Optimizing fast powder for shorter barrels.

[cosmic creepers]

Oh my, that's a word salad, and was a disincentive for watching the video.
By "optimizing" velocity, I read maximizing velocity.
As I have learned from decades of reloading and shooting, chasing speed is a fool's errand. Optimizing, to me, is finding that sweet spot marrying the most consistent MV and most accurate on target.
My understanding of what I read is that the ultimate intent of your experiment sought to determine if you could get the same velocity out of a shorter barrel by using a faster powder.
As @Doom wrote, burn rate is affected by pressure, and thankfully we (generally) don't have to worry about rifle powders detonating (runaway burn rate) once a certain pressure is reached.
Peak chamber pressures is the ultimate determinant of MV, and the completion of the burn as the bullet travels down the barrel will affect the rate of acceleration. The trade-off, as I believe @dellet mentioned, is higher pressure and report at the muzzle.
The higher the pressure behind the bullet as it exits the muzzle tests the consistency of your rifling and crown. There is a point where this has marked affects on your accuracy.
Coming back to your experiment, I hope you optimized powder charges for the same bullet in the same barrel, then repeated the optimization for the different powders using the same bullet in a shorter barrel.

I did not run the test as exactly you stated, but it's looking like I may have to go back and start over.


It appeared to me that this would be a slam dunk and I thought the faster powder was going to be faster velocity in the short barrel by a long shot.

Velocity is a fools errand for hunting accuracy, no doubt, but trying to get bullets to do what bullets are designed to do out of 11.5 inch guns is quite difficult at times and every 50 fps seems to matter.

And the loads which I developed for my varmint rifle shoot the worst out of that carbine at about 2 MOA, but I've never shot really anything out of that gun, I think due to its length and heavy barrel contour that don't shoot pretty decent, at least decent enough for the job.

The hunt for the maximum velocity in the 11.5 was to see whether it was intuitive to just make a fast burner powder load for the short barrel and get the best possible velocity, which doesn't exactly seem true. And the reason for the velocity hunt is that I've got 50 grain V-max loads for the 11.5 inch guns and 75 grain loads for the 18 inch guns, but if I could find a load that shoots 2500 feet per second out of the 11.5 with heavy bullets, I'd rather have that, so the fools errand is what it is, but I'm driven by a preference.

Lots of testing to do, but I'm going to keep plugging at it and you old boys do help as I go along, even when you're adversarial about the way I speak.

 

[dellet]

Oh I'm definitely going to continue the testing as we go on here, and yes I took presumptions and then ran the numbers in Gordon's [a friend ran them for me] and P-max, which I ran myself, and both had me slightly over max pressure. So yes, it was a pressure range we were at.

I'd love you to understand, I really enjoy getting you guys perspective on stuff like this, I'm not getting heated, just exploring the angle. On anything highly differential in result.

What we are going to do today is shoot the LT-32 out of both the rifle length 18 inch gun and the 11½ inch gun because the groups were very nice, and record velocity data and group size.

And you are correct these are 75 grain RMR. Not 73 grain ELD. So I've made changes to the "max charges, but the pressure models should not have changed much by the programs I ran.

And I've got velocity data from all of these loads except for the xterminator and the LT-32 out of a 18 inch barrel and their 24 inch test barrel when making the handloading book was also handy because i am then not required to shoot most similar loads out of that barrel length again, as I don't think Hodgton is lying to us.

We will see. I've upped the charge weight with the LT-32 a dangerous amount. I've got 21.3 grains where my former test was ran with 21.0 if that doesn't yield me some flat primers or some brass flow on my ejector orifice, I'll be surprised and we will see if it matches or defeats velocity from some slower powders.

Thanks again for your input.

Now the dirty little secret about this type of testing. It’s basically pointless without a chop saw. I have a 12” barrel that is consistently faster than most 16” barrels and generally very close to 18” barrels with the same load. A 24” that performs like a 20”.

To do this right, you need to start with a 24” barrel, record all the velocities, then start cutting the barrel off an inch at a time or specified lengths and keep the actual data. That way you eliminate most barrel to barrel velocity variations. So by those standards, my tests were not done entirely correct.

There is a lot of value the loading program, you would get a lot out of one I’m sur. They can lead to more questions and a fair amount of fun for an experiential type learner. This was an offshoot of testing burn rates to maximize efficiency for barrel lengths, gas tube lengths for cycling subsonic loads in an AR. It lead to questions about being able predict or control recoil, while maintaining bullet weight and velocity. Without the models from quickload this would have not been possible for a backyard ballistian.

Powder choice/burn rate and recoil. How are they related, How do you predict or measure effect?

After a few years of ignoring them, I started shooting my single shot rifles again. Two things have happened in that time. I've gained some knowledge about loading, and I have gained some years. It did not take too many shots to remember why casual competitive shooting was too many rounds in a...

forum.accurateshooter.com

 

[DiffEQ]

I wrote a long post telling a story about finding the best load for a 7mm-08, but suffice it to say, if you experiment carefully and keep close track of your data like @dellet suggests, the results may be very different than what you expect. May you be pleasantly surprised.
One note on two different barrels - they will shoot differently (Capt. Obvious). The results you uncover will only generally apply across different barrels.

 

[Jr solocam]

"In theory practice is just like theory, in practice it is not". One of my favorite sayings.....

QL will point you in the right direction, after that, start shooting!

 

[357Mag]

….” what happens in the chamber is way more important than what is happening down the barrel.”

Cosmic -

Howdy !

Kroger gave you the heads up… you are dancing all around a gun’s achievable
“ expansion ratio “. To quote ballistician Homer Powley: “ The expansion ratio determines how much of the chemical energy is converted into kinetic energy “.

As regards you comment, above:
You cannot as a practical matter, separate the combustion gasses within the chamber from those same gasses that expand; as the bullet travels to it’s ultimate exit from the barrel muzzle.

As Powley told us decades ago… expansion ratio calculations are made using “ the TOTAL volume of the gun “ ( chosen bore diam; chosen chamber volume; and selected barrel length ), along with a reference powder charge weight.

While current digital internal/external ballistics programs are fine, I have enjoyed reading Homer Powley writings and tech articles on internal ballistics, reloading, wildcats, gun design; and so forth. I have found his “ Powley Papers “ printed in the “ Guns & Ammo 1974 Annual “ to be immensely educational; and enlightening ! I am on my second copy.
Powley makes internal ballistics more readily understandable for the layman.
I highly recommend it, along with reading valuable insights he provided in the instruction manual for his “ Powley Computer “.

Embscomputerart.com


With regards,
357Mag

 

[357Mag]

Cosmic -

Howdy !

Kroger gave you the heads up… you are dancing all around a gun’s achievable
“ expansion ratio “. To quote ballistician Homer Powley: “ The expansion ratio determines how much of the chemical energy is converted into kinetic energy “.

As regards you comment, above:
You cannot as a practical matter, separate the combustion gasses within the chamber from those same gasses that expand; as the bullet travels to it’s ultimate exit from the barrel muzzle.

As Powley told us decades ago… expansion ratio calculations are made using “ the TOTAL volume of the gun “ ( chosen bore diam; chosen chamber volume; and selected barrel length ), along with a reference powder charge weight.

While current digital internal/external ballistics programs are fine, I have enjoyed reading Homer Powley writings and tech articles on internal ballistics, reloading, wildcats, gun design; and so forth. I have found his “ Powley Papers “ printed in the “ Guns & Ammo 1974 Annual “ to be immensely educational; and enlightening ! I am on my second copy.
Powley makes internal ballistics more readily understandable for the layman.
I highly recommend it, along with reading valuable insights he provided in the instruction manual for his “ Powley Computer “.

Embscomputerart.com


With regards,
357Mag

Correction to previous response….

“ Krogen “

Auto spell did not help. Sorry ‘ bout that error.


With regards,
357Mag

 

[cosmic creepers]

Hey thanks for some great reading material. I posted a second round of testing Here

It feels like I'm getting closer to establishing a really good point, or learning that it is a pointless endeavor, but curiosity drives me a bit here.

This test was still fast burner against medium fast, next test is going to be slow burners cfe-223 and Win748 against the fast LT32

We will record that catalog too.

 

[357Mag]

Hey thanks for some great reading material. I posted a second round of testing Here

It feels like I'm getting closer to establishing a really good point, or learning that it is a pointless endeavor, but curiosity drives me a bit here.

This test was still fast burner against medium fast, next test is going to be slow burners cfe-223 and Win748 against the fast LT32

We will record that catalog too.

CosmicCreepers-

Here’s the accurized link to the “ Powley Computer “ instruction manual:

embscomputerart.com>pdfs>powleysmanuals1

*** Take a look @ pages 3 -9 ***


With regards,
357Mag