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Thread: 35 gibbs update

  1. #1

    Default 35 gibbs update

    I finally got this thing in to action. Worked up to 59.5 grains reloader 15 giving 2740 fps with 250 hornady sp and CCI 200. 59 of re 15 was more accurate and gave around 2680 - 2705 fps which I am more than happy with. 3 grains less than 62g max load recomended by other Gibbs users. Only issue is excessive freebore, which I cannot play with due to magazine length 1.5 - 2 inch groups at 100 are ok but none went below 1.5. Freebore is .125 . Anyone loading .358 with the ogive further foreward than hornady? I will try their round nose. What about speer? I dont want to practice too much with partitions at 50 bucks a box.
    Recoil is stout but much less noticable than I was expecting. All in all I am well pleased.

    Dan

  2. #2
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    Default 35 Gibbs

    Gibber,

    A couple things I'd say. First contact Alaska Bullet Works in Juneau, 9978 Crazy Horse drive. Juneau, Ak. 99801 907-789-3834.

    He can make 358 250 grain bullets in round nose or protected point (my favorite) which is a little flat meplat on a round nose design. These can also be cannelured where they can be seated to your max magazine length and with that ogive, the bullet will fill more space in the throat. You could also try any round nose they will probably show an edge in accuracy due to the throat of your rifle.

    Also, I believe you had said your barrel was long but that is a fast rifle. The load does seem a little excessive, the velocity is equal to the 250 grain in a 338 Mag in a 24" barrel. It out runs the 35 Whelen by a bit. With RL-15, 53 grains it gives about 2500 fps. I don't know the exact capacity of the Gibbs but It is still the same case with more room for powder, I would limit that to about 56 grains and 2600 fps. That's enough to make that a real performer. Good luck with that one.
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



  3. #3

    Default

    Murphy

    I was a little surprised when i saw the chrono at 2740 but this is what other 35 Gibbs owners stated that they got from 62 grains of RE15. Alliant list 59 g RE15 and a 250 hornady rn as top load at just over 2500fps. for a 35 whelen. Which makes no sense as the same amount of powder in a larger case should produce less velocity and pressure. (I wonder if it is a mis-print?) The case has the shoulder moved way forward with a short neck and i understand about 5%- 7% increased capacity. Which of course would only be 2.5-3.5 grains.
    There are no signs of excessive pressure at all, but I know that might mean nothing. I started off at 54 grains thinking I would be quite safe and pulled the bullets from the last five cases of 59.5grains.

    I liked the 59g load as it gave very low velocity spread. Althought I am not sure what that means other than predicatable velocity..

    Could newer powders such as RE 15 be this good. I read an article in Handloader showing that a 30-06 with newer powders safely achieves velocities that a few years ago would require a 300 mag. Too good to be true?

    I use 160 speer mag tips in my 7X57 (the ogive is obviously further forward)and will likely try those or 250 grain grand slams and reduce to 2600-2650. As you suggest an extra 50-75 fps wont make a bit of difference to the moose. And to be honest I would be perfectly happy with a round nose. My budget doesn't run to custom bullets but thanks for the suggestion.

    Cheers

  4. #4
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    Default 35 Gibbs

    Gibber,

    I think you're ok with the 59 grains of RL-15. Looking at loads for the Whelen, the Gibbs should be a little slower with the same charge but no two rifle's are ever the same. You have a very good barrel. A smooth barrel is just faster with lower pressure, under the same charge of powder. Also your barrel may be longer that some. I would not be surprised at 100-150 fps gain and I've seen more with some Ackley improved rounds, and the Gibbs is a little bit more space. I've never put 59 grains of RL-15 in a Whelen case but got 2500 fps with less and stopped there.

    One of the things I do with the chronograph is check each load at .5 grain intervals and get an idea (chart it if need be) of the "gain per grain" with a given bullet. In this case the 250 grain Hornady bullet but stay with the same bullet/case/primer for the test. If you started at 53.0 grains of RL-15, just determine the average velocity gain per grain of powder increase (i.e. 60 fps/grain) over several grains of powder. When a one grain increase produces only 70% of the average gain, that's it. Maximum load. What this does is keep the operation in the linear portion of the curve. (The pressure vs time curve you've seen in loading manuals.) When the "gain per grain" drops off, you'e at the knee of the curve. I then go back to the last good load. (the one within 10% of the average.) This matches the load to the gun and gives the maximum benefit of the powder charge. Now if other things come into play such as accuracy or SD is higher, etc. then we must go back to the last known good load. But this is a good way to find the maximum load and is particularly useful when it is an unknown caliber without data available. I love this stuff!!!
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



  5. #5

    Default A question

    Yes this is what I'm looking for, I like this a lot more than "load er up until you flatten a primer and back er off a bit." I looked at a lot of data from 35 Brown whelen to ackley etc but the manuals and data are all over the place with often significant powder/pressure/velocity variations. A fellow on here helped with RE 15 as the powder of choice and compared to 4895 I think that he is right.

    I guess that you automatically do this sort of thing when reloading factory cartridges by using a chrono. and not exceeding the manual velocities. After I bought my chrono I found my .270 load to be 150 fps over the max velocity stated in the manual even though my powder charge was 1.5 grains under the stated maximum. It may have been ok, but i just couldn't relax at the range.

    How do factory come up with max pressure for a cartridge? Why is a .270 52000 cup and and 30-06 50000? I mean similar rounds here, I know the 30-30 has thin case walls and is used in lever actions. But what factors decide max acceptable pressure in terms of what is going on inside the case?

    The gain per grain makes total sense, but I imagine that I would need to shoot 10 shot strings to be accurate. I have the chrono data for 5 shot strings from last week so i'll look at it to see if it works. I could be in for some fun, and a sore shoulder.

    Cheers

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