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Strange Velocity
Discussion regarding the reloading of ammunition and tuning of loads for accuracy
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kbis
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PostPosted: Mon Jun 12, 2006 7:04 pm    Post subject: Strange Velocity Reply with quote

I posted this on another forum and wanted to get some input from the huntingnut folks.

I had 3 different loads that I was semi-happy so I loaded up 6 rounds of each load to shoot thru the chronograph to see how the speed was doing.

I was loading for a Marlin lever gun in 30/30 and Win. 94 in 44 mag. All brass is Rem. and was originaly factoy loaded. The primers all came from the same box. The 30/30 was Win LR primers and the 44 was Win. LP primers. All brass was trimed using a Lee trimer. This is the 1st reload for the 44 brass and the 2nd for the 30/30. All bullets were crimped using the Lee Factory Crimp.

Both guns started out clean and I cleaned the barrel of the 30/30 when I went to the 2nd test load. All bullets were in a plastic box with the bullets pointing down and I loaded each round individually (no rounds in the tube magazine). All were shot in a 40 minute time span and the shooting table and chronograph were not moved.

First load was a 173 grain cast bullet with GC over 27.4 grains of AA 2495. 5 of 6 shots measured between 1499-1568 FPS with the 5th shot coming in at 1881 FPS. That is a 313 PFS jump, not good if you are pushing the max.

The next load was with 170 grain Rem. Core Locks over 29.0 grains of AA 2495. 4 of the 6 rounds measured 1852-1897 FPS with # 1 coming in at 1657 and # 6 at 1604 PFS, about 200+ FPS slower than average.

Last test was with the 44 mag. using "Oregon Trails Laser Cast" 240 grain bullets over 23.8 grains of AA 5744. 5 of 6 shots measured 1519-1535 FPS which I thought was prety good, that is 1% deviation but shot # 3 went 1288 FPS, 231 PFS low.

The hits on the target reflect the speed, slow speed hit low and high speed hit high.

Any one got any ideas what I am doing wrong? I am sort of a accuracy nut and the jumps in speed don't help.

Thanks.
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Arizona Hunter
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PostPosted: Mon Jul 24, 2006 3:34 pm    Post subject: Re: Strange Velocity Reply with quote

Now I've been reloading only five years, but I have noticed that in my reloading area is a ceiling fan and A/C vent-both affect my scale. Is it possible that either the scale sticks at times causing you to add more powder, and then you get a "hot" load. Also, if an air current is from a fan or heating/AC duct is hitting your scale it will cause you to place less powder in the pan-hence the light loads.

I've had both situations in the past and sometimes end up pulling a few bullets when I noticed it while reloading. Hope your solution is as simple to correct as mine was.
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Blaine
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PostPosted: Mon Jul 24, 2006 4:32 pm    Post subject: Re: Strange Velocity Reply with quote

A couple of questions come to mind:

1) Are you seating the bullets out close to the lands? If so, are you measuring the OAL from the ogive or the point?
2) Was it very hot while you were shooting? Were the rounds (or some of them) in direct sunlight prior to chambering them.
3) How warm was the barrel/chamber between shots? Did you leave each round in the chamber about the same amount of time while sighting in?
4) Is your Chony set out directly in the sun, or possibly at an angle that allows sunlight directly on the sensors? Heat and sunlight can play heck with chrony's, particularly later in the evening when the sun hits the sensors at an angle.
5) Have you ever weighed your completed loads to see if they "measure-up" within a test group? I always check my test loads this way as a final check to be sure they are consistent. Because I weight batch my cases and bullets, as well as hand weigh each charge, if the completed loads vary by more than 1/2 gr, I have done something wrong, and they get pulled and re-loaded.

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popgun
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PostPosted: Tue Jul 25, 2006 1:16 am    Post subject: Re: Strange Velocity Reply with quote

The previouse posts are all good things to check but one thing in your explination caught my eye. You said that the bullets were nose down in the box. So, here is my question. Are your loads filling the case or close to full or are the charges much less than case capacity? Experiment results that I have read showed that powder position in a case not near a capacity charge caused great variations in velocity. Something to consider.

The cronograph problems mentioned above all apply along with the distance from the muzzel. Most cronographs specify that the distance should be 10' and as much as 20 feet from the muzzel. Any less can cause the blast to shake the screens and give some interesting results.
Something to try is use a black permanant felt tip marker and paint the bullets of your loaded rounds black to avoid reflections that can trick the sensors.

Keeping the rounds at the same temperature during testing is important. That is why varmint hunters who shoot volumes of rounds in a day, especially hot weather like we are having across the country this last week, go to extreems to keep their rounds cool and not let them sit in the sun and even keep the rounds inside coolers.

How you prep your brass can cause variations in velocity too like not deburing the flash holes.

It is interesting that your fluctuations are occuring with more than one rifle.

I hope you figure this one out.

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Vince
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PostPosted: Wed Jul 26, 2006 11:30 pm    Post subject: Re: Strange Velocity Reply with quote

Hm, a bit of a conundum.

I have experienced the same problem as Arizona Hunter when I left my garage door open. I have Redding balance beam scalesand even breathing over them is sufficient to induce errors. This is definitely a consideration if you hand weigh your charges.

The situation popgun mentions is also a strong consideration. I remember many many years ago when I first started pistol shooting I read an article in a copy of the American Handgunner called The 2.8 grain Bullseye Surprise. It talked about the problems with smaller loads in cases and how thes loads can effect pressures.

Good luck with the problem kbis.

Cheers, Vince

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kbis
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PostPosted: Thu Jul 27, 2006 9:39 am    Post subject: Re: Strange Velocity Reply with quote

The cases were about 70%+ full and I do not have a tool to debur the flash holes. I have read some articles that say it is a waste of time and some that say it might help. I do clean the pockets and holes.

I have never weighed the completed cases but do weigh every charge and there are no fans or A/C (I wish there were) where I reload.

The chrony was about 15 foot from the the bench.

Both the 30/30 loads were one the table while shooting, the 44 loads (shot last in the group)were in the house along with the rifle.

I have made up another batch to try, this time I measured the bullet weight, perhaps I should weigh the finished product. I am waiting for work schedules and mother nature to cooperate so I can try it again.
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steve4102
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PostPosted: Thu Jul 27, 2006 2:49 pm    Post subject: Re: Strange Velocity Reply with quote

Quote::
The hits on the target reflect the speed, slow speed hit low and high speed hit high.

It has been my experience that the slower velocities hit higher on the target and the faster ones hit lower. Me thinks that your velocity spread may be more related to the Chrony than the load.

Here is some reading on velocities and POI. www.thehighroad.org/sh...p?t=212202
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Jack
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PostPosted: Sat Jul 29, 2006 8:24 am    Post subject: Re: Strange Velocity Reply with quote

My guess is that you got some bad readings on the chronograph.
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Spacedone
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PostPosted: Sat Jul 29, 2006 9:20 am    Post subject: Re: Strange Velocity Reply with quote

my opinion only


ive been reloading now about a year.

i use lee reloading tools.

i found when i was weighing loads i had a large FPS differintial shell to shell.

i bought the lee loading scoops where now i dont weigh anything. i size my cases and trim when needed. i clean any primer pockets that i think need cleaned and have never deburred a single primer pocket. i use the powder scoop dipping it into my powder leveling it smooth and loading the bullet as the manual calls for.

my average FPS differential has dropped from up to 200 FPS down to a average of 50 FPS.

i dont need to worry im reading the scales correctly.

i dont worry about wind.

i can reload at the range out of a powder can and be assured all my loads are consistant.

every gun i reload for has improved accuracy.

some people think reloading is rocket science. remember people have been reloading shells since metalic cartriges have been made.

because of the nature of fire arms you can never ever get a perfect load.

temperature changes
wind
bullet differences
barrel temps
elevation
barametric pressure
weather
your stress level
how tired or hungry are you
ect

all will make any shells shoot differently.


a example

you load 20 shells all the same.

first shell you shoot from a cold barrel at 70 degrees with no wind and a rising barameter and you shoot 1 quarter inch high and a half inch left.

you wait 30 minutes and let the barrel completely cool. the co0nditions are exzactly the same except now the barameter is falling.

quess what

the bullet will hit differently.

now say you rise in elevation 1000 feet. the temp is still 70 with no wind. your bullet will again change where it hits.

its impossible to hit the same hole shot for shot consistantly.

you are using a slightly controled explosion to push a metal mass through the air at a high velocity.

a pound of powder wont even be consistant ounce for ounce. some ounces will have more power than other ounces. yes they try to get as consistant as they can but they are never perfect. moisture content in the powder can even make shot for shot hit differently.

you are going to have a FPS differential no matter how well you load any round.


i dont believe youve did a complete enough test using enough rounds. realize you will never be perfect. the idea is to be the most consistant you can. that may mean some rounds will be 200 FPS faster or slower.
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popgun
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PostPosted: Sat Jul 29, 2006 4:40 pm    Post subject: Re: Strange Velocity Reply with quote

We don't have to be kicked to know that we all hunt and reload differently for our particular situation because of location, finances, or other considerations. Some of us want good accuracy for hunting, others want extreme accuracy for long range shooting and match shooting.

Many things effect Standard Deviation in any given load on any given day. Something as little at your breath on the scale will cause variences in your charge weight and increase your SD's. For example I hold my breath while trickling in the last few grains to obtain uniform charges in the pan. Holding your breath is good practice for shooting too.

Uniforming Primer Pockets or deburing flash holes are not necessary on your hunting rounds unless you are shooting at extreme range (relative term) while hunting. It's a different story for varmint or target shooting. Each little piece of brass preperation, uniform case weight, powder selection, primer selection and seating, bullet selection and coating, seating depth, crimp, neck tension, runout, and measuring technique all contribute to smaller groups.

Reloaders weigh powder with the scoops, ballance beams, electronic scales, and by 'clicks' on a powder measure. All work but some allow more range in the charge weight. For example a scoop delivers a charge by volume that will usually weight the same from scoop to scoop if the same technique is used in dipping and leveling the charge. Finding the most accurate load may require differences in charge weight as little as .2 gr, depending on caliber. That small charge weight change is not possible with scoops but is if using a scale or powder measure.

Getting back to powder. There are always exceptions to everything but the most accurate powder listed in the manuals is usually the powder that fills the case at or very near capacity and the charge weight that usually gives the best accuracy, and many times, the lowest standard deviation of muzzel velocity. The less that a case is filled to capacity brings on the bad effects of powder position in the case at the time of detonation causing wider ranges of standard deviation and group size. This is also where you may get into excessive presures.

Moving on to primers, the primer seating technique is a factor in accuracy. A primer that is seated too hard, too deeply, and non uniform depths will give a wide standard deviation also. This is where cleaned and uniformed depth primer pockets have their positive effects, a more uniform ignition of the primer. Next, add the deburing of the flash hole and you get a uniform shaped flame from the primer to ignite the powder charge. Picture the focused exaust of an adjustable exaust engine on a jet fighter.

All of these things have their small effects on extreme accuracy. Not a big deal to the eastern deer hunter that makes shots 150-200 yds or less. Move to the longer distances in open country hunting, prarie dog shooting, and shooting from the bench in varmint or bench rest matches and all of the little things seperate the smaller groups from the small groups.

Standard Deviation is not the major factor in accuracy all of the time. There will be dime size groups at the smallest SD and equal groups at much higher SD's. Nothing takes the place of the load developement process and doing some things to your rifle to make it shoot better, i.e. blueprinting the action, bedding, recrowning, and keeping the bore clean. So every little factor has something to do with extreme accuracy for the shooter/reloader. It is up to you to decide if all of the little things are worth it to you.

Then there is Wind, Mirage, Temperature, Barametric Pressure, Humidity, Physical Conditioning, Sight Picture, Breath and Trigger Control, and Shooting/Reloading Records for your rifle. Yep, Records. These records tell you the personality of your rifle, loads, and your shooting ability in any given conditions. Did I mention the the weakest link in accuracy is the shooter? Very Happy

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kbis
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PostPosted: Sat Jul 29, 2006 4:53 pm    Post subject: Re: Strange Velocity Reply with quote

I am begining to wounder about the chronograph. Yesterday I fired 10 rounds thru my new Ruger #1 (45-70). These were rounds 21- 30 that have been fired in the gun. The load was 300 grain Rem JHP over 55 grains of IMR 3031 with Win LR primers. The brass was new, full sized and trimed. All bullets were crimped with the Lee FCD. All charges were weighed but the bullets were not (had not planed on using the chrony, but using these rounds for further barrel break in). When I shoot thru the chronograph I am not that interested in accuracy, but in the longevity of my chrony, but I was getting 2" groups at 50 yards. The load books say I should be getting in the mid 1900's FPS.

Weather conditions- 11:00 A.M. sun shining directly on screens, shades had no affect. Temp 88.4 (heat index 96). Hum 59%. Wind gust of 19 MPH to my left and from behind.

The chronograph was 13' 6" from the barrel.

Below is the list of speeds. I fired 3 rounds (starting with a clean barrel) and noticed how the speed kept increasing, so I decided to clean the barrel and see what happens and then I fired 2 more. After that I cleaned the barrel after every shot in the air-conditioned house. The bullets stayed out side but were covered to keep them out of direct sun light. The chrony was on its own. I don't know what other data I could list. Sorry for being so long winded.

1493 FPS
1519
2028
2054 cleaned
2092
2074 cleaned
2115 cleaned
2126 cleaned
2072 cleaned
1902 cleaned
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popgun
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PostPosted: Sat Jul 29, 2006 5:27 pm    Post subject: Re: Strange Velocity Reply with quote

Seven out of Ten velocities are in limits. I would say there is something that the cronograph missed on the first two shots and the last shot, maybe. If the sun was shining directly into the sensor it could be giving a false reading. That is nothing unusual about a cronograph. Try using a permanent marker to paint the bullets black and fire a five or ten round group. I do not think the cleaning is necessary for the testing because 3031 is not a very dirty burning powder like BL-C(2) or other dirty burning powders. The sun shining in the sensor or a reflection off of the bullet could be causing a false reading that is why I suggest painting them black with the permanent marker. It won't hurt your rifle and any left in the barrel will come out with solvent with the other residue. Do not expect every reading from your cronograph to be accurate. Many of the newer cronographs will delete the velocity readings like you received in shots 1,2, and possibly 10 and declare them an error.

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kbis
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PostPosted: Sat Jul 29, 2006 5:49 pm    Post subject: Re: Strange Velocity Reply with quote

What if I tried shooting out of my barn (I think I can get a long range shot there). That would eliminate the sun and some of the heating.
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popgun
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PostPosted: Sat Jul 29, 2006 6:29 pm    Post subject: Re: Strange Velocity Reply with quote

Calculating all 10 readings you get the below results. You can see that the bad readings trash the results.
Powder IMR-3031
Charge 55.0
Shot # MV
1 1493
2 1519
3 2028
4 2054
5 2092
6 2074
7 2115
8 2126
9 2072
10 1902
High MV 2126
Low MV 1493
Ave. MV 1947.5
ME 0
ES 633.0
SD 240.9
95%
Group

Drop the first two shots and you get these results.
Powder IMR-3031
Charge 55.0
Shot # MV
1
2
3 2028
4 2054
5 2092
6 2074
7 2115
8 2126
9 2072
10 1902
High MV 2126
Low MV 1902
Ave. MV 2057.88
ME 0
ES 224.0
SD 70.4
95%
Group

If you drop shot 1,2, and 10 you get a better story. That is probably the true story of your load.
Powder IMR-3031
Charge 55.0
Shot # MV
1
2
3 2028
4 2054
5 2092
6 2074
7 2115
8 2126
9 2072
10
High MV 2126
Low MV 2028
Ave. MV 2080.14
ME 0
ES 98.0
SD 34.1
95%
Group

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kbis
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PostPosted: Mon Jul 31, 2006 8:28 am    Post subject: Re: Strange Velocity Reply with quote

Popgun- Thanks for doing the math I am good until it gets to the SD. I re-read the directions and they suggest the same as you, mark the bullets. They also suggest tilting the chrony sideways on sunny days. That may help or I may try doing it in the barn. It would be nice if I could shoot north to south, but am forced to shoot east to west which only gives me a short period of time when the screens will block direct sun light. Thanks for the help.
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