Main question is in the subject line.  Basically, I am trying to pick a load for deer hunting this year (never been deer hunting and yes, my only rifle is my AR-15).

Others suggest I go with something a bit heavier, like a 64gr power point.  What if I sight in with this?  How much "off" will Q3131 be?

That depends largely on what 55gr bullet you use to sight in for hunting.  Even though a bullet may have the same weight, different bullet types will have different flight characteristics based on length, base design (boattail vs. flat point), tip design (hollow point vs. polymer tip vs. soft point), etc.  Also, assuming you are not handloading all yourself, different powder charges and types used by different manufacturers will have a major impact on bullet impact downrange.  I have no experience with Q3131 specifically, so maybe some others can help with that, but I think you would need to give a specific hunting cartridge that you are considering for folks to help you out a little more.

Ah well screw it, I guess I'll just sight in my new (first) ar with the Q3131 plinking stuff then right before hunting season sight in with the hunting ammo.

Quoted: Ah well screw it, I guess I'll just sight in my new (first) ar with the Q3131 plinking stuff then right before hunting season sight in with the hunting ammo.

Good answer!  Always re-zero when changing ammo.

That would be ideal, but the difference is pretty small so you could get away with just using your Q3131 zero.

According to Winchesters site:
Q3131A = 3270fps, BC .267
PP 64gr = 3020fps, BC .234

Using JBM Ballistics Calculator you can put in the data for the Q3131A and then note the Elevation setting.  Put in the 64gr data and the Elevation setting, then uncheck "elevation correction for zero range" and see where they'd go.  

Using a 50yd zero for the Q3131A (the Improved Battlesight Zero) the 64gr actually tracks POI closer to POA than the 55gr out to about 225 yds, without changing the settings.  After that the 64gr drops off fast.

Quoted: Quoted: Ah well screw it, I guess I'll just sight in my new (first) ar with the Q3131 plinking stuff then right before hunting season sight in with the hunting ammo. Good answer!  Always re-zero when changing ammo.

Bingo! Slight variations in powder, bullet composition, ballistic coefficient, etc will have an effect on how well your rifle shoots any particular ammunition. If you want it to do double duty, just sight it in for one, then shoot a few groups of the other and remember where the other ammo hits, then adjust your aim.

Edit: Generally, bullets of the same weight will have the same theoretical POI. The groups sizes are what will vary.

I actually did a little test once that may hel answer your question..

I zeroed my Bushy 16" HBAR and Compact ACOG at 50 Yards using Federal XM193. I then shot 5 round groups at 100 yards for the following ammuntion. Black Hills Blue Box 60 gr sp, Winchester Power Point, Wichester Power Point Plus, Federal Classic HiShok 64 JSP, and Remington 55 gr SP.

I also shot a 5 round group of XM193 as a control, and each group was shot on it's own bullseye target.





What I found for my rifle is that the BH BB 60 gr SP and the Remington 55 gr SP were almost dead on the same as the XM193, and they grouped slightly under 1 inch at 100 yards. The Federal 64 gr was low and to the left about 2 inches but groups were still about an inch. The Winchester 64 gr Power Points were about 5 inches to the left and grouped about 1 1/2 inch. The worst was the Wichester Power Point Plus, 6 inches low to the left but the group was about 3 inches. Still that is fine for deer hunting.


I did this for shits and giggles because I had the time and the ammo, and I wanted to see how this rifle would handle the different loads. I may try the same thing with my 1/7 twist LMT upper to see if the different twist rates affect performance.

-sc