OAL Work-Up: Increase powder charge as well?

[RescueRandyMD]

Hi All,

 

Currently have been doing a ton of load workup for a couple 9mm handguns (P226 and VP9) and trying to go more scientific. Been using 115gr CPRN with 4.2gr of Titegorup at 1.15" since it worked well and didn't question more parameters till now.. I have poked around this forum a bunch and read a lot about load workups... but one thing that has eluded every topic seems to be adjusting powder charge for varying OALs.

 

It makes sense doing a ladder workup for a powder. 115gr CPRN 9mm bullets with 4-4.5gr of TG at 1.10" OAL... and see which shoots best. While I found 4.2gr to be very accurate, I wanted your guy's opinion on changing to a longer OAL to see those affects on accuracy. I've read the longer OALs closer to rifling should improve accuracy if the jump to it in 5-20 thousandths... but I've also read that shorter OALs seem to be more accurate for 9mm. While I want to do a OAL work-up from 1.10-1.16" (Max OAL for both guns are 1.24" and 1.2"), I can't help but wonder how much the velocity will drop too with a longer OAL, more case space, and less pressure. Maybe my sweet spot OAL is at 1.3", but with a different pressure and velocity I now have more than 1 variable at play affecting accuracy  and it ruins the scientific work-up. As an example, the Lyman manual lists a 115 gr JHP @ 1.10" OAL and 4.5gr Titegroup making 31,400 CUP. Running some math on changes in case volume for longer OAL seating at 1.16", the pressure would be 27,100 CUP (or about the same pressure as if the 1.10" OAL load had just 4.0gr of Titegroup). While there are other factors at play for velocity and other variables had to be assumed... it shows that 9mm is sensitive to OAL variations.

 

So... my question is the following: For increasing the OAL for a load work-up should I

A ) Not worry about changing the best powder charge, find the best OAL working up from the min, then readjust the powder charge at the new found OAL.

B ) Chrono the longer OAL and adjust the powder charge to achieve the same velocities so the only independent variable is the OAL

[HoMiE]

Find OAL that runs in your gun and then tailor to PF and felt recoil. Unless Your Shooting bullseye I wouldn’t worry about OAL too much. 

[RescueRandyMD]

Gotcha. They all will cycle 1.1" or 1.16" so is there any dogma about increasing accuracy or short jump to the rifling that applies to pistol OAL?

[HoMiE]

10 minutes ago, RescueRandyMD said:

Gotcha. They all will cycle 1.1" or 1.16" so is there any dogma about increasing accuracy or short jump to the rifling that applies to pistol OAL?

 

Too many gun barrel, bullet, powder, etc. combinations to say one OAL is better or not. Some combinations might shoot more accurate with longer OAL and some may like to be loaded short. I take the middle route and tend to start at 1.135” for 9mm and once I’m around the PF I want to be I’ll adjust and see if longer or shorter OAL increases accuracy. I tend to end up around 1.145” for RN bullet profile but sometimes load longer to 1.165” with an IFP or lead TC bullet profile. 

[stick]

5 hours ago, HoMiE said:

Find OAL that runs in your gun and then tailor to PF and felt recoil. Unless Your Shooting bullseye I wouldn’t worry about OAL too much. 

+1

[MemphisMechanic]

You’ll see no appreciable difference in velocity between 1.100” and 1.125” and 1.150” in a titegroup load. I’ve tested it.

 

So try various OALs to see if one is markedly more accurate. Once you’re sure of the length you want to load at, try various powder charges as well, for accuracy.

[4n2t0]

Handguns won't show any appreciable difference in accuracy by changing the OAL, I wouldn't waste my time trying. If you do happen to notice an accuracy difference when changing the length it will be due to a change in velocity +/-.

Edited January 3, 2018 by 4n2t0

[Hi-Power Jack]

25 minutes ago, 4n2t0 said:

Handguns won't show appreciable difference in accuracy by changing the OAL 

 

My BHP showed some difference in accuracy, but I was forced to go with the

OAL which fed 100%, at the expense of accuracy.

 

Obviously, it was an acceptable trade off - not an unacceptable loss of accuracy.

 

[4n2t0]

1 hour ago, Hi-Power Jack said:

 

My BHP showed some difference in accuracy, but I was forced to go with the

OAL which fed 100%, at the expense of accuracy.

 

Obviously, it was an acceptable trade off - not an unacceptable loss of accuracy.

 

 

My BHP showed no difference, just like all my other handguns. I'd chalk it up to dumb luck.

Edited January 3, 2018 by 4n2t0

[wrench459]

7 hours ago, RescueRandyMD said:

.. I have poked around this forum a bunch and read a lot about load workups... but one thing that has eluded every topic seems to be adjusting powder charge for varying OALs.

Shorter OAL'S less powder ..longer is of course more.

Edited January 3, 2018 by wrench459

[RescueRandyMD]

2 hours ago, MemphisMechanic said:

You’ll see no appreciable difference in velocity between 1.100” and 1.125” and 1.150” in a titegroup load. I’ve tested it.

 

So try various OALs to see if one is markedly more accurate. Once you’re sure of the length you want to load at, try various powder charges as well, for accuracy.

Thanks. I'll just workup from 1.13" and it would definitely make things easier

[IDescribe]

Randy, from 1.1 to 1.16, you might need to adjust powder charge by .2-.3gr to maintain the same velocity. 

 

But if you want to get scientific, then get scientific.  There's no reason you should be tuning OAL for accuracy, but not velocity.    In other words, maintaining the exact same velocity should not be the goal.  You should be trying to find the right combination of OAL and velocity for the particular bullet in the particular gun.    If you're trying to find ONE OAL that's most accurate in both guns, you're most likely wasting your time, so you should be planning on coming up with two different loads for the two guns, as well. 

And if you want to make one general purpose round for both guns, but still want to improve accuracy, stop shooting plated.    

[RescueRandyMD]

9 hours ago, IDescribe said:

Randy, from 1.1 to 1.16, you might need to adjust powder charge by .2-.3gr to maintain the same velocity. 

 

But if you want to get scientific, then get scientific.  There's no reason you should be tuning OAL for accuracy, but not velocity.    In other words, maintaining the exact same velocity should not be the goal.  You should be trying to find the right combination of OAL and velocity for the particular bullet in the particular gun.    If you're trying to find ONE OAL that's most accurate in both guns, you're most likely wasting your time, so you should be planning on coming up with two different loads for the two guns, as well. 

And if you want to make one general purpose round for both guns, but still want to improve accuracy, stop shooting plated.    

True, the factors at play I feel I would be chasing my tail chasing one parameter and then neglecting another. I feel like most others stated just finding a OAL that works would be best, then work up powder/velocity. It would be a whole other story for 1 competition gun with a OAL/velocity workup because, like snowflakes, every gun is special 

 

And yes I only have the plated for plinking  I have 115gr HAPs and 124gr JHP MG that I will be doing the workup for to see which ones those guns like each

Edited January 3, 2018 by RescueRandyMD

[Darrell]

I've probable done more testing of 9mm loads than any other caliber. Here is the technique that has worked best for me. 

I modified a 9mm case to use the Hornady OAL tester. I then take all my barrels and test max OAL with that particular bullet. I then use my shortest barrel's OAL and subtract .010". I then look at max powder charge in my manual's and start 10% under and work up in .2 grain increments. I test for accuracy and velocity using a ransom rest and chrono. I use 10 round groups. Once I find the most accurate, I load another batch with that powder charge but vary OAL going up and down in .010 increments to the max OAL for that barrel. Test for accuracy again and which ever OAL is most accurate for my shortest barrel that is what I use for all my 9mm pistols. I used to take another step after by varying crimp also but have settled on .3785 for all my 9mm load both jacketed and coated. I've gotten some amazing accuracy results using this technique with various pistols. For example I've gotten 1.1" groups with a. Glock 17, and M&P 9, and .9" in my EAA limited 9. These were average of 3 five shot groups at 25 yds which is my normal test range. I have a spreadsheet on the forum if you do a search, I haven't updated it in awhile though. All the loads were shot by me in my guns. I have 15 different 9mm pistols. Here's my latest update.

Darrell's Load Data rev 081017.xlsx.zip

[Hi-Power Jack]

^^^^^   Read Darrell's posting Very Carefully .      ^^^

 

He knows the answer ....    

[RescueRandyMD]

4 hours ago, Darrell said:

I've probable done more testing of 9mm loads than any other caliber. Here is the technique that has worked best for me. 

I modified a 9mm case to use the Hornady OAL tester. I then take all my barrels and test max OAL with that particular bullet. I then use my shortest barrel's OAL and subtract .010". I then look at max powder charge in my manual's and start 10% under and work up in .2 grain increments. I test for accuracy and velocity using a ransom rest and chrono. I use 10 round groups. Once I find the most accurate, I load another batch with that powder charge but vary OAL going up and down in .010 increments to the max OAL for that barrel. Test for accuracy again and which ever OAL is most accurate for my shortest barrel that is what I use for all my 9mm pistols. I used to take another step after by varying crimp also but have settled on .3785 for all my 9mm load both jacketed and coated. I've gotten some amazing accuracy results using this technique with various pistols. For example I've gotten 1.1" groups with a. Glock 17, and M&P 9, and .9" in my EAA limited 9. These were average of 3 five shot groups at 25 yds which is my normal test range. I have a spreadsheet on the forum if you do a search, I haven't updated it in awhile though. All the loads were shot by me in my guns. I have 15 different 9mm pistols. Here's my latest update.

Darrell's Load Data rev 081017.xlsx.zip

 

That looks like an awesome method, thank you! Also I love the excel sheet too... I am logging my loads into something similar and it will hopefully be very useful in years to come