[MC-27056] You can blow the extension off a piston

The bug

When TNT explodes during the same tick a piston extends, it is possible for the head to be destroyed without the base being destroyed. An explosion during any other tick will correctly destroy both or neither.

How to reproduce

/setblock ~1 ~ ~ command_block{Command:"/setblock ~ ~1 ~ piston[facing=east] replace"}

/setblock ~1 ~ ~1 command_block{Command:"/summon tnt ~6.5 ~1 ~-1 {Fuse:0,NoGravity:1b}"}

```
/setblock ~ ~ ~ lever[facing=west]
```
Activate the lever

Linked issues

is duplicated by 12

MC-77611 Explosions can remove piston head Resolved

MC-96106 piston with setblock and a redstone circuit makes piston_head go away Resolved

MC-105454 Minecraft pistons have a bug on the top of nether. Resolved

MC-106660 "piston_extension" can be destroyed by TNT or TNT cart. Resolved

MC-108342 Piston Head is No & Explanation of Breaking Bedrock with Pistons Resolved

7 more links

Attachments

MC-27056.mp4

Comments 41

dirk (switched to Minetest) 2013-07-25T02:46:21Z

Tried some times but can’t reproduce in 1.6.2 on Linux.

GrygrFlzr 2013-07-25T03:16:13Z

Cannot reproduce even by controlling the explosion with different materials and positions. Either the entire piston explodes, or both the extension and the piston does not get affected.

kumasasa 2013-07-25T05:53:12Z

Please force a crash by pressing F3 + C for 10 seconds while ingame and attach the crash report here.

Tails 2013-07-25T12:00:46Z

This ticket is incomplete, please open a new ticket and provide details about the issue you are experiencing using the Bug Report Guidelines Here.

marcono1234 2015-03-06T16:55:21Z

Please reopen this based on MC-77611

31 more comments

marcono1234 2015-09-12T14:56:00Z

Confirmed for

15w37a

Example command

/summon MinecartCommandBlock ~ ~0.6 ~ {Command:"/kill @e[type=MinecartCommandBlock,r=1]",Riding:{id:MinecartCommandBlock,Command:"/setblock ~1 ~5 ~ lever 2",Riding:{id:MinecartCommandBlock,Command:"/setblock ~2 ~6 ~ piston 5",Riding:{id:MinecartCommandBlock,Command:"/setblock ~2 ~5 ~1 command_block 0 replace {Command:\"/summon PrimedTnt ~6.5 ~1 ~-1 {Fuse:0}\"}",Riding:{id:MinecartCommandBlock,Command:"/setblock ~2 ~5 ~ obsidian",Riding:{id:MinecartCommandBlock,Riding:{id:FallingSand,Block:activator_rail,Time:1,Riding:{id:FallingSand,Block:redstone_block,Time:1}}}}}}}}

You may have to flick the lever multiple times

marcono1234 2015-11-21T22:11:14Z

Confirmed for

15w47c

Updated example command

/summon FallingSand ~ ~0.6 ~ {Block:"minecraft:stone",Time:1b,Passengers:[{id:"FallingSand",Block:"minecraft:redstone_block",Time:1b,Passengers:[{id:"FallingSand",Block:"minecraft:activator_rail",Time:1b,Passengers:[{id:"MinecartCommandBlock",Command:"/setblock ~2 ~5 ~ obsidian",TrackOutput:0b},{id:"MinecartCommandBlock",Command:"/setblock ~2 ~5 ~1 command_block 0 replace {Command:\"/summon PrimedTnt ~6.5 ~1 ~-1 {Fuse:0}\"}",TrackOutput:0b},{id:"MinecartCommandBlock",Command:"/setblock ~2 ~6 ~ piston 5",TrackOutput:0b},{id:"MinecartCommandBlock",Command:"/setblock ~1 ~5 ~ lever 2",TrackOutput:0b},{id:"MinecartCommandBlock",Command:"/setblock ~ ~1 ~ command_block 0 replace {Command:\"/fill ~ ~1 ~ ~ ~-3 ~ air\"}",TrackOutput:0b},{id:"MinecartCommandBlock",Command:"/setblock ~ ~2 ~ redstone_block",TrackOutput:0b},{id:"MinecartCommandBlock",Command:"/kill @e[type=MinecartCommandBlock,r=0]",TrackOutput:0b}]}]}]}

SunCat 2016-03-19T13:27:25Z

Still in 1.9.1-pre3

SunCat 2016-05-25T17:33:25Z

Still in 16w21a

marcono1234 2016-08-17T21:44:59Z

Please update the command to

/summon falling_block ~ ~0.6 ~ {Block:"minecraft:stone",Time:1b,Passengers:[{id:"falling_block",Block:"minecraft:redstone_block",Time:1b,Passengers:[{id:"falling_block",Block:"minecraft:activator_rail",Time:1b,Passengers:[{id:"commandblock_minecart",Command:"/setblock ~2 ~5 ~ obsidian",TrackOutput:0b},{id:"commandblock_minecart",Command:"/setblock ~2 ~5 ~1 command_block 0 replace {Command:\"/summon tnt ~6.5 ~1 ~-1 {Fuse:0}\"}",TrackOutput:0b},{id:"commandblock_minecart",Command:"/setblock ~2 ~6 ~ piston 5",TrackOutput:0b},{id:"commandblock_minecart",Command:"/setblock ~1 ~5 ~ lever 2",TrackOutput:0b},{id:"commandblock_minecart",Command:"/setblock ~ ~1 ~ command_block 0 replace {Command:\"/fill ~ ~1 ~ ~ ~-3 ~ air\"}",TrackOutput:0b},{id:"commandblock_minecart",Command:"/setblock ~ ~2 ~ redstone_block",TrackOutput:0b},{id:"commandblock_minecart",Command:"/kill @e[type=commandblock_minecart,r=0]",TrackOutput:0b}]}]}]}

D 2018-05-20T11:28:40Z

If I were a dev I suppose I would intentionally keep this feature. 😉

Whether this's in the original game plan or not, this feature is always interesting XD

Blobs2 2020-04-21T16:45:31Z

This should be fixed, as it is the primary method for breaking the bedrock ceiling in the Nether. For comparison, here is the behavior in Bedrock Edition.

You can push the bottom of an end crystal, and its fire will replace the pistonarmcollision. Since the visual piston head is technically the piston block entity model, what you see is a fire occupying the same space as the piston head. Unless you set the random tick speed to 0, the piston disappears after a few seconds (probably because the fire increments in age, which updates the piston). If the random tick speed is 0 (or if you are fast enough) placing a block next to the piston causes it to disappear.

I think it makes sense that headless pistons disappear upon receiving a block update. Porting this feature to Java Edition may or may not completely fix headless pistons, but it would prevent them from being used to break bedrock.

Gabrijel 2020-05-19T08:15:30Z

Affects 20w20b

Steve Hsu 2020-07-03T01:33:30Z

Blobs2, breaking bedrock with pistons doesn't necessarily involve this bug. For example, this video by Rays Works (https://youtu.be/AcBMt7xBSN8?t=294) shows several methods that break bedrock using pistons, but without using headless pistons at all.

The more relevant piston behavior (probably not intended, but the closest issue I could find is MC-29349, which is resolved as an incomplete report) is that during a piston's retraction, the block in front of the piston (usually a piston head) is replaced with a partially retracted piston head. As documented in the video, if you destroy a piston during its retraction and replace it in the same tick, the new piston will also retract despite never having been extended. This results in the block in front of the piston being replaced with a piston head, which is actually visible in the video for one frame.

Avoma 2020-11-22T19:07:44Z

I'd like to request the ownership of this report as the reporter has been inactive since July 2013.

Avoma 2020-12-23T11:06:20Z

Can confirm in 20w51a.

Avoma 2021-01-28T14:47:52Z

Can confirm in 21w03a.

Avoma 2021-02-06T11:56:23Z

Can confirm in 21w05b.

Avoma 2021-02-12T13:32:56Z

Can confirm in 21w06a.

Avoma 2021-02-18T19:24:15Z

Can confirm in 21w07a. Video attached.

Avoma 2021-03-04T14:24:26Z

Can confirm in 1.16.5 and 21w08b.

Avoma 2021-03-29T12:36:14Z

Can confirm in 21w11a.

Avoma 2021-04-30T16:28:59Z

Can confirm in 21w17a.

冯锦元 2021-05-31T13:48:11Z

Can confirm in 21w18a, 21w19a, 21w20a, and 1.17 pre-release 1.

Brayden Diaz 2021-06-13T01:54:25Z

Can confirm in 1.17

Avoma 2021-07-13T15:51:54Z

Can confirm in 1.17.1.

PR0CESS 2021-07-21T07:01:05Z

This does not need to happen within the same tick. It just needs to happen while the piston head is still a `moving_piston`
This means the tnt fuse can be from 0-3.

Avoma 2022-01-01T14:25:50Z

Can confirm in 1.18.1.

Avoma 2022-03-30T13:33:16Z

Can confirm in 1.18.2 and 22w12a.

Avoma 2022-06-13T11:31:03Z

Can confirm in 1.19.

QWERTY 52 38 2022-08-05T08:53:50Z

Can confirm in 1.19.1.

NBG-bootmgr 2022-08-07T14:43:51Z

Can confirm in 1.19.2.