I have heard reports of the 75gr A-Max "dusting" in fast twist rifles but my experience would differ.
I have a 22-243AI w/8" twist and the rifle loves the big A-Max bullet. I shoot them @ 3,670 ft/sec and have never dusted a single bullet. Accuracy is exceptional and I made several one shot kills on groundhogs at over 800yds this season. [img]images/icons/shocked.gif[/img]
The 80gr bullets never shot as well in my rifle. If I had it to do over again I'd go with a 9" twist and keep everything else the same.
If you want to shoot the .224" heavies than you need some case capacity to generate horsepower. I like the 22-250AI as a minimum and would prefer the SwiftAI or 22-243.
I would also suggest getting a longer barrel than you need so that you can, at some point, set it back and rechamber without going for the expense of a new barrel.
Fifty Driver, My experience with both the 22/250 AI, and 220 Swift AI, found that the 220 Swift AI has a velocity advantage of 100 - 150 fps with bullets of 55 grains in weight.
However, that increases to well over 200 fps with bullets of 69 grains and above. I have found that this principle holds true with most larger cases in a particular calibre, that the biggest velocity gains are with the heaviest bullets. My records show that:
22/250 AI (28 deg) - capacity 48.0 grains
Rifle 1- Shilen SS 27 inch, 1 in 14 twist.
53 grain Sierra HP
40.5 grains IMR 4064 - 4,011 fps (max)
60 grain Hornady HP
46.0 grains Norma 205 - 3,782 fps (max)
22/250 AI (28 deg) - capacity 49.2 grains.
Rifle 2 Shilen 24.5 inch, 1 in 14 twist.
Sierra 69 HPBT
43.5 grains WIN WXR - 3,465 fps (Max)
44.0 grains Rel 22 - 3,442 fps (Max)
46.0 grains WIN WMR - 3,428 fps (Near Max)
55 and 60 grain bullet weights will be tested in near future.
220 Swift AI (40 degree)- Capacity 55.4 grns
Rifle 1- Shilen 25.25 inch, 1 in 12 twist
Sierra 53 grain HP
49.0 grains IMR 4831 - 4,146 fps (Max)
Sierra 55 grain SPBT
49.0 grains IMR 4831 - 4,128 fps (Max)
Nosler 60 grain SPBT
47.0 grains IMR 4831 - 3,906 fps (Max)
Sierra 69 grain HPBT (did not stabilise)
48.5 grains IMR 7828 - 3,653 fps (Max)
47.5 grains Norma MRP -3,782 fps (Max)*
* my gunsmith achieved this velocity prior to shipping to me. Unfortunately I could not source Norma MRP.
I also heard of rumors of the a-max blowing up and I agree completely that they don't. I even pushed them at 3700 fps out of my ridiculous .22-.284 and no blow-ups. They wouldn't hold a 3" group at 100 yards to save my life at that velocity though. I don't know if 50driver has ever really fired them or maybe he just got a bad lot.
I have heard good reports with these bullets used at higher velocities. Personally I have yet to see an A-Max handle anything over 3250 fps and hold extreme accuracy out of a true 1-8" barrel.
THe only experience I have with the 1-8 twist barrels with the A-Max bullets is with my personal 6mm-284 which shots the 105 gr A-Max into 1/5 moa levels at 500 yards until velocity gets to almost exactly 3250 fps. From there groups grow to about 4" at 500 yards.
The Berger 105 gr VLD was very similiar except that it grouped well only until 3200 fps.
With these velocities I might as well been shooting a 243 AI out of my 30" Lilja.
I have also witnessed one of my custom rifles chambered in 22-6mm AI do nearly the exact same thing with the 75 gr A-Max when velocities hit just under 3300 fps with this rifle.
THe 6.5mm was in a custom 6.5 STW with a 1-8 twist. It lost accuracy in teh 3200 fps range as well.
I am not saying that these bullets disintegrate in mid air, only that their accuracy dropped off greatly in these three different rifles using 1-8 twists.
In contrast, like I stated before, I also have a custom rifle that a customer is shooting the 105 gr A-Max out of a 6mm-06 at just shy of 3600 fps with groups in the 3's but this is with a 1-9 barrel.
I measure all of my barrels for twist before I start machining them. One would be suprised how a 1-8 barrel often turn out to be a 1-8.5 or even 1-9. This is especially true with the button rifled barrels.
Not so much a problem with cut rifled but alot of buttoned barrels are not what they are supposed to be.
I prefer and highly recommend Lilja barrels and they too are buttoned rifled but I have yet to see one that was not marked true.
I am not disclaiming you and your results, just stating that I have not had good results with the A-Max in 1-8 barrels loaded above 3250 fps.
Under that they are some of the most accurate bullets comercially made and on game performance is better then any other commercial long range bullet.
In all these cases I list, the barrels were 3 groove Lilja barrels. What barrels are you guys using to get these velocities with good accuracy?
Maybe its a 3 groove problem more then a velocity problem...
Have a good evening!!
Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.
Thanks for clearing that up. I have a Shilen select match barrel that seems to be exceptionally smooth and unusually fast. Maybe the reason we have had somewhat different summaries is because my barrel just happens to be an 8 groove! I don't know if it's good or bad but it does seem to work fine. Another thing that you might find interesting is that it was originally a .22-.284 chambering in 29.5" configuration. I shot 900 rounds through it very carefully when it started blowing up Bergers, and then 100 rounds after that it started blowing up Sierra's. I then cut off the bad parts(3 inches in the throught and 1 inch in the crown)and rechambered for the 22-250 AI. It's accuracy came back and shoots with a vengeance now. I actually got good accuracy at the 3250 fps mark you mentioned, but the standard deviation was around 25 fps and that just won't do for consistent 1000 yard accuracy. And when I talk about accuracy, I say "good" but that is a relative term. I alway got better groups at 400 yards than at 100. Honest. On a stack of Bibles. I think the best group I ever got with it at 100 was 7/8" and best at 600 was 2.5" 3 shot center to center. As for the twist changing further down the barrel, or actually not being a true 8", it could easy be. I have never really checked it, but I have read of such things happening before.
[ 09-15-2004: Message edited by: goodgrouper ]
thanks kirby and the rest of you gentlemen.
i am building a 220 swift using a pac-nor 1-9" 3 groove remington magnun contour and fluted on a remington 700 titanium action. i have grown tired and grumpy in my old age. tired of coyotes moving out to 500-600 yards, sitting there cussing me out. and yes this is a revenge thing. i am hoping the 75 gr amax or maybe the 65 gr sierra will get the job done.