TTSX seating depth?

coyoteking

coyoteking

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Barnes recommends seating 50 thousandths off the lands, just wondering if anyone has tried seating closer or further out and what were the results?

I’ve got a pretty good load developed for my .243, 80 grain ttsx’s are putting 5 rounds into .85” at 100 yards with an extreme spread of 32 FPS with the bullets seated at 50 thousandth. Should I mess with the seating depth or leave it there?
 
leave at .050" jump and tune the powder charge to find the accuracy node

A good friend of mine is loading Barnes .150" off lands in his rifle and getting sub moa 5 shot groups
 
I have been using the TSX and TTSX seated 0.025 off the lands in my 280 Rem., and .25-06. Previously a 260 Rem.
The advice for the "first generation" Barnes was 0.050.
 
Optimal seating length - jump varies and only testing will determine what provides best results. Barnes recommendation is a good place to start.
 
todbartell said:
leave at .050" jump and tune the powder charge to find the accuracy node

A good friend of mine is loading Barnes .150" off lands in his rifle and getting sub moa 5 shot groups
Click to expand...

I agree with this ^^^.

The reason Barnes and other mono metal copper bullet manufacturers recommend the large jump is to alleviate some of the start pressure.

A standard cup and core bullet will have a resistance (start pressure) of ~ 3600psi, a mono metal copper bullet ~6500psi. This (start pressure) is comparable to the different bullet construction and not the over all start pressure.

0.050" off the rifling will account for ~1500 psi reduction in start pressure.

Tune with powder charge. Bullet seating depth is just another way of adjusting start pressure, therefore overall pressure.....this can be done much easier with adjusting powder charge.
 
I’ve loaded those, but had a problem with them having enough tension when seating them with the case mouth ending up between the grooves.
The bullits would push back and forth between the groove.

I had to seat them with case mouth on the higher? Part of the groove.
 
BCBRAD said:
I agree with this ^^^.

The reason Barnes and other mono metal copper bullet manufacturers recommend the large jump is to alleviate some of the start pressure.

A standard cup and core bullet will have a resistance (start pressure) of ~ 3600psi, a mono metal copper bullet ~6500psi. This (start pressure) is comparable to the different bullet construction and not the over all start pressure.

0.050" off the rifling will account for ~1500 psi reduction in start pressure.

Tune with powder charge. Bullet seating depth is just another way of adjusting start pressure, therefore overall pressure.....this can be done much easier with adjusting powder charge.
Click to expand...

I was wondering if seating them further out would increase pressure, I’ll play with the powder charge a bit and see if that changes anything.
 
coyoteking said:
I was wondering if seating them further out would increase pressure, I’ll play with the powder charge a bit and see if that changes anything.
Click to expand...

Seating the bullet closer to the rifling will increase the starting resistance/pressure of the bullet, and at the same time increase the combustion space behind the bullet.

By adjusting the bullet seating depth further out does two things, alters the start pressure (increases psi) and alters the combustion space (decreases psi).

Mostly for a hunting load I will seat bullet to magazine length if I can keep the bullet 10-15 thou off the lands, for targets anywhere between 10 and 15 thou off the rifling as they are single loaded.

All tuning is done with powder charge weighed to 0.02 of a grain.

Alternatively, adjusting seating depth and powder charge, during a work up, gets things confused.
 
Going against all that I heard up to now I wondered why all the Barnes loaded ammo are loaded to the last of the groves?
Is it just for the looks of the complete cartridge or for safety or because they have best results
So with my loads that use barnes bullets I started to experiment with oal "the other way around"
as a start I load them with the 1rst grove inside the neck and then I make them longer with every test......some times (25-06) they want the shortest sometimes (300 weath) they wanted long
but since then I start with the shortest length possible (ie the 1st grove in the neck)
 
ago1 said:
Going against all that I heard up to now I wondered why all the Barnes loaded ammo are loaded to the last of the groves?
Is it just for the looks of the complete cartridge or for safety or because they have best results
So with my loads that use barnes bullets I started to experiment with oal "the other way around"
as a start I load them with the 1rst grove inside the neck and then I make them longer with every test......some times (25-06) they want the shortest sometimes (300 weath) they wanted long
but since then I start with the shortest length possible (ie the 1st grove in the neck)
Click to expand...

They seat them that deep so that they will work in any rifle.

The closer to the lands you are, the better chance you have of developing a tight group
 
coyoteking said:
Barnes recommends seating 50 thousandths off the lands, just wondering if anyone has tried seating closer or further out and what were the results?

Barnes doesnt do that with there Factory ammo ! They have to load it to Industry standard lenghts to feed thru all Factory rifles ! Lots of Factory Barnes ammo and others Have shot VERY WELL way off the lands ! The VERY best ammo grouping in my 240 Weatherby is a 85 TSX at Factory OAL and NOT seated 50 thou off the lands ! All im saying is maybe its a recommendation BUT its not End all Be All ! jmo RJ
Click to expand...
 
I wish I could seat TTSX bullets .050 off the lands with my 300WSM. 13 years ago when the Ron Smith barrel was new I could, but now the bullet base would barely be touching the case mouth with that seating depth! :)

Quite a few rounds downrange with it, might be time for a new barrel, but it's still shooting MOA or a little better.
 
Jamming the lands will usually result in good accuracy, but it's not always practical or desirable, and not all accurate ammo is close to or touching anyway. Unless you are only ever going to single load, may as well pick a seating depth that allows function in the magazine, and tune the powder charge to that seating depth.
 
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