Why has this happened, (bullet drop)

[Tikkat1x]

So on friday i was out doing some testing as i do now and agian as nothing seems to stay the same for long,
first group was at 100m with some home loads, 55gr sierra SPT's, there generally 0.4 - 0.6" groups,
this time it was 0.5", went out to 200m and it was a 1.6" group, 2.8" low, did the same saturday and it was a 1" group and still 2.8" low,
then i did some things with the 243, then before i went home i thought id check the 223 again, this time it was 10" low and a group size of 2.2"
gave it a good clean when i got home, full bronze brush and patch clean. when out today to check, fired a few fouling rounds with some 69gr sierras i have that had bent tips,
then did a 100m group at 0.6" so move back to 200m 9.5" low and a group size of 1.1",
so any idea why such a difference, iv made enough loads to be confident that there all done the same every time, and these were all made at the same time

also did the same test with some 69gr sierra tmks,
they worked out at 5.7 low, 5.5 low, 6 low and today 4.5" low, with an average of 1.5" groups,

 

[Klenchblaize]

Phase of the Moon?

A tongue-in-cheek suggestion that is as good as any without having your kit in front of us or being behind you when the trigger was pulled.

K

 

[safer]

Ambient temperature - some powders are very sensitive to ambient temperature. Head wind - small bullets like that will be affected by the wind especially because the 223 is not a particularly fast round. Barrel temperature - if you shooting more then five rounds from a standard hunting rifle it will get hot. Over-barrel moderators heat the barrels even more.
Other than that check the scope and mounts just in case.

 

[kenbro]

Is everything tight, including mod.if using one.
KB.
Ps. Last Sunday I had similar but only at 100 yds. Some 1” is groups then wild flyers, then back to smallish groups.
Picatinny rail (Factory fitted) was loose and after removing sight, tightening Pic. rail and putting sight back on this was result. First shot left and high, adjust ret to bullet hole then last 3 rounds with me went good.
KB.

 

[Tikkat1x]

in answer to all so far, id like to think im not that crap that anything im doing could result in a drop of 7" drop
the first 2 days were blue ish skys with a bit of sun but it was not hot in anyway, 2-4 mph cross wind which didnt have any affect of drift,
today was overcast and a tad colder, no more than a 3 mph head wind as i kept checking the wind, most of the time it didnt even register on the kestrel.
varmint barrel i fire 5 shots with a minute in between, and let it fully cool between groups, at least 20 mins, after 4 shots its hardly warm to the touch,
didnt really want to start taking it to bits to check but if i have to, as its the tikka t3x super varmint it came fitted with the pic rail, but tomorrow i will check it all over

 

[jcampbellsmith]

Can i suggest that you chronograph all your shots?

Regards

JCS

 

[Klenchblaize]

In all seriousness I do wonder if - under certain circumstances - a moderator can be given of some kind of independent 'environment' that negatively impacts a bullet's flight path that was not the case when last subjected to the pressures involved.

Whatever the reality, it would be a good test to compare the same group testing with and without the moderator before moving on to scope and mounts etc.

K

 

[Tikkat1x]

Can i suggest that you chronograph all your shots?

Regards

JCS

i used to have a chrono, magnetospeed V3, but that never really produced regular results, in speed, SD and ES, so sold that, but from what i can see in my records the the 69gr sierras were around 2600 and the 55gr sierras were 3000 fps, some times id would give me decent ES and SD the next it was miles off, this time iv just dont it from bang on at 100m then changed the speed in my Hornady app till it reach the actual drop, thats out of the window now with todays carry on, from what the previous 2 results were my speed on the app for the 69gr ended up at 2775 fps to meet the correct drop at 200m, and the the 55gr are at 3400 fps. as a rule id generally just shoot a few groups at said distance and just write down and remember them,

 

[Tikkat1x]

In all seriousness I do wonder if - under certain circumstances - a moderator can be given of some kind of independent 'environment' that negatively impacts a bullet's flight path that was not the case when last subjected to the pressures involved.

Whatever the reality, it would be a good test to compare the same group testing with and without the moderator before moving on to scope and mounts etc.

K

i will give that ago tomorrow if its not raining like forecast

 

[Jamsie]

i used to have a chrono, magnetospeed V3, but that never really produced regular results, in speed, SD and ES, so sold that, but from what i can see in my records the the 69gr sierras were around 2600 and the 55gr sierras were 3000 fps, some times id would give me decent ES and SD the next it was miles off, this time iv just dont it from bang on at 100m then changed the speed in my Hornady app till it reach the actual drop, thats out of the window now with todays carry on, from what the previous 2 results were my speed on the app for the 69gr ended up at 2775 fps to meet the correct drop at 200m, and the the 55gr are at 3400 fps. as a rule id generally just shoot a few groups at said distance and just write down and remember them,

With respect ... if a properly functioning (fitted iaw the instructions) Magneto V3 isn't delivering the results that you expect, then I would be inclined to look carefully at your reloading process. It may also be worth trying another chrono. Consistency is everything and as a target shooter, the chrono is an essential item in my reloading equipment toolbox. Churning out a consistent, single-figure SD is exactly where I want to be in my loading process and just not measurable without a decent chrono.

Jamsie

 

[Utectok]

If invest in a garmin or similar chrono.
Also a drop test at 200m is not really far enough 300m is better and removes some errors. Magnospeed are reliable accurate chronos if used properly and inconsistent results are probably true

 

[Tikkat1x]

id best buy another chrono then, see whats going on, thanks

 

[Tikkat1x]

If invest in a garmin or similar chrono.
Also a drop test at 200m is not really far enough 300m is better and removes some errors. Magnospeed are reliable accurate chronos if used properly and inconsistent results are probably true

i did shoot 1 group at 300m yesterday with the 69gr sierras, that was a 18.5" drop with a 2.3" group size

 

[Heym SR20]

Several things you need to look at.

At 200m plus a rifle starts to really show up errors. Given that the rifle seems to shoot consistently well in terms of group size, I would start looking at other sources of variability.

A 223 is a pretty high pressure cartridge and will set significant vibrations down the barrel. And there is sufficient recoil that will show up significant changes in hold on the rifle. This can and will show up in changes in point of impact. At 100 this will be minimal, but really shows up down range. Haven’t a clue about your technique, but the key to consistent accuracy and changes in point of impact is having a very consistent hold and body tension so that the rifle recoils in the same manner for each and every shot.

Easiest way to see if rifle will naturally recoil on target. Look at the target and bring the rifle into your line of sight. The sight should automatically align with the target. Close your eyes, breath in and out and open your eyes. Is the rifle still on target. If yes - all good, if not then your position needs changing so the rifles natural point of aim is on target.

Atmospherics also change things. There is a difference of nearly 10% between a deep low pressure and high pressure system. That has a significant change in air density, which in turn affect drag on the bullet and thus affects how it slows down and thus point of impact. And as range increases this effect is magnified as bullet slows down.

One of the very good reasons to set your sights for maximum point blank range, rather than zeroing at 100 at then dialing or holding off, is that error effects are somewhat minimised.

By using mpbr, your bullet hits a bit high at 100, but then a misreading of range, change in pressure, hold, etc means that it will still hit the vitals out to 200 odd (depending on cartridge).

And real world testing shows that there is a very big difference in what the book, internet etc says and what happens in practice. On the club range I have watched many shooters do perfectly well at 100. Rifle is all nicely zeroed etc. These then struggle to get consistency at 200 and 300. Normally after a few shots they are on target.

But when it comes to shooting live animals in the field its first shot that counts.

Edit - re reading this. Magneto Speed - aren’t these the chronos that attach to the barrel / rifle. They will have an affect on how the rifle recoils and thus point of impact if attached or removed.

 

[C h r i s]

Several things you need to look at.

Edit - re reading this. Magneto Speed - aren’t these the chronos that attach to the barrel / rifle. They will have an affect on how the rifle recoils and thus point of impact if attached or removed.

Also has a huge impact on barrel harmonics. Best to remove once MV and SD are established.

 

[C h r i s]

i did shoot 1 group at 300m yesterday with the 69gr sierras, that was a 18.5" drop with a 2.3" group size

That drop is about right for a 2600ft/sec MV.

 

[Tikkat1x]

Also has a huge impact on barrel harmonics. Best to remove once MV and SD are established.

the last one i had did change POI, but i only really used it for speeds, was not massively bothered about ES & SD as my groups were pretty good anyway,

 

[Tikkat1x]

If invest in a garmin or similar chrono.
Also a drop test at 200m is not really far enough 300m is better and removes some errors. Magnospeed are reliable accurate chronos if used properly and inconsistent results are probably true

id love a garmin, but no way on earth would i spend that on one of them, but then again iv said that about lots of things and then bought them, a forster co ax being the most recent
but at least that will get plenty of regular use, for me a chrono will rarely be used,

 

[Smellydog]

Think I'd put some powder in the case.
Seems slow!
You may just not of hit the sweet spot.

 

[Utectok]

id love a garmin, but no way on earth would i spend that on one of them, but then again iv said that about lots of things and then bought them, a forster co ax being the most recent
but at least that will get plenty of regular use, for me a chrono will rarely be used,

I think there is a cheaper garmin clone can’t remember name. It is so easy to use and doesn’t affect impacts you will find you use it most of the time you are practicing