Is “Overall length” a max or min

Discussion in 'Handloading and Reloading' started by daniel craig, Mar 21, 2021.

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  1. daniel craig

    daniel craig Member

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    1B23C5C7-22F6-42A1-85C3-9CB3737B9E00.jpeg My round measured an overall length of 2.75” which has me wondering if the length in the chart is a minimum or a maximum.
     
  2. rfwobbly

    rfwobbly Member

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    Neither. It's a base (or nominal) dimension with no tolerance given. You must consult other sources to gain the tolerance.
     
  3. AJC1

    AJC1 Member

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    It was the spec to replicate that load. Consult the Sami drawings for verifying cartridge specifications
     
  4. herrwalther

    herrwalther Member

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    It is a guideline for replicating a load. Some powders can be compressed in the case by the bullet and some cannot. The COAL measurement is a recommendation for keeping a load operating within safe pressure. According to my Lee manual the Max COAL is 3.037" for 7.62x54R
     
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  5. daniel craig

    daniel craig Member

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    Ok good to know. So if I’m .18 below coal I should pull and redo?
     
  6. Bfh_auto

    Bfh_auto Member

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    What made you choose that overall length?
    It isn't necessarily wrong.
    Usually I run based on chamber length, magazine length or cannelure location.
    If either of the first two conditions aren't met. I don't use the combination.
     
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  7. herrwalther

    herrwalther Member

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    That sheet says the round should be 2.975 and you made 2.75. That is a difference of 0.225" which is quite a lot as reloading goes. It also states that is a compressed charge and you seated much deeper than the data does. I would double check your powder and charge again.
     
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  8. wankerjake

    wankerjake Member

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    Are you using a swift scirocco bullet? If not that listed OAL doesn’t mean anything

    Agree with @Bfh_auto, how did you settle on that OAL?
     
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  9. daniel craig

    daniel craig Member

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    I didn’t have my die set up correctly and seated the bullet too deep. @wankerjake
     
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  10. daniel craig

    daniel craig Member

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    I am not. It was basically the only data I could find for a .311 180grain bullet and Varget powder.
     
  11. daniel craig

    daniel craig Member

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    Uuuh yeah that’s what I meant lol
     
  12. alfsauve

    alfsauve Member

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    Generally, SAAMI, for cartridges, gives the MAX dimension with a minus tolerance. Except for Overall Length, where they state both a MIN and a MAX. Which makes sense because of different bullets weights and shapes their isn't a single OL fits all.

    Interestingly, I don't think SAAMI has a 7.62x54R standard.
     
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  13. wankerjake

    wankerjake Member

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    Ok so that listed OAL just got not very important to you then. Why did you seat to the length you seated?


    I see you answered that above, alert came late

    What bullet are you using? Does it have a cannelure?
     
  14. Bfh_auto

    Bfh_auto Member

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    Seat one .311 into the case neck.
    See if it fits in the magazine. If not shorten it up slightly until it does.
    Color it with a sharpie once you get a length that will fit the magazine. Shorten it until you don't get marks from the rifling. This is your max overall length for this rifle.
     
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  15. daniel craig

    daniel craig Member

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    Ok. Does that impact the powder charge if the COAL is different than in the load data or can I use the same charge recommendations?
     
  16. wankerjake

    wankerjake Member

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    I think it’s prudent to start at the lower end of the spectrum with different bullet and length but yes I would likely use the same data if it’s a similar composition bullet (cup and core or bonded)
     
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  17. daniel craig

    daniel craig Member

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    Ok. You’re probably right. I got my die set up correctly. Do you think it’s worth seating a couple bullets at the deeper length (the one I messed up) to see what results I get?
     
  18. wankerjake

    wankerjake Member

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    What bullet you shooting?
     
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  19. Bfh_auto

    Bfh_auto Member

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    Start at the minimum weight and work up.
    Watch for sticky bolt lift and primer deformation.
    Both of these will mean you are way over pressure and need to back down a lot.
     
  20. NMexJim

    NMexJim Member

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    7.62 x 54R is a Russian rimmed cartridge. The C.I.P. specs give 77.16mm (3.0377") as max overall cartridge length. They do not specify a min dimension.

    Here's how I read the sheet:

    The publisher of the spec sheet (is that a Swift sheet?) you included tells you that a 2.975 COL is recommended for that bullet - 180 gr Scirocco. The specs also say that the particular optimal (read that as recommended or accurate) charge is 44.8 gr of Varget which is a compressed load. They also give you a min and a max charge at 43.0 and 46.5 respectively which tells you that you're somewhere near the middle at 44.8 gr and have a little room to go up should you want.

    In a box of bullets, no two will be exactly the same, and .018 could be reasonable, but you wrote down .180 which is way off. Hopefully, this is a typo. If you mean .018, then that's a reasonable variation. If not, then, yes, pull them and try again.

    If you've got a chronograph, use the recommended data and see if she's near 2492 fps.
     
  21. PapaG

    PapaG Member

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    Some books specify oal (min).
     
  22. Archie

    Archie Member

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    Perhaps. Did you start your load progression at the lowest charge level and work up? Are you now at the maximum charge level? If the answer to both questions is yes, I see no point in changing. If one notes excess pressure, perhaps adherence to the COL is needed.

    The COL is a maximum for operating through the action. The loaded round must be short enough to fit in the magazine, be it detachable or fixed. A revolver round must be short enough to not stick out the front of the cylinder and block rotation - or perhaps closing. On the other hand, too short a loaded cartridge will not cycle though the feed cycle of a semi-automatic arm (handgun or rifle). Lever action rifles require a certain maximum and minimum in other to function through the action (lifter and such).
    As far as pressure goes, seating a bullet too deep - resulting in a 'short' loaded round will increase chamber pressure to an unknown degree. Depending how deep, it may run up pressure to a cataclysmic degree. (Worse case would be the bullet jamming powder all together, unless directed to use such a 'compressed load'.)

    However, if everything works, the powder change is below an overcharge the maximum COL is likely meaningless within a few thousands of an inch.
     
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  23. daniel craig

    daniel craig Member

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    That’s the depth of response I was hoping for. Thanks!
     
  24. NMexJim

    NMexJim Member

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    Archie - go up and study the load data please. It plainly states compressed load for the 44.8 grain load.
     
  25. Archie

    Archie Member

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    Hello, New Mexico Jim. Read the last sentence in the second paragraph, please.
     
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