Velocity craziness with cast bullets

[Dolomite_supafly]

I am working up loads for a 45 ACP. I am using 200 cast flat points loaded to and OAL of 1.23". I am using Wolf large pistol primers with various types of brass. The bullets themselves are 21 brinnell.

I have tried several different powders and worked up loads to near max yet the highest velocity reading is a little over 300 fps. In the same string I have fired a 22lr as a control and the velocity is what I would expect. I have also fired factory ammo and it is within what I would consider normal. The gun cycles and ejects the brass and recoils similar to the factory loads yet I am getting extremely low velocity readings.

Is there some sort of magical reason why a cast bullet will only go so fast? I do not want to exeed the max recommended loads.

One load was 6.5 grains of Powder Pistol and the max being 6.9 grains. This produced velocities in the 280 FPS range.

Another load is 5 grains of Trailboss and the max is 5.1 grains.This produced velocities in the 310 FPS range.

And yet another load using 8.3 grains of HS-6 and 8.4 is max. The velocity was ~360 FPS. The recoil was at least as strong as factory ammo.

I have plenty of other powders to try but I don't want to spend the time chasing my tail and wasting components.

To throw something else in the mix these same loads that are giving me ~300 fps readings are giving me 1000+fps readings in a bolt action rifle (yes I have a bolt action 45 acp).

I am getting no leading at either the chamber end or the muzzle end of the bore. This tells me the velocity should be up there but the chronograph isn't showing it. Cycles strong and ejects the empties well.

I guess I could just load for what works best but this is a bit crazy to me.

Any ideas?

Dolomite

[mikegideon]

I'm not a reloading guy, but... I would load a few rounds with the same formula and jacketed bullets. I would also use some factory .45 ACP loads as the control. Something is lying to you... chrony, gun, or bullets.

[Dolomite_supafly]

I suspect the chronograph. Everything that should be over 800 fps reads correctly yest anything under that seems to be reading realy, really low. I have done a lot more testing since posting this and all the numbers indicate the chronograph is lying.

I tested the same loads in another 1911. It is a compact model with a 3 1/2" barrel but the numbers for it are also very, very low.

6.5 of Power Pistol and 200 grain cast FP= 219fps

6.0 of Power Pistol and a 230 grain FMJ=138 fps (you can see that there is no way that it is going that slow)

Out of the 5" 1911:

6.5 PP+200grain cast FP=336fps

6.0 PP+230 FMJ=235

Out of 17" bolt gun:

6.5 PP+200grain cast FP=1034fps

6.0 PP+230 FMJ=866

And just for kicks a factory WInchester PDX1 230 grain HP out of the 17" gun was 1078fps

I am definitely calling in the am to see what the chronograph maker says.

Dolomite

Dolomite

[mikegideon]

I suspect the chrony too. How close are you? It may be seeing some muzzle blast.

[Dolomite_supafly]

10 feet from the muzzle.

I think something is up with how the "brain" calculates.

Dolomite

[mikegideon]

You can also confirm muzzle velocity with bullet drop. If you can boresight the pistol at 25 yards with a laser, then the drop will be a direct indication of muzzle velocity. This chart is a 200 grain CCI flat nose bullet at 940 fps (spec) and 300 fps. If you wanna try this, give me the ballistic coefficient of your cast bullets, and i can rerun it. It's gonna be close to this one anyway.

EDIT: Note that trace 2 is labeled 940 as well, but I edited the mv to 300

Edited October 3, 2010 by mikegideon

[Dolomite_supafly]

I was able to see the impacts at 50 yards, it wasn't 3+ feet low with either 1911's.

Based on the possibility that unburned powder might be reaching the chronograph before the bullet I think I am gong to hang a peice of paper on the front of the chronograph to stop any from crossing the screens. If I still see the same results then I definitely will be sending the unit in for repair.

Not sure if I am gong to do that today but I will either today or tomorrow and give an update.

Dolomite

[mikegideon]

Well, we know the chrony is lying for some reason. You could also back it off some more if you're feeling confident . I'm thinkin' a 45 slug in the kisser might knock it out of calibration

[Dolomite_supafly]

It has to be the chronograph.

I covered the front with a piece of paper to prevent any unburned powder from causing a false reading. I fired 4 shots and they were all under 200 fps. They seemed to be dropping with every shot. As a matter of fact the last shot was measured at 84.16 fps.

All shots cycled the action and ejected the empties fine.

I checked the voltage of the two 9v batteries I have used. One read 8.6 and the other read 9.4 so the batteries are good.

The only variable that remained the same all day was the chronograph, everything else has been changed. The ammo, weapons, caliber, batteries have all been tried with the same results.

The onyl thing the confuses me is that as long as the velocity is above 800 fps it reads fine.

Dolomite

[timcalhoun]

Well that is a very light load for Power Pistol. Most of my load data starts at 7. grains of PP with a 200g bullet and goes up to as high as 8.3. But the FPS even at 6.5 seems low unless your lead bullets are not measuring .452. Strange.....

[Guest DaG]

Are you in direct or indirect sunlight? Are you using skyscreens? What type of chrono?

DaG

[Guest Lester Weevils]

Nominal open-circuit measured voltage of a 9 V Alkaline might be 9.6 V or higher. So it is possible that new batteries would work better.

[mikegideon]

Nominal open-circuit measured voltage of a 9 V Alkaline might be 9.6 V or higher. So it is possible that new batteries would work better.

The chrony probably runs on 5 volts. Most of that kinda circuitry does. Give it a couple volts to cover regulator droput, and it should run fine on 7 or above.

[Guest Lester Weevils]

The chrony probably runs on 5 volts. Most of that kinda circuitry does. Give it a couple volts to cover regulator droput, and it should run fine on 7 or above.

Hi Mike

I misread that his unit used two 9V batts. Rather than he had tried two different batts. Even so, high open-circuit voltage isn't real good 'proof' that a battery is good, though a low open-circuit voltage is real good proof that a battery is bad. Sometimes real weak batteries can show good voltage til you load em down under practical conditions. You know all that of course.

It is probably not the battery, but OTOH if a brand new fresh one is available for test, it wouldn't hurt to try. I've had instances where batteries had good open circuit voltage and still didn't have enough current drive to work properly.

[Dolomite_supafly]

After being loaded and then removed with an impact puller the bullet still measures .451" at the base. It is a bit smaller where the case mouth crimps it but above and below that crimp the bullet is at least .451". At 10 yards there are no key holes.

Also, I am not seeing any leading towards the chamber which seems to be indicative of blowby that can be caused by a small bullet or low velocity. The cases are showing a good seal with little to no soot around the case mouth. The velocities listed aren't what is happening. I can gurantee that the last shot that registered 84 fps was going faster than that. I seriously doubt the action would even cycle at 84 fps. As I said all tested loads are close to max so there is no way two different kinds of powders are bad, the scale was checked for calibration and it is right on.

Also I doubt something that generates only generates 336 fps out of a pistol will generate 1034 fps out of a rifle. I know there will be increases but I doubt that much.

I can't remember where I got the recipe for 200 grain SWC but I do remember the max being 6.9 grains of PP. I also loaded trailboss that was .1 grain off of max and got the same reduced velocities. I have used FMJ as well as plated bullets and they are showing the reduced velocities as well.

Tomorrow I will try upping the powder charges to see what happens.

This whole thing is frustrating because I am trying to get the velocity to about 900 fps but without knowing where I am now I don't want to take a chance on creating too much pressure.

Dolomite

[Dolomite_supafly]

Hi Mike

I misread that his unit used two 9V batts. Rather than he had tried two different batts. Even so, high open-circuit voltage isn't real good 'proof' that a battery is good, though a low open-circuit voltage is real good proof that a battery is bad. Sometimes real weak batteries can show good voltage til you load em down under practical conditions. You know all that of course.

It is probably not the battery, but OTOH if a brand new fresh one is available for test, it wouldn't hurt to try. I've had instances where batteries had good open circuit voltage and still didn't have enough current drive to work properly.

The unit only uses one battery. I replaced the one that I have been using with a new one. When that didn't change anything I decided to check the voltage of both batteries.

Dolomite

[Dolomite_supafly]

Are you in direct or indirect sunlight? Are you using skyscreens? What type of chrono?

DaG

It is a Chrony ALpha Master.

It was overcast today. Yesterday it was bright and sunny and these same loads were giving velocities of 1300fps-1400fps. I attibuted that to the direct sunlight so I gave up yesterday and decided to wait for an overcast day, today. And now we are here.

Dolomite

[mikegideon]

It is a Chrony ALpha Master.

It was overcast today. Yesterday it was bright and sunny and these same loads were giving velocities of 1300fps-1400fps. I attibuted that to the direct sunlight so I gave up yesterday and decided to wait for an overcast day, today. And now we are here.

Dolomite

I would loan you mine if you were closer.

[timcalhoun]

I get the best results with my CED with direct sunlight using the diffusors and canting the diffusors toward the sun so that the shadow of the diffusors are on the eyes. When I do this it gives me the same results as in the box using the infrared system. Very accurate.

My shooting chrony was very fickle but it was a much older model. It was my first chronograph I had maybe 20 years ago. It seemed to only function well on cloudy days and sucked on sunny days.

BTW, in general fast powder + heavy bullet = flat, soft shooting load. I have always had amazing results with Clays in 45 acp. FWIW

[timcalhoun]

Also,

Hornady reloading manual: 45acp 200g OAL 1.23 starts at 6.9 and goes to 8.5 grains.

Speer reloading manual: 45acp 200g OAL 1.200 starts at 7.0 and goes to 8.3

Both loads are for power pistol.

[Dolomite_supafly]

I used to use 4.5 grains of Clays under a 200 grain SWC as my plinking load. This was a few years ago. Now I have a selection of powders and actually like the power pistol.

I know my 6.5 load is a bit on the low side but all the data I can find shows that to be at least 700 fps with a 200 grain cast bullet. I am going to work up some loads starting at the 6.5 grains of power pistol. I'll increase by .5 grains until I get close to max to see how the velocity changes.

Yesterday I encased the chronograph in white paper to keep the suns glare down after I was getting high readings. Even doing that caused it to continue to read high. That is why I decided to wait until today to work on my loads some more. Overcast today and I get extremely low velocities.

I am still not 100% certain it is the chrono because with factory ammo it reads correctly, if anything it reads the lower velocities wrong but the higer ones are correct. I keep data on every round I load or try and all "control" shots were right on the money from a few months ago. My loads are a bit on the low side but all the data I can find shows the 6.5 PP load to be at least 700fps.

Dolomite