Pressure "Tuning"

I load for 9mm and 38spl.  I just picked up QuickLOAD and I'm going through the stages of getting acquainted and tuning powder burn rates to match my chrono results.
In the quest for the most accurate round, I've been doing lots of reading - mostly about rifles. But I figured hey, a pistol is just a really short rifle.

Ultimately, here's my question: When looking at pressure, should I tune the load to SAAMI specs, or to the BHN of the bullet (Like the "Lee Precision Modern Reloading 2nd Edition talks about).  

For 9mm I've mostly use Hi-Tek coated hard cast lead bullets, but recently started experimenting with Xtreme copper plated bullets. Both are advertised having a BHN of 18. Which upon linearly interpolating Lee's chart, gives me a compressive strength of 22,980psi.  Obviously SAAMI max pressure is 35,000psi for 9mm.

Side Note: The other think I'm looking at is barrel dwell time. I'm looking to see if it correlates to the resonance frequency of my barrel. I've calculated it using the "closed pipe" method.  3F = 0.512ms. I have a load that has a 0.522ms barrel time that is VERY accurate. Problem is, it's too slow to meet power factor for IDPA or IPSC if I ever get a chance to compete. -I digress.... this is a topic for another thread.

Tune for the target results.

w4ti wrote:I am curious- what does accuracy mean for your very accurate load? How are you measuring your group size?

I'm measuring by group size by scoring an NRA B-2 target.

I've made it through Sharp Shooter Bar9 thus far with my .22LR.  I guess I use my highly modified target .22 to set the standard on what a group size can be. Albeit, not going to be completely practice with a 9mm.

I understand that I need to tune for the group size, then worry about the rest. But I'm an Engineer, and I'm trying to correlate the math to get a better understanding of what is influencing all of this. If I can do that, then I can predict accuracy moving forward.

Ahhh, an Engineer....

Hammbone wrote:...I understand that I need to tune for the group size, then worry about the rest. But I'm an Engineer, and I'm trying to correlate the math to get a better understanding of what is influencing all of this. If I can do that, then I can predict accuracy moving forward.

OK, why not start with known loads for whatever gun you are shooting.  Ransom Rest it to confirm.  Once you are under 2" @50yds, then instead of spending time trying to figure out the math for some magic load that "might" get you 1/4' smaller group size, work on the biggest impact on group size, YOU.  Do yourself a huge favor and spend that time Correctly training, especially dry firing.
- Dave

FYI when we test ammo for accuracy it's more than likely @ 50yds not 50ft, a good group at 50ft or even 25yds does not necessarily translate to a good group @ 50yds.

it's deja vu, all over again.....

I've tinkered with QUICK LOAD (QL) for 32 acp and 45 acp.  All my efforts have been to get the lightest loads that work reliably.  The 32 acp chronograph data did not correlate with QL and measured velocities were low, by 100's of fps using Bullseye powder.  The 45 acp, with Bullseye, was not off too much.  The velocities calculated were still low but within 30 fps. 

It's an interesting exercise, and I have about four more different powders to try which are in QL. But, it seems all that doesn't improve my shooting much.  Still, I find it interesting - if a bit useless.  The bottleneck rifle shooters rave about QL (in forums).

When using small amounts of a fast burn rate powder such as Bullseye in a pistol case, you will normally get large ES numbers and the resulting low pressure/velocity due to the varying location in the case of the small amount of powder in relation to the primer.   Not so with bottleneck rifle cartridges which are also typically operating in a more optimal pressure range for the powder being used, hence much more reliable data with bottleneck cartridges.

Don

Actually, my chronograph measured data for 32 acp and 45 acp had reasonable standard deviations and extreme spreads.  Although, I did not chronograph hundreds of rounds.  I had read that QL was not suitable for straight wall brass.  But since I read that on the internet, was not sure how reliable that information was.  Hence, trying the software out.  QL provided a useful 'trend guide' for my 45 acp load development and a way to numerically compare 200 gr LSWC with 185 gr LSWC energy and powders - but required some knowledge of the software.

The basic approach I took was to get a bullet that was 'close' to the Laser-Cast 200 gr LSWC bullet (which, of course, is what my testing was done with) in QL.  I started with 3.1 gr of Bullseye, an OAL of of 1.23", and a 0.698" crimp.  This OAL and crimp appeared to feed OK in my stock Springfield RO.  Fifteen rounds each of ammunition using 3.1, 3.2, 3.3, 3.4, 3.5, and 3.6 gr of Bullseye were loaded and sorted.  I made those choices based on running QL, but that was because I had the software and 'wanted' to use it.  My goal was to find the lightest reliable (and reasonably accurate) 45 acp load for Bullseye competition for my Springfield RO. 

I wanted to find my '45 acp reloading' folder before responding, but it appears to have (ahem) disappeared.  Fortunately, I wrote down all my chronograph measurements using a high tech smart pen and paper.  Not that the data is phenomenal or highly revealing.

This ammo was tested using a ProChorono Digital chronograph (1% accurate?) on a beautiful October day.  I need to go back and do the statistics on the raw data again, since I lost the results, but with the stock 16 lb spring, down to 3.4 gr of powder worked OK.  I installed an 11 lb Wolff recoil spring and that allowed cycling down to the 3.1 gr powder loads.  However, the 3.1 gr was not 100% reliable.  The 3.2 gr of Bullseye over the 200 gr LSWC bullet cycled 100%.  Also, per the chronograph, the 3.2 gr powder load gave the lowest standard deviation. 

Comparing those chronograph numbers to QL, the trend was correct.  I'll have to go back and re-do the comparison between QL and the average velocities, but IIRC, the velocity was ~ 30 fps low for the 3.1gr and 3.2 gr load.


Ok, found a load- 3.2gr Bullseye under 200gr LSWC with OAL of 1.23" - as a starting point.  Now, I want to use a 185gr LBN bullet.  Upon running QL (and putting all the bullet dimensions in the software), QL showed 3.3 gr of Bullseye under the 185gr bullet will have the same muzzle energy as my tested load and slightly higher velocity.  Ok, that makes sense (i.e. has the right trend).

So, since I ultimately want to shoot 185 grain bullets in a light load, I loaded 3.3gr Bullseye under a 185 gr LBN bullet OAL of 1.13" (although, I seat the bullet on the shoulder, so the OAL can vary with casting tolerances).  I range tested that load and found it cycles fine and is now my current Springfield RO load. 

When I have more time, I'll get more chronograph numbers for the 3.3gr powder with the 185 bullet.  At my last match, this load functioned 100%.  I didn't shoot that great, but that was in no way associated with the ammo.  Hope this (somewhat convoluted) description helps in how I did my load development and used QL.

p.s. Having 4.0gr Bullseye powder under a 200gr LSWC or 185 gr Lead bullet would have worked just fine and not required all my 'tinkering'.

Edit: corrected OAL to 1.23"

james r chapman wrote:Ahhh, an Engineer....

Absolutely! And I worked my tail off for it too!

First of all - thank you everyone for showing an interest and responding.

I completely understand that "I" am the biggest contributing variable the entire system. I get that.

Since I started this post, I've been able to do quite a few simulations and validation runs with a chrono. It's been very educational.  I've got QL tweaked to the point that I can simulate loads with my equipment and components very accurately.  This will be helpful for future predictions.

For those who've worked with QL, you know there are lots of parameters it reports.  Basically I'm trying to figure out which of those parameters (or which combinations of them) attribute to an inherently accurate load and which don't.  I'm looking at; bullet hardness relative to pressure, bullet time in barrel relative to the resonance frequency of the barrel, % powder burned, ballistic efficiency, etc.  I started this post to see if anyone else has experience with this.

Are you planning on machine resting your loads in a proven pistol to verify your data?
Jon

Explain how you determine resonance frequency relative to barrel fit.

Jack,
First you fit barrel, then hit it with 5# ball peen hammer and see if the 5GBhz tuning fork flies off the front sight.....
Jon

Jon,   Would resonant frequency change between Hard hold and Limp wrist?

To the OP:  from one engineer to another, you're overthinking this.   Just load up some higher powder levels (using loading manuals to avoid over-pressure) and test them.  That is how you found...

Hammbone wrote:I have a load that ... is VERY accurate. 

With all due respect, solve any problems you currently might be dealing with.

Problem is, it's too slow to meet power factor for IDPA or IPSC.  if I ever get a chance to compete.

Jon Eulette wrote:Jack,
First you fit barrel, then hit it with 5# ball peen hammer and see if the 5GBhz tuning fork flies off the front sight.....
Jon

I used to use a penny on the front sight.  Oh, no that was dry firing, whatever that is.

Really I think every barrel fit is different, just like free float vs pressure points in my benchrest rifles.

Jack H wrote:Explain how you determine resonance frequency relative to barrel fit.

I didn't calculate the resonance frequency of the metal itself, I calculated the resonance frequency of the air column in the bare - (i.e., like a closed pipe. Same way you'd calculate it for a clarinet, trumpet, trombone, etc). Then I looked at octave nodes and converted frequency to milliseconds.

Yes, I DID do the math.  And NO, I will not post it here.

Jon Eulette wrote:Are you planning on machine resting your loads in a proven pistol to verify your data?
Jon

Yes.

Well if you decide to do it for the metal.... Haven't used this for 40+ years for figuring band pass and band reject filters but bet it still works.

Hell Len....you simplified it for him!
Jon ;l)

Well, I'm engineer too (Mechanical).  So have at it and let us know the results. Just post any good loads and keep shooting.

But, I've found three things that really suck, two of them related to shooting.

(1) Every time the book says "The student can easily see this equation reduces to:" which generally mean 20 minutes before "OK, I see.". 

(2) Finding a great load for one barrel and it just isn't as good in the next one that replaces it.

(3) My pistol doesn't seem to think its just a short rifle.   

CR

Hmm, I can see I've been going about this all wrong.   I've just selected a good bullet, loaded it at the velocity/pressure that I wanted, and tested it.   What was I thinking?

Don

Interesting - I am not an engineer, but have been learning about 22lr bench rest, "stopped muzzle" v. "positive compensation" hypotheses, etc.

How do you measure your bullet barrel dwell time to the microsecond level?

I've noticed using QUICKLOAD that Bullseye, W231 (HP38), and several other powders burn about 70% complete in a 5" barrel, but are still accurate.  Bullseye is a dirty powder, but I don't mind cleaning the gun.  I wish WST was in the powder database.  I've read about resonant tuning, mostly applied to rifle barrels.  IMO, QUICKLOAD is a rifle cartridge program - or I should say that it appears to perform best using physics based models for longer barrels. 

However, I am always interested in learning what others have found.  For the 45 acp, the chronograph numbers were fairly close without any parameter tuning.  I was disappointed with the 32 acp results.  I haven't tried the 32 S&W long with QUICKLOAD.

As a note, I initially bought QUICKLOAD for the 32 acp and 32 S&W Long in consideration for developing a load using common components (available in the USA) for those cartridges.  I've since rethought that plan, but may reconsider it in the future.  Between combustion dynamics, fluid mechanics/gas dynamics, resonant frequency effects and the typical variations in powder, bullets, and primers, I'm OK with QUICKLOAD results for the 45 acp.