Chasing the lands

[C Valentine]

As the throat wears and the CBTO of your cartridge gets longer, do you adjust your powder load to try and achieve the same pressure and velocity? That seems logical to me but being a relative newbie I thought I had better ask since my brand of logic is certainly not foolproof! After 735 rounds in my .223 my lands (according to my RCBS Mic) have moved out about 5 thousandths from when the barrel was new. Is that a lot?

 

[halfmoanut]

You will often hear this ( chase the lands) it means as the throat gets burned forward thru shooting you must move your seating depth out ( moving bullet out of the case) meaning if your .005 thou is accurate then to meet that measurement you would have a seating depth measurement .005 longer. For 700 plus rounds that would be believable. Each barrel will be different. My rule of thumb thinking is .001 for every 250 rounds, however that is just a theory not the gospel! I would not change the powder unless too much vertical arrives from the .005 longer seating depth change. Then I would probably got up or down .3 tenths and see if accuracy is as good or better!

 

[Lapua40X]

As the throat wears and the CBTO of your cartridge gets longer, do you adjust your powder load to try and achieve the same pressure and velocity?...

Only if the evidence on target suggests a change is in order.
If it ain't broke, don't fix it.

 

[Chappy]

As the throat wears and the CBTO of your cartridge gets longer, do you adjust your powder load to try and achieve the same pressure and velocity?...

Only if the evidence on target suggests a change is in order.
If it ain't broke, don't fix it.

"If it ain't broke, don't fix it."


These are words to live by.

 

[jsthntn247]

My 223's throat has moved .009 in 700 rounds. I measure it before I load for a match every time. I shoot the 90's and have a .002 window to be in or groups open up.

 

[barefooter56]

xhuntress,
Sometimes as you move the bullet out chasing the throat to stay on your seating depth sweet spot you may notice the accuracy falling off. This is mostly due to the capacity of the cartridge case increasing as you seat the bullet out. What this does is it may cause a decrease in pressure behind the bullet which may lower the muzzle velocity out of your velocity accuracy node. To fix this move your charge up in VERY SMALL INCREMENTS until your accuracy comes back. Look for pressure signs as you are reworking the load up also. Hope this help.

 

[chkunz]

xhuntress,
Sometimes as you move the bullet out chasing the throat to stay on your seating depth sweet spot you may notice the accuracy falling off. This is mostly due to the capacity of the cartridge case increasing as you seat the bullet out. What this does is it may cause a decrease in pressure behind the bullet which may lower the muzzle velocity out of your velocity accuracy node. To fix this move your charge up in VERY SMALL INCREMENTS until your accuracy comes back. Look for pressure signs as you are reworking the load up also. Hope this help.

Or the accuracy is falling off because the barrel life is also going as the lands are going.

 

[RDavies]

As the throat wears and the CBTO of your cartridge gets longer, do you adjust your powder load to try and achieve the same pressure and velocity?...

Only if the evidence on target suggests a change is in order.
If it ain't broke, don't fix it.

"If it ain't broke, don't fix it."


These are words to live by.

Yep. I used to live by these words.
It was easier to wait until you got home rom the big match then fix it in the comfort of your home club range the next week.

 

[Joe R]

barefooter56 said:
xhuntress,
Sometimes as you move the bullet out chasing the throat to stay on your seating depth sweet spot you may notice the accuracy falling off. This is mostly due to the capacity of the cartridge case increasing as you seat the bullet out. What this does is it may cause a decrease in pressure behind the bullet which may lower the muzzle velocity out of your velocity accuracy node. To fix this move your charge up in VERY SMALL INCREMENTS until your accuracy comes back. Look for pressure signs as you are reworking the load up also. Hope this help.

+1 If you are target shooting do the above.

Lapua40X said:
If it ain't broke, don't fix it.

+1 If your hunting do the above.