Bipod Experience

[WyoHunter]

I use a bipod when hunting antelope here in Wyoming. Have any of you experienced your rifle shooting higher than it should at ranges of 350 - 400 yards? Although I eventually got him I missed a good buck antelope at 385? yards by shooting over him twice. I shoot a .257 Weatherby Mag sighted in 3" high at 100 yards and according to ballistic tables for 115 gr Nosler Partitions I should have been 4'-5" low at 385 yards. I held slightly below his back and both times puffs of dust indicated that I hit high. Both holds were solid from the Harris bipod and the sight picture looked good when the Mark V went off. Any ideas or personal experiences with bipods would be appreciated.

 

[Michael Eichele]

First off, congradulations on getting your buck. A bi-pod shouldnt make that much difference, but that is subject to many things. One thing could be how well or well not the barrel is floated. Chances are if you are useing 100 yards to sight your rifle in at and using charts to do the rest, this is enough to make one bald. See what your rifle is doing at 300 yards, then check that to a "chart" The best thing to do of course is shoot your rifle and load with the pod at 100, 200, 300, 400 and 500 yards. If you want a 300 yard zero, zero it at 300 yards, NEVER at 100 yards at X amount high, this is ok for a place to start. Even according to a chart there are enough variables to mess it all up. By tuning at 300 yards, all the issues have a chance to iron themselves out.

Good shooting and happy hunting!!

 

[Perkules]

Yep,Michael is correct. The tables only give a hint,loads must be grouped and confirmed in the real world ,no matter what chronographs or tables one is using at 100 yds. Holding over is not the best way to go,one is better off by adjusting the scope to the (hopefully) known distance.

This is from a 257 Weatherby page,by Chuck Hawks:

In addition to Weatherby, Federal Cartridge also loads for the .257 Magnum. Federal offers two Premium loads, both with 115 grain bullets at a MV of 3150 fps and ME of 2535 ft. lbs. One is a Nosler Partition bullet, and the other is a Trophy Bonded Bear Claw bullet. At 300 yards the velocity of the Nosler bullet is 2440 fps and the remaining energy is 1515 ft. lbs. At the same distance the Trophy Bonded bullet is traveling at 2400 fps and retains 1470 ft. lbs. of energy. The trajectory of both bullets is very similar, with the Nosler bullet shooting just slightly flatter due to its somewhat superior ballistic coefficient of .389. The trajectory of that bullet looks like this: +3" at 100 yards, +3.3" at 200 yards, +1.7" at 250 yards, -1.2" at 300 yards, -5.5" at 350 yards, and -11.5" at 400 yards. With this load the .257 Weatherby has about a 335 yard point blank range on medium size big game animals.

I played around with "Ballistic Basics Pro". Assuming the real velocity was not 3150 but 3000 fps for whatever reason and exactly 3" high at 100 yds the drop at 380 would be 11-12"... just an example. What kind of velocities are you getting? And how does it group at 100, the group size is at least four times that at 400, adding more error? Are you absolutely sure you missed high,not low? That distance is where it starts to drop fast,20 yards more and the drop is 13". What if it was closer to 400 yds after all?

Or what if the distance was only 340 yds? Then,with the MV being 3150 fps, 3" high at 100 the drop is only 4" at 340... easy to shoot too high when the group size variable takes it high another three inches,for example. Just theory here,you had a question mark in the "385?" yards.

Looks like I have some extra time now... please don´t get my "what if:s" wrong,trying to be helpful here,waiting for the mailman to bring some bullets...and of course: Welcome to the forum and congrats for the buck!

EDIT: Also,if your scope is mounted very high (2" center-to-center) the drop becomes even less in the 340 yds scenario, only about 3". I know,only one inch less but if your rifle shoots 1 MOA it may take it high another 4"... Endlessly variables in this game, that´s why I like it.

Where is the mailman?

[ 10-16-2003: Message edited by: Petander ]

 

[Mysticplayer]

wyohunter, I am guessing that you did your load testing with a bench and front/rear rests. You then switched to a bipod during the hunt. If so, bad idea as you have found out.

bipods make all rifles behave differently then when shooting off a pedestal rest. Bipods are prone to bounce and certainly the rifle rests on a different spot. Another thing is that the stud used to hold the bipod may be hitting the barrel causing different harmonics (this happened to me).

lastly, your body position and eye relation to the scope may have changed leading to difference in sight picture and recoil control.

so do your drop table and practising under the conditions you are planning to hunt, always. If shooting prone off dirt or off the hood of a truck, work on your shooting from these positions to ensure that the variables during recoil are accounted for.

Better yet, practise under all the different set ups you might use in the field. You will be surprised at the results.

Jerry

 

[Bruce Hanson]

Wyohunter, good afternoon,

I have noticed on a couple of my rifles it makes a difference on what my bipod sits on. It shoots high if my bipod rests on stone, or hard ground, and right on when I rest my bipod on sod. Also, here in North Dakota if I zero at 100yards and go to Wyoming or Montana, and hunt at 5000 to 6000 feet elevation, I will shoot a couple inches high.

 

[Vern Harrison]

Hi WyoHunter,

At what angle was your shot taken? Was there any head or tail wind??

Vern

 

[versarest]

Great successful hunt at that range. We have also noticed with all the testing we have done that your not alone. We have found comparing the bi-pod to the Versa-Rest that some positions more than others cause
the bi-pod to jump during recoil. We solved that problem with a "Shot-Shock". Just an idea.

 

[WyoHunter]

Whistle pig.... I was shooting at a slight uphill angle.
To all the rest who replied thank you. I'm going to shoot it at the different yardages and do it off the ground similar to when I'd be hunting. Also the barrel is free floated and the rifle consistently shoots 3/4" at 100 yards. I'll be doing more shooting at the range to verify my trajectory. Thanks again for all the advice it is appreciated. A pic of my antelope follows.