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Thread: C.o.l>

  1. #1

    C.o.l>

    Have been playing about with some 180grn round nose in my 30-06 the bullets are pro-hunter with 56.5gns of H4350 behind them.
    The problem is the Hogden manual says the COL should be 3.3inches which only leaves me with .221 of the bullet in the case will this cause a problem.
    I also checked the length of the chamber at the same time and even with rounds at this length I still have 105 thou to the lands which seems a lot.
    There does not look to be a lot of wear to the throat of the rifling but it is a BSA and was made in 1956 ish.
    With factory 150grn it will shoot 1 1/2 groups at 100yds.
    AT THE AGE OF 50 I DECIDED I WAS GOING TO GROW OLD F***ING DISGRACEFULLY

  2. #2
    So it looks like you have a double edged problem. Is the bullet seating into the neck deep enough and is that jump too much. I have never worried too much about the COL in the manuals as I tend to seat to the base of the neck with minimum loads and work up. Having it seated deeper simply means that you will, if anything, reach your maximum pressure faster. Since the standard OAL for the 30-06 is 3.336 inches, you are only dealing with .036" below specified max OAL. If you want more neck tension, do as I do. Since you can't reach the lands, you might as well go for the neck tension. ~Muir

  3. #3
    I do not know why reloaders reference OAl or COAL data from manuals when making initial loads? They are usually of little relevance.

    For a hunting load. you need about one cartridge diameter of projectile in the case to hold it firm. If this makes contact with the lands, seat it deeper. If it will not fit in the mag, seat it a bit deeper. It it does not group well, try seating it a bit longer if you have room in the chamber and magazine or a bit deeper. RN projectiles tend to be a bit dumpy so you will have a loaded cartridge with a shorter OAL.

  4. #4
    Quote Originally Posted by sikadog View Post
    Have been playing about with some 180grn round nose in my 30-06 the bullets are pro-hunter with 56.5gns of H4350 behind them.
    The problem is the Hogden manual says the COL should be 3.3inches which only leaves me with .221 of the bullet in the case will this cause a problem.
    I also checked the length of the chamber at the same time and even with rounds at this length I still have 105 thou to the lands which seems a lot.
    There does not look to be a lot of wear to the throat of the rifling but it is a BSA and was made in 1956 ish.
    With factory 150grn it will shoot 1 1/2 groups at 100yds.
    Try as Muir suggested, seat the bullet so the base of the bullet is level with the neck should juncture. and see how it likes it then you can work the bullet outwards to see if the grouping improves.

    If you BSA was indeed made around that time then the barrel is a cut rifled and lapped one as that's the way BSA made them then and as you say it will shoot factory 150Grn in 1 1/2 MOA already you should be able to improve upon that methinks.

    Don't worry about the bullet jump as in my own experience none of my rifles shot best with small distances to the lands. In some rifles one cannot reach the lands like in the Gustav Swedish Mauser I have the 120 Grn and 139 Grn bullets cannot reach the lands as it's throated for the 156/160 Grn RN bullet. Likewise in my 30-30 with the 130 Grn Spire Point bullet as the throat was cut for the 170 grn RN or Flat Point bullet the short pointed 130 grain cannot reach the leade. Yet if one gets it right when behind the butt the load will put three bullets touching at 100 yards.

    To get the grouping to tighten up in my 7x57 with the Hornady 139 BTSP bullet I had to set the bullet so that the crimp ring was only just out of the case neck which means it has a considerable jump to the leade. Seating the bullet so it was about 0.020" off the leade gave grouping of close to 2 MOA yet seaing much deeper gave 3/4 MOA with the same powder and bullet. That rifle actually shot best with the Flat point 139 Grn bulltet but it wil no feed from one side of the magazine as the tip hangs up on the edge of the chamber.

    It was experiences like this that made me question this bullet almost touching the lands thing.

  5. #5
    Quote Originally Posted by sikadog View Post
    Have been playing about with some 180grn round nose in my 30-06 the bullets are pro-hunter with 56.5gns of H4350 behind them.
    The problem is the Hogden manual says the COL should be 3.3inches which only leaves me with .221 of the bullet in the case will this cause a problem.
    I also checked the length of the chamber at the same time and even with rounds at this length I still have 105 thou to the lands which seems a lot.
    There does not look to be a lot of wear to the throat of the rifling but it is a BSA and was made in 1956 ish.
    With factory 150grn it will shoot 1 1/2 groups at 100yds.

    The COL given in the manuals is simply the COL that they used when devloping the load.

    For hunting rifles and hunting bullets jamming into the lands is a bad idea on a few fronts. The main one from my point of view is the difficulty in unloading.

    I have grown unafraid of jumping bullets into the lands for this purpose, My loads start off with about calibre's worth of shank in the neck and I go tune from there after I've established a rough max load and looked for promising charge weights.

    In my 30.06 with 180 grain Hornady BTSPs I load at 3.250" (or 2.655" to the ogive, a more consistent method of measuring the length of rounds I find) which places just happens to put about .3" worth of shank in the neck, coincides with the crimping grove and gives this sort of accuracy:



    FWIW I found that 57.5gr of my lot of H4350 gave pressure signs and a velocity spike but and so-so accuracy, 56.5 was better in all counts but I found that 56gr of RL17 gave more velocity than the 57.5H4350 load and the sort of accuracy you see above.

    Various things happen as you change the COL.

    Perhaps counter-intuitively pressure can go down as the length is reduced and go up if increased due to what is in effect changing the freebore of the rifle.

    I recently developed a load with 200gr Nosler accubonds for heavy stuff, developing 20 thou off the lands ( 3.440" in my rifle) gave pressure signs at max, large velocity variations at the same and I couldn't find a group under an inch below that.

    I took the most promising powder charge ( 1.2 grains under max as it happened) and loaded more at 20" steps down to 3.340", fortunately my magazine can take rounds up to 3.5".

    The best accuracy came at 3.360" with the velocity reduced by 50 fps compared to the same load at 3.420", due I think to the increased freebore effect from the deeper seated bullets, but the ES reduced to a fantastic 8 fps over ten shots and the groups shrank to just over a half inch.


    Don't fear jump in a hunting rifle.

  6. #6
    Thanks gents you have given me a lot to play with.
    The BSA rifle is a long action imperial.
    AT THE AGE OF 50 I DECIDED I WAS GOING TO GROW OLD F***ING DISGRACEFULLY

  7. #7
    I dont know if this information will help you, it certainly did me when I had a problem the other week. The information was sent to me by Nathan at Terminal Ballistics Research, I am sure he wont mind we posting this. It gives methods of finding bullet seating depths etc

    Method 1

    Magazine empty. Cock the rifle on an empty chamber (do not pull the trigger as the firing pin will protude and ruin the measurement)
    Take a ram rod and carefully insert it down the muzzle to touch the bolt face
    Take a plastic clothes peg, slide it down the ram rod till its butted squarely to the bore
    Remove the rod a way, then mark where the peg is sitting using a fine tip pen at an angle of 45 deg
    Remove the bolt
    Dump a projectile in the chamber
    Use a dowel, another ram rod or something fine to place against the base of the bullet
    Re-insert the ram rod
    Re do the peg trick
    Mark the rod- same side of the clothes peg as you did last time

    This is your max COAL touching the lands. Experiment with 1mm bullet jump to begin with

    Method 2
    Size a fired case so that only 1mm of the lip of the case neck is sized
    Insert a projectile so that it is just started into the case neck
    Liberally coat the intersection of the ogive and bullet body with lee lube and allow to dry. No lube below the cannelure point / bullet body as the lands will grip the bullet and pull it back out again giving a false reading
    Chamber the cartridge, then extract it. This is your Max COAL
    Repeat this three times to be sure

    Method 3
    Same as above but 5 minute epoxy is used on the inside of the case neck. Once the dummy round is chambered, leave sitting for half an hour or so. I don't use this method but have heard others use it effectively and I can see why.

    Method 4
    One day when you have a few dollars, buy a comparator and measure COAL off the Ogive

    Double checking
    Make up a dummy round with final COAL on it. Lets say the max COAL was 86.5mm touching the lands, your dummy round will have some bullet jump incorporated into it, lets say you want to go minimal at 10 thou / .2mm- so your dummy round is 86.3mm. Take a vivid, mark the Ogive, let it dry. Dump the dummy round into the chamber, close the bolt. Extract the dummy round carefully, you'll need to guide it out with your fingers to stop the extractor forcing the bullet against the chamber wall, scratching up the bullet. Check for rifling land marks on the projectile, if there are land marks, your initial measurements were wrong. You can now carry on with this and use it as a method for determining the max COAL, setaing the bullet 5 thou deeper before each retest.


    Problems:

    Bullet sits halfway out of the case neck

    Check that your COAL is not so long that the final seating depth is not such, that the bullet sits only halfway down the case neck. If a bullet is only halfway down the case neck, there is a risk that it will not be squarely aligned to the bore. If this occurs, forget about close bullet jumps and seat for concentricity. A good example is the .308 Win and Weatherby cartridges. If the 168gr Amax is seated so the the boat tail/body junction is flush with the bottom of the case neck, bullet jump will be around 4mm / 100 thou. The bullet jump may be large but this load will be more accurate than a bullet seated to within a short distance of the lands.

    Magazine too short for my optimum COAL

    If your COAL is too long for your magazine, such as trying to hand load a .300 Win Mag in a Tikka T3, you will have to choose between single feeding or seating to the mag length. When seating to the mag length, as an example, the T3 has an internal mag length of 85.5mm. You will therefore need to seat loads to 84.5mm if you want to ensure smooth feeding from the magazine. In contrast, if developing an accurate load with the A-Max for long range, single feeding cartridges with a COAL of approximately 89mm might prove accurate. Some experimentation may be required, as another example, instead of going forwards and single feeding, you might want to try going deeper, to see how this effects timing (when the bullet leaves the bore / harmonic effects).

    Berger VLD

    The ogives of VLD projectiles differ from bullet to bullet by up to 20 thou / .5mm. To avoid problems, use a bullet jump of 40 thou or 1mm. Occasionally, a VLD will not shoot at 40 thou jump, though I firmly recomend that shooters adopt this bullet jump for preliminary testing. If this jump proves finnicky, try a close bullet jump. Oddly, some rifles do like to have the VLD seated close, with some VLD's engraged in the lands while others will be 10-20 thou off the lands. This is due to timing, a sweet spot in the whip of the bore. The barrel in this instance is showing great consistancy. Think of it like a bull whip (if you have ever tried to crack a whip). if you don't time your flick correctly, the whip wont crack. The whip cracker first learns the correct timing, then learns how to do this each and every flick.

    Bullet jump

    Recommended experimental seating depths (where concentricity and mag length is not a problem) include:

    10 thou- metric users round off to .2mm- especially with SST
    20 thou or .5mm
    40 thou or 1mm- especially with VLD.
    Concentric seating (where the COAL has the bullet sitting out of the case neck)

  8. #8
    Quote Originally Posted by sikadog View Post
    Thanks gents you have given me a lot to play with.
    The BSA rifle is a long action imperial.
    An original "Hunter" is still on my desired list. The Hunter line became the Royal line with the Imperial being the Long action one and another that I desired for the collection. I own a Regent in .222 Rem which is a cracking rifle.

    Oh yes in .308 and 30-06 I used the 165 Grain bullets too good effect.

  9. #9
    Chikenman
    Thanks for the right up but it does not help but is very good imformation
    Thanks
    AT THE AGE OF 50 I DECIDED I WAS GOING TO GROW OLD F***ING DISGRACEFULLY

  10. #10
    Brit
    Out of all the rifles I own my Imperial is the one I have a soft spot for I have owned it for 20 years and about once every year I dig it out of the cabinet and go and play it never needs re-zeroing it just shoots.
    This year I intend to shoot some red stags with it in thick forestry hence the 180grn bullets.
    I normaly shoot my first/first pattern Monarch 270 at Sika.
    AT THE AGE OF 50 I DECIDED I WAS GOING TO GROW OLD F***ING DISGRACEFULLY

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