Seating Long Vs Seating Short

[daj]

Much has been written about keeping a projectile's bearing surface above the case's neck/shoulder junction.

Donut and powder volume issues aside, is there any evidence that accuracy is affected one way or the other by seating bullets deeper than the N/S junction?

For example, if we have two 260 Rems, one chambered to seat 140 VLDs long (3"+) and jammed Vs one chambered to seat short (2.8" mag fit) and jammed, all else being equal, could we expect similar accuracy? (The former has the projectile bearing surface above the N/S junction, the latter well below it)

 

[fdshuster]

Seat them to different length's then take them out & try them side by side, under identical conditions.

It won't take long to find which seating length works best for you.

 

[Cort]

Unfortunately, all things are never equal. If you had two "identical" rifles, you would be very unlikely to find a single load that shot best in both rifles. One might prefer jammed bullets where the other one might prefer jumped bullets. There is enough difference in metallurgy and machine work, etc. that no two rifles are ever identical in performance. One might perform best at a slightly lower velocity than the other so the decreased powder capacity from seating the bullet deep in the case may or may not be meaningful. Or the increased pressure caused by the slightly reduced case volume created with the deep seated bullet may or may not affect best performance.

As Frank said, try it and see what your rifle likes.

Cort

 

[daj]

Thanks Guys. I already know what my rifle likes best - 140 VLDs seated long and jammed 20T.

Before ordering my next reamer with a shorter FB for mag loading, I need to know if I will be giving up any accuracy potential by seating deeper in the case.

 

[mikecr]

A bad thing about seating through the neck shoulder junction is the tension variance that results.
You cannot really control bullet grip at the junction(which could also change with each body sizing).

The neck shoulder junction is thicker and stronger than the rest of the neck. Depending on your chamber you might also run out of clearance there creating a dangerous loaded condition.

Nothing is ever free

 

[daj]

Thanks Mike. Good points.

Based on those considerations, perhaps the 6.5L, 6.5CM and 6.5SLR are better options for mag use. (?)

 

[brian427cobra]

My 260 started life with a 139 Scenar touching the lands, ojive length 2.150, in a AICS mag I had more than .120 room to grow, now after 3250 rounds I got .010 left in the mags, for a mag fed rifle there are trade offs, one of them is seating bullets deep in the case, another is bullet selection, a VLD might run out of room so a jump tolerant bullet will have to be used

 

[daj]

Brian, by my reckoning your 139s initially had the bearing surface well below the N/S junction.
Did you have any problems with variable bullet grip (re mikecr post above)?
What accuracy were you getting with that setup?