Real world drop

[MuleyFever]

I sighted in my 280ai at 100yds with factory Nosler 140 ABs this morning then shot at 200 and 300. My drops were about 3.5" and 13".

My average velocities the last 2 times out were 3270 and 3262.

I am no where near what the ballistic charts show for drops at 200 (2.2") and 300 (8.4"). I have to put in a velocity of about 2825 to get the drops to match. I am using a G1 BC of .485.

Any ideas?

 

[ChrisAU]

What is your barrel length?

 

[MuleyFever]

24" with a 9 twist.

 

[VAHunter01]

Are you measuring your actual drops or going off what your scope is supposedly dialing?

That also seems a bit fast, have you checked your chrono?

 

[MuleyFever]

Yes, I measured the drop on the target. No scope adjustments. I agree my chrono could be off but not that much. I don't see 2825 as a realistic velocity. I have heard Nosler BCs may be suspect. Any truth to that?

 

[VAHunter01]

Yes Nosler’s published BCs are often inflated, but that still wouldn’t cause it to be off that much at short ranges.

So, since it can’t be scope adjustments as you weren’t using them, next place to look is velocity.

Parallax can cause weird issues as well.

 

[bradb]

Scope height above gun, correct?

 

[ChrisAU]

How far from the end of the barrel are you placing the chrono?

 

[ChrisAU]

And yeah I didn’t even notice, that is a screaming velocity. I assume 140 AB? Even Nosler only claims 3150 and it’s probably actually around 3000.

 

[MuleyFever]

I shoot in the morning before the sun hits me to minimize any effects on the chrono or mirage. Chrono is at about 10'. Scope is at 1.5" from what I can measure. I try to adjust parallax.

Any idea of a more reliable BC on the 140ABs?

So best just to shoot groups and average the drop and go with it? I don't want to go real long range. Just hope to dial to about 500 if I can get acceptable groups.

 

[deadwolf]

Sounds like you’re sighted in at 100, I’d shoot in 100yrd increments to 500, then use your correction at 500 to determine your actual muzzle velocity. That being said, if your 140 is dropping 13” at 300 then something is really out of whack.


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[MuleyFever]

Leica Geovids. Its a public range with markers as well at 100, 200 and 300. I use my rangefinder to verify as the markers are a yard or 2 different than my rangefinder.

 

[16Bore]

The only number Nosler gets correct is their phone number.

Seems like a .190 BC or a velocity of 2,800 FPS.

 

[MuleyFever]

Its hard to wrap my head around a velocity 350fps slower than advertised by Nosler.

 

[N2TRKYS]

I've found Nolser velocities to be pretty dang accurate for my rifles. Idk or care if their BC numbers are correct, though.

 

[Muley Buck]

Its hard to wrap my head around a velocity 350fps slower than advertised by Nosler.

It seems to be that way for me also. Don't sweat it, what really matters is finding a true arc of where that bullet is actually going so you can be more precise with your shots. Pretty sure my chronograph is constantly reading high, because all of the bullets I end up putting through it end up lower on the target also. I drop my MV to match the correction needed usually out to 800 but sometimes closer depending on the bullet and it's capabilities. Then shoot at 100 yd increments all the way back out, starting at 100 or 200 yds in order to fine tune my desired POI.

 

[Tumbleweed]

Tell us about your scope, no one's talked about that yet. If it's under tracking your impacts will be low. Has the scope been tested against a precise MOA grid or a box test performed?


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[VAHunter01]

He wasn’t dialing. That was my first thought as well.

 

[MuleyFever]

Yes, not dialing, just trying to find the trajectory using the drop. The scope is a SWFA.

I grabbed another box of ammo yesterday and went back out this morning, and forgot my targets.

I had brought some 150LRABs and was able to find a box someone left behind and shot at 100. I just wanted to confirm they don't group well as the last time I shot them was before I did anything to the rifle. Still shot poorly so that's confirmed anyway.

I will head back out next weekend and shoot a little farther. We have a long range section but the berms are at random ranges. One is at 420yds so I will shoot that. I think the next one is at about 700 and I just don't shoot well enough with this rifle to get any reliable data at that range. I really think my real world max range with this rifle will be about 400 anyway so that will give me a confirmed drop and some confidence. At least this year and with factory ammo I don't expect to push it any farther.

 

[16Bore]

Tell us about your scope, no one's talked about that yet. If it's under tracking your impacts will be low. Has the scope been tested against a precise MOA grid or a box test performed?


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I don’t think he moved the crosshairs, but that would be part of the picture if he did.

I shot a 500 yard target 150 LRAB’s in the same manner and my group was right at 48-50” below POA. Actually worked for about a .550-.575 BC.

Then I decided 350 yards was enough to worry about all that kinda stuff went out the window.

Edit: 270 Winchester, MV=2,840