Thread: Chronograph in taupo wanted.

Anyone going up to the deerstalkers range in the next few weeks with a chronograph? Just wanting to send a few rounds down range to check speeds. Have chronographed the load with a mates one but when shooting out at long range to validate the load something's not adding up. Either the BCs on the projectiles are wrong or the load is faster than the chronograph is saying by about 180 fps.
Can't figure it out so want to confirm speed against another chrony.
Cheers

BCs get better the faster you push the bullet. The stated BC is more than likely from a test using a moderate load, set at saami AOL (unlike your load which sounds like it is optimised yes?)

Trust those real world results mano. The bullet doesnt lie

Originally Posted by T.FOYE

BCs get better the faster you push the bullet. The stated BC is more than likely from a test using a moderate load, set at saami AOL (unlike your load which sounds like it is optimised yes?)

Trust those real world results mano. The bullet doesnt lie

284 win with 59.6 grns of superformance. 150 grn long range accubond and Norma brass. The chronograph rekons 2805 out of an 18 inch barrel.
Yet to get the dope correct out to 610 yrds we had to input a speed of 2980 fps to be bang on with applied ballistics.

Assuming you are adjusting the scope, it could be the clicks on the scope aren’t exact, some of my quarter click scopes are actually 0.28.
If you are shooting out to 610 yards and measuring drop without adjusting the scope, disregard the line above!

I would say youd probably be nearer to 3000fps with that combo @Kudu?

Originally Posted by Cigar

Assuming you are adjusting the scope, it could be the clicks on the scope aren’t exact, some of my quarter click scopes are actually 0.28.
If you are shooting out to 610 yards and measuring drop without adjusting the scope, disregard the line above!

Two different scopes. A VX5 and a delta titanium both dailed exactly the same with two shooters and the same moa come up each time. I think the chrono is out or the bc is wrong. Will find out and report back.

Just a thought if you haven't already checked your measurements on the app. I had the same problem worked out I had put the wrong scope height from the bore in the app corrected it and was pretty good after that.

I had a 19" barrel with 54.5gr of 2209 and 150 gamekings doing 2750-2770 so imagine yours with a slicker pill, hotter load and a faster powder will be going alot faster than 2805. Trust your drop not a chrono(unless it is a lab radar type)

Originally Posted by Blackfern

284 win with 59.6 grns of superformance. 150 grn long range accubond and Norma brass. The chronograph rekons 2805 out of an 18 inch barrel.
Yet to get the dope correct out to 610 yrds we had to input a speed of 2980 fps to be bang on with applied ballistics.

Yes, I'm getting 3000 with my 150gn Ballistic tips and RL26.

Originally Posted by Blackfern

284 win with 59.6 grns of superformance. 150 grn long range accubond and Norma brass. The chronograph rekons 2805 out of an 18 inch barrel.
Yet to get the dope correct out to 610 yrds we had to input a speed of 2980 fps to be bang on with applied ballistics.

Putting the projectile into the lands vs say .05" can result in a change of mv of 100fts. Also there's using magnum over large rifle primers (not heaps but it can effect it).
AB needs you to put in ALL atmospherics and data in order to get it right. Are you fairly confident? Density altitude can cause a few inches of POI change too.

If it were me, i would buy the litz bc drag profile (for $3 or whatever) and adjust the mv to suit your actual drop
- try 400m and 800m an see if its still on. If its within +-1 click then dont worry. Your hold can cause this, unless your 100m groups are flawless (mine aren't).

All chronies have a degree of error too. Another thing, shooting your string too fast will see your mv climb, did you let your barrel cool for a couple of mins. Was your gear in hot sunlight all day?

I test my trajectory in a few types of conditions. That helps you build confidence in your estimated MV.

Rubbish In rubbish out.
A few basics.
Perfect zero, correct above bore height, check your scope for elevation correction as there's not many scopes that dial truly.
Use applied ballistics and buy their custom drag curve.
Watch the truing video and copy that.
If you are truing at longer distance you should really be using a weather station to get your environmentals.
Trust your real world data rather than a chono.
The only thing a chrono will do is tell you if your ammo has low SD which is pretty important.
This has worked for me for a long time and trusted accurate method.

Sent from my SM-A025F using Tapatalk

Originally Posted by andyanimal31

Rubbish In rubbish out.
A few basics.
Perfect zero, correct above bore height, check your scope for elevation correction as there's not many scopes that dial truly.
Use applied ballistics and buy their custom drag curve.
Watch the truing video and copy that.
If you are truing at longer distance you should really be using a weather station to get your environmentals.
Trust your real world data rather than a chono.
The only thing a chrono will do is tell you if your ammo has low SD which is pretty important.
This has worked for me for a long time and trusted accurate method.

Sent from my SM-A025F using Tapatalk

Cheers for all the advice guys. Will double check all my inputs next week and have arranged for another chrony next week to double check speed.
I'm not reloading for the 284. A mate who is very experienced is doing it for me. The load he worked up shoots .35 moa out of the t3x and has an ES of 3fps so is working well. The accubonds seem to be working well on the animals so far as well. Just need to fine tune the drop.
Trying to create one rifle to rule them all instead of a gun safe full off different rifles and scopes etc.
Maybe work up a simple cup and core projectile if the accubond is a bit soft up close in the bush.
The Tikka with a VX5 is lighter than my last bush dedicated rifle

Be sure to store your ammo somewhere cool to whilst hunting and at range time on a bench in the sun will be a bad time

Originally Posted by Blackfern

Two different scopes. A VX5 and a delta titanium both dailed exactly the same with two shooters and the same moa come up each time. I think the chrono is out or the bc is wrong. Will find out and report back.

If you can get out and measure actual bullet drop, chronograph is irrelevant. Just check you actual drop at 2-3 ranges and tweak your velocity or BC in your app to be correct with actual drop.