Horizontal POI changes???

[surfclod]

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???

[OldTurtle]

In both of my .204s, if I change bullets, even with a minor change in bullet weight, my point of impact and group size will change as well..

That's using the same powder, primers and brass that was prepped at the same time. I will usually prep a large number of cases, including the primers so all I have to do is charge them and seat the bullets and I'm ready to go..

Since my .204s are used for Prairie Dogs and punching paper, I just stick to one combination....Fortunately both rifles seem to like the same loads..

Once in a while, I'll run some factory loads, just to verify the results since I have a bunch of them in reserve..

[Qtiphky]

Not unusual. I just worked up a bunch of loads for both my 204 and my 223. Every different powder weight, with the same bullet, had a different point of impact. Some went up, some went down, left, right, whatever. The harmonics of the gun dictate where the bullet will go and each change in the load, whether it be powder, powder charge, bullet, bullet weight will have some slight difference in the poi.

For example, I just shot test loads for 34 grain Dogtown bullets out of my 204. While I was going for groupings to determine the best load, each load impacted at a different location compared to the bullseye. I was using Varget and loaded 26, 26.5, 27, 27.5 and 28 grains. They all shot pretty good groups, now I just need to decide on a load and sight it in.

Here were their POI's in comparison to the bullseye.

26 - .5 inch high, .25 inch right
26.5 - .25 inch low, 1 inch right
27 - .25 inch high, 1 inch right (spread of .35 inches, best load)
27.5 - .25 inch high, 1.5 inch right
28 - .34 inch high, .5 inch right

The 223's were even more exciting in where they impacted. I changed, powders, powder weights and bullets. More data to sift through than time permits here, but the point is, yes, every little change you make in a load MAY change your point of impact.

Hope this helped.