270 Accubond Expansion Test

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by royinidaho, Sep 13, 2008.

  1. royinidaho

    royinidaho Writers Guild

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    I another thread it was reported that Nosler stated that at least 1800 FPS was necessary for Accubond expansion.

    Hmmmm, a data point. I like data points. One can pretty much hang their hat on them.

    If I could duplicate this stated performance, more or less, it would be a good test of this media I am developing.

    I set up the container and added what I estimate would be sufficient moisture to the media.

    The first shot impacted @ 1845 FPS. Terminal performance was dismal by some standards and impressive by others. Penetration included the full 24" of the media and the 1/2" plywood back end barrier. The bullet hit the back end of the plastic barrel but only dented it and fell to the bottom of the container.

    This shot began tumbling upon entrance to the media, passing through the 14" plastic divider and the plywood end horziontally. The impact on the rear of the container was also horizontal.

    Penetration was linear until the penetration of the rear board was completed when the bullet deflected about 3" in 9".

    Deformation to this bullet was a loss of the front end leaving 133.2 grains, which in this case is not good.

    A 200 FPS increase in impact velocity to 2050 FPS was tried to see if proper opening could be achieved. The bullet again tumbled and passed through the 14" divider cross ways. It hit the back board horizontally, only denting it. The bullet then bounced up hitting the top of the container landing on top of the media. I would suppose that if it were not for the container top being fastened properly the bullet may well have come back and thumped ol' Roy.:rolleyes: (gonna get me a helmet......)

    Penetration was the full 24" of media with a little energy left. With higher velocity a little more was broken off leaving 100.5 grains of the original 140.

    These two similar performances appeared to reveal the need for a bit more moisture which was added.

    Shot number three entered the media @ 2014 FPS.

    Penetration path was a straight line from front to back. The penetration of the 14" barrier was large and round. The blunt front end of the bullet hit the plywood rear barrier leaving a visible dent. The bullet was found immediately at the front base of the rear back board. Bullet performance was near perfect. Mushroom diameter is 0.511".

    Effective range of this shot is 1545 yds & 1565 FPE when launched at 3645 FPS. I wonder what kind of game it would be sufficient for, at that distance.

    BTW, 1545 yards is a bit beyond my system's capability. The week part of the system being the driver.


    [​IMG]

    This test would suggest that an impact velocity of at least 1800 FPS as reported stated by Nosler, at least the 270 140gr Accubond will more than likely open and upon entrance into an antelope or larger animal, maintain orientation, open properly, at least to 0.5" diameter, and penetrate a sufficient distance even at extraordinarily long distance (if started at something like 3600+ FPS;)) There ain't no dustin' these suckers even in a very tight twist 3-groove 30" barrel.

    Using the 270 140 Accubond as the first recognized reliable expansion calibration point, it was easy to determine the amount of moisture to the media to replicate the Accubond's advertised performance.

    My drop cart is developed and tested. I haven't developed the 140 NAB load to its best but quit when 200 yd grouped consistently printed less than 0.5 MOA. SDs are fairly good. Confirmation of down range drops will show if the NABs will shoot along with the 150 Ballistic tips which are super outstanding accuracy wise.

    With the additional confidence in terminal performance of this particular accubond I otta be ready to start harvesting stuff......... It's about time!
     
  2. Broz

    Broz Well-Known Member

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    Thanks for all the info. I just recently worked up a load for my 25-06 using 110 AB's and I was very pleased with the accuracy.

    Jeff
     

  3. gamedog

    gamedog Well-Known Member

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    Great post Roy. We all know that manufacturers claims can be off a "touch". Nice to see real world data.
     
  4. Slopeshunter

    Slopeshunter Well-Known Member

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    Great information Roy! Thanks
     
  5. JD338

    JD338 Well-Known Member

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    Roy,

    Great job on the test, good information. Thanks for all your efforts and post!

    JD338
     
  6. Nomosendero

    Nomosendero Well-Known Member

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    Thanks for reporting the test & your efforts. I used a 270 last fall for Wy. Antelope & Mule
    Deer & Ar. Whitetails. None of the shots were long by LRH standards, only out to 410 yards,
    but 1 Whitetail was close & high shoulder shot. All showed great expansion & total penetration in every case. It is also the most accurate bullet I have fired in that rifle, doing 1/2" (3 shot) groups quite often, in fact the first group tried with this bullet was .187". With the BC it has it is a great 270Win allround choice in my view.
     
  7. davewilson

    davewilson Well-Known Member

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    Roy, great stuff as always. my only thought to your results would be the reason the bullets tumbled wasn't the lack of speed, but lack of rpm's. just as a bullet has to spin at a certain rpm to go straight through the air, it also has to spin at a certain rpm to go through "media". it takes more rpm's to stabilize going through media, than it does through air.

    wasn't Kirby gonna build a gun for every caliber so we can test all bullets in regular twists at 1500 fps?
     
  8. dmgreene

    dmgreene Well-Known Member

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    Roy if you keep this up some bullet company is going to hire you. Just think what kind of testing you could do if someone else was furnishing you free powder and bullets:rolleyes:. Just don't forget us little people when you make it big.

    David
     
  9. royinidaho

    royinidaho Writers Guild

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    Dave,

    I kind of agree with you on the RPMs but how in squat am I gonna hit the media 100% dead center every time at a distance giving the appropriate velocity?

    I have developed the process to the point were those three shots were made in 45 minutes including 2 trips to the house for reloading and a phone call.

    Put the media at 1 mile and this little old man ain't gonna hit it plus the time involved is prohibitive.

    When I added the moisture to a more appropriate level the penetration was straight with appropriate expansion for the velocity.

    Wish I had more answers than questions.:rolleyes:

    The process however seems to be a step in the right direction.
     
  10. davewilson

    davewilson Well-Known Member

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    Roy, i undersatand what you're saying. every time i test bullets at distance, it's very time consuming and not an easy thing to do. this year when i tested the Hat's at 700 and last year the 250SMK's at 1k, i had a helper. each time i have to carry all the stuff a half mile to where i shoot, and then carry it another 1k. i found that a milk jug is not quite 6" wide and it works best if you hit them fairly close to the middle. if you hit within 1" from the sides it seems to direct the bullet to the outside.

    we need a switch barrel savage with some throw away barrels in different calibers chambered with small cartridges. 338 federal, 30BR, the smaller stuff would be easier. big bullets could be shot at slow enough speeds to get a very similar to actual circumstances type of results. might have to use an 8 twist barrel to get enough rpm's at slower speeds.
     
  11. edge

    edge Well-Known Member

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    Great info :)

    Now that you found the correct amount of moisture for the media do you intend to shoot the NAB's slower and slower until you no longer get expansion? You can't let those rascally Nosler engineers off the hook :)

    Thanks for all of your testing.

    Thanks,

    edge.