300 yard range(WIND) test with 257 AM

Discussion in 'Long Range Hunting & Shooting' started by Fiftydriver, Sep 29, 2005.

  1. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    As many of you know I am preparing for a pronghorn hunt that is coming up in a couple weeks. For the hunt I put together a very light weight (for a 30" barreled/wood stocked) rifle chambered for my 257 Allen Magnum.

    The barrel used was a very light #5 contour with Dan Liljas heavy 50 BMG style flutes, their ain't much steel in that barrel. As such, load development has been a significant challange and at time flat out frustrating.

    The problem is the light contoured barrel combined with the huge 156 gr ULD bullets, 1-7 twist barrel and 3300 fps velocity. Things have to be tuned perfectly to get any quality accuracy and even then its not what I would say is up to my usual specs at moderate range. Does better at long range though.

    At 100 yards groups are running in the 1" to 1 1/4" range with the first two generally in the sub 3/4" range. At 200 yards its printing in the 1.5" range again with the first two shots generally the under 1". This is pretty typical for a long skinny barrel with a long bullet and fast twist. Barrel heat is always an issue here!

    Wanting the most accuracy I could get I tried several bullets ranging from the 115 gr Ballistic Silvertip at 3860 fps, the 130 gr Wildcat BCFBHP at 3645 fps and finally the big 156 gr ULD at 3300 fps.

    In all honestly, the 115 gr is the flattest shooting out to 800 yards where it has roughly 5" less drop then the other two. It is also the most accurate on average at closer ranges, 200 yards and under. The 130 gr and 156 gr are ballistic twins out to 500 yards as far as trajectory goes.

    The accuracy with the lighter bullet is I am sure due to the deduction in barrel strain from the much shorter and lighter bullet.

    Still, after working up loads for each bullet and running the two extremes against each other, I decided the 156 gr ULD is really the only way to go. As far as trajectory out to 800 yards, yes the 115 gr BST is the flattest shooting because of its extreme velocity.

    Still, bullet drop is not a major concern of mine at long range. There are three areas that I do look for in a good long rang hunting load though, Velocity retention, Energy retention and wind drift.

    Comparing the best 115 gr load with the best 156 gr load it was pretty clear to see which was the best for long range shooting. The energy numbers look like this:

    Yards........115 gr BST........156 gr ULD RBBT
    Muzzle.......3822..............3782
    100..........3330..............3489
    200..........2896..............3215
    300..........2513..............2960
    400..........2174..............2712
    500..........1874..............2499
    600..........1609..............2292
    700..........1375..............2099
    800..........1169..............1920

    As you can see the 156 gr ULD RBBT has more retained energy at 800 yards as the 115 gr pill has at 500 yards. No contest here. I am not saying bullet energy kills game better but it is a factor in making a big game bullet perform as it is designed to at extended range.

    As for velocity comparisions. The 115 gr does better in this aspect but keep in mind it also starts with a +500 fps velocity advanatge.

    Yards.........115 gr BST........156 gr ULD RBBT
    Muzzle.........3860..............3300
    100............3611..............3174
    200............3367..............3047
    300............3137..............2923
    400............2917..............2803
    500............2709..............2686
    600............2510..............2573
    700............2320..............2462
    800............2139..............2354

    On average, the 115 is loosing 200-220 fps for every 100 yards the bullet travels, thats compared to about 110-130 fps of velocity for every 100 yards for the 156 gr ULD. It does take 550 yards for the loafing 156 to catch the 115 but from there out its dramatic. Still, at 550 yards comparing a 156 gr bullet at 2620 fps is alot different then a 115 gr bullet at that same 2620 fps!!

    The real reason I decided to go with the 156 gr ULD even though its groups at 200 yards and less are slightly larger then the 115 gr BST is wind drift. This is my main concern here in Montana.

    This is how the two compare.

    Yards......115 gr BST......156 gr ULD-% of drop
    100.........0.5.............0.3 - 40% less
    200.........2.0.............1.3 - 35% less
    300.........4.6.............3.1 - 33% less
    400.........8.4.............5.5 - 35% less
    500.........13.5............8.8 - 35% less
    600.........20.1............12.9- 36% less
    700.........28.4............17.9- 37% less
    800.........38.4............23.9- 38% less

    This is what I like to see. The 156 gr ULD even though its started at more then 500 fps less velocity at the muzzle has more then a FOOT less drift at 800 yards. All that does is cushion any possible error in wind speed you may make on the range or in the field. They both get blown off course but I would much rather have nearly 15" less wind drift then a 5" flatter trajectory.

    Anyway, this brings me to this morning. Woke up and the wind was howling at 25-35 mph from the south west. I decided to test the 257 AM with the 156 gr ULD load out at 300 yards and see how it performed. I set up and shot off the ground using a 6-9" Harris bipod and a small rear support back. The range to the target was 300 yards. I did not allow for the wind which was quartering toward me from left to right at about a 45 degree angle.

    I simply ran three rounds through the rifle as it there was no wind at all. The first shot out of the clean oily barrel landed off to the right of the second two which landed roughly 2.5" to the right of my aiming point and 2" high. This is exactly where it should be sighted in for its 340 yard zero.

    I let the barrel cool which with the big fluted, small barrel and 30 mph wind took about 2 minutes!!!

    I launched another three down range and this time they formed a nice 1.6" triangle. Again the first two were right at .755" ctc with the third shot dropping lower.

    Here is the pic of those last three shots. In a 30 mph quartering wind I was actually suprised they were not blown off more then this but the rifle is hitting about an inch to the left in calm conditions as I have not fine tuned the sight in yet. Still, pretty impressive in my book. There is nothing I have seen in a big game hunting bullet that will chew up the wind like these Wildcat Bullets.

    [​IMG]

    I hope to get out to the range and do the final tweaking out to 800 yards on the drop chart this weekend as the opening day is coming up very soon!!!

    This rifle has been a good experience for me as I have learned alot about the limits of barrel stiffness with these extremely long bullets driven to high velocities. Mainly that I now consider a #6 contour as minimum for my 257 AM in 30" barrels and a #7 would be even better in my opinion.

    For the 270 and 7mm, a #6 contour would be VERY minimum I would use and I would highly recommend a #7 if 30" barrel is to be used. Learn something new with every Allen Mag rifle, just have to keep my eyes open to see what is in front of me and learn from these lessons!!

    Have a good day,

    Kirby Allen(50)
     
  2. lerch

    lerch <strong>SPONSOR</strong>

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    Looks good Kirby,
    I am ready to see what you will do with that thing in a couple of weeks /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif

    I am hopeing to get out this sunday and try to push the 270 AM to 1500yds and see if I can land one of those big 169.5's on a pdogs head.

    Good Luck
    Steve
     

  3. victor

    victor Well-Known Member

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    Fifty,

    Thanks for keeping us posted on the cutting edge of barrel design. I am very interested in keeping barrel weight down by cutting deep flutes in barrels, as well.

    From your report it seems that a #5 contour at 30" long is stretching things too far. Perhaps for your next experiment you could try to keep the same #5 contour and fluting, but shorten the barrel to maybe 25". This should make it a little more stiff. Also, for all practical purposes, a much friendlier rifle to handle in the field. Sometimes you may want to take that rifle into some trees, rather than open prarie.

    I don't know if I'm alone in my perpective, but I don't think I would ever care to carry a 30" barreled rifle in the field. I have plenty of trouble with a 26" barrel getting caught in dense brush. It seems to catch every freakin branch overhead,(strapped over shoulder) and when climbing up slippery slopes, I have been so frustrated with the barrel catching everything in site, that I just want to pitch it over the cliff I just climbed up.
    But after several explicatives, I get over it and decide to hang on to the rifle.
    Now I know, some will say, hey the long barrel is for plains hunting, but we don't all have the funds to have rifles dedicated to all the different types of terrain that we hunt. Some comprimise is in order to keep us all relatively happy.

    And one more thing, How about a close up picture of this barrel. I sure would like to see the depth of those flutes!

    Take care,
    Vic
     
  4. sure shot

    sure shot Well-Known Member

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    Kirby, I to would like to see a pic of the #5 BBL with the BMG fluting. How many flutes can they get on a #5 contour BBL with the wider .312 cut? After this season and the holidays are over and done with I will be sending you my parts for the 7mm buildup that we talked about. I picked up that HS thumbhole stock have the SS700 LA receiver and will have the Jewell trigger soon. I think that BBL finished off at 24’ will work out great. I’ve been poking around Dan’s site doing some weight calculations and it seems that BBL combo will weigh around 3lb. Its going to make for a good mountain rifle. Good Luck with the 257.
     
  5. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Here are a couple pics of the Heavy flutes on the #5 contour Lilja.

    [​IMG]

    [​IMG]

    There are six flutes on this contour barrel and thats all you can fit on. As you can see there is not alot of steel in those ribs between the flutes on the muzzle end.

    Victor,

    This rifle was an experiment in how far I could push the weight issue down while still retaining the full performance with a 30" barrel. For a 500 yard rifle, this system works acceptibly well but for longer range shooting I would say a #6 contour should be considered minimum.

    I would agree with you that in areas where you are moving through cover this barrel length would be very impractical. But for the areas I hunt in 95% of the time, we have to set up in fixed locations and take shots from there as there is no cover to use for a stalk. Here are a couple examples of my hunting areas.

    [​IMG]

    The white dot in the box is a 1 gallon milk jug filled with water that is about to be vented at 685 yards with another of my 257 AM rifles. The creek bottom in the back ground is 1125 yards from this position and a great place to hammer yotes early in the morning and late in the evening.

    [​IMG]

    This is another view of the same area. In this picture, notice the little white dot. That is a 4 ft x 4 ft target board set at 930 yards for testing the drop chart on my 270 AM Extreme Sporter rifle.

    As you can see there is nothing for a long barrel to hang up on. We simply set up on the ridges before day light and take what opportunities present themselves through the morning and evening. For this type of hunting, a 40" barrel is not overly long and this time next year we will be talking about just such a beast getting ready for the big game season(338 AM)!!!

    Good Shooting!!

    Kirby Allen(50)
     
  6. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Tommy B.

    Whenever your ready my friend let me know and we can get rolling on your project. That barrel with these flutes will make a VERY light packing rifle!!!

    Kirby Allen(50)
     
  7. sure shot

    sure shot Well-Known Member

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    How long does it usually take to get a BBL from Dan? I wanted to have this rifle built for this season but that’s not going to happen /ubbthreads/images/graemlins/frown.gif the end of Dec. beginning of Jan sounds about right. That BBL is down right sharp looking if you ask me. Is there a 7mm Rem Mag IMP? The 7 mag seems like it would be a good candidate to IMP with the amount of taper on them cases, bump the shoulder up a bit. What are your thoughts on this? If so would it be worth the trouble forming brass for the slight performance gain.
     
  8. skip AI

    skip AI Well-Known Member

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    Those Pills are moving!!!! Is the Allen Mag hard on barrels?
    Have you already posted a pic of the rifle on a different thread? if not can you post one?

    Thanks

    skip /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/cool.gif
     
  9. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    TommyB,

    Dan is getting me barrels on average 8 weeks after ordering them. He has supprised me with a few as soon as 6 weeks after order but that is not the norm. IT is pretty consistant with the 8-9 week shipping time.

    Yes there is a 7mm Rem Mag improved. I believe it is called the 7mm Mach IV. There is an entire family on this case design including the 6mm, 6.5 and 7mm. There may be others, these are the three I am familiar with.

    TO be honest, my recommendation would be against this round. The reason, and this is from an accuracy minded gunsmith so take it for that please, is that the current production belted magnum brass is relatively inconsistant in the headspace measurement, that being from the base to the forward edge of the rim.

    Now we all know that a belted magnum headspaces off the shoulder once fired in the chamber which is as it should be but with my rifles, I chamber the barrels very tight. Doing this with a belted magnum round can result in a certain percentage of brass not fitting the chamber because their headspace dimensions are out of spec, often by a fair margin.

    TO get around this problem, you chamber deeper then I like to because this headspace measurement will not conform to the chamber when fired, it will always be this way as the belt is part of the solid case head.

    Now, non belted brass is the same way, in fact it generally has a wider variation in headspace BUT... The soft thin shoulder WILL conform under fireforming pressure. What this means is that the first time you fire the case it may be a tight fit chambering but after that it will drop in perfectly because it can conform to the chamber specs.

    I do not know if this would interest you but I just drew up a reamer print and submitted it for a custom dimensioned 7mm Dakota reamer. It is throated to take advantage of the Rem 700 receiver length.

    This in my opinion would be a vastly superior choice over the 7mm Mach IV. The 7mm Dakota will match the 7mm STW in same length barrels and do so with a case length no longer then the standard 7mm Rem Mag. It also gets rid of the belt and all the problems associated with it.

    The brass is more expensive but starting late this fall and winter, Norma will be making Dakota brass for them, at least that is the rumor going around.

    Other advantages of this round, no fireforming needed, standard dies instead of having custom dies built, much higher performance then any 7mm Rem Mag based wildcat and I will have the reamer here in a couple months so that would not cost you extra either.

    In a lightweight rifle it is alot of power but with a Holland QD brake it would be a pussy cat to shoot. The lighter the rifle, the better the brakes work.

    Just another idea to muddy the waters a bit more /ubbthreads/images/graemlins/grin.gif!!

    Kirby Allen(50)
     
  10. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Skip AI,

    Yes they are clipping right along out of all the AM wildcats, heavy too /ubbthreads/images/graemlins/grin.gif!!

    I have always been upfront about these rounds being designed specifically for big game hunting which for this purpose, shooting volume is generally quite low.

    There is no other way to look at these rounds. TO get X amount of performance you need a certain amount of powder and pressure. Our performance goals for these rounds were extreme to begin with and as such we knew that the throats in these rifles would not last 2000 rounds. That said we did everything possible to increase throat life as much as possible by using stainless 3 groove barrels designed specifically for wildcats. We also use the very slow burnign ball powders which offer longer barrel life over stick powders because of lower flame temps and less friction as the powder passes through the throat of the chamber.

    Still, even with all this, I would say they are 1000 to 1200 round rifles for big game hunting purposes. It all depends on how you use them and how you care for the barrel. If you abuse them you will get about 400 rounds of throat life. If you take care of them you will get 1000 rounds through the 257 AM easily and still be able to hammer a whitetail at 600 yards.

    The larger caliber Allen Mags are certainly more bore friendly and I would say they will get you 1200 rounds of top level big game hunting accuracy before needing either a barrel set back to new pipe installed.

    [​IMG]

    [​IMG]

    Here are a couple pics of the rifle so you can see what she looks like. With a #5 contour barrel, that 30" looks pretty skinny on the end and in fact it IS!!!

    Good Shooting!!

    Kirby Allen(50)
     
  11. ssandberg

    ssandberg Active Member

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    Fifty, I have enjoyed reading your reports on your Allen Mags. I especially appreciate your candor in reporting the good with the not so good. You have explored the lighter side and found that accuracy degrades a bit and you reported it on an open forum! That kind of info really helps in making decisions. Thanks and keep it up.
     
  12. davewilson

    davewilson Well-Known Member

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    50,
    are you sure a case that big would be the ticket for a 24" barrel in 7mm? i think that's the length of barrel he said he wants.i'm votin for a 7wsm for his light carry gun.
     
  13. Fiftydriver

    Fiftydriver <strong>Official LRH Sponsor</strong>

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    Dave,

    The kicker is getting the stub of a WSM to feel well in the long action Rem 700. This is why I would prefer the 7mm Dakota. It may be more case then the barrel can efficently use but it will still outperform anything smaller in this caliber.

    I was going to recommend the 7mm AM. But though that may be a bit to much for a 24" pipe /ubbthreads/images/graemlins/grin.gif! What do you think.

    Kirby Allen(50)
     
  14. sewwhat89

    sewwhat89 Well-Known Member

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    Dakota chambers their own rifles with the Dakota line in barrels as short as 23". Is that optimum? Doubt it. It is a potent round though, just brass is a little overpriced imo.