Neck sizing with an RCBS FL Die? - Page 2

msta999 · July 9, 2009, 12:11 AM

Here is my factory Weatherby 150 Non BT rounds and some Hornady 180 gr loads I made.

Quite a bit of difference between these and the boattails.

Bart B. · July 9, 2009, 06:39 AM

Partial neck sizing with full length sizing dies has been done since the 1930's. It typically moves the fired case shoulder forward as it sizes the case body down a bit. This usually results in a slight binding of the bolt when the partially sized case is chambered. All of which results in the bolt binding at different places each time its closed.

If one full length sizes rimless bottle neck cases too much using full length dies setting their shoulder back too far, accuracy will suffer. Partial sizing tyically produces better accuracy than too much full length sizing.

However, if the full length sizing die is set such that the fired case shoulder's set back no more than about .002 inch, best accuracy is virtually guaranteed. You'll need a case headspace gage to measure it to see exactly how much sizing is happening. This is how Sierra Bullets sizes their cases used to hold their bullets when tested for accuracy in rail guns. Most high power rifle competitors size cases this way. Benchresters are moving in this direction, too. Some of these folks get 50 to 80 reloads per case doing this. One doesn't need to size the fired case body any more than .003 inch smaller to do this.

It's an old myth that boattail bullets wear out barrel throats and bores moreso than flat based bullets. But in any chamber with long throats such as Weatherby put in their barrels will wear out faster than a shorter, standard throat. I used to shoot rifle matches with the stock maker who designed Weatherby's first stocks. He had tried the .300 Wby. Mag. round in long range match rifles with a more normal throat and Sierra's boattail match bullets didn't wear it out any faster than other similar cartridges did. Bullets don't wear out barrels; burning powder's hot gasses are the culprit. The more hot gas there is that blows around the bullet eroding the barrel before the bore's plugged up by the bullet, then there will be excessive erosion of the barrel steel. Smaller diameter bullets let more gas blow by than larger ones. Measure your bullets to the nearest ten-thousandths of an inch and see the difference.

msta999 · July 13, 2009, 12:35 AM

This is from todays shots. Getting better, but still not where I want to be.

July 9, 2009, 12:11 AM	#26
msta999 Senior Member Join Date: June 7, 2009 Location: Western, WA Posts: 123	Here is my factory Weatherby 150 Non BT rounds and some Hornady 180 gr loads I made. Quite a bit of difference between these and the boattails.

July 9, 2009, 06:39 AM	#27
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	Partial neck sizing with full length sizing dies has been done since the 1930's. It typically moves the fired case shoulder forward as it sizes the case body down a bit. This usually results in a slight binding of the bolt when the partially sized case is chambered. All of which results in the bolt binding at different places each time its closed. If one full length sizes rimless bottle neck cases too much using full length dies setting their shoulder back too far, accuracy will suffer. Partial sizing tyically produces better accuracy than too much full length sizing. However, if the full length sizing die is set such that the fired case shoulder's set back no more than about .002 inch, best accuracy is virtually guaranteed. You'll need a case headspace gage to measure it to see exactly how much sizing is happening. This is how Sierra Bullets sizes their cases used to hold their bullets when tested for accuracy in rail guns. Most high power rifle competitors size cases this way. Benchresters are moving in this direction, too. Some of these folks get 50 to 80 reloads per case doing this. One doesn't need to size the fired case body any more than .003 inch smaller to do this. It's an old myth that boattail bullets wear out barrel throats and bores moreso than flat based bullets. But in any chamber with long throats such as Weatherby put in their barrels will wear out faster than a shorter, standard throat. I used to shoot rifle matches with the stock maker who designed Weatherby's first stocks. He had tried the .300 Wby. Mag. round in long range match rifles with a more normal throat and Sierra's boattail match bullets didn't wear it out any faster than other similar cartridges did. Bullets don't wear out barrels; burning powder's hot gasses are the culprit. The more hot gas there is that blows around the bullet eroding the barrel before the bore's plugged up by the bullet, then there will be excessive erosion of the barrel steel. Smaller diameter bullets let more gas blow by than larger ones. Measure your bullets to the nearest ten-thousandths of an inch and see the difference.

July 13, 2009, 12:35 AM	#28
msta999 Senior Member Join Date: June 7, 2009 Location: Western, WA Posts: 123	This is from todays shots. Getting better, but still not where I want to be.