Question about velocity

Discussion in 'Reloading' started by fireworks, Apr 8, 2014.

  1. fireworks

    fireworks Member

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    Ive been playing around with a new bullet. I have the VLD down and shooting nice in my 270 A bolt SS. Now I'm toying with the sought after nosler 150 ALRB. I have it close but a question on velocity: At .050 off (coal of 3.402 56.5 IMR 7828 ssc ) at 100 yd. a five shot group will get me 4of 5 inside a dime at 100 and 5 for 5 in a nickel with a mean velocity of 2940 FPS. I've verified this 3 times. Go .5 grains up to 57.0 it falls apart, move the coal 5 thou either way regardless of charge it falls apart. The question is given most powders, a little more room will generate a little more expansion and pressure, am I thinking backwards on bumping the powder trying to get the magic 3000FPS? I know this is the case with pyrotechnic powders, would I be better to try 56.0 gr.at the 3.402 and not come apart?
     
  2. FearNoWind

    FearNoWind Well-Known Member

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    I'm stumped. What will 60FPS get you? What you described would be considered pretty close to optimum by most of the shooters I know. There is nothing magic about MV of 3000 FPS. 3000 FPS will get your bullet on the target .01 seconds faster than 2940 FPS. Your barrel, if it' stock 270 A bolt SS, should be 1:10 twist. To achieve your goal and stabilize the 150 grain bullet you may need something closer to 1:8.
     
  3. gohring3006

    gohring3006 Well-Known Member

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    sounds like you found a load your rifle likes 60fps from 3000fps is basically 3000fps don't over think it I wish I could get my 06 to shoot 168s good at 3000 but they won't but get them at 2900 and look out they scare me there so accurate
     
  4. fireworks

    fireworks Member

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    I forgot to mention, my chronograph is a cheap green fold open box called the chrony, made by " chrony inc". $100.00 Candaian deal. A buddy of mine told me he used to have one and says they are 100-130 Fps high so if he's right, im only about 2850. Trouble is, I can only get 7828 ssc to play nice with these things so I have my powder. 56.5 is actually .5 light of max charge but I still get a sticky bolt every 3rd or 4th shots. No sign of trouble on the brass or primer though. Given my experience with different pyrotechnic powders ( i actually am a licensed pyrotechnitian) certain powders give a better result with some expansion room over a compressed charge. But as a realoader Im pretty new to it and kinda got caught up in the more is better theory. My thought is can I back off .5, get at least as much velocity via expantion room in the brass if not a little more, and not get the occatsionall stiff bolt after firing. Im thinking this way because .050 off with a bullet this long is pretty deep in the case. Probably pushing the capacity. If I go to 57 gr. My velocity actually drops and i can dump sooty residue out of the spent brass. IE; not completely burnt.
     
  5. gohring3006

    gohring3006 Well-Known Member

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    first off, I wouldn't compare pyrotechnics to reloading now I'm no pyrotech and I'm no reload expert but equating the two won't work you can't compare a tight rifle chamber with a brass case and a barrel that squeezes the bullet to cardboard in a PVC pipe with pyro the best thing you can do is to listen to these guys on reloading and leave 4th of July out of reloading I say this with all do respect also don't trust that cheap chrony until you compare with a proven one, good luck...
     
  6. RT2506

    RT2506 Well-Known Member

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    If you are getting that accuracy and even with between 2850 and 2950 fps with 150,s in a Browning A bolt you should be elated. You should not expect more just enjoy what you have been blessed with. :D
     
  7. Pa Grizz

    Pa Grizz Well-Known Member

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    If your chorny has been taken care of I would go by what it reads.I have had one for twenty years and have sat next to people useing some of the best made and mine is right with them.
     
  8. g0rd0

    g0rd0 Well-Known Member

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    You have a winner! What more can be said. Your rifle likes 56.5 of IMR 7828 ssc stick with it.
    I have a savage 111, in 7mm rm and I have toyed with 139 hornady, 162 amax , 150 sp and etips, and 175 speer all of these I have tried with different powders. What I have discovered is 150 (sp or etip) cci mag primer 67.0 grn IMR7828 10 thou off the lands (3030fps), this load punches 3/4" groups all day long. This is what I stick with. Note this same load in a friends Remington 700bdl groups like a 12 gauge.
     
  9. fireworks

    fireworks Member

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    I suppose I should call it good on the load. Afterall, I have gone through a 100 lot box last fall and still didnthave it dialed. Then, it took all the way to spring to score another one and I only have 35 left. Who knows when I may find them again. However I do question the chrony, and should try to x compare. Reason being, last fall when I dialed in the VLD I ordered a turret from leupold based on the data. It came back quite high across the board zeo at 100. It took alot of fiddling with it to figure out the expotential amount to back off on the turret in relation to the rangefinder. About another 40 round worth and a cheat sheet laminated to the stock. Reason why it came back two weeks ahead of the elk hunt. I dont want the same result when I order a turret for this load. Based on that info the chony, if off should be reading low not high.
     
  10. Pa Grizz

    Pa Grizz Well-Known Member

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    I do not know what to tell you.Maybe I have a differant chorny than you have.I have shot several of my guns over mine and shot the same loads over friends.The largest variance was on my 280 and it was only 10fps
     
  11. varmintH8R

    varmintH8R Well-Known Member

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    I tend to agree with the attitude that chasing a velocity number is probably a fools errand if your rifle is shooting lights out at 60fps slower.

    My bigger concern would be that it appears your load has a very small window for variance. If +\- 5 thou OAL or 0.5gr charge weight makes it "fall apart", I would expect future variance in lots of powder, bullets, primers, etc to cause you a real problem.

    My 2C only

    Brandon
     
  12. MNbogboy

    MNbogboy Well-Known Member

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    Agreed with Brandon on all points.

    Before you order your turret a thought might be to do some drop tests at longer range...With your rifle shooting as good as it does a drop test should prove the reliability of your Chrony...

    Using the results of the actual drop test you can back pedal through a ballistics program with your advertised bullet BC, temperature, barometric pressure and scope height.....The velocity the program shows that gives your measured drop should be very close to actual....(advertised bullet BC will now become the biggest variable)....All this information is necessary for the turret maker anyway......(I have had two Chrony's over the years and have seen them both very consistent and very erroneous depending on how you handle the ambient light conditions)....But a drop test at 500 or 600 yards has proved a good way to confirm the chronograph.

    Good luck,
    Randy