Hard Cast +P .45 colt loads hitting 12" lower @ 50yds than Light Jacketed Loads?

[Golovkin]

1885 Browning Low wall .45 Colt 24" Barrel using Semi Buck horn Sights @ 50 yard Target. Bought the gun used, but it seemed to have been unfired. I've only put about 50 rnds thru it so far.

I've shot these loads while prone off a sand bag and these are my baffling results...

1. American Eagle 225 Grain jacketed bullet @ 863 FPS is hitting the target dead center @ 50 yards with rear sight ramp at mid point

2. 250 gr. cast HSM Cowboy loads (fps unknown but slow) are hitting 8" low

3. 325gr. Hard cast HSM Bear loads @ 1150fps are hitting 10" low

4. 325 gr. Hard cast Buffalo Bore @ 1325fps are hitting 12" low


With the big hot loads I don't think my rear sight ramp could put these loads on paper at 50 yards. I would have thought the bigger faster bullets would have hit higher than the lighter slow bullets, but the total opposite is happening in the extreme!


My only two theories so far are:

1. the slow bullet is leaving the barrel during maximum muzzle jump, the fast ones are leaving before it?
2. the Hard cast bullets aren't correctly engaging the rifling and are falling out of the sky?

Anyone have any insight into this?

Thanks

[CraigOK]

Thats does seem odd, normally the impact rises, as the slow bullets take longer to get out of the bore. What are the bullets sizes to? Can you recover some to check out?
I assume they arent keyholing...

[Rick459]

did you actualy chronograph these loads or are these speeds stated by the manufacture of the ammunition? what is the twist rate of the barrel? has the barrel been slugged to determine the bore diameter...452?...454? are you reloading this ammunition? HTH
Rick

[Golovkin]

Thats does seem odd, normally the impact rises, as the slow bullets take longer to get out of the bore. What are the bullets sizes to? Can you recover some to check out?
I assume they arent keyholing...

Not sure of the actual bullet diameter, I'll have to shoot some cardboard to see if they are key holing next time.

[Golovkin]

did you actualy chronograph these loads or are these speeds stated by the manufacture of the ammunition? what is the twist rate of the barrel? has the barrel been slugged to determine the bore diameter...452?...454? are you reloading this ammunition? HTH
Rick

I didn't chrono any of the loads, these are factory rated velocities, but based on recoil - the heavy loads were indeed heavy and they were doing much more damage to the the back stop than the light loads.

The twist rate is 1:16

I don't know the actual bore diameter, and these were all factory loads.

[DougGuy]

It's all dwell time in the bore apparently. Look at the velocity increases as POI drops, boolits are leaving the muzzle before recoil lifts it enough to hit point of aim. Take those same boolits that are shooting low and load them down to standard pressures and observe change in POI.

[MT Chambers]

If you want to use those heavy loads in your gun you may have to get a lower FRONT sight, might be a good time to switch to a tang sight of some kind as well.

[John Boy]

American Eagle 225 Grain jacketed bullet @ 863 FPS is hitting the target dead center @ 50 yards with rear sight ramp at mid point
Your sights are not calibrated for the rifle and good possibility you need a different front sight
With my 45LC and a 24" barrel - shooting 50yards & 100yds... the rear sight elevator is in the 1st notch
Sight Correction Calibrator ... http://www.brownells.com/GunTech/Sight_Correction_Calculator/detail.htm?lid=13093

[Rick459]

you need to find some one with a chrongraph and actualy chrongraph all those rounds. i take it you do not reload?
Rick

[Golovkin]

It's all dwell time in the bore apparently. Look at the velocity increases as POI drops, boolits are leaving the muzzle before recoil lifts it enough to hit point of aim. Take those same boolits that are shooting low and load them down to standard pressures and observe change in POI.

Good idea

[Golovkin]

I normally do reload, but i've always done modern centerfire magnums with jacketed bullets. This is my first time shooting big slow moving slugs. I just bought a few different bullets to acquire brass and get a feel for this thing before handloading. - I have a lot to learn about the .45 colt before I start loading it...

[Golovkin]

Update: The cast 325gr bullets that are dropping low are .451 Diameter, Given that these loads are so hot, I'm thinking they are not sufficiently engaging the rifling. I'll be loading up 250gr. Hornady XTP's (jacketed .452) at various velocities to see what happens...

[BK7saum]

I'm really not sure that 451 vs 452 is going to make a bit of difference in the amount of drop. Have you confirmed that they are not stable and keyholing in the target? If they are stable, then they are engaging the rifling. The fact that they are hot and you aren't getting a leaded barrel indicates to me that they are engaging the rifling and bumping up if necessary. Otherwise you should have a leaded barrel.

[fredj338]

With rifles, diff bullets can do a lot of diff things. Generally though, heavier bullets will shoot higher. It has been my exp for decades with many diff calibers, pistol or rifle. This could just be one of those anomalies.