PUBG: BATTLEGROUNDS (UP)

Quick note:
As for most of the [kill x amount of players with x weapon or equipment] achievements, in DUO or SQUAD modes, you can down an enemy by any means, so long as you finish the player off with whatever you're trying to progress the achievement of. This essentially makes the rest of the solution obsolete if this is how you plan to do it.

Short version:

This can be a fairly tricky weapon to get kills with. Personally I just crept up on some noobs in solo games to get this, however as with most other "Kill x amount of people with x weapon" achievements, you can shoot an enemy that you yourself knocked down; With a crossbow, and it will count towards the achievement. Considering it's only 10 kills this might be a valid alternative if you can't/don't want to do it in solo games.

detailed version:

Attachments:
This weapon has 2 attachment slots:
- Optical
- Quiver

I strongly recommend AGAINST using any Optical attachment on this weapon, this because the built in sight offers aimpoints which provide useful assistance to allign your shot at range.
As for the quiver, this significantly increases your reload speed, no reason to not equip this should you be lucky enough to find one.

Damage:
Note that a headshot with this weapon will always be lethal, even through a level 3 helmet, hence why this section will be focused on body damage, although I strongly recommend aiming for headshots exclusively.
The following damage values are therefore only for body damage:
Non armored: 104 damage. This will instantly kill (in solo, or down in duo/squad) an enemy.
Level 1 vest: 72
Level 2 vest: 63
Level 3 vest: 47

Again, these numbers are more for the sake of covering every aspect, as hitting more than one bolt on an enemy without them running away or killing you is very unlikely.


Accounting for bolt-drop and travel time:

In reference to the image below:
bolt-drop:

The top/center dot is of course the main aimpoint.
The 2nd dot from the top is the height you should aim to account for the drop of the bolt at 50 metres
Likewise for the third dot at 100 metres, and the bottom dot at 200 metres respectively.


(Screenshot taken from Youtube user WackyJacky101, who has a lot of in-depth videos on the game (some outdated due to updates and patches to the game, but definitely worth a look for those interested.)


Accounting for travel time:

That covers the drop, as for leading a sideways moving target,
The initial speed of the bolt is 160m/s if the target is moving perpendicularly to you, that means for every 20 metres your target is away, you need to aim rougly 60cm/the width of an enemy player ahead of them.

The drop is fairly manageable, however leading a sideways moving target is still really tricky, so I just recommend sneaking up on a player and waiting for them to stop moving so you can easily line up your shot.

Considering this is way easier to do on stationary targets anyways, I didn’t think anyone would be interested in the specifics on how to use the weapon.

Figuring out distances if you're not able to make accurate estimates:

For figuring out the distance between you and the enemy, you could make a guess based on the squares on your minimap representing a 100x100m area, this however only really works if you have some knowledge of the map as it may be hard to pinpoint where your target is if they are out in the open and not near a landmark such as a house.
Alternatively, you can use the markers on the built-in scope to measure how a player standing upright fits in between the stripes at different distances by lining up the bottom line with the targets’ feet, and seeing in between where your target fits. These lines connect to the aimpoints showing you where to aim before shooting.

A tip from 'Acurate Bob':
If a teammate crossbows a down that YOU make, you get credit. I did not test this but it might be useful sometimes

Easy method: play duos or squads and anytime you knock an enemy with ANY weapon you can then fully kill them using the crossbow which is a 1 shot to the head and they will more or less be stationary due to them being knocked. Very easy to get 10 kills using this method. Alternatively you can go into casual mode as you are allowed 3 casual matches a day (90% bots) and you can just kill bots using the same method above but it is even easier to knock as most players are bots.