Al Nyhus re Da' Pup
- Thread starter alinwa
- Start date
alinwa: With the base of the bullet .075 below the neck/shoulder junction, 44.0 gr. of water will just touch the bullets base. Throated this way, the bullet just rests on top of 38.0 of H4198. Best accuracy comes from 37.5 to 38.2 of H4198. What a strange coincidence...... 
Case capacity w/o a bullet averages 45.7.
Stan and I have played with quite a few throat lengths over the past four seasons, from Stan's swiveling-in-the-neck personal favorite, to one that I have with a short throat (base of bullet .150 below the n/s junction). Best performance has always been with the longer throats (the base no more than .075 down).
The '.075 down' throat is obviously dependent on which bullet you throat it for. Throating to '.075 down' with the BIB 118 1.00" 7 ogive (.420-ish base to ogive) puts the base of my 'Dakota B1' 118 1.00" 8 ogive (.370 base to ogive) at the bottom of the neck. There's only .050 difference between the b-o's of those bullets, but the profile difference, combined with the throat angle, makes the actual just-touching seating depth difference around .085.
Probably more than you want to know or ask for, but there it is.
Recent changes in the Lapua 6BR case we use as the parent case are really giving us some gas, though. Whether we can continue to use this case looks doubtful at this point. We may need to look at shortening the 6.5X47L case for use in our 'Pup chambers..which defeats the entire purpose of the 'Pup in the first place.
Good shootin'. -Al
Case capacity w/o a bullet averages 45.7. Stan and I have played with quite a few throat lengths over the past four seasons, from Stan's swiveling-in-the-neck personal favorite, to one that I have with a short throat (base of bullet .150 below the n/s junction). Best performance has always been with the longer throats (the base no more than .075 down).
The '.075 down' throat is obviously dependent on which bullet you throat it for. Throating to '.075 down' with the BIB 118 1.00" 7 ogive (.420-ish base to ogive) puts the base of my 'Dakota B1' 118 1.00" 8 ogive (.370 base to ogive) at the bottom of the neck. There's only .050 difference between the b-o's of those bullets, but the profile difference, combined with the throat angle, makes the actual just-touching seating depth difference around .085.
Probably more than you want to know or ask for, but there it is.
Recent changes in the Lapua 6BR case we use as the parent case are really giving us some gas, though. Whether we can continue to use this case looks doubtful at this point. We may need to look at shortening the 6.5X47L case for use in our 'Pup chambers..which defeats the entire purpose of the 'Pup in the first place.
Good shootin'. -Al
Al....
"Recent changes in the Lapua 6BR case we use as the parent case are really giving us some gas, though. Whether we can continue to use this case looks doubtful at this point. We may need to look at shortening the 6.5X47L case for use in our 'Pup chambers..which defeats the entire purpose of the 'Pup in the first place."
I haven't compared new to old. What changes have you noted, if you don't mind sharing? The pup got run over, eh? --Greg
"Recent changes in the Lapua 6BR case we use as the parent case are really giving us some gas, though. Whether we can continue to use this case looks doubtful at this point. We may need to look at shortening the 6.5X47L case for use in our 'Pup chambers..which defeats the entire purpose of the 'Pup in the first place."
I haven't compared new to old. What changes have you noted, if you don't mind sharing? The pup got run over, eh?
--GregGreg, as you know, we blow the shoulder foward .240 on the standard Lapua 6BR case necked to .30 to make our WolfPup cases. With the earlier Lapua 6BR cases, we had zero issues doing this. Starting last season with some of the later lots of lapua 6BR cases, we started experiencing sporadic longitudinal stress risers that started basically where the original body/shoulder junction was. About 15-20% of the time, these stress risers would actually result in a split along the case length.
No amount of annealing, either before or after, sems to settle this down. After sectioning quite a few of these cases, I can only conclude that the material has changed enough to cause this. The cases that don't show these stress risers when fireforming don't ever crack during subsequent use, though. But they just don't shoot like the 'old' Lapua cases did, either.
We've been limping along with our carefully hoarded 'early' cases...rehabing them as needed, so far.
This isn't meant to imply that the Lapua 6BR cases is substandard...quite the opposite. In any sort of normal use, these issues will never be a factor.
No amount of annealing, either before or after, sems to settle this down. After sectioning quite a few of these cases, I can only conclude that the material has changed enough to cause this. The cases that don't show these stress risers when fireforming don't ever crack during subsequent use, though. But they just don't shoot like the 'old' Lapua cases did, either.
We've been limping along with our carefully hoarded 'early' cases...rehabing them as needed, so far.
This isn't meant to imply that the Lapua 6BR cases is substandard...quite the opposite. In any sort of normal use, these issues will never be a factor.
Al, those figures would mean that the neck on a 30X47L holds 8.8 gr. of water.
-A 30BR neck (around .300 in length) holds an average of 5.3 gr. of water.
-The 30X47L has a shorter neck than a 30BR (about .270 long).
-For a .30 cal. neck to hold 8.8 gr. of water, it would need to be .475-.480 long.
-Alhmmm,
Here's what I did.
I zero'd on an empty case, dribbled the case full about up to the n/s junction. Visually under a bright light it looked to be touching the junction. The surface of the water was concave. I was tempted to run a caliper down in and would if precision was necessary. I would also add some soap...
I then filled 'er up.... wiped off with a paper towel and weighed the case.
YES, my conclusion was that my neck held around 8.5 gr water.
I'll redo the experiment to see did I goof! And I'll measure my necks, my case is not really a "30X47L" it's my own creation.
al
al
Here's what I did.
I zero'd on an empty case, dribbled the case full about up to the n/s junction. Visually under a bright light it looked to be touching the junction. The surface of the water was concave. I was tempted to run a caliper down in and would if precision was necessary. I would also add some soap...
I then filled 'er up.... wiped off with a paper towel and weighed the case.
YES, my conclusion was that my neck held around 8.5 gr water.
I'll redo the experiment to see did I goof! And I'll measure my necks, my case is not really a "30X47L" it's my own creation.
al
al