Bullet modification

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by Topshot, Dec 19, 2013.

  1. Topshot

    Topshot Well-Known Member

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    I thought I would start a thread on Bullet modification. Some of the larger calibres have a poor selection of long range hunting bullets and a few of us have had a play at modifying bullets to perform better on game.

    Here is a batch of bullets that I recently produced. They are .375 calibre 350gn SMK's that have had Corbin tips installed using a lathe.

    After much experimenting I found out that the tips must be held in quite solid or accuracy will suffer. Slight misalignment of the tips however did not seem to effect accuracy as much as you would think.

    Expansion at distance is greatly improved with these tips and the BC is slightly higher. The weight however ends up being 339gn so they can be driven faster.

    I have made a few other modifications to them and will post results when I can.

    [​IMG]
     
  2. Erik Kiser

    Erik Kiser Well-Known Member

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    I'd love to see a step by step process of how you do that. Very cool
     

  3. benchracer

    benchracer Well-Known Member

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    +1!!!!!!!!!
     
  4. royinidaho

    royinidaho Writers Guild

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    Topshot,

    I think this thread will get some traction. There are enough folks around here that think a bit outside the box that may well go for this "open architecture" approach.

    I don't have the patience to wait for those such as Berger and others to fill a niche that needs to be filled.

    Kirby Allen has also done some work with SMKs and Alum tips. He also discovered that a little wobble made little difference in accuracy.

    I started my efforts in 270 cal to attempt to fill a gap there.

    My thought was to come up with a way that the typical hand loader could do his own repointing if he had access to decent tips.

    Corbin's tips are way too large for a 270 cal size bullet. Too much weight is lost.

    Thus I came up with a tip design that worked well using brass.

    Learned a ton about machining doing this. Also learned that I'm not very good at sharpening cutting tools. Too get the points just right the cutter had to be just right. Frustrating.


    As I selfishly have sufficient high bc LR 277 bullets I'll switch to the 375 cal efforts in an attempt to get more weight and higher bc with more consistent terminal performance.

    I'll still work with brass tips as the Corbin tips seem too easy.:roll eyes:

    Here is a pic resulting from some terminal testing. These were Nosler 270 Ballistic Tips converted to 160 grains with a calculated bc of 0.658. Calculations were done by Eaglet.

    The shot well enough to hit the media entrance opening @ 300 yards.

    MV was 3650 FPS

    http://i12.photobucket.com/albums/a243/royinidaho/Bulletswithbases.jpg
     
  5. benchracer

    benchracer Well-Known Member

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    I am assuming the .277 Ballistic Tip started life as a 150g bullet? Going from an advertised bc of .496 to a calculated bc of .658 is pretty darned impressive! You definitely have my attention!

    I know the focus for those of you with large cased .375's will rightly be the 350g SMK, but I am wondering if something similar could be made to work well with the 300g Accubond or even the 300g SGK?
     
  6. Topshot

    Topshot Well-Known Member

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    The profile of the bullet needs to be just right for this process. I don't see any advantage of working on a 300gn Accubond as it already has a tip. The 300gn SGK may have some potential but I think it is a bit stubby for this as well.

    Another option may be to change the internals of the SMK. By maintaining the outside shape and thinning out the front of the jacket from the inside the bullet maintains its original BC but will perform better on game.
     
  7. phorwath

    phorwath Well-Known Member

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    Now all I need is a small miniaturized, affordable lathe! :)
     
  8. IdahoCTD

    IdahoCTD Well-Known Member

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    I've messed with the Corbin tips a bit too. It looks to me like the bullet needs to be shortened a little more to get a better transition from the tip to the bullet. That is unless your trying to keep it with the tip slightly larger. It also looks like your pushing the tips in with the tail stock of the lathe like I did originally. I've used the inside of a Hornady seater die as well and it doesn't leave the marks in the tips. If someone was going to do a lot of these probably the best thing to do would be to have a reamer made to cut the recess and face the bullet off so it was more consistent bullet to bullet. You could also do a bit of a hollow cavity behind the tip (in the lead) to help with low velocity expansion. It would be somewhat like Roy did with his brass tips that are angled on the back.

    I'll probably chamber up one of my .375 barrels in .375RUM to play with the 350SMK's a bit. I'm still undecided on weather to do a .375 Snipetac or a .375-.338 Lapua Imp. based .375 but I do have a couple barrels, a reamer, brass, and dies for a .375RUM. It's easy enough to rechamber it later when I decide which case.
     
  9. royinidaho

    royinidaho Writers Guild

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    Several years ago I purchased a Harbor Freight 8 X 14" lathe for this specific purpose.

    I've turn out hundreds of brass tips made specifically to fit Nosler offerings in 270 cal.

    Of those 100s maybe 20 were acceptable shooters.

    I learned that there is a difference in the configuration of the Nosler points between BT and AB bullets. That was a bummer.

    I used a Legos Mindstorm robot kit to cnc the HF lathe. I learned through tons of trial and error that tolerances could be kept darn good, better than my HF measuring devices could measure, through proper programming.

    Mindstorms programming is easy and straight forward but is the pits for sophistication especially being a MAC fella. Took tons of work to get it working on the Mac.

    My next effort will be with Arduino and quality stepper motors. CNC is the only way to get a decent consistent throughput especially when ones temperament is as bad as mine.:)

    I agree with the 338 and 375 Nosler offering modifications. If brass instead of Alum is use a net weight gain can be achieved.

    A little bit ago I sacrificed one of my precious 350 SMKs and fitted one of my 277 tips to it. Gain in length was a bit over 0.200". Weight gain was 4.5 grains. When a proper point shank is created weight increase should be a solid 0.5 grains and maybe a bit better.

    Form factor looks really good. I run the 350 SMK @ 0.88 bc but haven't really tuned her in at distance to get a good accurate bc. With the looks of the brass point bc will surely increase. We'll see how much when some shots are made.

    I'll run Lilja's bc calculator and get a bit of an idea of what the potential is. It's a pretty crude calc but lets ya know which inputs carry the most weight.

    IdahoCDT,

    I learned that using the tail stock was the worst way to seat the tips. I tried it as an experiment and it was definitely not a good in several ways than the primary method. It may be that I am not even close enough to decent to be called a machinist.

    I had a real machinist and gun smith/sponsor on here to make a modified meplat trimmer and point seater that runs in my Rochchucker press. The press idea wasn't a good one. When the press was replaced with a small plastic mallet things came together rather nicely.

    I gave the fella some tips and a tip holder was made up that leaves no mark and doesn't grab the tip. I'd like to know how that was done.

    BTW, when I went to a Swiss Screw Machine company with my point design the quote was a figure of $15,000.00 minimum order. Pretty much choked me. . . Wanted to be able to market points for $0.25 ea in a DIY set up. A fella bought his own Noslers with a one time expense of tools for under $300.00 and tips for $0.25 each. Would have been a good deal if I could have brought it about. . .
     
  10. Topshot

    Topshot Well-Known Member

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    IdahoCTD,

    There is a huge air cavity inside the nose of the 350gn SMK, this creates some issues to deal with.

    The tips were put in with a .22 cal seater and a chuck in the tailstock. There are better ways to seat the tips I am sure. Smaller tips are the way to go. These Corbin tips were too large.

    Roy's brass tips sound better.
     
  11. benchracer

    benchracer Well-Known Member

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    I had not cross-sectioned any of the 350g SMK's in my possession, so I did not know that. That is very interesting. I knew that Sierra had done something similar with the 6.5mm 107 SMK and had been wondering if the same design principle might offer some benefits in .375 bullets. Apparently, the answer is yes, although I realize that presents a problem when it comes to installing tips.

    This is a whole new universe to me. I am sitting back and taking notes. Questions will come later when I know what to ask...
     
  12. elkaholic

    elkaholic Well-Known Member

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    My kinda guy! Tips do make a difference!............Rich
     
  13. royinidaho

    royinidaho Writers Guild

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    In the interest of openness here are some tho'ts. Corrections/adjustments willing accepted.

    It may be a decent approach to start with something written to shoot holes in. I like making holes in stuff. Letterip!

    Starting with the 375 SMK as the only high bc ELR factory offering of reasonable price, and with inherent tendencies for cheap/tight and down right orneriness the objectives are (add other considerations if you wish).

    Here goes:
    + Higher bc 0.375 offering. 0.805 isn't too shabby but doesn't outweigh other considerations.

    + There seems to be 'some' consensus that the SMK produces inconsistent terminal expansion.

    + CEBs are proving themselves within the limits of the new paradigm. That's accurately made and properly designed "solids" :D) as compared to lead core technology. CEB and others have to be given credit for changing the century old practices.

    + Better cost/price for better terminal performance.

    One of the best reasons for doing things is simply because you can.:) Its satisfying though not overly cost positive. But hey, someone has to try. Apparently there are a few trying.

    What are the things wrong with the SMK?

    Nothing, if it is used for the purpose for which it was developed. That is, I believe, competition target shooting and Military use. Apparently the Geneva Convention has something to do with the SMK. Sierra isn't about to change that. Otherwise they would groove the ogive as with the announced smaller calibers. All hunting problems would be solved. So that's out.

    Choices are to goto CEBs and work out problems using the less expensive non-hollow point 352 grain offerings which are exactly like the 350 hollow points except for the lack of the hollow point.

    It'll cost ya a bit under $2.00 a pop to learn. Tuition is steep in this school!

    Or, come up with a workaround using SMKs starting @ around $0.50 plus time and materials per shot for cost of bullet.

    To make any sense of this at all the following must be deleted from price/cost.
    Powder, primers, case life, barrel life and of course, life. I figure if you're gonna waste a little life it may as well be doing something you enjoy.:roll eyes:

    I've chosen to go with modding the SMK because
    I can,
    It shoots a good solid 1/4 MOA to 1200 when the fella that made it drives it.
    (I'd rather waste time than money because I'm too lazy to work so my time isn't worth much except when I'm volunteering to help others. Then its priceless and no one has enough coin to compensate.)

    Important point. When a brass cylinder is compressed to a smaller diameter the wall thickness increases. In the case of the 375 SMK a 0.375" outside diameter cylinder/tube is compressed to where a 0.024" pin will not insert into the hollow point. Think about that one. We'll continue from there.

    Chime in folks or I'll talk yur leg off.:)

    Here's a poor pic but you'll get the gist.
     

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  14. royinidaho

    royinidaho Writers Guild

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    In the interest of openness here are some tho'ts. Corrections/adjustments willing accepted.

    It may be a decent approach to start with something written to shoot holes in. I like making holes in stuff. Letterip!

    Starting with the 375 SMK as the only high bc ELR factory offering of reasonable price, and with inherent tendencies for cheap/tight and down right orneriness the objectives are (add other considerations if you wish).

    Here goes:
    + Higher bc 0.375 offering. 0.805 isn't too shabby but doesn't outweigh other considerations.

    + There seems to be 'some' consensus that the SMK produces inconsistent terminal expansion.

    + CEBs are proving themselves within the limits of the new paradigm. That's accurately made and properly designed "solids" :D) as compared to lead core technology. CEB and others have to be given credit for changing the century old practices.

    + Better cost/price for better terminal performance.

    One of the best reasons for doing things is simply because you can.:) Its satisfying though not overly cost positive. But hey, someone has to try. Apparently there are a few trying.

    What are the things wrong with the SMK?

    Nothing, if it is used for the purpose for which it was developed. That is, I believe, competition target shooting and Military use. Apparently the Geneva Convention has something to do with the SMK. Sierra isn't about to change that. Otherwise they would groove the ogive as with the announced smaller calibers. All hunting problems would be solved. So that's out.

    Choices are to goto CEBs and work out problems using the less expensive non-hollow point 352 grain offerings which are exactly like the 350 hollow points except for the lack of the hollow point.

    It'll cost ya a bit under $2.00 a pop to learn. Tuition is steep in this school!

    Or, come up with a workaround using SMKs starting @ around $0.50 plus time and materials per shot for cost of bullet.

    To make any sense of this at all the following must be deleted from price/cost.
    Powder, primers, case life, barrel life and of course, life. I figure if you're gonna waste a little life it may as well be doing something you enjoy.:roll eyes:

    I've chosen to go with modding the SMK because
    I can,
    It shoots a good solid 1/4 MOA to 1200 when the fella that made it drives it.
    (I'd rather waste time than money because I'm too lazy to work so my time isn't worth much except when I'm volunteering to help others. Then its priceless and no one has enough coin to compensate.)

    Important point. When a brass cylinder is compressed to a smaller diameter the wall thickness increases. In the case of the 375 SMK a 0.375" outside diameter cylinder/tube is compressed to where a 0.024" pin will not insert into the hollow point. Think about that one. We'll continue from there.

    Chime in folks or I'll talk yur leg off.:)

    Here's a poor pic but you'll get the gist.