How to determine best COL (9mm)?

Discussion in 'The Ammo & Reloading Forum' started by prof_fate, Feb 21, 2012.

  1. prof_fate

    prof_fate Former Guest

    Joined:
    Jan 20, 2012
    Messages:
    143
    Location:
    Western PA
    I'm new to reloading and ran a batch of LRN and wasn't impressed with the accuracy. Not sure what to blame or work on first (tried 3 different loads of the same powder - all were about the same). Same COL.

    From what I've read COL is a big determinate in how accurate the ammo/gun is.

    Recipes list a min COL and there is a max for the caliber of course.

    So how do you determine the best COL? If you change bullets (weight or shape or material) or powder (type or charge) do you have to start over from scratch, or would the COL for your remain the same?
  2. cranky cj

    cranky cj New Member

    Joined:
    Jan 23, 2009
    Messages:
    62
    Location:
    Northern Colorado
    I don't know about all the rest of the stuff but this is what i do; look up the book's max COL listed and set the first one to that and see how well it chambers, if it won't chamber I keep shortening, or pressing it in, until the round will chamber without any hangups. So, i end up with the max COL for my particular gun. the last 9mm and 45acp reloads were, I thought, accurate. I've measured factory ammo and it usually comes in way under my layman COL listed length. Lets see what everybody else has to say.
  3. JLA

    JLA Well-Known Member

    Joined:
    Feb 26, 2007
    Messages:
    18,271
    Location:
    Heart Of Texas
    In a rifle yes, seating depth and how the case is sized makes a difference. With handgun ammo the powder used is the biggest accuracy factor. If you arent getting an accurate load with any charge weight within the recipe for that powder then switch powders. Ill tell you now that one of the absolute best powders I have ever burned in 9mm loads is Unique. It gives near 100% load density with all bullet weights and is just plain accurate. Only trade off is, its a little dirty. So if you shoot a stainless gun, itll be black after just a few mags. But the groups will be worth it.
  4. 76Highboy

    76Highboy Well-Known Member Supporting Member

    Joined:
    Jan 1, 2012
    Messages:
    8,663
    100% ditto on that. I shoot a lot of Unique. And Bullseye as well.
  5. JLA

    JLA Well-Known Member

    Joined:
    Feb 26, 2007
    Messages:
    18,271
    Location:
    Heart Of Texas
    I use titegroup and bullseye for light bullet 9mm loads. They are both well suited to that end of the chart.
  6. bntyhntr6975

    bntyhntr6975 Member

    Joined:
    May 5, 2009
    Messages:
    572
    Location:
    Wichita, Ks.
    Were the LRNs that you tried sized to the correct diameter for your barrel? A lot of people never bother to even check. My best load in 9mm is 124g cast RN ahead of a max charge of Power Pistol. I don't recall overall length right now but I know its close to the listed length. Pistols are not near as picky as rifle as far as seating depth vs. accuracy. Pretty much, find a length that functions well and then adjust the powder tiny bits. Be careful not to seat most pistol loads too short, this can cause severe pressure spikes and you might not get a second chance at it. And since alot of pistol loads have a small amount between min and max, take caution there too. 9mm is alot more forgiving than some others and its a great little round.
  7. American Leader

    American Leader Well-Known Member

    Joined:
    Mar 1, 2011
    Messages:
    1,715
    Location:
    Iowa
    OAL makes a big difference in pressure and velocity which in turn can make a difference in accuracy. When your reloading manuel notes a minimum OAL for a specific load it is telling you not to load this recipe below the stated minimum overall length. Generally that length is best for that load, however, there's a difference between safety and how well a specific load operates in a particular firearm. A reloading manuels information gives specific data and ballpark specific results. You do have some variation to work with as noted to find what shoots best in your gun, but follow your manuel and be very careful when deviating from it. When you start adjusting lengths "OAL" at random, you're looking for trouble. Whatever you do needs to make sense.
  8. prof_fate

    prof_fate Former Guest

    Joined:
    Jan 20, 2012
    Messages:
    143
    Location:
    Western PA
    I know lead bullets are available in different diameters, but .356 is the one that is common and what I got.
    I'm using W231 - recomended by many as a versatile and easy powder to learn to work / reload with.
    Unique was one I considered as well.

    Does crimp have an affect on accuracy? I'm using a lee factory crimp die as it supposedly eliminates any issues with case length variation regarding accuracy.
  9. American Leader

    American Leader Well-Known Member

    Joined:
    Mar 1, 2011
    Messages:
    1,715
    Location:
    Iowa
    Because crimping has an effect on pressure as well, it will keep each rounds pressure more consistent and consistency leads to accuracy.
  10. prof_fate

    prof_fate Former Guest

    Joined:
    Jan 20, 2012
    Messages:
    143
    Location:
    Western PA
    consistency from round to round (be that powder, crimp, length, etc) will make each round consistent to the next. Fine, I get that.

    But when I read tests in magazines some ammo groups at 1" and others at 4". I want to make ammo that groups at 1" of course.

    So what is the best procedure to follow to get there? If I make 20 rounds and get 4" groups, what do I change first? Length, bullet, powder, primer, crimp?
  11. American Leader

    American Leader Well-Known Member

    Joined:
    Mar 1, 2011
    Messages:
    1,715
    Location:
    Iowa
    prof, I'll send you some info via private message. Give me a little time, it's past bedtime!
  12. JLA

    JLA Well-Known Member

    Joined:
    Feb 26, 2007
    Messages:
    18,271
    Location:
    Heart Of Texas
    If youre using an OAL that works in your gun then adjust the powder charge til you hit one that jives. Youll know when you hit it, that little gun will sing and if you know what youre doing behind the trigger it wont miss.

    As for crimp, I put a taper crimp on all auto pistol ammo and a roll crimp on all revolver ammo. for 9mm, the casemouth should measure .379 - .380 after crimp.
  13. carver

    carver Moderator

    Joined:
    Jul 28, 2008
    Messages:
    16,821
    Location:
    DAV, Deep in the Pineywoods of East Texas, just we
    I've been reloading for .45ACP, and .380 in auto pistols for some time now, and I have never had such a problem! Guess that's just me! With lead bullets I put a light crimp at the crimp ring, and what ever the COL comes out to is what I shoot. So far I have had no problems with accuracy, and everything shoots where I point the gun. Now if I wanted to make ultra accurate bullets for competitive shooting, I might be looking at "all" the factors in making a bullet. I make mine to plink with, and the ammo I carry in a SD gun is the best factory ammo I can buy.
  14. prof_fate

    prof_fate Former Guest

    Joined:
    Jan 20, 2012
    Messages:
    143
    Location:
    Western PA
    for IDPA 8" at 15 yards is fine.
    To do well in PPC you have to get your shots into an index card sized target at 25 yards from multiple positions.

    I'll measure my crimp
  15. JLA

    JLA Well-Known Member

    Joined:
    Feb 26, 2007
    Messages:
    18,271
    Location:
    Heart Of Texas
    Gee whiz, those are pretty big requirements. Pretty much any gun with any good ammo should be able to best those requirements in the hands of a good shooter id think.
Similar Threads
Forum Title Date
The Ammo & Reloading Forum Burn rates...... how do they help determine which powders to choose? Jul 30, 2014
The Ammo & Reloading Forum What powders meter the best? May 18, 2014
The Ammo & Reloading Forum best hand primer Mar 25, 2014
The Ammo & Reloading Forum Best Place to Get .308 Cases Mar 18, 2014
The Ammo & Reloading Forum Best dies for 9mm on LNL progressive? Jan 27, 2014

Share This Page