Twist rate question


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marcodo
February 12, 2009, 08:25 AM
I recently bought a AR15 built by someone else. I asked a friend to help me purchase it and he found one out of the classified. DPMS lower marked 5.56/.223. Not sure of the upper to be honest. It has a heavy stainless bull barrel. I took off the handgards and the barrel has no markings what so ever.

It shoots great and I have no issues with it functioning.

My question is "How can I determine the twist rate on this" so that I can select the proper bullit weight for this gun.

I have been just plinking with handloads of .223 winchester 55 grn fmj and H335

I can try to get a picture if that is needed...

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lej
February 12, 2009, 09:17 AM
Take it to a gunsmith if you really want to know. If it were me id (and your trying to workout what your rifle is capable of) just get a selection of different bullet weights and see how you go with each. Most now days are either 1/7, 1/8 or 1/9 . even if it is a slower 1/9 it will still stablize everything up 69 grs. You will see clear signs that your spinning projectiles to fast or too slow when your accuracy goes out the window. Having said that no two barrels are the same, i have a savage 10fp with a 1/9 twist that stablizes 77gr sierra matchkings beautifully into less than a min at 100 yards.:)

Cohibra45
February 12, 2009, 09:25 AM
Just measure it yourself. Take your cleaning rod, jag, patch, piece of tape and ruler. Start the cleaning rod in your barrel, not chamber and go in around 2-3". Place the tape on the back of your cleaning rod and begin to measure. When the tape makes one complete revolution, measure the distance the rod traveled and that is your twist rate...1 revolution in x inches.;)

Very easy...

Jim Watson
February 12, 2009, 09:29 AM
A cleaning rod with swivel handle will tell you the twist.

Start a tight patch in the barrel and make marks on the rod to show the top and the starting point. Advance it down the barrel until the rod has made a full turn and mark the location. Distance between the start and finish marks is the rifling pitch in inches per turn.

That will not necessarily tell you the BEST bullet to use, but it will give you a handle on the longest/heaviest bullet you can use. Might not be the most accurate, there are plenty of 9 twist barrels made to stabilize a 69 grain bullet that are still the most accurate with a 52. I have one.

You just have to shoot the gun. Not all answers are on the internet.

Boba Fett
February 12, 2009, 10:29 AM
A cleaning rod with swivel handle will tell you the twist.

Start a tight patch in the barrel and make marks on the rod to show the top and the starting point. Advance it down the barrel until the rod has made a full turn and mark the location. Distance between the start and finish marks is the rifling pitch in inches per turn.

...Not all answers are on the internet.


Maybe not all answers, but certainly some excellent advice. I had been wondering how to find out what the twist rate of some of my older rifles is and your suggestion is a cheap and easy way for me to figure it out.

I'm going to give it a try later. :D

JohnBT
February 12, 2009, 11:33 AM
I bought a Bore Tech rod some time back and was surprised & pleased to see a dot near the handle to use for measuring twist.

John

Jim Watson
February 12, 2009, 02:11 PM
Good for them. There has gotten to be a lot more interest in twist rates ever since the Army started fooling with .22s. I think a lot of it is misplaced, as P.O. Ackley once said "A customer said I ruined his barrel by reboring it with a 14 twist when he wanted 16. Which must make Winchester wrong because they used 12."

Eb1
February 12, 2009, 02:26 PM
I worked up the twist for my 30-30 150 grain bullet at 2270 fps. It was 1:15.

I am going to give the AMAX 75 grain a shot this weekend in my 1:9 Colt HBAR. I hope it works out.

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