7.82 Warbird - - - Reloder 33

morning, all.

took some time yesterday morning to chrony some test-loads using this brand new alliant powder in my sako trg-s.  its a powder advertised to do amazing things with large caliber magnum but was specifically made for improvements in the .338 lapua cartridge (hence it's r 33 name).

my starting load for this development was going to be my max charge for the cartridge using hodgdon's retumbo.  the first bullet i choose to work with was nosler's 180 gr accubond.  my max load of 104 grs of retumber averaged 3511 fps out of the rifles factory 26" barrel.

i was not interested in wasting alot of powder or bullets with this initial test run.  accuracy was not a concern.  i simply wanted to see where the upper limit of velocity was once we got to a max working pressure.

increasing in full grain increments, i started at 104 grs and loaded 5 groupings.  the chrony read :

• 104 grs  -  3267 fps  3300 fps  -  3284 fps average
• 105 grs  -  3316 fps  3300 fps  -  3308 fps average  + 24 fps
• 106 grs  -  3333 fps  3350 fps  -  3342 fps average  + 34 fps
• 107 grs  -  3384 fps  3367 fps  -  3376 fps average  + 34 fps
• 108 grs  -  3392 fps  3401 fps  -  3397 fps average  + 21 fps

hmmmmmmm.  not necessarily what i was expecting to see.  i was using a new lot of virgin cases.  even when sized, they tend to have slightly rounded shoulders that are blown sharp once submitted to the pressures of firing.  the 108 gr load was just starting to sharpen these angles.  based on this and the fact that i was some 120 fps off my max retumbo velocity, i knew, even at 108 grs of r33, we were well under working pressures.

i was out with my brother this morning and we were starting to have our doubts as to weather the slower burning r33 would be a good candidate for use in the 7.82 warbird with it's relatively light 180 gr bullet.

my brother suggested we run back to his shop and using individual rounds over the chrony, find what the upper limit is when pressure signs start to present themselves.

we decided to skip 109 through 110 grs.  here's what we got :

• 111 grs  -  3454 fps - sharp shoulder angles, no flattening of primer or cratering, no ejector markings on the brass.
• 112 grs  -  3499 fps  -  no flattening of primer or cratering, only the slightest ring of the ejector.
• 113 grs  -  3518 fps - esssentially bringing me back to my original max retumbo velocity.  no flattening of primer or cratering, the same slight ring of the ejector.

this is where we stopped.

i am going to pop these primers to confirm the pockets remain solid but from these results, it's pretty evident, the faster burning retumbo is much more conducive to proper 7.82 performance with a 180 gr bullet then the slower r33.

learning the tendencies of these newly released powders is frustrating and exciting.

so, what i'm wondering is     ...     will the slower r33 come closer to providing the performance boosts advertised (or any boost) if i move to a heavier for caliber bullet?  i've worked up loads in the round using both the 200 gr accubond and 208 gr a-max with retumbo but both were done using some very poor quality, early production lazzeroni brass.  as such, i wouldn't have the benefit of being able to have an apples to apples comparison as i did here between these two powders and the 180 gr accubond.  maybe the 210 gr smk?  obvious concern would be, will the 1:12 twist of this factory sako barrel accurately shoot a 210 gr bullet?  the velocity potential would help.  the 200 and 208 did very well, so it might work.  i'm just not sure it's worth the effort.

my brother is convinced, through his development projects using r33, that the powder does not like jumps to the lands either.  i have witnessed this in his rifles with large velocity spreads tightening the closer he got to the lands.  then i go and shoot this warbird and get very consistent velocity spreads with a fairly long jump to the lands (because of the magazine box contraints).  so i've no idea what to conclude on that front just yet.

decisions?   decisions?

 

k