Range Report Strange ammo behaviour...

[spawn_mm_jtf2]

I hope I'm posting in the right place... Let me introduce my self before going with my issue.
I'm Stéphan, from Northen Québec. I'm 27, teacher, hunter. I was looking for a long range weapon on a extremly tight budget. Please know that that rifles and mamunitions are much more expensive here in Canada. I wanted a Savage 10FCP in .308 or a Remy 700... but they were either not available here, or well over 1000$. So please, don't flame me for having bought a mossberg. Has my sig say, I have bought a Mossberg 4x4 in .270 and top it with a Millett LRS-1, low rings, bubble level. Total cost: 1050$CDN.

I start shooting two mount ago... I got 200 rounds down the tube so far. I've try three type of ammo so far: Remi Cor-Lokt 130 gr., Fusion 150gr and Hornady SST 140gr.
No need to tell you which one groups the best.. but may be I can surprise you with numbers.. best 3 round groups (Haven't shot 5 rounf one yet)
Fusion 150gr: 1.25 inch at 200yrd
Hornady 140gr: .90 inch at 200yrd
Euh... this is like, .5 MOA right??? From a 500$, hunting grade .270 rifle it has to be good no?
I shoot from the prone position, trigger set at 2lbs, barrel cleaned every 15-25 rounds...

Okay, I'm sure you got the picture... Here is my issue... scope is centered at 200 yrd with the hornady SST. Yesterday, tried my Fusion on the same target..it should have hit a little bit lower...but surprise surprise.. every fusion roungs were landing 2 inches HIGHER!

Here are the official speed for those two ammo:
Fusion: 150gr @2850 fps, BC .460
Hornady: 140gr @3090 fps BC .495

My LOS is 1.5 inches above my LOB. Outside air temps was around -5C when zeroed, yesterday temps was +7C (25F??) POI was not really changed by this little temp difference...

So, any of you have a clue of why the heavier, slower bullet were landing 2 inches above my POI at my zeroed range?

Thanks a lot guys!!!

 

[Topstrap]

Re: Strange ammo behaviour...

Possibly the slower/heavier round is taking longer to exit the barrel which is rising due to recoil (contrary to some arguments on here) which will make it hit slightly higher. Further out it'll have the same POI as the other round then it'll start to drop off.

Just my thoughts but I'm no ballistic engineer.

Topstrap

 

[spawn_mm_jtf2]

Re: Strange ammo behaviour...

Possible, forgot to say, it's a 24 inches barell, with a 2 inches ported MB, total lenght, 26 inches...

 

[spawn_mm_jtf2]

Re: Strange ammo behaviour...

Looking at it from your perspective Tops, I might be able to mix load those two ammo in my clip for bear and moose hunting... Most of our shots are under 300 yrd.. I would shoot this litlle caliber any further on a big game any way... I'll have to test it at 300 and 100 to see how it hold.. Considering the size of the killzone for my two games... It's looking good. Awkward, but in a right direction for hunting... By the way, I'll test the SST at 400 and 600 yrd this weekend if it's not too cold... -30C like we had in the last months tend to kill MV no?

 

[jwoolf]

Re: Strange ammo behaviour...

When I load and shoot ammunition, when changing from load to load, I find that the point of impact changes. It's likely that this is what you're seeing. Different ammo having a different point of impact.

 

[spawn_mm_jtf2]

Re: Strange ammo behaviour...

Yeah, I was not expecting both to have the same POI, but my understanding of physic law were telling me it was gonna hit lower... I think the explanation higher that said that the fact the bullet is slower by 300 fps let it spend more time in the barrel thus be more influanced by the recoil motion of the rifle... The stock Mossberg stock might let the barrel to jump more under recoil than a good tactical stock would...

 

[timelinex]

Re: Strange ammo behaviour...

To be honest, unless you've shot alot of rounds then I wouldn't find this interesting at all. What I mean is that a 'floating zero' is a pretty common experience, unless you zero with alot of rounds. So even though you zero'd the first ammo, it might not really be a solid zero. 2 inches at 200 is 1moa, so not that drastic. Add a little parallax error into both zeros and your observation isn't too crazy.

 

[spawn_mm_jtf2]

Re: Strange ammo behaviour...

I understand, I'll go shoot a box of each in alternance: 1 sst, 1 fusion, 1 sst, 1fusion so on. Probably next weekend. We'll see what it gives...40 rounds should be a good ground to base my observation on?

 

[Augustus]

Re: Strange ammo behaviour...

Shoot them both at 100 yds, the two loads probably will not have the same POI. I bet your mystery will be solved.

 

[spawn_mm_jtf2]

Re: Strange ammo behaviour...

BTW, Timelinex, Nice 'vette sir!