you estimate the penetration in ballistic geletin it would have gotten, given how far through the water it went.

As to the original problem, I would mostly suspect the chronograph in the absence of other obvious causes. I'd fire more than 5 rounds per test, and if there's an outlier, just throw it out. If there are several outliers, then maybe you've got a problem.

My general rule for outliers is to calculate the mean and S.D. without the suspected value. If the suspected outlier is more than 3 times the S.D. away from the mean, OR if you have a known reason that it could be bogus (e.g. you dropped the cartridge on its nose and set back the bullet, or the primer showed definite high pressure signs and the others didn't), then throw the outlier out.

Just my $0.02,

Albert

PaulS · Posted: Sat Jun 17, 2006 11:41 pm Post subject: Re: Strange Velocity

Albert is right on with his description - Mine holds 48 one gallon bags of salene solution (sea water - salt water) It is enough denser than fresh water that bullets behave better than in the plain water.

I don't like "throwing out" fliers on targets or on the chronograph. Sometimes you might get erronious readings but if they are enough of a problem that you need to start throwing them from your calculations you need to change your equipment or fix the loading problem.

In this case I think your problem is the chronograph and the conditions you are using it.
I always use 15 feet from the muzzle to the midpoint between the screens. At that range you will rarely have any interference from gases modifying your readings. With you chrony try testing on overcast days - those days with gray skies and no direct sunlight or shadows.
If that is not possible then use filters that prevent direct sunlight from hitting the screens - it may take a fabricated cover over the entire chronograph plus a few feet in the direction of the sun. You need to eliminate the interference if you want accurate readings.