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Twist Rate (#1)

6/11/2004 - For dual use in .30 calibre (i.e. both supersonic and subsonic ammunition), the very best compromise is a 1:10" twist rate. Our extensive testing has proven that there is NO accuracy degradation with supersonic high-velocity ammunition, and that with the correct subsonic ammunition, this twist rate will give more than acceptable, sub-minute accuracy.

For use with subsonic ammunition ONLY, a 1:8" twist rate is best. This gives added stability and permits the use of less than optimal projectiles. The use of the 1:8" twist will mean that this gun is dedicated solely to the use of subsonic ammunition.

Twist Rate (#2)

6/11/2004 - We are often asked what is the best twist rate for use with different calibers of subsonic ammunition. Here are some basic guidelines that will help you to achieve the best results:

For subsonic pistol calibers, the factory barrel/twist is usually just fine, as most pistol ammunition is just marginally supersonic anyway, with a very few exceptions.

Rifles: First of all, if you are going to go to the expense and trouble of creating a platform for use with a suppressor, it only makes sense to pitch the factory barrel and have it replaced with at least a decent mid-grade tube.

Companies such as Schneider, Shilen, Douglass and several others can provide you with an air-gauged and properly finished barrel, installed and threaded by them for in the $300 range. This is just $100 more than the cost of the tax stamp for your suppressor, and will ensure that you do not experience accuracy and safety problems due to a poorly finished or inspected barrel, and is therefore worth the investment!

Accuracy is almost always enhanced by this move, and for some unknown reason, many U.S. factories still make .308 barrels with the obsolete 1:12" twist rate, and 5.56/.223 rifles using the 1:12" twist rate.

For .308, 1:10" is best for dual purpose use and for 5.56/.223, 1:7" or 1:8" is best if the operator wishes to use both supersonic and subsonic ammunition.

While you *might* get lucky with the factory tube, often it is the source of many headaches when trying to utilize subsonic and even supersonic ammunition. This is true regardless of the original maker.

Engel Ballistic Research, Inc.
Phone (512) 360-5327 | Fax (512) 360-2652
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