Trajectory Problem?

[al4x]

Been there done that shot straight over its back I dont know who was more surprised me or the buck it stood there long enough for me to reload and I repeated the shot I mean repeated exactly missed over its back at 20 yards at this point buck decided I was useless and walk off I had to agree with him and packed up and went home to meet up with my mate jack Daniels

 

thats pretty strange as at very close range scopes shoot low, simply because the barrel is 1.5 to 2" lower than your cross hairs. I had a reminder of this at the weekend when I went a little low on a roe at 8 Yards or so nicely still visible in the scope though the target was rather large

[Harnser]

 

 

To be honest, this is what I could do with - some practical knowledge. The 'ammo in the box' appers to be in good condition and all indications are that it's leaving the barrel at the speed it should, it groups very accurately but does not impact where previous experience says it should throughout its trajectory.

 

From your experience, what do you think could be the problem(s)?

For many years I have only shot home loaded ammo in my .308 .I have developed a load that shoots where I point the gun (150 grain soft point driven by 45 grains of vit 140 ) this load performs time after time with out any problems at all . I do have some factory loads in my cabinet and have tried them quite recently in my ruger and found them to shoot 3inchs low and 4inches to the left of my home loaded ammo . Proberbly not a fault with the ammo ,just a different load as I am sure that I could zero the rifle to shoot the factory ammo .

 

A long shot for me is 200 yards and most of my deer are shot at 100 yards or less .As you know home loaded ammo is more consistant than factory loads if loaded properly . I weigh every load on the scales for consistancy . UnLike some people I dont go overboard with case prep ,but do tend not to use cases to many times and I allways but allways crimp . Incidently the best group I could get with the factory ammo (Norma )was 3inches at one hundred yards as opposed to MOA with the home loads and I did notice quite a few flyers with the factory stuff .

 

For accuracy and consistancy home loads are deffinately the way to improve accuracy . Being confident in your ammo is a big plus .Being not confident in your given load will cause stupid misses .

 

Harnser .

[Gerry31]

 

 

thats pretty strange as at very close range scopes shoot low, simply because the barrel is 1.5 to 2" lower than your cross hairs. I had a reminder of this at the weekend when I went a little low on a roe at 8 Yards or so nicely still visible in the scope though the target was rather large

[Gerry31]

It is more to do with the IIC. rule then the scope. Idiot in charge. I just panicked I think it was the first time id ever been so close to my qarry

[coyotemaster]

Hi Phil,

BCs are often a lot different than advertised and do change somewhat with MV. I do think you ae going the correct direction in trying to determine bullet path through ballistics, it is the best way to short cut firing from numerous distance provided you have the correct BC and MV. Taking full advantage of trajectory is what makes rifle shooting interesting. I dial in high at 100 and check at 300 and then can figure in betweens accurately.

[Vermincinerator]

Hi wymberly, i think another chrono session may be in order mate, i can only think that a change in velocity would be responsible for your impact change.

 

Ian.

[wymberley]

Hi wymberly, i think another chrono session may be in order mate, i can only think that a change in velocity would be responsible for your impact change.

 

Ian.

 

Yep, I've got a slack handful of rounds loaded to see if I can bring the 100 yard velocity up to where it should be for the existing MV even though this will inevitably push the MV up a tad (while I'm at it, I'll poop a few rounds of various factory loads down to check the chrono'). I've got a few to also check that the existing superb accuracy (grouping) is not messed up. After that, it's all on hold as the harvest is finally underway and it's bunny whacking time.

 

Actually, Yarmite has a point with his uphill down dale idea even though I tried to make sure (at the risk of breaking my neck - why do all the best fields have to be full of cows?) that as the range altered I was keeping a horizontal aim. So I'll look into that too.

 

Cheers,

Phil

[simon6ppc]

ive spent years reloading amo and just trying it out,thats what i enjoy doing. i think to many people depend on computers these days.but saying that ime on one now,but like other guys ave said just get out there and try it out...

[wymberley]

ive spent years reloading amo and just trying it out,thats what i enjoy doing. i think to many people depend on computers these days.but saying that ime on one now,but like other guys ave said just get out there and try it out...

 

To be honest, getting a tad hissed off now.

 

You have two knees, two hips and one back. How many of the 5 are in full working order?

 

If you're out there and trying it, I'll wager that the answer is four more than me.

[simon6ppc]

To be honest, getting a tad hissed off now.

 

You have two knees, two hips and one back. How many of the 5 are in full working order?

 

If you're out there and trying it, I'll wager that the answer is four more than me.

sorry pal, just trying to put a polite answer for you thats all, i try to be nice on ere not like some folk i ave had replys from .. just to me you cant beat the old the practise makes perfect.....

[kent]

Ok, there are many things that can effect the dope developed via any balistic program. Atmospheric pressure is the biggest external one, zero a gun in Norfolk then bring it up here and it will shoot flatter as we are over 850 ft more in elivation. A bullets actual BC is often mis stated more than one might imagine and will very with the barrel etc. barrels are not always 100 % true to the action and the scope mounts (remember 1 MOA is only 1/60 of a single degree).

 

without harping on and creating greater confusion. Enter acurate data- no guesses, check it, print it then prove it in the field everytime no exceptions and no shortcuts. British forces snipers carry a shooters record log, yet they shoot the same rifle and issued ammo as every other sniper- yet thier personal hold and the individual guns will shoot slightly differently so they record what is termed in thier book as a heading "real world data" and this is compiled personally for all ranges and in different winds on different days with different temprature, humidity and elivation. All this could be issued to them as std data but it just wouldn't cut it for everyone the same equally

[wymberley]

Ok, there are many things that can effect the dope developed via any balistic program. Atmospheric pressure is the biggest external one, zero a gun in Norfolk then bring it up here and it will shoot flatter as we are over 850 ft more in elivation. A bullets actual BC is often mis stated more than one might imagine and will very with the barrel etc. barrels are not always 100 % true to the action and the scope mounts (remember 1 MOA is only 1/60 of a single degree).

 

without harping on and creating greater confusion. Enter acurate data- no guesses, check it, print it then prove it in the field everytime no exceptions and no shortcuts. British forces snipers carry a shooters record log, yet they shoot the same rifle and issued ammo as every other sniper- yet thier personal hold and the individual guns will shoot slightly differently so they record what is termed in thier book as a heading "real world data" and this is compiled personally for all ranges and in different winds on different days with different temprature, humidity and elivation. All this could be issued to them as std data but it just wouldn't cut it for everyone the same equally

 

Thanks for that. I don't think I can blame it on altitude as I'm about half a mile from the sea at about 100ft ASL.

 

I spent over 10 years as a senior range warden on the ranges complex where the RMs do their sniper course and hopefully did not waste my time - my son is a marksman sniper. All of any load development work is done in one field and It's not necessary to use the mildot master. As the groups are good and any scope adjustment is precisely reflected down range, this tends to suggest that the kit is OK, I think that when I go back to it, I'll try an alternative bullet and if that checks out as normal, I'll look again at the BC aspect.

[wymberley]

Any chance your target at 90 yards used for zeroing was higher than you (i.e. you were aiming up slightly) and the target at 160 yards was below you (i.e. you were aiming slightly downwards?). This would give the effect you describe....although I can't determine the sort of distances versus error we might be talking about any more, as I lost my trajectory spreadsheet!

 

Also, a cold, high pressure day gives more air resistance than a warm, lower pressure day. For example, 950 mbar and 25 degC air has only 92% the air resistance of 1000 mbar, 15 degC air.

 

By the way - with the BC, MV and scope height you give, the Hawke ballistic software also predicts 162 yard zero for ~1" high at 90 yards.

 

Let me know if you work out what the problem was...

 

Don't think I'll ever know for sure.

 

Putting it to one side while I scratched my head, I checked out the other Hornet - long range rabbit, opportune fox - which performed precisely as Infinity said it would as usual. Once this was done I had another look at the problem. I upped the ante velocity-wise and achieved an SD, which I managed to repeat, of 12.5. Down range it was a load of garbage, only hitting the backing and missing the target completely. I should have believed the programme as I decided to start from scratch and reloaded to the original spec. I've discovered that the velocity was actually lower than the original chrono' results indicated which suggested that I should have fired more shots than I did to get an average figure. This afternoon, with a muzzle velocity deemed acceptable, everything worked out well and I'm well pleased. I'm going to put the hiccup down to turbulent air from the very close woodland plus the lower than thought MV.

 

Two lessons learnt: Trust the ballistic programme if it has a history of reliability and as the man said, do not over compress Lil'Gun.

[Yarmite]

Don't think I'll ever know for sure.

 

Putting it to one side while I scratched my head, I checked out the other Hornet - long range rabbit, opportune fox - which performed precisely as Infinity said it would as usual. Once this was done I had another look at the problem. I upped the ante velocity-wise and achieved an SD, which I managed to repeat, of 12.5. Down range it was a load of garbage, only hitting the backing and missing the target completely. I should have believed the programme as I decided to start from scratch and reloaded to the original spec. I've discovered that the velocity was actually lower than the original chrono' results indicated which suggested that I should have fired more shots than I did to get an average figure. This afternoon, with a muzzle velocity deemed acceptable, everything worked out well and I'm well pleased. I'm going to put the hiccup down to turbulent air from the very close woodland plus the lower than thought MV.

 

Two lessons learnt: Trust the ballistic programme if it has a history of reliability and as the man said, do not over compress Lil'Gun.

 

Thanks for letting me know. I have also found the ballistic software very good - as a design engineer, I am used to using predictive mathematical models to minimise the amount of actual testing required....and where shooting is concerned, time, effort and expense getting your rifle zero'd in for the range you want!