A Tale Of Two Powders.....and Two Barrels

[Spokerider]

I have experienced an unexpected occurance at the range today, wondering if you have any insight as to what has happened.





I have worked up some loads for my TC encore carbine 44 mag 12" barrel, and the same frame with a 44 mag 12" barrel that I had a smith cut to 6". The 6" version I shoot as a pistol.
I used the exact same loads for the 6" barrel as I used for the 12" barrel, and have made no adjustments to the dillon reloader when loading both, except for the powder charge.

1] 330gr WNGC water cooled wheel weight cast bullet, new starline cases, 1.860 OAL, Win primer, H110 20.5gr.
In the 12" carbine, these loads chronographed an average 1284.8 fps. In the 6" barrel, the average speed was 1676.5 fps.
The SAME LOAD almost 400 fps faster in a barrel 1/2 the length??? Whats with this?
For those of you in the know, 1676 fps for a 330 gr bullet in 44 mag is smokin.


2] Exact same as above except for Lil'gun 18.5 gr.
In the 12" carbine, average speed was 1435 fps. In the 6" barrel the average speed was 1421 fps.

Why the extra velocity with the H110 load and short barrel? The bullets are sized .430 I have not slugged either bore. I double checked and triple check my notes, and the aveage speed for the 12" barrel is correct. I could verify this, as I had worked up H110 loads from 19.5 to 21.5 grains in 1/2 grain increments, and the speeds corresponded with the loads.

On a side note, this is the 1st time I have shot the encore in pistol form. It is fun. The Pachmayr grip is very comfortable and the ball of fire is quite something. Getting a bloodied trigger finger after the 5th shot was no fun, but 10 layers of tape over the cut enabled me to keep shooting.

[Moonie]

How close is the Chronograph? the shorter barrel will have more muzzle blast which could be affecting the chrony.

[leftiye]

How were your pressure signs? It would seem that the shorter barrel would HAVE to be running at a higher pressure to keep up with the longer barrel. Scary actually. As for your trigger fanger, I'll stick to the carbine and rifle configurations. 30 years ago, I was amazed at the recoil of a .357 Herrett contender pistol. And then they came out with the 45-70s!

[David2011]

You're shooting the 12" as a carbine? With a shoulder stock? That would require a $200 permit in the US for a short barreled rifle. Very cool if that's legal in Canada without a permit.

In USPSA/IPSC matches the loads are shot through a piece of cardboard in front of the chronograph to keep powder from skewing the velocity readings. That might be worth a try. Maybe cut the cardboard to fit the sky screen wires so you don't shoot the chronograph?

David

[Chicken Thief]

I'm with Moonie on this one!
It is due to Chrono faults.

Occams razor!
The simplest solution is probably the best one

[Spokerider]

Thanks for the thoughts.

I had the chrony about 5ft to 6ft from the muzzle.
I'll move the chrony further away and try again.

There were no signs of high pressure, I looked carefully.........but after reading John Linbaugh's writings on the 44 mag and 45 colt extreme high pressure load testing, he didn't see any high pressure signs with loads that were known to be 70 000 psi, 80 000psi and beyond.

[Moonie]

Thanks for the thoughts.

I had the chrony about 5ft to 6ft from the muzzle.
I'll move the chrony further away and try again.

There were no signs of high pressure, I looked carefully.........but after reading John Linbaugh's writings on the 44 mag and 45 colt extreme high pressure load testing, he didn't see any high pressure signs with loads that were known to be 70 000 psi, 80 000psi and beyond.

With lots of muzzle blast 5-6' is way too close. Move it to at least 10' and try again.

[leftiye]

The pressure sign that you will see (fer sure) - unless you have an undersized non standard chamber the pressure ring (bulge at the front of the head) will become more and more short/sharp as pressures increase. In the 45 colt, the cases will split (one or two per 50) as the cartridge is .472, and the chamber is .486. Scuffing don't happen at low pressures. Primers get flat for various reasons, some having nothing to do with pressure.

[Spokerider]

Thanks for the insight. The chrony was too close as suggested.
I moved it out to 10ft, and sure enough, the reading is now accurate.

The H110 loads read about 100 fps slower in the 6" barrel compared to the same load in the 12" barrel. Ditto for the Lil Gun loads, about 100 fps slower.

[leadman]

I see the OP is in Canada so the ATF rules don't apply there. Don't know what the Canadian rules are though.