77 twist rate help

[Bitman]

Regarding a M77, RL, MKII, ultralight, in .223 with a 20" barrel.
Anyone know what the twist rate on this rifle would be?
Thanks.

 

[mattsbox99]

It depends on when it was made, if its a newer MKII then it should be 1-9", if its older it could be 1-12". The best way to find out is a tight patch on a cleaning rod. Just make a dot on the rod and when it goes around once measure that distance.

 

[Bitman]

It's a 1 in 12 twist, they changed to 1 in 9 twist in 2007.

 

[JohnM]

Does a 1-14" sound right for a 1979 220 Swift with a 26" varmint barrel?

 

[MADISON]

Start a tight patch; being sure the jag is tight on the rod.
Mark the rod with a felt tip to indicate Top Dead Center and a starting point.
Advance the rod until it comes back to Top Dead Center.
Measure the distance traveled from the start mark. That is the rifling twist, one turn in xx inches.
A lot easier than trying to estimate the amount of twist in a foot.

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223 Remington / 5.56 NATO rule of thumb.....

1:12 - 55 grain max, best with 50 grain or less

1:10 - 60 grain max, best with 55 grain or less

1:9 - 69/70 grain max, best with 65 grain or less

1:8 - 77 grain max, beat with 69/70 grain or less

1:7 - made pretty much for the 77 - 80 grain VLD bullets

With a fast twist (1:9 or faster) and a light (like 40 grain) bullet pushed to a high velocity (3700 fps+), depending on bullet construction, you can cause the bullet to self-destruct from centrifugal force.

 

[JohnM]

My Ruger 26 inch barrel measures 1-14.
I guess they don't make that barrel anymore, but it shows 1-14 used for the 24 inch barrels so I guess I get a good measurement.
My Remington 24 inch 22-250 barrel is also 1-14.

 

[mattsbox99]

Most 220 swifts and 22-250s are 1-14 anyway, some newer 22-250s are 1-12.