Horizontal POI changes???
Posted: Sat Apr 18, 2009 6:34 pm
Here is something that has me a bit confused, maybe others with more experince can shed some light on it.
The previous summers of varmint shooting I have used the Hornaday 32 Grain V-Max bullets exclusively with good results, accuracy is usually around 5/8-3/4 MOA. I hope to take my kill zone beyond 350 yards this summer so I wanted the ballistic advantage of the Sierra 39 Grain SBK. (Many on this forum have had good results hence my choice).
Over the winter I installed a new SSS Competition recoil lug and bedded the action on my Savage 12 VLP, (Unfortunalty my Shilen barrel is still in production so I guess the factory tube will be used this season). All my brass has had the primer pockets uniformed, trimmed, annealed, neck turned (just cleaned up about 25-50% of neck surface). All loaded rounds were checked for runout, those over 0.0015" were used for foulers. For testing the OCW method was chosen over the Auddette ladder method for these reasons....
-200 yard max range
-don't have spotting scope to see .20 cal holes beyond 150 yards
-wind is always a factor here in southern Alberta
I began the day by zeroing the scope with some factory rounds, then cleaned barrel and tested my Hornady 32 Grain V-Max bullets using Hornady brass, H322 powder, and CCI BR4 primers. After 2 fouling shots this test pretty much confirmed that the load I had been using previously for these bullets was the one to stick with. The surprise came when switching to the Sierra 39 Grain SBK's pushed by H4895 powder and the same brass and primers. My two foulers (after complete cleaning) impacted to the left and all of the 39 Grain SBK test groups impacted about 1.5 MOA to the left of where my 32 Grain handloads, as well as 32 grain, 40 grain, 45 grain factory loads had.
Now all the factory loads were Hornady bullets and they printed the same POI while the Sierra bullet was the difference when the POI changed so I suspect bullet brand more so than bullet weight is the cause of POI change.
Should I try 40 grain Hornady or maybe Nosler to see if POI remains consistent?? Or maybe I should abandon my "proven" 32 grain V-max and try to see if the 32 Grain SBK's have the same POI and the 39 grains. (I have yet to sort out all data on velocity deviation and group sizes but at a glance I wold have to give the edge to the Sierra bullets for accuracy)
Or am I asking for to much to be able to swap between bullet types depending on shooting conditions???
The previous summers of varmint shooting I have used the Hornaday 32 Grain V-Max bullets exclusively with good results, accuracy is usually around 5/8-3/4 MOA. I hope to take my kill zone beyond 350 yards this summer so I wanted the ballistic advantage of the Sierra 39 Grain SBK. (Many on this forum have had good results hence my choice).
Over the winter I installed a new SSS Competition recoil lug and bedded the action on my Savage 12 VLP, (Unfortunalty my Shilen barrel is still in production so I guess the factory tube will be used this season). All my brass has had the primer pockets uniformed, trimmed, annealed, neck turned (just cleaned up about 25-50% of neck surface). All loaded rounds were checked for runout, those over 0.0015" were used for foulers. For testing the OCW method was chosen over the Auddette ladder method for these reasons....
-200 yard max range
-don't have spotting scope to see .20 cal holes beyond 150 yards
-wind is always a factor here in southern Alberta
I began the day by zeroing the scope with some factory rounds, then cleaned barrel and tested my Hornady 32 Grain V-Max bullets using Hornady brass, H322 powder, and CCI BR4 primers. After 2 fouling shots this test pretty much confirmed that the load I had been using previously for these bullets was the one to stick with. The surprise came when switching to the Sierra 39 Grain SBK's pushed by H4895 powder and the same brass and primers. My two foulers (after complete cleaning) impacted to the left and all of the 39 Grain SBK test groups impacted about 1.5 MOA to the left of where my 32 Grain handloads, as well as 32 grain, 40 grain, 45 grain factory loads had.
Now all the factory loads were Hornady bullets and they printed the same POI while the Sierra bullet was the difference when the POI changed so I suspect bullet brand more so than bullet weight is the cause of POI change.
Should I try 40 grain Hornady or maybe Nosler to see if POI remains consistent?? Or maybe I should abandon my "proven" 32 grain V-max and try to see if the 32 Grain SBK's have the same POI and the 39 grains. (I have yet to sort out all data on velocity deviation and group sizes but at a glance I wold have to give the edge to the Sierra bullets for accuracy)
Or am I asking for to much to be able to swap between bullet types depending on shooting conditions???