Long Throats and Accuracy

Written by Sierra Bullets Ballistic Technician Paul Box

This is a question that we get on a daily bases on our 800 line. Will my rifle give good accuracy if it has a long throat?

Today long throats are very common in a factory rifle compared to thirty years ago. Most questions we get concerning this is that the shooter will have a new rife throated long enough that they can’t seat a bullet close enough to the rifling and still maintain any bearing surface in the case neck.

First of all, most rifles have two sweet spots on its’ seating depth. One will be up close somewhere like .010″ to .020″ off the rifling. The second sweet spot can be .050″ to as much as .080″ off. Today a lot of shooters only look for the “up close” location and never even consider the far back approach. I’ve got one 22-250 that shoots its’ best .070″ off the rifling.

If you have just bought a new rifle and it has a long throat, don’t be afraid to try the “far back” approach on your seating depth. Many shooters are surprised to find their new rifle will shoot its’ tightest groups with a lot of bullet jump.

There’s also another thing to consider on a long throated rifle as well. Many of these will have a throat that is wide in diameter. It might run .005″ to .008″ wider than bullet diameter. If your rifle has a wide diameter throat, it might very well shoot a flat base bullet with far better accuracy. I’ve seen rifles like this that was giving 1.5″ accuracy at 100 yds. with boat tail bullets start turning in groups in the three quarters of an inch range but just simply switching to a flat base bullet.

So if your new rifle has a long throat, remember to try a flat base bullet and also deeper seating. You might be surprised at the results.

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11 Responses to Long Throats and Accuracy

  1. Frank says:

    How does one measure and determine throat size?

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  2. David Ruppel says:

    How do you measuring of the diameter of the throat?

    Rupe

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  3. Paul Box says:

    The best way is to run a chamber cast, then measure the troat diameter from that.

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  4. Frank says:

    Thanks…… Now if I could only get the lead out…; >)

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  5. David Ruppel says:

    Hahaha. That was funny!

    Rupe

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  6. Bill says:

    what would measuring the diameter of a fired casing neck tell us, realizing that the brass will spring back some.

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  7. Paul Box says:

    It would only give is a good idea of the diameter of the neck in the chamber itself, but not the throat area.

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  8. Yes your exactly right , Palma team shooters have experiments that prove the same. One of the best bullets was the old 2155, 155gr 30 cal bullet. It was a whole different situation it did need a short tight dia throat , but boy was that a great bullet when the rifle was properly set up. I’ve only shot a few thousand 2156’s and I believe they would shoot in anything, thanks for the constancy and quality in your bullets.

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  9. Paul Box says:

    Thanks Mitchell. You guys make us look good out there. We wouldn’t be here without you guys.

    Like

  10. Frank says:

    I wouldn’t have it any other way, Ditto!

    Like

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