slodsm Posted February 16, 2011 Share Posted February 16, 2011 I'm just curious if anyone can help me out with this question because I can't find anything in the search. When a published load for a bullet you want to use states 1.169 as an OAL but your gun starts having issues around 1.145, how much would you reduce the load when working it up to start with? I've not been able to find anything "concrete" on changing OAL. The load I'm wanting to try will be 147gr MG over x.x of WSF using a CCI 500 primer. The load is listed with a longer OAL than my gun will reliably digest so would 10% down be a good starting place? I'm a shot shell loader, pistol loading is fairly new to me so I'm still learning (and I learn a LOT from this place using that little box in the upper right hand corner hahaha). Link to comment Share on other sites More sharing options...
GrumpyOne Posted February 16, 2011 Share Posted February 16, 2011 I would start at LEAST 20% down from the minimum. Pressure increases exponentially when the OAL decreases (especially with very fast powders), so I wouldn't take too many chances without starting low and working up. Link to comment Share on other sites More sharing options...
Foxbat Posted February 16, 2011 Share Posted February 16, 2011 (edited) As a rough approximation, the pressure would increase by 10-12% from such a change in OAL. Reducing the charge by 10% would more than compensate for that pressure raise, 5% would be closer to optimal compensation. These are just simulated numbers, to give you some initial handle on the situation, not a guide to safe reloading. Edited February 16, 2011 by Foxbat Link to comment Share on other sites More sharing options...
Guy Neill Posted February 16, 2011 Share Posted February 16, 2011 Years ago Speer tested changing OAL in a 9mm by developing a load giving 28,000 CUP. They then pushed the bullet 0.033" deeper and measured 62,000 CUP. (I'm working from memory here, so the number may be slightly off, but, in degree. it virtually doubled the pressure). It's written in a couple of the Speer Manuals. A small case like the 9x19 will see drastic changes for relatively small changes. Larger cases will have more leeway. Guy Link to comment Share on other sites More sharing options...
slodsm Posted February 16, 2011 Author Share Posted February 16, 2011 Thanks for the information. I figured it would be fairly high being such a small volume case but doubled ??? Glad I asked first. Link to comment Share on other sites More sharing options...
GrumpyOne Posted February 17, 2011 Share Posted February 17, 2011 As a rough approximation, the pressure would increase by 10-12% from such a change in OAL. Reducing the charge by 10% would more than compensate for that pressure raise, 5% would be closer to optimal compensation. These are just simulated numbers, to give you some initial handle on the situation, not a guide to safe reloading. Uh, no....It depends on the powder as well. Take Clays (if he were using Clays), it gets nasty spiky under shorter OALS, which causes much more than a 10-12% increase in pressure. Link to comment Share on other sites More sharing options...
Sarge Posted February 17, 2011 Share Posted February 17, 2011 I'm just curious if anyone can help me out with this question because I can't find anything in the search. When a published load for a bullet you want to use states 1.169 as an OAL but your gun starts having issues around 1.145, how much would you reduce the load when working it up to start with? I've not been able to find anything "concrete" on changing OAL. The load I'm wanting to try will be 147gr MG over x.x of WSF using a CCI 500 primer. The load is listed with a longer OAL than my gun will reliably digest so would 10% down be a good starting place? I'm a shot shell loader, pistol loading is fairly new to me so I'm still learning (and I learn a LOT from this place using that little box in the upper right hand corner hahaha). I've never used WSF so you will have to do a search. Somewhere on here in the 9mm section you will find 147MG CMJ @1.14 with WSF for your exact gun. Trust me it's in here somewhere. Then back off from what you find by 10% or so and work up. Link to comment Share on other sites More sharing options...
Foxbat Posted February 17, 2011 Share Posted February 17, 2011 (edited) As a rough approximation, the pressure would increase by 10-12% from such a change in OAL. Reducing the charge by 10% would more than compensate for that pressure raise, 5% would be closer to optimal compensation. These are just simulated numbers, to give you some initial handle on the situation, not a guide to safe reloading. Uh, no....It depends on the powder as well. Take Clays (if he were using Clays), it gets nasty spiky under shorter OALS, which causes much more than a 10-12% increase in pressure. The same simulation with Clays shows the increase from 30,000 to 33,000, or 10%. Edited February 17, 2011 by Foxbat Link to comment Share on other sites More sharing options...
GrumpyOne Posted February 17, 2011 Share Posted February 17, 2011 As a rough approximation, the pressure would increase by 10-12% from such a change in OAL. Reducing the charge by 10% would more than compensate for that pressure raise, 5% would be closer to optimal compensation. These are just simulated numbers, to give you some initial handle on the situation, not a guide to safe reloading. Uh, no....It depends on the powder as well. Take Clays (if he were using Clays), it gets nasty spiky under shorter OALS, which causes much more than a 10-12% increase in pressure. The same simulation with Clays shows the increase from 30,000 to 33,000, or 10%. Sorry, don't trust a simulation. A little bit of bullet setback and then what? My question is: What exactly is doing the simulating? Link to comment Share on other sites More sharing options...
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