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300 yard range(WIND) test with 257 AM

 
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  #1  
Old 09-29-2005, 09:50 AM
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300 yard range(WIND) test with 257 AM

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.



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)
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Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

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Web Page: www.apsrifles.com

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  #2  
Old 09-29-2005, 11:42 AM
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Re: 300 yard range(WIND) test with 257 AM

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

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
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  #3  
Old 09-29-2005, 01:47 PM
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Join Date: Dec 2004
Posts: 139
Re: 300 yard range(WIND) test with 257 AM

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
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Old 09-29-2005, 09:39 PM
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Join Date: Jun 2004
Location: PA
Posts: 139
Re: 300 yard range(WIND) test with 257 AM

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 24í will work out great. Iíve been poking around Danís 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.
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Old 09-29-2005, 10:30 PM
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Re: 300 yard range(WIND) test with 257 AM

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





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.



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.



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)
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Kirby Allen(50)

Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

Farther, Faster and Flatter then ever before.

Web Page: www.apsrifles.com

allenmagnum@gmail.com
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  #6  
Old 09-29-2005, 10:34 PM
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Re: 300 yard range(WIND) test with 257 AM

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)
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Kirby Allen(50)

Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.

Farther, Faster and Flatter then ever before.

Web Page: www.apsrifles.com

allenmagnum@gmail.com
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  #7  
Old 09-30-2005, 01:19 AM
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Join Date: Jun 2004
Location: PA
Posts: 139
Re: 300 yard range(WIND) test with 257 AM

How long does it usually take to get a BBL from Dan? I wanted to have this rifle built for this season but thatís not going to happen [img]/ubbthreads/images/graemlins/frown.gif[/img] 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.
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