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Variations in OAL

jayteejaytee Member Posts: 62 ✭✭
I've noticed when I'm reloading, that my overall length sometimes will vary by a few thousandths and that I'm occassionally having to use the bullet puller to slide them out a little, then place them back in the seating die and carefully seating them by feel so to speak and measuring all the while and trying to get them all the same size. Once the die is set, shouldn't they all come out the same if you use a full stroke? Its really a PITA to do this and very time consuming. I'm using standard RCBS dies. Is this normal, am I missing something or what? Thanks for any help!!

Comments

  • bpostbpost Member Posts: 31,140 ✭✭✭✭
    edited November -1
    The OAL will vary because all bullets are not alike. They vary in length by several thousandths from bullet to bullet. As you seat the bullet the seating stem is pushing on the bullet somewhere down the shank from the tip. Your rounds will be of consistent length from that point of contact.

    You are wasting time trying to get all rounds exactly the same OAL. The critical measurement is from the case base to the point the bullet touches the rifling. Sinclair International makes a hex shaped tool with precision ground holes that give you a repeatable reference point to measure from.

    If you are trying to control length to fit into a magazine of a rifle a few thousandths difference should not cause a problem feeding. If you are doing it for the sake of accuracy then measuring from the engraving contact point is more accurate than OAL.
  • nononsensenononsense Member, Moderator Posts: 10,645 ******
    edited November -1
    jaytee,

    Two things will contribute to the inconsistancies of measurements for OAL:

    The manufacturing and damage to the bullet tip - hollowpoints are made by swaging the jacket closed around the core. The edges of the hollowpoint are irregular at the final position so the length of each bullet will vary. Soft ponts suffer from damage in packaging and transportation yielding differences in length.

    Measuring technique - inconsistant pressure on the calipers.

    Practice and concentration will solve the problem with calipers.

    The first one is solved simply by changing the method of measurement. You need to buy a tool that uses your calipers to measure from the ogive and not from the point.

    Or you could uniform the tip of each of the hollowpoints by using one of two tools. One uses a cutter to cut all the tips to the exact same length. The other swages the tips of the hollowpoint more closed with more precision. There isn't much you can do with soft points so learn to use the tool for measuring ogives.

    Best.
  • jayteejaytee Member Posts: 62 ✭✭
    edited November -1
    bpost, just wondering why I am wasting my time if I'm trying to maintain concistency when working up a load? Sure, 2.780 OAL for my .260 Rem may not be the best, but how can you find the best unless you eliminate the worst? What would be your suggestion of finding the best OAL for my rifle? Granted, this is "just" a hunting rifle, but I always like to get 'em to shoot the best that I can and sometimes I can get very *....just ask my wife! [:D]Thanks for the replies!!!
  • bpostbpost Member Posts: 31,140 ✭✭✭✭
    edited November -1
    quote:Originally posted by jaytee
    bpost, just wondering why I am wasting my time if I'm trying to maintain concistency when working up a load? Sure, 2.780 OAL for my .260 Rem may not be the best, but how can you find the best unless you eliminate the worst? What would be your suggestion of finding the best OAL for my rifle? Granted, this is "just" a hunting rifle, but I always like to get 'em to shoot the best that I can and sometimes I can get very *....just ask my wife! [:D]Thanks for the replies!!!

    This is an easy way to get real close to the optimum seating depth to START from, make sure rifle is EMPTY and close the bolt. Take a cleaning rod and run it into the muzzle until it contacts the bolt face. Take a sharp knife and mark the end of the muzzle on the cleaning rod. Next, remove the bolt and drop a bullet into the chamber. Use a second cleaning rod or wood dowel to gently hold the bullet in place. Run the marked cleaning rod back into the muzzle until it just touches the bullet tip. Mark that spot on the rod also. Using calipers measure the distance between the marks. You will be accurate to within a thou. or two. That is the OAL to just touching the lands.

    From that point you can start trying different seating depths. MOST of my guns seem to shoot best with the bullets jammed into the rifling by about .0010. Some rifles seem to shoot better with it getting some jump. testing will show you what your rifle likes.

    A couple of cautions. Be VERY careful of the cleaning rod as you slide it down the muzzle. Be even more cautious when marking the rod, you dont want to scratch the crown with the sharp knife. You want to avoid damage to the crown like the plague. Next, put a old nylon style cleaning tip into the cleaning rod threads. Otherwise the darn bullet tip will go into the hole on the rod tip and mess your measurements all up. I took an old 30 caliber one and cut it square with a knife.
  • JustCJustC Member, Moderator Posts: 16,038 ******
    edited November -1
    as stated by Nononsense, rule #1, measure off the Ogive and not the tip. Tips will vary as bullets are mass produced, heck even boattails can even vary a bit. You will get much better measurements by buying a comparator that is either hand held or caliper blade mounted.
  • jayteejaytee Member Posts: 62 ✭✭
    edited November -1
    I know that some rifles shoot better with the bullets seated just off the lands and some shoot better with the bullets touching the lands. I know several companies make tools to measure this, Sinclair, Midway, ect. Why couldn't you take a sized, umprimed case seat the bullet several thousandths out, chamber the round and then close the bolt. If the bullet strikes the lands and is pushed back into the case, wouldn't this give you the chamber length? Am I shooting in the dark here or would this work? Thanks for all the reply's so far, I appreciate them!!
  • nononsensenononsense Member, Moderator Posts: 10,645 ******
    edited November -1
    jaytee,

    Of course you can do what you describe. It's been done for decades. One suggestion is to slit the neck of the case with a Dremel cutoff tool and sand off the burr. Clean the inside of the neck and slightly seat a bullet straight in the neck. Chamber this dummy and carefully extract the dummy. Add a drop or two of Super Glue to the neck to seal and hold the bullet in place. Measure and write down the dimension of the OAL measured from the ogive not the tip. Use this dummy as a tool to set your dies. Keep it in your die box labeled.

    Best.
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