Tyler,
Well, I must admit that in desiring to share my ideas with others, (and seeking input) I often do what amounts to a lot of thinking out loud. But, through all the rambling, you understood the underlying message I was trying to get accross when you made these comments pertaining to me:
His logic seems pretty accurate to me. I think his premise is to EXCEED the .20, you need to shoot a bigger bullet and push it faster.......What is so strange about his idea that using a mild 6mm offers no advantage to a .20 under 500 yards?"
Yes, Tyler, that in a nutshell is exactly the point I've been making. Thanks.
To VarmintGuys delight, I will reiterate the facts; my 20 is ultra flat shooting, ultra wind bucking, shoots 1/4" groups, at 3,820FPS, recoils low enough to maintain a sight picture at 100 yards. ( With my 16lb rifle, I can see the bullet holes appear on the paper) All this while providing a very long barrel life.
For a couple of years now I had believed that the 6XC cartridge (or at least some sort of an improved Dasher style 6BR cartridge) would be my ultimate "long distance" PD rifle. Because I had always heard how the .243 bullet was more wind resistant then a .22 bullet, I eroneously concluded that it had to be even that much better then when compared to a light 20 cal bullet.
So when the 6x47L Lapua brass case came out, I thought I had my dream gun all figured out. So, I purchased my HS Varmint stock, a new .243 bolt faced 700 SS action, before I had even finished putting a scope on my custom 20Tac and trying it out.
Well, I fired my 20Tac for the first time during the last month......exactly a year after my gunsmith had handed it over to me. (oh did I mention that I'm a procrastinator?
) I couldn't believe the accuracy I was getting with my bore foulers and first time experimental loads!
I had previously always considered the 20 cal some kind of small and fringe cartridge. I had always thought of it as too small and light. After the firing range results, I started to take the rifle more seriously and ran a series of ballistic comparisons. I ran it against practically every 6mm weight bullet out there. For a 400 to 450 and maybe up to 500 yards, nothing compares to it. There is no reason to use a harder recoiling gun for the first 450 yards of PD shooting. And to closely maintain the same kind of impressive ballistics, you are absolutely right that I would have to push a heavy bullet out of a big case. And, at that point, as Ackman would say, "their are no fee lunches". Their is going to be significantly more powder useage, recoil, and barrel wear involved. Where I had previously printed many pages of ballistics using the Hornady ballistics calculator from their websight, it only went up to 500 yards. I just discovered this ballistics calculator, and printed sheets to compare and study all the 6mm grain bullets side by side:
http://www.eskimo.com/~jbm/ballistics/traj_basic/traj_basic.html
This websight allows me to calculate the ballistics beyond 500 yards and out to 700 which would likely be my desired practical max. I keep coming up with the same conclusion that the 87 Grain Vmax with a 400BC at a MV of 3150 FPS, is better then any other weight bullet. (And I also calculated somebody elses preference; the Nosler 55BT with a .276BC doing a MV of 3800) The lighter bullets shine for the first few hundred yards, but start to substancilly lose their advantage where I can't justify using them. Yes, their might be higher velocity loads possible with these lighter bullets in a 6x47, but so too with the 87. So I picked safe and doable muzzle velocity numbers, without getting carried away with max figures that might be pushing the limits.
I don't believe I want to try a 243 AckleyI. I just can't stand to think of the barrel wear. In fact, if a barrel burner, is an option, I would seriously consider a 20/250. There's some intersesting posts about it by guys like "1holer", "DAA", and "20-250AI" over at Saubier. Some really serious yote hunting done with this round. (not that I ever intend to use my rifle for that) There's some posts about the 50 grain bullet doing 4,100- 4,200fps, but I'm satisfied enough with the ballistics of that 20 cal 50 grain berger doing 4050fps, and did calculations on that number. At 600 yards the 87 grain 6mm bullet drops -36.3" zeroed at 400 yards....while the 50 grain Berger 20-250 drops only -25.7
Like I said, a 20 cal is one very impressive cartridge for a varmint rifle. It makes it hard for me to be enthusistic about a 6mm. But, the fact is from all ballistic data indications, that the 6x47L (using 87grVmax) will still be a fairly qualified improvement at 500-700 yard shooting over my 20Tac. As good as the 20Tac ballistics are, 500-700 yards is no longer its practical range.
I'm still leaning on the 6x47Lapua with an 87 grain bullet as a pretty darn good compromise. It would do very well on PD for the 600-700 yards. What I have found is that the ballistic show that it goes 40FPS faster at 600 yards then what the 55 grain BT bullet is doing at 600 yards.But because it so much heavier it hits with 688ft.lbs vs the 413ft.lbs of the 55grain bullet. Though the 87 grain bullet drops 5" more then the lighter 55 grain BT bullet, it blows over 6" less! Those are pretty good numbers, and I suppose a sacrifice of the 5" drop is a good trade off for the wind bucking and powerfull hitting energy. The 50 grain 20-250 bullet on the other hand would hit with 493 ft lbs of energy at 600 yards, and drops 6" less then the 55BT 6mm bullet! But the "lunch" to pay here is using a badly overbore bullet.
I still haven't ruled any of the 20 or 6mm cartridges out.
Like I say, the 20's got me spoiled and it's hard to find a good 600-700 yard supplement.
As far as Ackman goes....I think he's a good guy....just opinionated. (yea...like I'm not?) I find this amusing as he kind of reminds me of that TV Marine gunny guy, or "Red" from "That 70's Show". It's kind of neat to have the temperment and skill like that to make your point known just short of calling someone a dumb ass.
I think a lot of this information on this thread might be enlightening to some folks that weren't fully versed in the 20's and the 6mm's for varmint purposes. Other guys like Ackman will be content with what they have......and I can accept if they don't care to see things my way.
