Severe bullet weight POI Shift

[cdwjohnson]

A WTF moment in shooting.

Back story: I built my lr308 with a .308 20” barrel named the comet. The upper (and lower from same manufacturer) has. 20 moa built in. Dropped a good scope on it and called it ready. As with most all lr308 I went through the mag function problems and ftf, fte, ftho problems and now it runs perfect.

Perplex: when shooting handloaded or factory ammo. 147/150gr vs 168. Win white box. HMS. Federal. I have a massive 20” (yes 20 inch) POI SHIFT. I HAVE TO COME UP 20ish moa to re-zero for 168 gr after 150 gr.

Detail: factory load checked out over chrono. My hand loads are considerably faster. 100-250 fps. I have been reloading for years and the factory longer than me. 168 federal 2625. Hand loads 2780. Both are Sierra 168 HPBT. RELOADING 150’s next. 2 years ago I loaded 150’s to 2900 fps. Load is still in chrono app. All loads are safe with no pressure signs to speak of.

Has anyone ever seen this before.

 

[gigamortis]

I've seen a 7" POI shift at 100 yards on a friend's 30-06 sporter weight hunting rifle between two different factory loads. One load was low recoil Federal Fusion, and the other load was Remington Core-Lok. Rifle barrels definitely have their own personalities with different ammo recipes. The different loads you are shooting are definitely leaving the barrel on opposite whip directions for sure.

Perhaps a barrel tuner device will help close up the POI differences. I can see the value of tuners and tuner/brake combos if you are trying to optimize accuracy with factory ammo. For hand loaders, the perfect load can be custom tailored for that particular barrel and no tuner will be needed.

 

[RegionRat]

Has anyone ever seen this before.

It does sound like a bigger shift than normal.
It isn't large if the context is things like light guns shooting heavy recoil as in big bore pistols, but with a rifle this is a bigger shift than typical.

If I were you, I would not shoot till I went over the rig with a critical eye on everything, but especially any loose threaded fasteners, optics, sights, barrel nuts, stocks, etc.. I would also chronograph the two different types of ammo and shoot from front/read bag rests.

Recoil is the first mode of any gun with all the structural modes and their flex being secondary. If the gun is being shot from body support, there is a chance this was all just technique and recoil, but to be on the safe side I would check the whole thing over.

 

[cdwjohnson]

Yea… again? No! GOD NO!!

 

[Dead Eye Dick]

Had an XP 100 chambered in 7BR that showed almost that much shift to the right when I swapped a 140 grain Sierra to a 145 grain Speer. As I understand it (take not with a grain of salt, but with an entire Salt MINE) the way the bullet leaves the barrel has a lot to do with poi shifts. (Different lengths, different bearing surface length, different length of boat tail.).

 

[cdwjohnson]

That’s kinda where I’m at. I just thought of a test. Get or reload some 150, 168, 180, maybe others too and see which hit closest to each other. As most reloaded understand… you don’t shoot what you like you shoot what the gun likes.

Nice to see I’m not the only one.