Some more hollow base SST’s

I again was playing in the shop with another method to create a hollow base in the Hornady SST. Previously I had been doing it on the lathe. This time I used the milling machine. I have a collet vise that bolts to the table on the mill. With the countersink in the collet of the mill and the vise lined up with a pilot, I proceeded to hollow base some more 300 gr. SST’s plus a few 250 grainers. They look pretty good to the eye but was not sure how they would fly compared to the ones done on the lathe.

To start the 17* morning off (we got our shooting room up to 46* before the morning was over) I fouled the barrel with three 300 gr. SST’s with a wad and a 10/60 …Unique/H-4198 duplex. The first sot was somewhat slower than the succeeding two and the group was just 1.9”



Next I went to the 280 gr. SST ( a 20 gr. loss by creating a hollow base) with my old standby 10/60 Clays/H-4198 duplex. NO WAD! And done on the mill. Five shots averaged 2925 fps and had a 34 fps ES. Not a good group @ 2.8” with the best 3 @ .8”



Moving along to the same bullet WITH A WAD the average of 5 shots was 2797 fps with a 22 fps ES. 3 shots (in a row) went .5” with 4 @ 1.1” and all five in 2.0”. Better but not what I was looking for!



The fourth group was shot with the same bullet, NO WAD but lathe turned. Here, 5 shots came in at 2805 fps with a 19 fps ES. Three shots went .5” with all five in .9”. Considerably better……….and maybe they will not get any better? I will still play!



For the 5th. group, I went with the 230 gr. SST (hollowing the base removes, like on the 300’s, approximately 20 gr. of copper and lead) NO WAD and the same 10/60 duplex. I kind of had a mix of velocities (not sure why?) 1, 4 and 5 averaged around 2955 with only 13 fps ES but somehow, 2 and 3 were at 3020? It did not effect the first three shots as they measured .5” in a nice cloverleaf? Four @ 1” and five @ 1.4”.



In any event, I decided to try them at 300 yards. I only had five left and used one on our steel gong to make sure I would be on target. The next four, of which the chronograph only captured two shots (sun) 2992 and 2994 created a decent 1.7” group. That was encouraging for some plain old modified generic bullets.

I am thinking the lathe produces a better balanced bullet………at least as of this test.



For the gentleman asking about velocities with wads vs. no wads, in group 2 and 3 you can see that the wad had actually created less velocity than (group 3) than no wad. In this particular case my theory is (and part of what I was testing for) that with no wad, the pressure is allowed easy access into the hollow cavity and more easily expanding the bullet giving a better seal which in turn creates more pressure and more velocity?

On the other hand, a lot can depend on the bullet being used? Hank uses a lot of Parker bullets which have a .015” wall thickness………much thinner than the Hornady’s. So he can easily get away with no wad and still get a good seal. With the thicker jacketed bullets a wad might be necessary to build pressure. Kyle’s bullet should also be a good candidate for no wads. Lots of stuff we do is not carved in stone and it is necessary for individuals to test for themselves. Hopefully some of the stuff I post will get you in the right ballpark but you will need to fine tune for your rifle and bullet/powder.



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