Strange Velocity

kbis · Posted: Mon Jun 12, 2006 7:07 pm Post subject: Strange Velocity

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.

Daveyboy · Member Joined: Jan 22, 2006 Posts: 143

Lets start with the obvious.

There must be at least one thing that it changing. So, what is the one thing that either you did differently or that the gun did?

Is it a new rifle or an old one? Are you coating the barrel with copper? OAL the same?

Can you achieve consistant results with any other firearm?

D

mc223 · Posted: Tue Jun 13, 2006 1:29 am Post subject: Re: Strange Velocity

Is the placement of your chronograph an adequate distance from the muzzle, cloudy or sunny. My Shooting Chrony Beta gets finiky on those partly cloudy days of sun, shade, sun , shade. So I always try to do my chrony stuff eithe early in the morning or later in the afternoon.

Bushmaster · Posted: Tue Jun 13, 2006 7:48 am Post subject: Re: Strange Velocity

Load 6 more of each and try it again. Then let us know what you get. This time let the barrel cool between shots. The information really isn't enough to determine what is going on. Each time you may have had a flyer that could be caused by a hot barrel.

kbis · Posted: Tue Jun 13, 2006 7:51 am Post subject: Re: Strange Velocity

Both of the rifles are not new, but don't have a lot of rounds thru them, the Marlin has probably 150+ rounds on it and the Win. has about 100.

There is no copper fouling, I did have some lead in the Win. but it was removed before I shot.

As to the OAL, I have a problem getting the bullets on the 30/30 to seat at the exact same depth so I usually check each one. I keep them to +_ .005". Would that little change show a 300+ FPS jump?

The other rifles that I load for (243 and 308) don't seem to have that problem.

The chronograph was about 12-15 foot out and there were a few high clouds, nothing that you would notice.

I do have a few factory round left in both 44 and 30/30. I guess a good test would be to shoot them over the chronograph and see what happens. That would eliminate a few of the variables. That is when ever I get another day off .

kbis · Posted: Tue Jun 13, 2006 8:03 am Post subject: Re: Strange Velocity

Would the barrel heat up that much after six rounds? I would fire one then then use the scope to see where I hit, I was not rapid firing, loading one round at a time. I cleaned the 30/30 after the first 6 rounds.

The outside temp was about 90F. If I have to wait for a cool day, I may not be shooting until November Smile

.

I plan on loading up some more and see what happens, just have not had a chance. They have me working wierd hours plus it has been so hot here and where I reload is not air conditioned.

Bushmaster · Posted: Tue Jun 13, 2006 8:22 am Post subject: Re: Strange Velocity

kbis. I shoot an older .30-30 Winchester mod 94. I have never seen the problem you are having. With Remington cases loaded with 32.0 grains of W-748 under a Speer 170 grain flat soft nose bullet, primed with a CCI-200.
Averaging 2040 fps. 30 fps Extreme Spread. 15.2 Standard Deviation. I use a Lee FCD and I don't check OAL. I just crimp in the cannelure and let it go at that. Mod 94's just don't see OAL that much.
I shoot 3 shot strings and let the barrel cool before starting the next 3 shot string. I am getting consistently three holes in a 3" orange dot at 100 yards.
Using your components. Try the above. Also let your barrel reach ambient temperature before shooting. Shoot the breeze with someone for about 30 minutes.

Jack · Member Joined: Oct 19, 2005 Posts: 98

I think repeating the test is a good idea.
One thing you might look for: make sure you don't load a cartridge into a warm barrel and let it sit there for 10 minutes. If you have a barrel at 150 degrees, and the loaded cartridge sits in the chamber for 10 minutes, you have a powder temperature of 150 degrees.
If all the other cartridges you fired were at a powder temperature of 90 degrees, that could make a significant difference.
If you wait for a barrel to cool, do it with the action open, chamber empty (cools faster that way, too)
In general, I'm not a big believer in powder temp differences, but one that big could make a definite difference.

Bushmaster · Posted: Tue Jun 13, 2006 8:29 am Post subject: Re: Strange Velocity

And what Jack said...

squirrelbait · Posted: Tue Jun 13, 2006 12:10 pm Post subject: Re: Strange Velocity

Jack, good input. Never thought of that that way.
Also, isn't .005 enough to cause a change if the one extreme is in the rifling and the other not?

Bushmaster · Posted: Tue Jun 13, 2006 12:29 pm Post subject: Re: Strange Velocity

Squirrelbait...It's a .30-30 and a .44. both have cannelures. When you try to set OAL on .30-30 with a tubular magazine the rounds will go to the top of the cannelure anyway. Set them there in the first place. On other rifles with bolt actions the OAL may, indeed, make a difference. The .44 mag. will be the same as the .30-30. He needs to look somewhere else.

squirrelbait · Posted: Tue Jun 13, 2006 12:33 pm Post subject: Re: Strange Velocity

Bushmaster, thanks. That is why I am here. I need to be educated. An education from the experts is the best. Thanks

guncollector · Posted: Tue Jun 13, 2006 12:36 pm Post subject: Re: Strange Velocity

kbis -

0.005" OAL is definitely not enough to make a difference unless in one case the bullet is touching the lands and the other case it is just off the lands. Even then, I doubt it would make a 300 fps difference. OAL +/- 0.010" will not make a detectable difference in my experience.

My guess, based on my experience, is that the chrony gave a bad reading because of either muzzle blast reaching the sensor or variations in light from clouds drifting by as suggested by another poster.

The second most likely culprit, in my experience, would be some variation in your load. Inconsistent neck presssure could do it. Obviously a couple of grains extra powder could as well. Did you check for signs of overpressure like flattened primers? If the primers look the same for the slower loads as they do for the faster loads, it again points to the chrony.

Bushmaster · Posted: Tue Jun 13, 2006 12:43 pm Post subject: Re: Strange Velocity

Flattened primers are not a sign of over pressure, unless they are cratered or blown out(sooty). I have several firearms that flatten primers and are not over pressure loads. Split cases, bulged cases, hard to eject cases are the most common indicators of over pressure.

The chronograph is 12 to 15 feet away. I doubt that is the problem either as most are set at 8 feet and have no problem. Broken clouds? Yes. That could acount for it.

PaulS · Posted: Tue Jun 13, 2006 3:22 pm Post subject: Re: Strange Velocity

Lets examine this from a different point of view.

What chronograph are you using - does it have shades?(the filters that sit above the screens?

Place it at 15 feet - measure it with a tape - if for no other reason than that way you can calculate a more accurate muzzle velocity

Are you weighing each powder charge?
Are all cases the same length (I know you said that you trimmed them but I have 357 cases that have been fired many times and still are not at the trim to length) if they are short you don't get a crimp.

Shoot the a set of ten rounds of each with the barrel in the same condition. That means either clean and cold for each shot or warmed and fouled. The condition of the barrel has a dramatic effect on the friction and therefore the velocity of the bullet.

This caught my eye-
You said the slow bullets hit low and the fast bullets hit high - That is backwards from every experience that I have had - Slow bullets stay in the barrel longer and that puts them at the end of the barrel during a later stage of recoil and they always hit higher on the target than faster bullets. Slow heavy bullets always hit highest on the target and fast light bullets always hit lowest.
Keep better records - record where each bullet hits (mark it with a circle and the number of the shot on a target on the bench with you) before shooting the next, record the velocity of that bullet, record the sky conditions and the chronograph used, whether it had filters or not and the EXACT distance from the muzzle of your gun that your chronograph was.
For your reloading records you will want a lot more information than what you listed. Give all the information you can to the people you want to help you because one change somewhere along the way can make a big difference.