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Thread: 338-06 Chamber Length

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    Default 338-06 Chamber Length

    I recently picked up a 338-06 rifle based on a 98 action/24" barrel. Information on this site and others plus firing different rifles and calibers reduced my new caliber search to a handful and finally the 338-06. Already having and loading for a 30-06 definitely influenced the final decision as I needed to pickup very few items before the first rounds were ready for range testing.

    Very impressed with the 100 yard accuracy (5/8" @ 2690fps ave) using Hornady 225g SST and IMR 4060. Need to fix one issue: The measured chamber OACL is 3.483" using the 225g SST but the magazine measures 3.36". Very good accuracy when I load to 3.48" OACL but everything opens up (1.25" plus) when I load to magazine length of 3.33"-3.35". Loading single rounds at the range is ok for testing but I need accurate rounds in the magazine during hunting season.

    Anyone run into the same issue and what did you do to solve it?
    mtnhiker06

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    Try different bullets, or have the barrel turned to accommodate your current bullet selection and magazine.

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    Supporting Member iofthetaiga's Avatar
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    Quote Originally Posted by mtnhiker06 View Post
    I recently picked up a 338-06 rifle based on a 98 action/24" barrel...
    Just for comparison sake, do you know what your chamber length - bolt face to ogive/lands - is on that gun? Mine is 2.700.
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    Quote Originally Posted by mtnhiker06 View Post
    I recently picked up a 338-06 rifle based on a 98 action/24" barrel. Information on this site and others plus firing different rifles and calibers reduced my new caliber search to a handful and finally the 338-06. Already having and loading for a 30-06 definitely influenced the final decision as I needed to pickup very few items before the first rounds were ready for range testing.

    Very impressed with the 100 yard accuracy (5/8" @ 2690fps ave) using Hornady 225g SST and IMR 4060. Need to fix one issue: The measured chamber OACL is 3.483" using the 225g SST but the magazine measures 3.36". Very good accuracy when I load to 3.48" OACL but everything opens up (1.25" plus) when I load to magazine length of 3.33"-3.35". Loading single rounds at the range is ok for testing but I need accurate rounds in the magazine during hunting season.

    Anyone run into the same issue and what did you do to solve it?
    mtnhiker06
    1.25 inches@ 100 yds is plenty good for hunting conditions out to as far as one should be shooting at game anyway as it means a 5 inch group at 400 yards. I would challenge anyone to shoot a 5 inch group at 400 yards from positions typically encountered in a hunting situation. What you are referring to is typical in long throated chambers and I have experienced the same when loading bullets especially in Weatherby rifles.

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    Quote Originally Posted by elmerkeithclone View Post
    1.25 inches@ 100 yds is plenty good for hunting conditions out to as far as one should be shooting at game anyway as it means a 5 inch group at 400 yards. I would challenge anyone to shoot a 5 inch group at 400 yards from positions typically encountered in a hunting situation.
    I keep thinkin bout this, ever since I read it last night. It is one of the wisest things you ever said, regarding group size. It puts things in proper perspective.

    I've always strived for 1" groups or thereabouts, and been happy with same. See, I was right all along.

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    Thank you for the replies and input.
    Correction: Powder is IMR 4064 (fat fingered that one)
    iofthetaiga: 2.706
    .338WM: Based on your comment, I contacted the folks at Pacific Tool & Gauge and they are aware of the overly long throat issue associated with some 338-06 reamers. I mailed them a 3.33 set-up round with a Hornady 225 grain SST on the front end (Hornady book OACL for 225 grain SST). They will send me a new reamer putting the bullet .003 off the rifling. After some barrel and chamber work, I am hoping to have a round that will fit the magazine and group 1 or less at 100 yards in the 2600 fps range.

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    Quote Originally Posted by mtnhiker06 View Post
    Thank you for the replies and input.
    Correction: Powder is IMR 4064 (fat fingered that one)
    iofthetaiga: 2.706
    .338WM: Based on your comment, I contacted the folks at Pacific Tool & Gauge and they are aware of the overly long throat issue associated with some 338-06 reamers. I mailed them a 3.33 set-up round with a Hornady 225 grain SST on the front end (Hornady book OACL for 225 grain SST). They will send me a new reamer putting the bullet .003 off the rifling. After some barrel and chamber work, I am hoping to have a round that will fit the magazine and group 1 or less at 100 yards in the 2600 fps range.
    Super! Let us know how it turns out after all of the work is completed.

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    Quote Originally Posted by mtnhiker06 View Post
    Thank you for the replies and input.
    Correction: Powder is IMR 4064 (fat fingered that one)
    iofthetaiga: 2.706
    .338WM: Based on your comment, I contacted the folks at Pacific Tool & Gauge and they are aware of the overly long throat issue associated with some 338-06 reamers. I mailed them a 3.33 set-up round with a Hornady 225 grain SST on the front end (Hornady book OACL for 225 grain SST). They will send me a new reamer putting the bullet .003 off the rifling. After some barrel and chamber work, I am hoping to have a round that will fit the magazine and group 1 or less at 100 yards in the 2600 fps range.
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    Quote Originally Posted by mtnhiker06 View Post
    Thank you for the replies and input.
    Correction: Powder is IMR 4064 (fat fingered that one)
    iofthetaiga: 2.706
    .338WM: Based on your comment, I contacted the folks at Pacific Tool & Gauge and they are aware of the overly long throat issue associated with some 338-06 reamers. I mailed them a 3.33 set-up round with a Hornady 225 grain SST on the front end (Hornady book OACL for 225 grain SST). They will send me a new reamer putting the bullet .003 off the rifling. After some barrel and chamber work, I am hoping to have a round that will fit the magazine and group 1 or less at 100 yards in the 2600 fps range.
    "overly long throat issue associated with some 338-06 reamers."

    Is that an issue?

    Are you trying to get your bullet closer to the lands, for better accuracy? That may not help.

    I guess, there is nothing wrong with having your throat length ground for a particular bullet, but some jump to the lands must be a good idea.

    .003 doesn't give much leeway to keep the bullet from sticking in the lands. There could be that much variance in seating.

    If you decided to choose .030 off the lands, which you might want for a hunting round, your bullet would be .027 deeper in the case.

    There is another thing to consider. After you set the barrel back, or install a new one, chambering with this Reamer, will your rifle still shoot the same size groups, at the same OACLs as before?

    If you shoot a lot, your throat will lengthen from erosion.

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    ....and at 2.706 your existing case head/bolt face to lands distance is near dead on SAAMI spec., no? I guess I don't understand the "overly long throat issue" reference.
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    Quote Originally Posted by iofthetaiga View Post
    ....and at 2.706 your existing case head/bolt face to lands distance is near dead on SAAMI spec., no? I guess I don't understand the "overly long throat issue" reference.
    OK, someone is bound to point this out, so I may as well be more specific. SAAMI spec. breech face to lands is 2.7300, minimum. So at 2.706, you're already 0.024 shorter than minimum spec.
    ...he who knows nothing is nearer to truth than he whose mind is filled with falsehoods & errors. ~Thomas Jefferson
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