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Post by Bullshop on Jul 27, 2016 20:23:16 GMT -7
Its been about two years now since I finished my long term (35years) project building a 6.5-06 Ackley. I bought the loading dies 35 years ago but put the build off for a bit.
With this build I wanted a rifle that was not too heavy to carry but would get the highest velocity possible with the chosen bullet for this rifle a Hornady 100gn A-max.
I went with a 28" Paknor heavy sporter barrel to get the longest push time on the bullet but still be in a weight that was packable. The idea was to gain any possible velocity advantage no matter how slight but staying with the 06 case thus the Ackley case and long barrel. Another possible velocity advantage I felt would be in twist rate. Standard twist rate in 6.5mm caliber is normally 8.5" or 9". Since I had decided that this will be a one bullet rifle with the Hornady 100gn A-max I felt I might realize a small velocity gain by going with a slightly slower twist so decided on a 1/10" twist for this rifle.
I also already had an old palma rifle built on a single shot FN Mauser action chambered for the 6.5x57. This rifle has a very heavy barrel with standard 9" twist also at 28" length.
While I had possession of the 6.5-06 Ackley reamer I also reamed the chamber on the 6.5-57 since it didn't cost any more to do two chambers than to do one. So now I have two rifles with the same barrel length but with different twist rates in the same 6.5-06 Ackley chambering.
After working up loads for each rifle with the same bullet and powder I think I may have evidence that I was right about the slower twist rate possibly achieving slightly higher velocity than the faster rate.
Here are the max loads for each,
10" twist - 60.5gn AA#4350 @ average 3690 fps
9" twist - 57.5gn AA# 4350 @ average 3515 fps
So was I right about the twist or was I lucky?
One thing I can say with certainty this rifle shoots flat. Jr. and I were out a couple days ago confirming some ballistic data. We were shooting at 737 yards. The rifle was zeroed at 100 yards and it only took 2.7 mils of correction to get on at the 737 yard range we were shooting. With the mil-mil Bushnell scope I have mounted that is 27 clicks of elevation.
I let Jr. have a go with the rifle and he was grouping right at 1/2 moa at the 737 yard range. This is the rifle I used to fill my elk tag last year. My shot was 639 yards and landed exactly were I was trying to put it and one shot is all that was needed. I am well pleased with the shooting system I have put together with rifle, cartridge, scope, laser, and ballistic program. My only disappointment is that I waited until my youth had passed before I finished the build. In fairness in my youth we did not have the optical technology nor the electronic ballistic technology available. If we had there would likely be no coyotes left!
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jsh
Bullet Head
Posts: 14
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Post by jsh on Jul 28, 2016 17:55:20 GMT -7
I still have the wants for a 6.5-06 myself.
Now Dan I won't say I am old but I dang sure ain't as young as I was lol.
I picked up a 270 savage that I wanted to rebarrel to 6.5-06. I contacted shaw as they have it listed. I pretty much have given up on them as they have never responded back to me in several tries on my end.
I read all I could find on this cartridge and most guys told me to go to the vanilla 6.5-06 rather than the AI. Some case capacity to be gained but not enough in speed and anything in accuracy to say much about. Case life seemed to be about equal.
I too am looking at one bullet,but not sure which one as it seems the just keep getting better every year.
What I need, another project:-).
Look forward to your findings.
Jeff
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Post by Bullshop on Jul 28, 2016 19:03:54 GMT -7
For my build I was looking for every possible velocity advantage in a .264 caliber using the 06 case. If you compare the velocities I am getting with book loads for larger cartridges you will see that this build gives up nothing to the 264 Win or 26 Nosler with their standard 8" twist and shorter barrels.
No doubt ballistics from the larger cases could be improved with the same longer barrel slower twist treatment but would eliminate the heavier bullets in the caliber. I am perfectly satisfied sacrificing the heavier bullets in the caliber for the increased velocity afforded by the slower twist with the mid weight bullets. There are some very high BC bullets in the 100 to 110gn weight range in 264 cal.
I am thrilled with the performance I am getting from this build. This rifle makes what I once considered long range shots too easy. Now long shots start at 500 yards and go out as far as I have ballistic data for. I started out limiting my ballistic data to 900 yards but after shooting this rifle a bit have now extended that to 1200 yards.
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Post by todddoyka on Jul 28, 2016 21:03:16 GMT -7
you gotta luv them ackley improved!!! good work and great shootin!!!!
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Post by Bullshop on Jul 29, 2016 7:04:59 GMT -7
This experience has demonstrated at least to my mind that yes there was a gain to be had going with the Ackley version of the 6.5-06 case over the standard. In comparison published data for the 6.5-06 is substantially less than the ballistics this rifle is giving all things considered. Adding all the small ballistic gains however slight attributed to barrel length, Ackley case, and slower than standard twist come together to show a substantial gain over the more conventional shorter barrel, faster twist, standard 06 case.
I feel that comparing the two rifles mentioned here having both chambers cut with the same reamer and both having the same barrel length shooting loads using the same powder lot and bullet and being different only in twist rate demonstrates that in itself slower twist rate alone shows a ballistic improvement of 175 FPS from an allowable 3 gn increase in powder charge.
9" twist 57.5gn AA-4350 @ 3515 fps
10" twist 60.5gn AA-4350 @ 3690 fps
There could be other things at play here in why one barrel is faster than the other but of the things I have control over this is the difference I am seeing. This is why I opened with a question, was I right or just lucky? Either way I am good with it!
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cobbmtmac
Bullet Head
NRA Life Member since 1978
Posts: 11 
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Post by cobbmtmac on Jul 30, 2016 8:21:15 GMT -7
Dan,
This is so interesting, I am use to, (now I have to say, short range accuracy). I am a fairly seasoned old guy, to general hunting and the importance of accuracy. I just cant imagine a 1/2 moa at 737yds. I congratulate both you and Jr!
Keep up the good work and Keep having FUN! Mac
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Post by Bullshop on Jul 30, 2016 12:01:29 GMT -7
Thanks Mac! Lord willing will try to keep up the fun part! Actually 1/2 MOA at 700+ yards doesn't get us too excited. That's just a little over a 3.5" group at that range. That keeps us inside the self ascribed 6" kill zone for coyotes though. Under good conditions we should be able to stay inside that kill zone to about 1000 yards. The real trick come with doing it in one shot
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The next tool I have to add to my shooting system is a cosine angle indicator. At these ranges a miscalculation of a few degrees in angle of sight can amount to a total miss on a small target. Real time atmospheric conditions are also a must if you hope to make one shot hits at long range.
Here is a good example, when Jr. and I were out last time shooting at 737 I had two range cards with all dope being computed with the same data accept for temp. One card was computed at 80*F and the other at 20*F one for summer and one for winter. The more dense atmosphere at 20*F called for a 3.1 mil correction while the dope computed for 80*F called for a 2.6 mil correction. I used the wrong card for the first shot and the shot went exactly where it should have .5 mil high. Finding the mistake and clicking down 5 clicks put us in the money.
Now 5 clicks isn't much but at the 737 yard range it amounts to .36" per click at 100 yards so x 7.37 yards x .36 = 2.65" per click. At 2.65" per click 5 clicks was moving POI at 737 yards 13.25" which is right about where the first shot landed.
Jr. might think the mix up was deliberate because this sort of thing has happened before in a match where we were competing against each other. I wont confess to anything for certain other than to say I am teaching him to stay alert.
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Post by Junior on Jul 31, 2016 16:31:42 GMT -7
I was in cabelas looking at used guns last night, and ran into a young gentleman who ended up buying a 03a3 to rebuild into a 6.5/06 AI.
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Post by Bullshop on Jul 31, 2016 17:55:32 GMT -7
Where ya been Jr.? Lets go shooting. I promise to give you the correct sight setting this time.
The 6.5-06 Ackley is becoming quite popular. We used a reamer from Fred Zeegland and of the several reamers he had available there was a back log that required us to wait several weeks to get a reamer.
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cobbmtmac
Bullet Head
NRA Life Member since 1978
Posts: 11
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Post by cobbmtmac on Aug 5, 2016 8:32:32 GMT -7
Dan,
Alrighty, I now understand, the 1/2" is at 100. Still 3.5" @ over 700 greatly impresses me! I'll follow along.
Thanks, again, Mac
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Post by Bullshop on Aug 5, 2016 17:37:45 GMT -7
Here is another interesting tidbit to ponder and that is of angle of sight. I was out yesterday evening just having fun with a 308 Win I put together several years ago. I don't shoot it much because a plain vanilla 308 is just not as interesting as other toys we have available.
I hade a box of Hornady 150 SST bullets with no other purpose than to just shoot up so worked up a good shooting load with 41gn of AA-2200 at 2870 fps. A hot load but shoots very tight. I then ran the Sierra Infinity ballistic program for this load and bullet and printed out the data to take along shooting.
I didn't park quite exactly the same as last time so this time the laser said 740 yards.
I clicked the data into the scope a 16X SWFA SS with .25" clicks. Settling in for a few shots showed I was consistently hitting about 1.5 minutes high.
Why I asked myself. Bad data? The infinity program has always come very close for shots to or slightly more than 1000 yards so why not now?
Pondering ALL considerations to predict bullet flight path I realized I had not considered angle of sight for the shot. I blew it off because the slight uphill angle didn't seem enough to worry about but I was wrong. The uphill angle I did not measure but guessed it to be about 10 to 12 degrees.
The data I had available only gave angle corrections at 20*, 30*, and 45* The correction for a 20* angle from level was .5 MIL or 1.8 MOA.
So doing the math 1.8 minutes at 740 yards is 13.32 " of shift in POI. Blowing off the slight angle of sight from my ballistic data put my POI over a foot high. Trying to hit a coyote at that range and leaving out the angle of sight data would have only resulted in a more educated coyote.
This is exactly why I said earlier that my next addition to my shooting system will be a cosine indicator. This is nothing more than a gravity indicator dial that corresponds to either a cosine or angle scale or both. Very simple tools that mount on the scope much like a scope level but not at all cheap or I would already have one. There is an inexpensive tool called " the slope doper" that I may add to my range bag until I can afford a good quality scope mounted cosine indicator. Making money shooting coyotes requires that the majority of my attempts are one shot hits.
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