Results 1 to 15 of 15

Thread: Scope Height-Over-The-Barrel Question

  1. #1

    Default Scope Height-Over-The-Barrel Question

    I'm firing 300 grain lead hard cast bullets at 2100 FPS out of my 45-70 1895SBL. I put my Leupold 2-7 scope on it using Burris Xtreme extra high rings (advertized as 1-inch high rings).

    So the question...how do you figure out the scope height for ballistic programs when you want to calculate trajectory at a given range? Do I need to measure stuff or should it be published somewhere? If I need to measure, do I measure to the center of the scope tube or the bottom of it and to where on the rifle?

    So, can you help me?

    MyTime

  2. #2
    Member 1Cor15:19's Avatar
    Join Date
    May 2009
    Location
    Dillingham, AK
    Posts
    2,482

    Default

    Quote Originally Posted by MyTime View Post
    If I need to measure, do I measure to the center of the scope tube or the bottom of it and to where on the rifle?

    So, can you help me?

    MyTime
    Scope height is measured from the center of the bore to the center of the scope.
    Foolishness is a moral category, not an intellectual one.

  3. #3
    Member
    Join Date
    Feb 2008
    Location
    Fairbanks
    Posts
    301

    Default

    I do not know of a listing of heights anywhere, for most bolt actions with medium to low rings 1.5" is a good number. Using the exact right value is not a real big deal.

    In you case just measure from the center of the scope to the center of the bolt with a tape measure and use that. It may help to lay a tape measure on the action and read it from a little distance to avoid looking at it with to much angle difference. But again a real exact value is not a big deal.

  4. #4

    Default

    1Cor and bandhmo, thanks for the info!

    MyTime

  5. #5
    Member marshall's Avatar
    Join Date
    Nov 2007
    Location
    Near Phoenix, AZ
    Posts
    1,814

    Default

    If you want an exact measurement use a caliper. With the scope mounted measure the distance from the top of the scope tube to the bottom of the barrel directly below the scope.

    Measure the diameter of the scope tube and barrel independently at that location and divide each number by two.

    Add the total of each answer together and subtract from the total distance. The answer is the center to center measurement.

    Example:

    Top of scope tube to bottom of barrel 2.8"
    scope 1.6" divided by 2 equals 0.8"
    barrel diameter divided by 2 equals 0.4"
    Center to center is 1.6" with these hypothetical measurements.

    It's fairly quick and easy with a bolt action rifle. With your lever gun it may require a little extra effort.

  6. #6

    Default

    If you're shooting a rainbow trajectory like a 300 gr bullet out of a 45-70, then depending on what kind of accuracy at what range you're looking for, exact scope height might be important. Marshal's technique is a good one. Some other things to consider are accurate BC and acculturate velocity which you are not likely to get from published manufacturer data. Best thing to do is shoot it various ranges and make a good drop chart.

  7. #7

    Default

    Thanks for the input guys.

    Montana Rifleman, I hand load Cast Performance lead hardcast 300 grain. That load I use chronographs at 2100 FPS. As for an accurate BC, I'd like to have that. They don't publish it on the boxes and their website does not have it either. I think I'll have to write the company on paper and ask that way.

    MyTime

  8. #8

    Default

    scope height over bbl... the best height is whatever height gives you a solid yet comfortable cheek weld and puts your eye looking down the centerline of the scope...

    will changing scope height over the barrel by fractions of an inch have any noticable effect on the trajectory... the answer is NO

  9. #9
    Member marshall's Avatar
    Join Date
    Nov 2007
    Location
    Near Phoenix, AZ
    Posts
    1,814

    Default

    Quote Originally Posted by AK-49 View Post
    will changing scope height over the barrel by fractions of an inch have any noticeable effect on the trajectory... the answer is NO
    Sorry but the answer is yes. In a short range 45-70 scenario it isn't a big deal, perhaps that's your meaning.

    However, with a long range shot a 0.3" ring height difference will make a 3.0" point of impact difference at 1000 yards with no other changes.

  10. #10
    Member marshall's Avatar
    Join Date
    Nov 2007
    Location
    Near Phoenix, AZ
    Posts
    1,814

    Default

    Quote Originally Posted by MyTime View Post
    As for an accurate BC, I'd like to have that. They don't publish it on the boxes and their website does not have it either.
    A few of the flat nose 300gr bullets I've looked up range between .194 and .206BC. Those big flat nosed bullets don't have high BC's but they are perfect for your hard hitting rifle.

    Don't worry about the ring height either. Just mount the scope for a comfortable fit with a solid cheek weld and use a quality base and rings.

  11. #11
    Member broncoformudv's Avatar
    Join Date
    Apr 2006
    Location
    Anchorage, Alaska
    Posts
    4,670

    Default

    Quote Originally Posted by marshall View Post
    However, with a long range shot a 0.3" ring height difference will make a 3.0" point of impact difference at 1000 yards with no other changes.

    Yeah but who changes rings and does not sight in their rifle again?

    This entire thread has me confused? I have always mounted my scopes in rings that gave me the most natural sight picture, if the rings are too high or too low you will not be able to easily aquire the sight picture which is the entire point I thought. Now you guys are talking abotu trajectory and BC have fun with that its way above my little brains ability to do that math.

  12. #12
    Member marshall's Avatar
    Join Date
    Nov 2007
    Location
    Near Phoenix, AZ
    Posts
    1,814

    Default

    Bronco,

    Just answering the question pardner. I too like a low ring setup with a comfortable cheek weld that allows me to acquire the scope center consistently every time I bring it up for a shot.

    The BC doesn't really matter with a low speed heavy flat nose bullet like the one in this thread. It's just a reference that was added by another and I applied the math to answer the question for entertainment purposes.

    Just for a little more humor consider this. In this 45-70 thread if the said load is zeroed at 100 yards which seems reasonable, the difference in a 0.3" scope to bore measurement would only be the difference in bullet diameter at 300 yards. In reality there are several other factors that would cause greater point of impact differences than that.

    By the way, the higher rings would offer less drop down range when zeroed at 100 yards. Again, just trivial since the 45-70 isn't considered a long range cartridge by most.

  13. #13

    Default

    if you want to improve the ballistic trajectory then look at something called "maxium point blank range" and find the scope ring height that give you the the most comfort and still allow the scope to clear the bbl... Most of the good ballistic programs allow you to find the best max point blank range for your situation.

  14. #14
    Member marshall's Avatar
    Join Date
    Nov 2007
    Location
    Near Phoenix, AZ
    Posts
    1,814

    Default

    Quote Originally Posted by AK-49 View Post
    Most of the good ballistic programs allow you to find the best max point blank range for your situation.
    Agreed, with his numbers a 3" high 100 yard zero would offer a 191 yard point blank range with +/- 3" trajectory.

    50 / +2.0"
    75 / +2.8"
    100 / +3.0"
    125 / +2.5"
    150 / +1.2"
    175 / -1.0"
    200 / -4.2"

  15. #15
    Sponsor ADfields's Avatar
    Join Date
    Nov 2008
    Location
    Missing Palmer AK in Phonix AZ.
    Posts
    6,416

    Default

    I donít know a thing about these programs but yaíll got me wondering and got to ask. I have a 50bmg set up for 1000 yard paper punching and the scope is pitched down in front so that at 1000 itís about middle of the adjustment range. So, what do you do if your scope is mounted with pitch and not parallel to the barrel? Would that effect your measurement, where do you measure it then, does the program allow for that or is it just so small it's irrelevant?
    Andy
    On the web= C-lazy-F.co
    Email= Andy@C-lazy-F.co
    Call/Text 602-315-2406
    Phoenix Arizona

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •