B23
Well-Known Member
My 6-284 was built on a short action Rem 700 so maybe that has something to do with it but I've never had a feeding issue with mine.
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Which 6mm in long action Remington 700? Quality Brass is issue...
- Thread starter cdherman
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Trickymissfit
Well-Known Member
Ackley said that the standard 6mm Remington case volume was about max for the 24 bore. yet along the way we've seen everything from the 6BR all the way out to a 6mm/.300WBY. The 6mmAI is moving slightly into an over bore condition, but not enough to even be concerned about. The 6/284 is fairly close to the 6mm-06 in case volume (the 06 case is slightly greater in volume). A few years back Precision Shooting did a road test of the .243, .243AI, 6mm, 6mmAI, and the 6mm/284. Velocity wise they found the 6mmAI was slightly faster than the 6mm/284 (seems like it was less than 50fps). All rifles tested used match quality barrels and chambers (think they were all Remington, or clones). The tests used several different hand loads, and also used well known loads that were known to produce serious velocities. The standard 6mm was the tightest grouping, but that was only by a few thousandths of an inch over the others. A month later somebody threw in a ringer that sorta embarrassed the others. That of course was the little 6BR! Using about 2/3rds the powder and going about 200fps slower. But a little later they happen upon a guy who was seriously developing the 6BR, and he was only running about 75fps to 150fps slower than the .243 with 105 grain bullets!! Of course he never let anybody know his chamber pressures, and they must have been serious. But the group size was a fraction of the others! Kinda shows that Ackley knew what he was talking about.
I shoot the 6/250AI with 105 grain bullets. It'll do 3000fps with some pretty hot loads. So will the .243, but also use more powder. Now I for one see needed changes in the case design (6/250AI), and working on that. There's also the 6mm Vias, and that round is very hot! It'll push a 70 grain bullet faster than a .220 Swift can push a 50 grain bullet. Case is well designed, and would fit in a mag well better than the 6mm Remington. The Vias case starts out as a 6.5x55 improved, but has the shoulder pushed back about .05". I think the lost .05" is moved into the neck. Sorta makes Ackley's thoughts right on again.
I had three buddies that shot the 6/284 extensively at some very long ranges. They were a barrel maker's dream come true, as they usually ate two barrels a year; if not three! They bought very expensive barrel blanks, and they burnt out as fast as the cheaper ones. One of them came up with the grand idea of shortening the base to shoulder .100", but added .07" to the neck length. He lost about 75fps, but shot the same barrel all year long. His buddies did him one better and reamed the chamber .150" short, and added .07" to the neck length (used the same reamer). He lost about 100fps, but his groups were better. He more than doubled his barrel life at the same time. The third guy kept the old style chamber till it went south. He did a barrel set back .100" short, and was actually slightly faster than the other guys. Their dies were simply reworked Reddings.
gary
I shoot the 6/250AI with 105 grain bullets. It'll do 3000fps with some pretty hot loads. So will the .243, but also use more powder. Now I for one see needed changes in the case design (6/250AI), and working on that. There's also the 6mm Vias, and that round is very hot! It'll push a 70 grain bullet faster than a .220 Swift can push a 50 grain bullet. Case is well designed, and would fit in a mag well better than the 6mm Remington. The Vias case starts out as a 6.5x55 improved, but has the shoulder pushed back about .05". I think the lost .05" is moved into the neck. Sorta makes Ackley's thoughts right on again.
I had three buddies that shot the 6/284 extensively at some very long ranges. They were a barrel maker's dream come true, as they usually ate two barrels a year; if not three! They bought very expensive barrel blanks, and they burnt out as fast as the cheaper ones. One of them came up with the grand idea of shortening the base to shoulder .100", but added .07" to the neck length. He lost about 75fps, but shot the same barrel all year long. His buddies did him one better and reamed the chamber .150" short, and added .07" to the neck length (used the same reamer). He lost about 100fps, but his groups were better. He more than doubled his barrel life at the same time. The third guy kept the old style chamber till it went south. He did a barrel set back .100" short, and was actually slightly faster than the other guys. Their dies were simply reworked Reddings.
gary
Fiftydriver
Official LRH Sponsor
Before the 6.5mm crazy took off, the 6mm-284 was by far the most popular wildcat chambering available on the 284 case. I guess it still is as the 6.5-284 is not a standard chambering. There are lots of dies, reamers and data for the 6-284!!!
Outlaw6.0
Well-Known Member
Very interesting data Gary. Makes me want to dust the 6mmAI off again. The particular loads shot from my 6AI & 6-284 have the x284 slinging 107's faster than the AI is slinging 85's...??
From a pure design standpoint, I believe the AI is where it's at, shoulder angle & neck length leads me to believe the AI will last a LOT longer than the x284. Then again, the x284 is (at least in my 2 respective rifles) a fair leap in performance.
Like I said, I need to dust off the AI & play around a little.
t
I don't believe in the magic of the Ackley shoulder angle. There have been a lot of smart people build a lot of new cartridges since the Ackley era and I don't know of even one that has a 40° shoulder. I have never seen any test data but I think there is a better than average chance a 40° shoulder angle will impede gas flow from the case into the barrel.
MontanaRifleman
Well-Known Member
I got my barrel nitrided along with a couple other overbores hoping to stretch the barrel life out. We will see... I just picked it up today after being reassembled and will be putting a lot of rounds down the tube in the next few months.
Probably because they don't feed as well as 35* or 30* shoulders.
Outlaw6.0
Well-Known Member
I want pictures dern it!
I was also thinking of the feeding issues. My 6mmAI has been a PITA ever since it was built, it never has fed right (sav receiver). I know i can fix it, i'm just lazy
It's been collecting dust for 3-4yrs. t
B23
Well-Known Member
Outlaw6.0, do you by chance have one of your 6mmAI fireformed cases laying around handy you could measure the case capacity in water grains. I've always thought the AI version of a 6mm would pick up quite a bit of case capacity of the non Improved version.
Outlaw6.0
Well-Known Member
B23
Well-Known Member
I've always thought, if there are two cases that are just begging to be improved, it's the Rem 6mm and 220Swift!!
Thanks for measuring that.
Thanks for measuring that.
Trickymissfit
Well-Known Member
I personally like the 30 degree shoulder version better than the 40 degree shoulder one. But the 40 degree is more common, and load data should be very close for either one anyway. The reason for the 30 degree shoulder is that it doesn't get the dreaded doughnut as easily as the 40 degree one.
Parker Ackley was a man way ahead of his time, and anybody that would knock him is a fool. But he actually learned from somebody else; just like we all do. His two volume set is a must read for anybody experimenting with fire arms and reloading. Yes a bit of it is dated, but the vast majority is still spot on. I take exception with his thoughts on metallurgy, and of course his barrel thoughts are now very dated. Yet the vast majority if his thoughts are still quite viable this morning.
gary
Trickymissfit
Well-Known Member
the first time I ever read that the 6mmAI was faster was from Boyd Mace, and he often shot both rounds side by side. My data says the 6mmAI everytime, but as I also said the velocity differences are nil. The gist of my post was that the 24 bore will only handle just so much powder; no matter how big and fat the case is. That's why I pointed out the two different short versions of the 6/284. I know the velocities are correct as they shot them thru my chronograph.
Back to the 85 grain bullet in the 6mm, and a couple thoughts (just about my favorite bullet size in the big six). I had little trouble doing 3350fps with standard Remington cases, and with very old .257 Roberts cases necked down (they hold about one and a half grain more water) I hit the 3400 to 3425fps mark with some very stiff loads out of a 24" barrel. Now I'd expect the 6mmAI was good for about 100fps to 125fps over the Roberts cases, so we'll just round it off at 3500fps. Yet I found my accuracy load was about fifty feet per second less (big coyote will never know the difference). This was why I spoke highly of the 6mm Vias. It's nothing but a basic 6.5x55 improved case necked down to 6mm with a slightly shortened shoulder length. Velocities are right there with the 6mmAI and the 6/284 with a smaller case volume. Looks like Ackley was right again.
gary
Fiftydriver
Official LRH Sponsor
This reply is not directed at any comments made by Gary in any way, just general comments so please do not take any offense to this as its not ment that way at all because my references here are not directed toward his load data or findings, more toward the major reloading manual companies.
You see this data all the time in loading manuals where you look at a chambering that is listed to far outperform a larger chambering and then when you look at the loads used, pressure generated, you just have to sit there and shake your head. I think it was in the last Nosler manual or the one before it where they listed the 300 Wby as at least as fast or even faster then the 300 RUM which is on its own a joke but it was also listed to match the 30-378 Wby.
When you look at the loads used however, they used the very best powders possible in the 300 Wby and loaded it to 100-105% load densities. In the 30-378 Wby, most of their loads were in the 85 to 95% load density range and using powders that were far to fast in burn rate for this chamber.
You can make any chambering LOOK Better then another if you want to. Not saying this is what happened in this mentioned article but the fact is that velocity is a simple function of pressure and time. The amount of pressure behind a bullet and the amount of time that pressure acts upon the bullet while its in the bore.
Now certainly there are many other factors such as twist rate, bore diameter, throat length and diameter but if all else is the same, the 6-284 will pull away from the 6mm AI dramatically, especially if using bullets over 100 grains in weight. With lighter bullet weights, the advantage will not be nearly as larger but it will still be there.
My opinion, you can talk about case design, shoulder angles, neck length, etc... all you want, in the end, just as with gas powered engines, it all comes down to displacement and in the end the case with the largest case capacity will produce the highest performance level when all is loaded to same chamber pressures with correct powders for each application and when used with same length barrels.
With the powders we have available to use today, the 6-284 is certainly not oversized for top performance. We have a huge selection of powders and many will take the larger cased 6mm wildcats well over what we could get even 10 years ago.
Hell, you can take a 6 mm AI, throat it to seat a 105 gr berger out as far as possible, then take a 6-284, throat it so the 105 gr berger is seated as deeply as possible and see which performs the best. In that application, I would bet the 6mm AI would match or even slightly exceed the 6-284. If you leave the comparision there, it APPEARS that the 6mm AI is the full equal to the 6-284, BUT if you take that 6mm-284 and throat it in the same manor as the 6mm AI, the 6-284 will blow it away, again, need to make useful comparisons and that unfortunately rarely happens. I am sure not intentionally but it happens none the less.
