Ok to start, in Warzone I find my self time and time again losing more long distance BR duels than I am winning…and I know I hit them a couple of times for at least the “de-scope” to happen and yet a lot of their shot after the “de-scope” still seem to be dead on. This is at some pretty long ranges as well.
So I am asking for some hints and tips on how to better my aiming and what I should be looking for to help win, or at least stay alive longer 
Thanks
No idea. Happens a lot with me too, even when I’m strafing and thrusting I still get killed by a “perfect kill” even though I know several shots missed.
Here are some tips that might help you…
In arena i would say just don’t zoom-in with riffles, because the maps are pretty small and you wont need to worry about de-scope.
In warzone don’t forget to switch out your weapons for a better version.
Only aim for the head if your opponents shield is down. Better to just hit the body until it’s down that way your aiming at a bigger target with smaller chance of missing.
Aiming
One thing I try to do while aiming is to use my movement stick (Left by default) to keep my target in the center of my screen by strafing and use my look stick (Right by default) to move my sight up and down vertically try to avoid horizontal movement with your look stick could cause you to overshoot your aim and miss if your strafing.
Evade
The TTK is low like back in the halo 2 days so if you get caught of guard better find cover rather than engage in a losing battle. I try to evade of flee and engagement any time i see my shield about to be knock out knowing that next shot could be the kill shot. You can also try crouching while in an engagement to throw off your opponent.
Hope these tips help
If you like friend me on live
GT same as above
They could be using a scoped BR with higher magnification.
Get a BR with insane zoom. makes them extra easy targets.
> 2533275031285681;5:
> Get a BR with insane zoom. makes them extra easy targets.
This. I had similar frustration as the OP until I picked up one of these BR’s (Sentinel?) off the field and realized how much of a disadvantage the other BR’s had against these at long range.
Sentinel BR with either long range or kinetic for damage or laser sight for more accuracy would kick major -Yoink-! I personally have the Sentinel BR with laser sight due to Gamestop and that -ish owns at long range. Definitely either makes people run for cover for my team to move in or get an insane kill that no normal BR can accomplish.
Use the power weapon light riffle.
In Warzone, obtaining a Longshot BR or Sentinel BR would definitely help give you an advantage or equalize it.
When you’re de-scoped, you have to compensate for leading.
In Hce, 2,3, reach you had to take into the bullet speed. Not so much in h4 if you were used to it.
In h5 the lead is tiny but you still have to adjust to it when you’re not scoped in. Best advice, play without zooming in for 1 Day (force yourself). You will get used to it, and notice how you should aim when unzoomed. Once you are used to it, start scoping and as you suspect you are gonna get un-scoped, quicky unzoom, and it should be an easy transition. 
hope it helps out.
You’re playing the RNG game by using a spittle weapon at long distance.
Either team-shoot, reduce the distance or use a DMR.
Otherwise you’re just as well using an AR or M6 to engage the BR user at those same “extreme” distances.
just keep playing. try a lower sensitivity. try to zoom in as fast as you can after getting unzoomed. if you keep getting unzoomed duck behind cover. If they have the first shot on you and they unzoom u first, jet pack strafe so they miss a shot and try to get teh zoom advantage and try to keep them from zooming in. IDK i guess its just practice tbh. i average 36 kills a game in warzone mostly from BR fights, but tbh i dont do anything special 
No harm in finding cover if you’re getting hit before you can return fire. More often than not, if you are engaged at long-range first, you’re in trouble. But, the tried and true tactic with BR…body shots until shields pop, then headshot.
Your opponent likely had a longshot BR and you didn’t at the time.
> 2533274831950975;9:
> In Warzone, obtaining a Longshot BR or Sentinel BR would definitely help give you an advantage or equalize it.
This. If this isn’t the problem, many people know how to long-range no-scope with a BR nowadays.
> 2535451563140277;10:
> When you’re de-scoped, you have to compensate for leading.
>
> In Hce, 2,3, reach you had to take into the bullet speed. Not so much in h4 if you were used to it.
>
> In h5 the lead is tiny but you still have to adjust to it when you’re not scoped in. Best advice, play without zooming in for 1 Day (force yourself). You will get used to it, and notice how you should aim when unzoomed. Once you are used to it, start scoping and as you suspect you are gonna get un-scoped, quicky unzoom, and it should be an easy transition. hope it helps out.
That’s where this comes in handy.
Simple: when a player is descoped, their reticle doesn’t move, they just zoom out. So they pull the trigger with ought moving the right stick, hit you, and then zoom in a again
In all honesty the minute i know i haven’t won a BR duel i evade behind cover and live to fight another day. I try to avoid getting into too many long range duels until i can get my DMR or a BR with a long barrel.
I pretty much avoid using the BR in 1v1 duels at really long range. It just takes too long and while you’re trying to wrestle with the BR’s spread at long range, someone could get in close ambush you from the side or from behind.
Only time I use the BR at really long range is if I see a battle in the distance and I wanna help my team by putting pressure on & chipping at the shields on the other team.
The exception is the scoped BR’s, those can really peg someone from a distance.
Use the increased accuracy attachment if you have it available.
At TIER 5 I get the long scope BR…makes a difference