Give you a statement and table with its title in Markdown format, please determine whether the statement is supported or refuted by, or is unrelated to the table. It'a binary classification problem, you should choose the answer between supported and refuted. Table cells in one row are seperated by '|', and different rows are seperated by '
'.

Table:
| colt model no | name | stock | fire control | rear sight | forward assist | case deflector | barrel length | barrel profile | barrel twist | hand guards | bayonet lug | muzzle device |
| ar6320 | ar - 15 lightweight | 4th generation | s - 1 | a1 | yes | yes | 16 in | a1 | 1:9 | short ribbed | yes | a2 |
| ar6450 | ar - 15 9 mm carbine | 4th generation | s - 1 | a1 | no | removable | 16 in | a1 | 1:10 | short ribbed | yes | a1 |
| ar6520 | ar - 15a2 government carbine | 4th generation | s - 1 | a2 | yes | yes | 16 in | a1 | 1:7 | short ribbed | yes | a2 |
| ar6520sp | ar - 15a2 government carbine | 4th generation | s - 1 | a2 | yes | yes | 10 in | a2 | 1:7 | short ribbed | yes | a2 |
| ar6525 | ar - 15a2 government carbine | 4th generation | s - 1 | a2 | yes | yes | 16 in | a2 | 1:9 | short ribbed | yes | a2 |
| ar6721 | ar - 15a3 tactical carbine | 4th generation | s - 1 | flattop | yes | yes | 16 in | hbar | 1:9 | short ribbed | yes | a2 |
| ar6721sp | ar - 15a3 tactical carbine | 4th generation | s - 1 | flattop | yes | yes | 10 in | hbar | 1:9 | short ribbed | yes | a2 |
Title:
none
Statement:
a1 is the muzzle device with barrel twist of 1:7
Answer:
refuted