Going back to my original post in January, motivated by an impending outing to the Highlands, I've finally found the time to run a load development on the Fox 130gn classic hunters, which I acquired, to develop a non toxic load for the 7mm-08.
Some of the delay was due to waiting for the arrival of some neck turning components as I’d decided to go down that route as a bit of an experiment ( playing about, just fancied seeing if it made much difference) as regards case prep.
So for those that showed interest here are my findings, along with the usual caveats, that this info is from my rifle and shouldn’t be replicated without the usual safe reloading procedures being followed.
Case, new Lapua 7mm-08 once fired, full length sized, bumping the shoulder back by .002”, turned to clean up and uniform the neck, then expanded using a mandrel to give .002” of neck tension.
The Quickload data I’d acquired suggested that 42 grains of RS 52 loaded at 2.800” coal (head to tip), ignited by a BR2 primer, predicts peak pressure of 45647psi out of a possible max pressure of 60191psi, which should achieve a velocity of 2805fps out of a 24”barrel and a propellant burn of 99%.
My rifle has a 20” barrel so realistically you could probably knock 25fps/ inch off that, so I was expecting around about 2700fps.
The first problem I ran into as highlighted by Ed at Edinburgh rifles, the supplier of the Fox bullets, was that because of the shape of the ogive of the bullet, they’d have to be seated quite a bit deeper than usual. So running a seating depth check showed that the bullet was engaging the lands with the bullet seated at COAL 2.697”(head to tip), using that as a datum, I elected to use an initial seating depth of .035” off, as with various loads in the past, I’ve had good success in and around the .030” off area.
I loaded up a range of powder weights, which I’ll give in a table later, from 38gns to 42gns, the first three at .5 grain increments just to verify safe pressures and from 39.2 grains onwards at .2 grain increments.
The principal is to shoot these over a chronograph to observe where at least three adjacent loads, give the least amount of variation in velocity, therefore indicating a load which will ultimately give a low ES, being tolerant to slight variation in load weight. Also if shot at a paper target, classically, you can usually see each shot gradually print higher on the target as the velocity increases, with hopefully, the shots, with the closest velocity, printing closest together on paper ( that’s the theory anyway) and it works more often than not.
The problem was that this first ladder produced a target where the bulk of the shots produced a group of a little over 1 1/2” @ 100m, with the higher velocity loadings, regularly printing lower than higher. The velocity’s achieved ranged from 2682fps from 38grains to 2919fps from 42grains.
I settled on a load of 40.8 grains which gave an average 2862fps and after a bit of messing about with different seating depths showed no improvement and gave a group of just under 3/4” @ 100m.
No pressure signs whatsoever were observed throughout the whole series of loadings.
I’ll try all of this again later with standard cases to see if the prep made any difference and I’ll probably do a better seating depth ladder as well. But this loads good enough to take stalking, so I’ll see how it performs on the beasties.
The main observations.
RS52 yet again shows to be more lively than Quickload predicts, Laurie's absolutely spot on, as per usual.
The Fox bullets appear to give very good accuracy and aren’t very fussy about velocity variation. They need to be seated about 0.150” deeper than the average lead bullets of an equivalent weight (up to the bottom of the last cannelure)
Hopefully they’ll do the business !!!
| LOAD DEVELOPMENT OCW POWDER TEST | | | |
| | | Date: |
| RIFLE: | Sako 75 | | |
| CALIBER: | 7mm-08 | | |
| CASE: | Lapua new | | |
| BULLET: | Fox 130gn | | |
| SEATING DEPTH: | 2.800 oal (2.200) | | |
| POWDER: | RS 52 | | |
| | | |
| POWDER WEIGHT | VELOCITY ACHEIVED | |
| 1 | 38 | 2682 | |
| 2 | 38.5 | 2709 | |
| 3 | 39 | 2737 | |
| 4 | 39.2 | 2764 | |
| 5 | 39.4 | 2774 | |
| 6 | 39.6 | 2795 | |
| 7 | 39.8 | 2782 | |
| 8 | 40 | 2784 | |
| 9 | 40.2 | 2798 | |
| 10 | 40.4 | 2824 | |
| 11 | 40.6 | 2849 | |
| 12 | 40.8 | 2842 | |
| 13 | 41 | 2858 | |
| 14 | 41.2 | 2861 | |
| 15 | 41.4 | 2901 | |
| 16 | 41.6 | 2892 | |
| 17 | 41.8 | 2904 | |
| 18 | 42 | 2919 | |
| 19 | | | |
shoots great in both my 7-08s
