what bushing would you recommend for my .284?

[Dutchie]

Just seeing if anyone could help recommend to me picking out the right bushing for my .284 Winchester. I have neck turned the lapua brass down to .3095. My chamber is .315. A loaded case with a 180 grn hybrid 7mm bullet measures .311. Once fired it measures .313.........any help would be appreciated, Thanks

 

[coford]

If my math is correct you should need a .310 or .309 bushing. If your loaded round measures .311 and your bullet is .284, then your necks are cut to .0135 each side. A .310 or .309 should give you the proper neck tension but bushing size is not always perfect - that is why most of us have a box full of them from past guesses.

Remember the .3095 measurement means nothing without knowing the arbor diameter. The important number is the case neck thickness (.0135).

 

[ShootDots]

If my math is correct you should need a .310 or .309 bushing. If your loaded round measures .311 and your bullet is .284, then your necks are cut to .0135 each side. A .310 or .309 should give you the proper neck tension but bushing size is not always perfect - that is why most of us have a box full of them from past guesses.

Remember the .3095 measurement means nothing without knowing the arbor diameter. The important number is the case neck thickness (.0135).

Gonzos is RIGHT ON THE MONEY! My 284 Shehane brass is turned down to "clean up" about 90-95pct. of the necks. My neck wall thickness is .0135. I am currently using .310 bushing. However, I shot my last 1000 yard match and I got a few shots that opened my vertical to just outside the 10 ring. I THOUGHT I had eliminated ALL the vertical but evidently over the course of fire, there were a few. I ordered a .311 bushing and will use that after I finish firing the box and I believe that will "fix" the few that went high. I was using a .309 bushing during load development and was shooting EXCELLENT groups at 300 yards. However, when I went to test the loads at 1000 yards, I found LOTS of vertical. I went to a .310bushing and it appeared that all the vertical went away.

I have come to the conclusion that, at least in MY Shehane, less neck tension translates to less vertical dispersion. So my suggestion is get a .310 AND a .311 and use the .311 first to see what takes place.

 

[Erik Cortina]

Ben, why don't you just adjust seating depth and reduce vertical that way?

 

[ShootDots]

Ben, why don't you just adjust seating depth and reduce vertical that way?

I tried that from 20K in to 30K off.. Seating depth had almost no effect on vertical at 1000 yards.. I tried everything. The last variable was neck tension. On the last 1000 yard competition, when I missed the 10 ring from vertical it was just by less than 1inch outside of the 10 ring.. We were shooting the "summer schedule" of 15shots for score and 2 sighters after the first match. I dropped 3 into the 9 ring from vertical >> the rest I missed from not catching the switch.. Even with annealing, I noticed a bit if "differing tension" on some rounds, when seating the bullets. I bought the .311bushing and sized a half dozen of the fired cases (no annealing yet>>>that will come after the next match) and with the .311 the seating of those "test" rounds, as it were, went in like smooth butter.. Tests will be in the offing, however, I believe it will stop the few vertical shots that went awry..

 

[Erik Cortina]

The reason seating depth had no effect was for to the coarse adjustment.
Start at .005" jump and work away from lands in .003" increments. You will find the sweet spot before you get to .030" jump.

 

[ShootDots]

All of that seating depth testing was done in 5K increments. If the .311 bushing does not rid me of the rest of that vertical, I will do the 3K incremental movements..