What manuels to Follow?

Huntingtrc · February 10, 2009, 08:48 AM

I am loading for a .300 win mag and I have the Vihta Vouri Reloading Manuel and the the Nosler Reloading manul both the 6th Editions. I am loading the 150gr CT Ballistic tip Nosler with N160, the Vihta Vouri book shows the starting load to be 73.9gr with max being 77.7gr of N160 for this bullet. The Nosler book shows the Starting load to be 71.5gr and max being 75.5gr and I was warned that under loading can be as dangerous if not more than over charging. Which one would be the best to follow because that is a pretty substantial difference?

markr · February 10, 2009, 09:15 AM

Were the test guns from the two manuals the same or different? Barrel length, rifling twist?

SL1 · February 10, 2009, 01:04 PM

One thing that most people seem to forget is that the pressure readings are NOT develped in the "test guns" listed in the manuals. That was done in some cases years ago when some manual authors were using measurements of fired cases to guestimate pressures. But, not so today.

Modern manuals have loads developed in special test barrels that are cut to SAMMI minimum specs to make pressures as high as any (within-spec) barrel that is out there commercially. Those special barrrels are instrumented to measure pressure by one of the available methods (CUP, PSI, CIP). Then, to give the handloader a realistic expectation for velocity of the loads that were developed in the special barrels, those loads are chronographed in a specified "test gun" that is available commercially. The commercial test gun velocities AND pressures are probably different than what was produced in the special pressure-gun barrels.

SO, differences in maximum charges between two manuals (for same bullet, seating depth, powder, case and primer) are NOT due to using different test guns. Only the published VELOCITIES vary for that reason.

But, pressure-gun barrels do erode from repeated exposures to hot gases, just like your rifle. Some allegatrions have been made about some of the notoriously "hot" loads in a few manuals having been developed in manuals that had eroded too much and produced much lower pressures than barrels a SAAMI minimum specs. There have also been some allegations about early manuals having been developed without adequate temperature controls.

So, when I am faced with this situation, I start at the lowest minimum and work up from there, in case the higher data was developed in an eroded barrel.

One other thing to ask: do both of your manuals use the same bullets? I don't have them, so I don't know. My experience with other Nosler manuals was that they gave pretty accurate data for my rifle, while data for other same-weight bullets was higher and produced MUCH higher velocities (and probably pressures) in my rifles when applied to Nosler bullets.

SL1

jdscholer · February 10, 2009, 01:40 PM

Different case brands can also differ substantially in capacity, especially in a large cartridge like 300 Win. jd

February 10, 2009, 08:48 AM	#1
Huntingtrc Junior Member Join Date: January 27, 2009 Posts: 12	What manuels to Follow? I am loading for a .300 win mag and I have the Vihta Vouri Reloading Manuel and the the Nosler Reloading manul both the 6th Editions. I am loading the 150gr CT Ballistic tip Nosler with N160, the Vihta Vouri book shows the starting load to be 73.9gr with max being 77.7gr of N160 for this bullet. The Nosler book shows the Starting load to be 71.5gr and max being 75.5gr and I was warned that under loading can be as dangerous if not more than over charging. Which one would be the best to follow because that is a pretty substantial difference?

February 10, 2009, 09:15 AM	#2
markr Senior Member Join Date: January 23, 2008 Location: Arsenal of Democracy Posts: 405	Were the test guns from the two manuals the same or different? Barrel length, rifling twist? __________________ I like to make beer, bullets, and jerky.....but not at the same time. Washed up 11B1P Last edited by markr; February 10, 2009 at 09:56 AM.

February 10, 2009, 01:04 PM	#3
SL1 Senior Member Join Date: November 8, 2007 Posts: 2,001	"Test Guns" don't matter for charge data. One thing that most people seem to forget is that the pressure readings are NOT develped in the "test guns" listed in the manuals. That was done in some cases years ago when some manual authors were using measurements of fired cases to guestimate pressures. But, not so today. Modern manuals have loads developed in special test barrels that are cut to SAMMI minimum specs to make pressures as high as any (within-spec) barrel that is out there commercially. Those special barrrels are instrumented to measure pressure by one of the available methods (CUP, PSI, CIP). Then, to give the handloader a realistic expectation for velocity of the loads that were developed in the special barrels, those loads are chronographed in a specified "test gun" that is available commercially. The commercial test gun velocities AND pressures are probably different than what was produced in the special pressure-gun barrels. SO, differences in maximum charges between two manuals (for same bullet, seating depth, powder, case and primer) are NOT due to using different test guns. Only the published VELOCITIES vary for that reason. But, pressure-gun barrels do erode from repeated exposures to hot gases, just like your rifle. Some allegatrions have been made about some of the notoriously "hot" loads in a few manuals having been developed in manuals that had eroded too much and produced much lower pressures than barrels a SAAMI minimum specs. There have also been some allegations about early manuals having been developed without adequate temperature controls. So, when I am faced with this situation, I start at the lowest minimum and work up from there, in case the higher data was developed in an eroded barrel. One other thing to ask: do both of your manuals use the same bullets? I don't have them, so I don't know. My experience with other Nosler manuals was that they gave pretty accurate data for my rifle, while data for other same-weight bullets was higher and produced MUCH higher velocities (and probably pressures) in my rifles when applied to Nosler bullets. SL1

February 10, 2009, 01:40 PM	#4
jdscholer Senior Member Join Date: March 23, 2008 Location: Jefferson State Posts: 1,197	Different case brands can also differ substantially in capacity, especially in a large cartridge like 300 Win. jd __________________ "We're all dummies, just in different ways." Old Okie Philosopher