40S&W, F&F, OAL, and Excessive Pressure

Spur0701 · February 27, 2009, 04:47 AM

I'm starting to reload 40S&W and my research prior to starting revealed warnings to watch the minimum OAL and always be sure to crimp to avoid a reduce case space since pressurers can build up fast. These are for a Styer M40 and some Sigma 40EVs (no Glocks). Inital loads were 5.3 g Unique (Salut), 180 g Cast TC (from a Lee mold), with OALs of 1.135, 1.130, and 1.125. There were problems with chambering and failure of the slide going fully back into battery with the OAL 1.135 ones, with the problem almost disappearing with the OAL 1.125s. My question is can I safely go to 1.120 or even 1.115?

DWARREN123 · February 27, 2009, 07:11 AM

Go with what the manual says for OAL. You might get away with a .001 or .002. Also check your crimp.
Can you easily chamber a round with the barrel out of the gun, if not the crimp is the problem.
The crimp should be tight enough to chamber easy but just barely and no more.

SL1 · February 27, 2009, 09:01 AM

Spur,

I think you are going about your load development the wrong way and drawing the wrong conclusions.

You want to pick an overall length that feeds OK from your magazine and then work up the load with that length. What you are doing is starting with a load that is too low to cycle the slide with the 1.135 OAL, then INCREASING THE PRESSURE by making the OAL shorter. You should be holding OAL fixed and increasing the charge weight.

I don't have the particulars on your exact bullet in my QuickLOAD database, so I used another 180 grain lead FP bullet. Therefore, these pressures are NOT likely to be YOUR pressures. (So, don't make that assumption and get yourself into trouble!) I used your charge of 5.3 grains of Unique and got the following pressures as a function of OAL:

Code:

   1.135"   22,288 psi   944 fps
   1.130"   22,767 psi   948 fps
   1.125"   23,288 psi   953 fps
   1.120"   23,792 psi   958 fps
   1.115"   23,343 psi   963 fps

This is a prettylight charge of Unique for this case/bullet combination. It is producing low pressure, and not increasing pressure very much as you reduce the powder space by shortening OAL. I'll bet it is burning "dirty" and leaving you a lot of black residue. The SAAMI max pressure for the 40 S&W is 35,000 psi. Unless you want to go to a weaker recoil spring, you are probably going to need to get velocities (and pressures) up higher to reliably cycle your slide.

You are usually best-off using the cartridge OAL that is provided with the powder charge weight data that you are using. I don't know what data you are using, so I will assume it has a 1.135" OAL and do some more example calcs with different charge weights.

Code:

powder     pressure   velocity
(grains)        (psi)      (fps)
  5.20         21452      930
  5.33         22667      950
  5.46         23929      969
  5.59         25240      988
  5.72         26602     1007
  5.85         28015     1026
  5.98         29482     1045
  6.11         31004     1063
  6.24         32584     1082
  6.37         34222     1082

(Sorry about the steps in powder weights not being 0.1 grain, but QuickLOAD was written by a German, and he uses the mertic system for his computations, converting to English units for input and output if you request that.)

As you can see, pressure and velocity go up faster at higher charge weights than at smaller charge weights, when you add the same increment of powder.

Another thing I should show you is that the effect of changing OAL is greater at the higher charge weights than I showed you for the light charge that you are using. For example, with a charge weight of 6.3 grains of Unique instead of 5.3 grains:

Code:

  1.135"  33,332 psi   1090 fps
  1.130"  34,138 psi   1095 fps
  1.125"  35,019 psi   1101 fps

These charges appear to be compressed, so QuickLOAD may not be very accurate in this charge range. But, the point is that the same OAL change that did not make the pressure increase very much when the charge was only 5.3 grains of Unique can take a safe max charge of the same powder to the SAAMI pressure limit. Also, note that the change in velocity is NOT much, even though the pressure is increasing a lot. So, a chronograph is NOT going to show you that your pressures are going up, whether it is happening because you intentionally changed the OAL or because your bullets are getting set-back when they are auto-cycling up the feed ramp.

Actually, Unique is pretty forgiving in the 40 S&W. It is a decent choice for full-power loads, but faster powders can burn cleaner for light loads.

But, with faster powders, the pressure effect of changing OAL can be MUCH greater, too. So, pelase do not try to use the apparent relationships between OAL and pressure in these calcs with any other powder or cartridge.

SL1

Spur0701 · February 28, 2009, 02:10 PM

Got you SL1, thanks for all the effort you put into your answer. Now I think my problem was that the bullets were dropping from the mold a little large, they were dropping out at 183 g and were measuring at .403 to .404, I sized to .401 and made up 5 dummy rounds with an OAL of 1.135 and they fed fine. I'm going to try 5.5g Salut and see how those perform.

The load data came from the Lee load sheet that came with the die set. For 180 g lead it was giving a min as 5.2g and a max of 5.5g of Unique so I went with 5.3. My Lee manual doesn't give a load for 180 g lead but does have one for 180 g jacketed which is a min of 5.8 and a max of 6.2.

What I'm using is that "Russian Unique" (Salut) which is a little bulker than regular Unique, tables are susposed to be the same as unique, I've been using a lot of it in .45ACP reloads and it's been great.

I do have some Accurate Arms #7, but my Lee manual didn't have a load for that in lead, only jacketed.

Spur0701 · March 1, 2009, 07:23 PM

Just an update, loaded with 5.5 g Salut and an OAL of 1.135....all 50 rounds I made up functioned great........thanks for the help......

Gregory Gauvin · October 20, 2009, 11:45 PM

I am glad I came across this post. I have been looking for data points showing velocity and pressure across different COAL points. I have always loaded my rounds long, generally longer than what my load manual listed. For example, I like my 45 acp rounds at 1.265" versus the load manual which say 1.090". I see that increasing charge weight increases velocity more so than increasing OAL (particularly at low pressures) and that decreasing OAL at near max pressures is VERY BAD!!!

I do have wondered if I could "save a little" but loading my rounds shorter and using less powder. I never thought of loading shorter than minimum OAL, but loading to the listed length versus MAX OAL. I see that .1 grain of charge weight has about about the same effect as playing around with velocity changes using OAL that spike pressures up to scary levels to attain a few FPS.

February 27, 2009, 04:47 AM	#1
Spur0701 Senior Member Join Date: February 2, 2005 Posts: 208	40S&W, F&F, OAL, and Excessive Pressure I'm starting to reload 40S&W and my research prior to starting revealed warnings to watch the minimum OAL and always be sure to crimp to avoid a reduce case space since pressurers can build up fast. These are for a Styer M40 and some Sigma 40EVs (no Glocks). Inital loads were 5.3 g Unique (Salut), 180 g Cast TC (from a Lee mold), with OALs of 1.135, 1.130, and 1.125. There were problems with chambering and failure of the slide going fully back into battery with the OAL 1.135 ones, with the problem almost disappearing with the OAL 1.125s. My question is can I safely go to 1.120 or even 1.115?

February 27, 2009, 07:11 AM	#2
DWARREN123 Senior Member Join Date: January 22, 2006 Location: BETWEEN TN & KY Posts: 1,758	Go with what the manual says for OAL. You might get away with a .001 or .002. Also check your crimp. Can you easily chamber a round with the barrel out of the gun, if not the crimp is the problem. The crimp should be tight enough to chamber easy but just barely and no more. __________________ Have a nice day!

February 27, 2009, 09:01 AM	#3
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	Spur, I think you are going about your load development the wrong way and drawing the wrong conclusions. You want to pick an overall length that feeds OK from your magazine and then work up the load with that length. What you are doing is starting with a load that is too low to cycle the slide with the 1.135 OAL, then INCREASING THE PRESSURE by making the OAL shorter. You should be holding OAL fixed and increasing the charge weight. I don't have the particulars on your exact bullet in my QuickLOAD database, so I used another 180 grain lead FP bullet. Therefore, these pressures are NOT likely to be YOUR pressures. (So, don't make that assumption and get yourself into trouble!) I used your charge of 5.3 grains of Unique and got the following pressures as a function of OAL: Code: 1.135" 22,288 psi 944 fps 1.130" 22,767 psi 948 fps 1.125" 23,288 psi 953 fps 1.120" 23,792 psi 958 fps 1.115" 23,343 psi 963 fps This is a prettylight charge of Unique for this case/bullet combination. It is producing low pressure, and not increasing pressure very much as you reduce the powder space by shortening OAL. I'll bet it is burning "dirty" and leaving you a lot of black residue. The SAAMI max pressure for the 40 S&W is 35,000 psi. Unless you want to go to a weaker recoil spring, you are probably going to need to get velocities (and pressures) up higher to reliably cycle your slide. You are usually best-off using the cartridge OAL that is provided with the powder charge weight data that you are using. I don't know what data you are using, so I will assume it has a 1.135" OAL and do some more example calcs with different charge weights. Code: powder pressure velocity (grains) (psi) (fps) 5.20 21452 930 5.33 22667 950 5.46 23929 969 5.59 25240 988 5.72 26602 1007 5.85 28015 1026 5.98 29482 1045 6.11 31004 1063 6.24 32584 1082 6.37 34222 1082 (Sorry about the steps in powder weights not being 0.1 grain, but QuickLOAD was written by a German, and he uses the mertic system for his computations, converting to English units for input and output if you request that.) As you can see, pressure and velocity go up faster at higher charge weights than at smaller charge weights, when you add the same increment of powder. Another thing I should show you is that the effect of changing OAL is greater at the higher charge weights than I showed you for the light charge that you are using. For example, with a charge weight of 6.3 grains of Unique instead of 5.3 grains: Code: 1.135" 33,332 psi 1090 fps 1.130" 34,138 psi 1095 fps 1.125" 35,019 psi 1101 fps These charges appear to be compressed, so QuickLOAD may not be very accurate in this charge range. But, the point is that the same OAL change that did not make the pressure increase very much when the charge was only 5.3 grains of Unique can take a safe max charge of the same powder to the SAAMI pressure limit. Also, note that the change in velocity is NOT much, even though the pressure is increasing a lot. So, a chronograph is NOT going to show you that your pressures are going up, whether it is happening because you intentionally changed the OAL or because your bullets are getting set-back when they are auto-cycling up the feed ramp. Actually, Unique is pretty forgiving in the 40 S&W. It is a decent choice for full-power loads, but faster powders can burn cleaner for light loads. But, with faster powders, the pressure effect of changing OAL can be MUCH greater, too. So, pelase do not try to use the apparent relationships between OAL and pressure in these calcs with any other powder or cartridge. SL1 Last edited by SL1; February 27, 2009 at 09:13 AM.

February 28, 2009, 02:10 PM	#4
Spur0701 Senior Member Join Date: February 2, 2005 Posts: 208	Got you SL1, thanks for all the effort you put into your answer. Now I think my problem was that the bullets were dropping from the mold a little large, they were dropping out at 183 g and were measuring at .403 to .404, I sized to .401 and made up 5 dummy rounds with an OAL of 1.135 and they fed fine. I'm going to try 5.5g Salut and see how those perform. The load data came from the Lee load sheet that came with the die set. For 180 g lead it was giving a min as 5.2g and a max of 5.5g of Unique so I went with 5.3. My Lee manual doesn't give a load for 180 g lead but does have one for 180 g jacketed which is a min of 5.8 and a max of 6.2. What I'm using is that "Russian Unique" (Salut) which is a little bulker than regular Unique, tables are susposed to be the same as unique, I've been using a lot of it in .45ACP reloads and it's been great. I do have some Accurate Arms #7, but my Lee manual didn't have a load for that in lead, only jacketed.

March 1, 2009, 07:23 PM	#5
Spur0701 Senior Member Join Date: February 2, 2005 Posts: 208	Just an update, loaded with 5.5 g Salut and an OAL of 1.135....all 50 rounds I made up functioned great........thanks for the help......

October 20, 2009, 11:45 PM	#6
Gregory Gauvin Senior Member Join Date: March 6, 2009 Posts: 368	I am glad I came across this post. I have been looking for data points showing velocity and pressure across different COAL points. I have always loaded my rounds long, generally longer than what my load manual listed. For example, I like my 45 acp rounds at 1.265" versus the load manual which say 1.090". I see that increasing charge weight increases velocity more so than increasing OAL (particularly at low pressures) and that decreasing OAL at near max pressures is VERY BAD!!! I do have wondered if I could "save a little" but loading my rounds shorter and using less powder. I never thought of loading shorter than minimum OAL, but loading to the listed length versus MAX OAL. I see that .1 grain of charge weight has about about the same effect as playing around with velocity changes using OAL that spike pressures up to scary levels to attain a few FPS.