Powder loads for FMJ, copper jackets, XTP

drholmes · May 21, 2017, 01:16 PM

Lee lists different starting loads for FMJ, copper jacketed and XTP bullets of the same weight. There must be varying pressures generated to explain the differences. Can someone offer explanation why this is apparently the case?

Nick_C_S · May 21, 2017, 02:14 PM

Welcome to TFL.

I don't have a Lee manual, so I can't see it directly.

One major factor that can change load data among bullets of the same weight is how deep the bullet seats into the case. The deeper the bullet sits inside the case, the quicker pressure builds upon ignition. All else being equal, it's like the powder having a faster burn rate - and correspondingly higher peak pressure.

More specific information could bring us closer to a less generalized answer.

74A95 · May 21, 2017, 04:03 PM

Caliber please.

drholmes · May 21, 2017, 04:13 PM

I am loading 45 APC cal. 230 grain Hornady XTPs.

Jim Watson · May 21, 2017, 04:15 PM

Lee copied the data from different sources - they do no testing themselves - and three different PV guns with three different bullets and three different sets of other components got three different answers.

There is not much you can do about it.
Either reload by recipe for the EXACT set of components you have, or apply handloading principles and sneak up on a serviceable load.

A chronograph to tell me when I am at a desired velocity is essential to the way I go about loading.

Reloadron · May 22, 2017, 12:47 PM

As Jim points out the Lee Load Data is a compilation of other load data and Lee does no load testing. Not a bad thing but not quite a good thing either. Just worth knowing.

Below are pictured a 230 grain Hornady XTP and a 230 grain Speer Gold Dot, two very similar bullets but they are not the same length, close but not the same and they share a common 230 grain weight.

Hornady suggest a C.O.L. of 1.210"
Speer suggest a C.O.L. of 1.200"

So we have a difference of 0.010" difference in the suggested C.O.L. The 230 grain Hornady XTP has a bullet O.A.L. of right around 0.635" and is pictured on the right and the Speer Gold Dot on the Left comes in with an O.A.L. right around 0.655" or about 0.020" longer than the Hornady bullet but the suggested C.O.L. difference is only 0.010".

Starting and Maximum loads are suggested based on the test methods used by the original publisher of the data based on their test and test setups. For example, taking a real common .45 ACP powder like Unique and the 230 grain bullets we just looked at:

Hornady Start 5.2 grains and Maximum 6.6 grains ranging from 700 to 900 FPS fired from a Springfield 1911 5.0" barrel.
Speer Start 5.4 grains and Maximum 6.0 grains ranging from 721 to 806 FPS fired from a Sig P-220 4.4" barrel.

Each bullet maker has their own data suggested for their bullet. The main idea being to start safe and stay safe working up your loads. Again, the Lee data is a broad compilation of published data of everyone else.

Hope that helps and doesn't lend to confuse

Ron

drholmes · May 23, 2017, 07:36 AM

Thanks for input. I can understand variations in pressure related to bullet seating depth which can be effected by overall bullet length but I guess my real question is whether there is differences in the coefficient of expansion of copper plated vs full metal jacketed and do hollow points expand relatively more because there might be less resistance to expansion? I know this probably makes little practical difference but I just would like to understand the physics.

May 21, 2017, 01:16 PM	#1
drholmes Junior Member Join Date: May 20, 2017 Posts: 3	Powder loads for FMJ, copper jackets, XTP Lee lists different starting loads for FMJ, copper jacketed and XTP bullets of the same weight. There must be varying pressures generated to explain the differences. Can someone offer explanation why this is apparently the case?

May 21, 2017, 02:14 PM	#2
Nick_C_S Senior Member Join Date: March 21, 2013 Location: Idaho Posts: 5,523	Welcome to TFL. I don't have a Lee manual, so I can't see it directly. One major factor that can change load data among bullets of the same weight is how deep the bullet seats into the case. The deeper the bullet sits inside the case, the quicker pressure builds upon ignition. All else being equal, it's like the powder having a faster burn rate - and correspondingly higher peak pressure. More specific information could bring us closer to a less generalized answer. __________________ Gun control laws benefit only criminals and politicians - but then, I repeat myself. Life Member, National Rifle Association

May 21, 2017, 04:13 PM	#4
drholmes Junior Member Join Date: May 20, 2017 Posts: 3	I am loading 45 APC cal. 230 grain Hornady XTPs. Last edited by drholmes; May 21, 2017 at 04:26 PM.

May 21, 2017, 04:03 PM	#3
74A95 Senior Member Join Date: November 26, 2016 Posts: 1,568	Caliber please.

May 21, 2017, 04:15 PM	#5
Jim Watson Senior Member Join Date: October 25, 2001 Location: Alabama Posts: 18,541	Lee copied the data from different sources - they do no testing themselves - and three different PV guns with three different bullets and three different sets of other components got three different answers. There is not much you can do about it. Either reload by recipe for the EXACT set of components you have, or apply handloading principles and sneak up on a serviceable load. A chronograph to tell me when I am at a desired velocity is essential to the way I go about loading.

May 22, 2017, 12:47 PM	#6
Reloadron Senior Member Join Date: June 8, 2016 Location: Cleveland, Ohio Suburbs Posts: 1,750	As Jim points out the Lee Load Data is a compilation of other load data and Lee does no load testing. Not a bad thing but not quite a good thing either. Just worth knowing. Below are pictured a 230 grain Hornady XTP and a 230 grain Speer Gold Dot, two very similar bullets but they are not the same length, close but not the same and they share a common 230 grain weight. Hornady suggest a C.O.L. of 1.210" Speer suggest a C.O.L. of 1.200" So we have a difference of 0.010" difference in the suggested C.O.L. The 230 grain Hornady XTP has a bullet O.A.L. of right around 0.635" and is pictured on the right and the Speer Gold Dot on the Left comes in with an O.A.L. right around 0.655" or about 0.020" longer than the Hornady bullet but the suggested C.O.L. difference is only 0.010". Starting and Maximum loads are suggested based on the test methods used by the original publisher of the data based on their test and test setups. For example, taking a real common .45 ACP powder like Unique and the 230 grain bullets we just looked at: Hornady Start 5.2 grains and Maximum 6.6 grains ranging from 700 to 900 FPS fired from a Springfield 1911 5.0" barrel. Speer Start 5.4 grains and Maximum 6.0 grains ranging from 721 to 806 FPS fired from a Sig P-220 4.4" barrel. Each bullet maker has their own data suggested for their bullet. The main idea being to start safe and stay safe working up your loads. Again, the Lee data is a broad compilation of published data of everyone else. Hope that helps and doesn't lend to confuse Ron

May 23, 2017, 07:36 AM	#7
drholmes Junior Member Join Date: May 20, 2017 Posts: 3	Thanks for input. I can understand variations in pressure related to bullet seating depth which can be effected by overall bullet length but I guess my real question is whether there is differences in the coefficient of expansion of copper plated vs full metal jacketed and do hollow points expand relatively more because there might be less resistance to expansion? I know this probably makes little practical difference but I just would like to understand the physics.