What first? Powder or seating depth?

Discussion in 'Reloading' started by Chris89lx, Oct 3, 2011.

  1. Chris89lx

    Chris89lx Member

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    Finally have most pieces together to start reloading for my7MM Rem Mag.
    Its a model 700 SPS with detachable magazine.

    I'm loading 168 Berger hunting VLD's with RL-22 powder and Federal 215 primers. It's going into once fired Federal brass.

    Here is the load data Berger sent me.

    Load data was generated using Quick Load a 26 inch barrel a COAL (cartridge over all length) of 3.290 inches and your COAL and velocity could be a little different.
    Bullet----Powder-----Start Load--Approximate Start Velocity---MAX LOAD--Approximate Max Velocity -----Fill Ratio
    168 Grain--RE-22---------58.5---------2701-----------------------------65.0----------2984----------------------------------96.2%


    Here is were I am thinking of starting...

    As long as the recomended 3.290 COAL fits into my magazine. I will use that as a COAL to start building up a load for my rifle.

    Then if I want more acuracy out of it after that. I will start adjusting seating depth.

    Am I going about this the correct way??
    Any other recomendations?
     
  2. 80Maro

    80Maro Well-Known Member

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    After finding a load for my rifel with a couple different bullets I have learned a few things that if I knew before hand I could have saved a bit of money in components.

    1.) First I would find out where the lands are in my rifle. What I do is take a case, cut a slit in the neck and insert a bullet, chamber the round and then slowly unchamber it and measure the coal at least 10 times to get an average. I keep this particular bullet and mark on it the coal that gave me the distance to the lands. This particular bullet does not get loaded to be fired. I use it and the case with the slit to set up my bullet seating die when I am ready to load.

    2.) Next I would load 3 rounds starting at 58.0 at the coal that I determined was touching the lands and go up in 1.0gn increments untill I saw pressure signs and stop.

    3.) After firing the groups from step 3, I would get the most accurate of the 3 (lets say that was at 61.0gn) and load 3 shot strings using the same bullet and case used to find the coal in the rifle (the case with the slit in the neck) to set up the bullet seating die at .010, .020, .030, .040, .050, .060.... etc untill you find the most accurate of that.

    4.) So by now I would know apx the best powder charge weight (somewhere around 61.0gn) and the best distance off the lands (lets say .030).

    5.) Now I would start 1gn less and load in .3gn increments to 1gn above 61.0 at .030 off the lands to find the best powder charge to finish off load development.

    6.) Once the load is found, load up a few five shot strings and go and shoot to confirm results.

    Now if you have a coal guage then you can find out where your lands are without making a dummy cartridge.

    This is what I would do, I in now way say it is the best, just my advice.

    Edited to add:
    By starting load development with the bullets touching the lands, that is where you will find pressure spikes first. If you get pressure signs at lets say 65.0gn and you back off the distance to the lands, the pressure should go down. Where as if you start with the bullet loaded off the lands and load up to 66.0gn that seemed ok pressure wise then decide to try that load with the bullet touching or jamed into the lands you my have excess pressure. Make sense?
     
    Last edited: Oct 3, 2011

  3. tomt

    tomt Well-Known Member

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  4. Edd

    Edd Well-Known Member

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    Use H1000 instead of RL-22.
     
  5. rscott5028

    rscott5028 Well-Known Member

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    My method is similar to the other posts.

    In a nutshell...

    Start with good bullets (Berger) and brass (Norma for 7RM). Use good brass prep techniques.

    Pick a powder that's known to work for the cartridge. RL22, H4831sc work for me. Others are good, but I had no need to try them in my 7RM Sendero.

    Choose a seating depth that makes sense based on success that others have had. I usually start .010" off the lands.

    Run a ladder test to find one or two nodes or sweet spots. A chrony is very helpful as part of the ladder test process.

    If nothing looks promising, then check your rifle and perhaps start over with a different bullet or powder.

    Fire some five shot groups for the chosen nodes to make sure it wasn't an accident.

    Choose the best node and hold the powder constant while shooting groups with various seating depths.

    Shoot your best load long range with at least 4x 5 shot groups.

    Fine tune with smaller increments of powder and/or seating depths, primers, etc, if you think you need to. Don't forget that your throat will errode. So, periodically, you may need to adjust your seating depth.

    -- richard
     
  6. mtnwrunner

    mtnwrunner Well-Known Member

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    Chris, I had never used berger bullets before this year. So what I did and it worked well for me is to figure out what the COL was so that the cartridge would fit in the magazine as that was important to me for the kind of hunting and shooting that I do. After that, I just started experimenting with different powders and grain weights. It didn't take too long for me to find out what it liked. I never once messed around with the seating depths--i just made sure that the bullet was off the lands and basically used SAMII specs.
    I shoot a 300 win mag and am shooting 1/2 to 1/4 inch at 100 with a 190 grain berger. Like I said, I have not used the berger before and my season starts on the 10th of Oct, so i hope to see what they do.

    Randy
     
  7. Chris89lx

    Chris89lx Member

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    Finally had a chance to experiment with an OAL that fits in my magazine.

    Made up a dummy round and found that a 3.400" OAL fits in my magazine nicely with a little clearance and cycles through the gun just fine. (3.290" is book spec)

    After that I wanted to know how far off the rifling the bullit was sitting.

    I dropped a bullit into the chamber but when I tipped the barrol up the bullit would fall out. I dropped it in again and with a very light tap of the barrol on the carpeted floor. The bullit was stuck and would not fall out when I tipped the barrol up.
    Then I used the rod from my cleaning kit and ran it up the barrol ever so slowly until I felt it touch the tip of the bullit. I then put a score mark with a utility knife blade on the rod. After that a slight tap with the rod and the bullit came out.
    I then chambered in my dummy round. I took my cleaning rod again and slid it into the barrol untill it touched the tip of the dummy round. I once again scored a mark on the rod at the end of the barrol with a utility knife blade.

    I know this method is not the most acurate for measuring this but I think it worked pretty good.
    The measurement between the two score marks was approx .060"

    I'm not sure if I will even play with the seating depth. But a least I know approximitly were it is.
    Time to start loading and testing.

    Thanks for the great info everyone.
     
  8. Casing

    Casing Well-Known Member

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    Try other powders other than RL 22, tryH 4831sc or H1000. You will get good velocity and probably good groups with RL 22 but when the weather changes so will your point of impact! Very temp. sensitive.
     
  9. Chris89lx

    Chris89lx Member

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    Wish you would have chimed in on my other thread on choosing a powder.

    I was told RL-22 was temp sensitive and if I developed a round when it was cold out I may see pressure spikes in hot weather. If I develop it in average temps it would he fine.

    Got any first hand examples of this change on POI due to temps?
     
  10. Tumbleweed

    Tumbleweed Well-Known Member

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  11. CryptoChief

    CryptoChief Member

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    I would say you are going in the right direction. With any luck, your rifle will take to Berger's data right from the start. However, each rifle is different in what it likes to digest. Stick with one powder through your load development. Adjust seating depth to fine tune. If your rifle doesn't like anything you are doing, I would at that time, try a different powder. I use H4831 in my 7mm with the 168 Berger. I do not have a rifle that will not shoot the Berger VLD in everything from my 6XC to my 30-338 and everything in between. Good luck.
     
  12. Goofycat

    Goofycat Well-Known Member

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    I'm no expert, but I fail to understand why people still use cartridge over all length as a guide. Ogives differ with different bullets; hence, you can have different bullets in a case, all set to the same COAL, yet due to ogive differences between the bullets, they may differ in how far they are off the lands.
    If you use a Stoney gauge, or something similar, you will always know what your seating depth is, regardless of the COAL. The COAL might be a ballpark guide, but since bullets differ, even within the same batch, it seems to me that it is not an accurate way to know their relationship to the lands when determining seating depth. Am I wrong on this?
     
  13. Fitch

    Fitch Well-Known Member

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    Well ... no, while you are right in theory, I disagree in practice because there is often significant variation in ogive shape from bullet to bullet within a box of bullets. This can result is as much as 5 or 10 mills of variation in distance off the lands for some bullets.

    Any gage system that measures to the lands only tells you what the base to ogive distance is for that particular bullet used to measure it. Take a box of bullets, measure the base to ogive distance variation on the bullets themselves and you may be surprised to see how much variation there is in some bullets. That translates into variation in ogive to lands with the seated bullet unless the bullet seater in the die is shaped exactly like the lands in the chamber (made using the exact same chamber reamer as was used to cut the chamber).

    I'm not convinced seating depth variation within those limits is important, but for those searching for the "exact" same distance off the lands for all cartridges loaded with bullets from the same box, it will be frustrating because it is almost impossible to achieve in any practical sense.

    COAL is probably close enough for bullets that don't have to be jammed. One can measure to the ogive for quality control, but adjusting the seating to make them all the same is going to be really difficult with out using some sort of custom die.

    For the reasons you have stated (variation in bullet ogives and tip distances), the only way to know exactly where your bullet is relative to the lands is to "lightly" jam it in. For some bullets, that results in more accuracy than seating it to be someplace around 0.020" or <insert your favorite distance>. For other bullets, it doesn't.

    I check several bullets and use the average with my Sinclair tool to establish a COAL that will give an ogive to lands gap of ~0.020" because I've never measured a box of bullets that had enough variation to allow them to contact the lands and cause a pressure spike when seated like that. It's the least jump I'm comfortable with other than when the load is developed specifically for lightly jammed.

    A bullet seater that pushes on the ring of contact where the lands would touch the bullet might (probably would) deform the bullet and probably screw up accuracy (and distance to lands due to distortion of the ogive at the point of contact) more than seating depth variation that occurrs due to bullet variation. So one lightly jams it and hopes that doesn't distort the ogive enough to cause accuracy problems.

    The only bullets I shoot barely touching to lightly jammed are 168 hunting VLD's in my 7mmMAG (they are the only VLD's I shoot so far). The VLD bullets have such a long nose I think it's important to have them exactly centered in the bore and lightly jamming them does this. But the load was developed from the beginning with this in mind. Jamming may cause pressure to spike several thousand psi higher than it would if the bullets had at least some jump.

    Every other bullet in every other rifle (except my CZ Hornet which is magazine limited), and that rifle, is seated about 0.020" off the lands because that's far enough that the +/- the variation in factory produced bullet ogives won't allow them to touch.

    Trying for exactness (variations of less than .003" to .005", or "just" touching) with production bullets and brass is like using a micrometer to take quality control measurements for precision cheese slicing.

    Finally, worrying all this to death, and getting the base to ogive distance exactly the same on all bullets, assuming that was practiacly possible, with out measuring and fixing variations in eccentricity is a waste of time. I have a heck of a time getting the ammo for my 7mmMAG to be straight (have zero run out on an RCBS Case Master). Using an RCBS competition seating die I still end up with ammo that measures from ~0.000" of runout to 0.012" of runout. The CaseMaster is a wonderful tool for feeding endless frustration unless you also have a way to straighten cartridges. I purchased a small tool that looks like a piece of stainless steel angle iron with a bunch of what appear to be reamed holes in it. I stick the neck of the bullet in the best fitting hole with the case oriented so the bullet is pointing down and pull up on the base. With just a tiny bit of practice I've gotten pretty efficient at getting the runout to under 0.002" (+/- 0.001") first time.

    I recently read an article where the author demonstrated an improvement in accuracy by straightening his cartridges in this manner which pretty much matches my experience.

    Fitch

    PS: FWIW, I bought the CaseMaster specifically to measure case wall thinning just above the base after having head seperation in my .30-06 ('53 Win Model 70). The load is nicely within manual maximums for the bullet and showed no pressure signs, but the case was stretching a lot resulting in an annular reigon of significant thinning after 3 reloadings just where the base taper joins the straight wall.

    Resetting the sizing die to bump only 0.002" and lightly polishing the chamber of the rifle significantly extended brass life. Being able to measure the thinning allowed monitoring of the situation and enabled setting a service limit that eliminated case head seperations. But the only way found to measure it was with the CaseMaster. I don't know of any other commercially available tool for making that measurement.

    frw
     
  14. Goofycat

    Goofycat Well-Known Member

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    Good post, Fitch. Thanks for the input. Another question: (I know that this discussion could go on and on), If the ogives vary enough within a given batch to be a concern, what about variations in bullet length? The Sinclair Reloading and Shooting Handbook states, "When you seat the bullet against the rifling when fire forming, it will help center the entire round in the chamber, which is more likely to give you an evenly fire formed cartridge.

    ....The handloader must find the true overall length of a cartridge that will result in the bullet touching the rifling. Remember that this length will be different in every rifle and will be different for each different type of bullet....."

    They don't mention differences in ogives or bullet lengths, either of which could affect the relationship of the loaded cartridge to the rifling. So, it appears that we have two possible ways of COAL discrepancies that would affect how far the bullets end up from the rifling: ogive differences and bullet length differences.

    I know I am getting nit-picky, and these differences might be so slight that they don't have any real statistical importance, especially to varmint hunters who don't need the extreme accuracy required for shooting competition---at least for shorter shooting distances.

    So, getting back to COAL, would you recommend that I just use OAL, determined by (1) taking one bullet, using it as a guide, (2) taking several bullets and checking them to see if their ogives are so close to each other that any small differences would be meaningless because their standard deviation would be so small, or (3) should I not worry about the ogives, but give more attention to individual bullet lengths? Again, I am more than likely beating this dead horse into the ground.