I ran into something while I was shooting some loads over my chronograph today and the results surprised me. I was shooting 120 gr. Hornady SSP's and 120 gr. Nosler B/T's out of my 15" 7mm BR Encore with an identical load of 27.5 grs. Reloader 7 (1 grain under max in the Nosler manual) and I have shot this load before with B/T's without any problems. After shooting the B/T's I shot the Hornady SSP's. After checking the chrono I saw at least a 50 fps. jump in velocity per shot with the SSP's over the B/T's. When I saw this I checked the rounds loaded with the Hornady's and found each of the five SSP rounds I fired had cratered primers and shiny spots around the primer pocket. Time between shots was at least 2 minutes for each round. I have always been cautious when switching to B/T's from another bullet due to their solid base deign and have never encountered any sort of problem. This time I thought I outsmarted myself but thanks to the chrono, I may have avoided a serious problem.

Has anyone ever noticed this sort of increase in pressure and velocity with the 7mm SSP vs. the B/T? After 25+ years of reloading I am happy to report that I learned something new and still have five fingers on each hand.

Dennis

I've had a similar experience as yours with 7mm-08 when shifting from 140 grain ballistic tips to 139 grain Hornady spirepoints. Velocity jumped about 75fps and pressures high enough to crater the primer.
I backed off 1 grain on the hornady loads and got similar velocity to the BTs and accuracy improved significantly.
If you look at Hornady bullets, they have significantly more bearing surface than most any other bullets, that must be what raises the pressures.

regards,
Graycg

I noticed app. 50 fps difference in my .270 between 150 Hornady's and 150 Nosler Partitions, the Hornady's being the faster loads. This was with 59 grains H 4831 in WW cases w/ WLR primers. No noticeable presssure increase though. The Noslers were a bit over 2,900 fps anfd the Hornady;s @ 2,960 + & -.

Rich Elliott

Not sure if this could explain your situation but I have noticed that Nosler bullets tend to at or below nominal barrel bore diameter while Hornady and Sierra are slightly above. For example, Sierra and Hornady in 6 mm measure about .2433 to .2434 while Nosler measure .2397 to .2430. Could this small change in diameter cause higher pressure? May also depend on your specific bore diameter.
Ron

This is why all the loading books and manuals that you can find, will tell you to go back to a starting load, and work up, when you change ANY component.

NEVER assume that two bullets of equal weight, in the same gun, will have the same pressure/velocity with the same powder charge. 50fps and a little pressure jump are mild, next time it may be significantly more. Bullet diameter, bearing surface, jacket hardness and thickness all have a bearing on what happens when the pressure starts to build. I have seen lighter bullets reach max with lighter powder charges.Hate to sound like I'm preaching, but I have been there. Fortuneately the worst I have ever experienced is a stuck bolt, others may not be so lucky.

I agree to start back with the starting load and work your way up. Something is different with the jacket material or the bearing surface. (If you are loading close to the lands the SST might be out to far.) Work your way back up. also check out Hornady's site or call them about loads for that bullet and caliber. Check that OAL length.

Good luck. Let us know what happens

Hcliff