.17 HMR sight in issues, need advice

[Coyote3855]

My truck gun for ground squirrels is a New England Firearms single shot with a Leupold 3.5x10. Checked it out yesterday after missing some easy shots. Over a solid rest, it's right on at 25 yards, but about an inch low at 12 yards with Hornaday 17 grain bullets. I've looked at trajectory charts that show the over/under bullet path for 100 yard zero. One chart and table for the 17 grain shows 1.5 low at the muzzle, .48 low at 25 yards, .15 high at 50 and .34 high at 75.

So I understand that the bullet crosses the line of sight twice between the muzzle and 100 yards. but an inch difference between 12 and 25 yards seems excessive? Extrapolation from the chart would indicate perhaps the 1 inch difference is normal?

I only shoot nuisance rodents on my own property. Most of my shots are between 10 and 35 yards. My advanced age and infirmities mean I can't hold close enough for longer distances. I can only shoot 3/8" to 1/2" groups at 25 yards. I understand the cartridge/rifle/scope combination is capable of much greater accuracy but I am not.

Any advice about sight in distance or other corrective measures would be appreciated. My current plan, absent input here, is to hold over on the closer shots.

 

[Milt1]

Before I would do anything else. I'd have the trigger pull tested to see where that was at. It should be down to around 2 & 1/2 or 3 # pull.

 

[Fine Figure of a Man]

Differing scope height and velocity will change the holdover values. If you are going buy published velocity, it is unlikely yours is the exactly the same.
I'd zero the rifle at the distance you shoot most often, then shoot at 15 or 20 yards closer and farther and take note of the hold over/under.
Another thing with 17's is fouling in the small bore will ruin accuracy. My 17 is amazingly accurate as long as I keep it clean.

 

[LoonWulf]

Short range deviation from sight path can be affected by scope over bore height. If that leupy is a 50 and mounted high youll have more deviation than expected.
I believe most drop tables use a 1.5" over bore height.

 

[RecoilRob]

Yep....the scope is mounted high on that rifle so it's going to shoot low up close. If most of your shooting is going to be around 35 yds...why not just zero there? Anything longer is going to shoot high out to pretty far, but if that kind of shot is rare then it shouldn't be a bother...plus you can use one of the available trajectory calculators to see what it would do out farther should you ever want to use it.

 

[redbullitt]

Definitely measure your scope over bore. I bet it is not 1.5 inches. A little difference here can show up more than you would expect.

Chronograph of your actual rifle and ammo would be helpful too, though I would lean more towards the scope height being an issue.

 

[Coyote3855]

Difficult to get an exact measurement of scope over bore, but as best I can tell it's about 1 3/8", so correct that it's a bit less than 1.5". I cleaned the bore as drunkenpoacher suggested. Managed a 3/8" group at 25 yards, but still about 3/4" low at half that distance. One group at 12.5 yards all holes touching, another 1/4" center to center. If the wind dies down (unlikely in Wyoming), my next experiment is to where it hits at 50 yards. I'm betting it will be a bit high as RecoilRob speculates. I appreciate all the input, thank you.

 

[RecoilRob]

Difficult to get an exact measurement of scope over bore, but as best I can tell it's about 1 3/8", so correct that it's a bit less than 1.5". I cleaned the bore as drunkenpoacher suggested. Managed a 3/8" group at 25 yards, but still about 3/4" low at half that distance. One group at 12.5 yards all holes touching, another 1/4" center to center. If the wind dies down (unlikely in Wyoming), my next experiment is to where it hits at 50 yards. I'm betting it will be a bit high as RecoilRob speculates. I appreciate all the input, thank you.

Quick question: are you measuring from center of bore to center of scope? I just looked online for Leupold 3.5x10's and am coming up with either 40 or 50mm versions, then comparing some 40's hanging on the wall even when very nearly touching the top of the barrel they're well over 1.5" and I'd really expect yours to be the same or higher.

In the end it really doesn't matter all that much, if you're normally shooting up close...zero there and it'll be slightly low in closer or slightly higher farther away. Just remember that the closer you zero the steeper the bullet must rise to meet the line of sight...and therefore the higher over the LOS it'll fly until coming back down across at some much greater distance.

We used to set 'Battle Sights' at 1000" with M-16's which then had the bullet crossing back down somewhere out around 200yds.

 

[Coyote3855]

Yes, I tried to measure from approximate center of bore to center of scope but it wasn't exact. I agree this and all the other factors don't matter much at the ranges I'm shooting. I did a couple of groups from 50 yards and as expected, about 3/4" inch high. Since shoots to point of aim at 25 yards now, I'm going to leave well enough alone and remember to hold over for close shots. Your warning that a closer zero causing a steeper rise is good advice. Thanks to all for comments and advice.

 

[mountian girl]

loonwolf,,,have you seen broc luno on here,,,tell that feller ;;don"t anticapate tha shot,,,breatheeeeeeeeeeeeee,,,tyvm,loonwolf,,oh i found some ammo,,,thanks guys

 

[LoonWulf]

loonwolf,,,have you seen broc luno on here,,,tell that feller ;;don"t anticapate tha shot,,,breatheeeeeeeeeeeeee,,,tyvm,loonwolf,,oh i found some ammo,,,thanks guys

Havent recently, but i havent been on that much... tho im sure he'll wander by eventually.

 

[mountian girl]

loonwolf,,a friend o mine,,say jd i got a old war rifle that look like that,,i bring it,,,it was a brother to tha 1 i got,,,li"ll rust,,,chrome bore,,c. bolt,,it got tha airplane wing rear sight,,,all bands,,best i can tell match,,,he say jd,,,merrrrry christmas,,i say ty,sandy claus,,wow i liked to fliped,,,they is no wood on top,,,,boyyyy,,,that is hard to b found,,,tha mum is gone but not tha jap type 99,,,crooked letters,,,,nayaga arsenial,,,type 3 i think,,i kant see that good,,,b safe & tyvm,,,,jd & mtn girl