.270 question

[gonehuntin68]

I have a Browning A bolt Medallion .270 I sight in about 2 inches high at 100 yards and it shoots about 2 inches low at 200 yards. Does this seem normal? I have been shooting the Remington Core Loks 130 grain with good groups. Thanks Guys or Gals.

[Biggerhammer]

All depends on your scope adjective size and your ring height. In other words the overall distance from center of bore to the center of the optic/scope.

[gonehuntin68]

The bottom of the front of my scope is about a half a inch from the top of the barrel. If that helps.

[rover758]

I think I'd have to agree with bighammer.  It isn't so much where the bottom of your scope as it is the distance from the center of your bore to where the crosshairs are.  I shoot a Remington 700 BDL .270 which I bought new back in 1976.  I put a Redfield 2x7 Accutrac scope on it.  That is a rectangular scope versus a round scope.  It's very low profile and I'll wager the distance from my bore to crosshairs is 1/2 inch less than what you may have.  I shoot the same 130 grain bullet that you mentioned and sight the same 2 inches high at 100 yards.  When I move to 200 yards I'm dead on.  (Shooting from a table with a good bench rest.)  You may want to check the manufacture's specs on ballistics (bullet drop) and try a box of ammo that has a higher muzzle velocity.  Not all manufactures put their specs on the box.  For example, my Fusion 7mm mag ammo says at the muzzle it's 2760 fps, 2590 fps and zero at 100 yards, and 2430 fps at 200 yards with a -3.6" drop.  So, with my 7mm, if I sight 2 inches high at 100 yards theoretically I should be in the neighborhood of 1.6" low at 200 yards.  More to the point of what bighamme said, the box also says "Height of bullet trajectory is in inches above or below line of sight if zerored at 100 yards."  And, then the most important point .... "Sights 1.5 inches above bore line."  It really does matter how far your crosshairs are above your bore.

[jrebel]

I guess I don't understand?  Ballistics should be 2" high at 100 = dead on at 200 (real close) and approx 7 inches low at 300.  Why would your scope mounting have anything to do with it?

Please be patient as I am trying to learn...but all my .270's have always been this way, regardless of the scope.  I shoot 150 grain bullets and these rules have always pertained to my shooting. 

jrebel

[mountainman]

The higher the scope is above bore. The higher the 200 range impact will be. The lower the mount, the lower the impact will be perceived. In essence, the higher mounted scope will effectively gave the rifle barrel pointed higher, resulting in a longer point blank range.

[gonehuntin68]

I was doing a little research on the core lokt and some say its a fast dropping bullet. Anyone have that experience?

[bobcat]

I was doing a little research on the core lokt and some say its a fast dropping bullet. Anyone have that experience?

It may have a slightly lower ballistic coefficient than some other bullets, especially boattails, but it's certainly not going to be a significant difference until you get well beyond 300 yards.

[Bob33]

According to Remington the .270 130 grain Pointed Soft Point Core-Lokt bullet has a ballistic coefficient of .336. While low, that's not low enough to explain an impact of 2" low at 200 yards, if the load is hitting 2" high at 100 yards. Even with a scope mounted 1" above the bore (which is almost impossible), and a moderate velocity of 3000 ft/second the bullet should still be slightly above point-of-aim at 200 yards.

That said, a 2" low impact at 200 yards could  easily be shooter or ammunition variation. My guess is that with a large enough sample you would not see an average 4" drop from 100 to 200 yards.

[gonehuntin68]

Hmmmm. Thanks guys, Probably is just me, need to spend more time at the range. 

[RadSav]

It may have a slightly lower ballistic coefficient than some other bullets, especially boattails, but it's certainly not going to be a significant difference until you get well beyond 300 yards.

I agree with Bobcat on that one.  Not specific to just the Core-Lokt.  But similar in all B.C's around 400 or less.  Though I doubt many will notice inside 600 yards with a 270.

The .270 Win's that I have had were all sighted in to 3" high at 100 yards.  That put zero around 270 yards depending on load and barrel length.  My old S&W (Husqvarna I believe) loved the Core-Lokt and with it's 22" barrel it held zero at 268 yards and was -3" at around 310 yards.  I was shooting it with a Leupold scope 3-9X40 with medium rings.

[Wazukie]

According to my range software, Ballistic AE, the Remington 130gr Express PSP Core-Lokt  has a BC of ,336(G1)  and a Muzzle Velocity of 3060 FPS at 10ft.  In perfect conditions with a 100 yard zero, 2" high and sight height 1.5", at 200 yards impact will be .99" high. 

You should be .02" high at 31 yards and .01" high at 223yrds.  5" drop at 294 yrds.  This is all with perfect conditions, no wind and at sea level.

Cheers

[coachcw]

Every gun is a bit different . my 270 is 1.25 hi at 100 and zero at 200 with hornady super performance sst's. don't rely on charts shoot your weapon , fresh ammo makes a difference . after a couple years the copper and brass will stick .