.260 REM vs .260AI vs 6.5 REM Mag vs 6.5x284 Norma - Page 2 - RimfireCentral.com Forums

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  #16  
Old 06-18-2009, 06:26 PM
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Opps, I did it again ... Spoke Too Soon



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Quote:
Originally Posted by natman View Post
So I don't see how the 6.5-284 can be "over-kill" since its capacity is slightly less than the 6.5 RM.
Poor choice of words ... I spoke too soon.
My comments were primarily directed at the .264 WIN Mag.

Rather the 6.5x284 is an unknown cartridge to me.
And, from what I've read ... maybe too specialized.

Quote:
The 6.5mm Rem. Mag. is a better design than the 6.5mm-284 Norma for feeding from the box magazine of a repeating hunting rifle.
It has also been around longer as a factory standardized cartridge and there are more factory produced rifles available on the used market.
Remington ammunition is more widely distributed than Norma ammunition in the U.S. and usually less expensive.
A detachable magazine is important to me.
It is what I want and prefer in a rifle.
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  #17  
Old 06-18-2009, 07:44 PM
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Being a Perfectionist ... A Lot of Gun Guys Are ... I Am

Quote:
Originally Posted by natman View Post
It seems to me that your requirement is to get a velocity (2600-2800fps) that matches your choice of scope. The 260 Rem does that out of the box.
With 140 gr and 130 gr bullets respectively.

My goal was 2600 fps (155-160 gr bullets)
and 2800 fps (139-142 gr bullets) with a 22-inch barrel.

Quote:
Originally Posted by natman View Post
Your goal of an extra 100 - 150fps isn't required to match the scope.
It seems more like a rationalization to justify doing something you've already decided to do - convert to 6.5 RM.
Which is fine, it's your rifle, your time and your money.
The extra 200 fps would match the bullet drop compensations characteristics
of a Leupold Medium Range Mark 4 - with higher ballistic coefficient bullets.

With all of the advice and experience this thread has exposed me to,
I need to reevaluate whether my goals are reasonable and feasible.

What do I want ... what do I or really need.
Detachable box magazine
Low recoil
Prefer 22-inch barrel (will accept a 24-inch barrel)
Not a heavy rifle (less than 9 lbs with scope)
High ballistic efficiency
500 yard effective range
2600 fps 155-160 gr bullet (will be satisfied with any reasonable round nose)
2800 fps 139-144 gr bullets (will be satisfied 137-142 bullet)
Not burning-out barrels too fast
As a perfectionist, am I asking too much?
Is it possible? Maybe.

But, from what everyone has advised or brought to my attention.
.260 REM handloaded ammunition may work for me if I'm willing to compromise.

Thank you one and all for all of your insight and information.
It is wonderful having so many knowledgeable people willing to provide advice and guidance.
You all have given me a strong dose of reality.
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  #18  
Old 06-18-2009, 07:56 PM
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All this chatter has got me to thinking. Yeah, dangerous, I know. But, I think I may just have to consider rebarreling a Stainless Classic Model 70 WSM to a 6.5RM. I have a hunch this would be a very easy conversion. Wonder if a Featherweight contour barrel would work with the 6.5RM? Probably not, since Winchester never did chamber any magnums, short or otherwise in the Featherweight contour barrels, to my knowledge. Also, the WSM Model 70's don't have the spacer in the back of the magazine, like the .243 and .308 versions do. I'll have to give this more thought!
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  #19  
Old 06-19-2009, 07:52 AM
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Quote:
Originally Posted by aom22

Originally Posted by natman
It seems to me that your requirement is to get a velocity (2600-2800fps) that matches your choice of scope. The 260 Rem does that out of the box.


With 140 gr and 130 gr bullets respectively.

My goal was 2600 fps (155-160 gr bullets)
and 2800 fps (139-142 gr bullets) with a 22-inch barrel.
So what the heck is wrong with a 130-140 grain bullet? It will match your scope and kill any game suitable to hunt with a 260 Rem.

Your "goal" serves no useful purpose. It all boils down to boosting 160 grain bullets to 2600 fps, so they will "fit" the scope.

Once again: because of the low BC of 160 grain 6.5mm bullets, they WILL NOT MATCH the trajectory of a 7.62mm NATO 118 LR, which uses a very high BC bullet.

If you want to use 160s for "brush busting", you won't need a BDC scope to do it.

BTW, I understand that you don't handload. Unless you do, you will be far better off with a 260 Rem than a 6.5RM. The 6.5mm was obsolete for years until Remington defibrillated it recently. Ammo and brass availability will be much better for the 260.
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  #20  
Old 06-19-2009, 09:53 AM
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Diverse Hunting and Shooting ... Diverse Rifles ... Gun Nut Perfectionist

Quote:
Originally Posted by natman View Post
So what the heck is wrong with a 130-140 grain bullet?
It will match your scope and kill any game suitable to hunt with a 260 Rem.
I agree with you for the most part.
My desire was to take advantage of the above 140 gr bullets
that promise an even higher ballistic coefficient.
An additional 200 fps I think would pose a real ballistic advantage.
For stand or crop field hunting with the occasional long-range varmint shot.

Where I live, hunting and shooting areas are very diverse.
From wide open spaces that present clear, long-shots of antelope.
To dense mesquite brush teeming with deer and hog.
The same can be said of coyote and jackrabbits.
But, they represent snap shooting opportunities more than anything else.

Often times, when passing from one brushy area to another,
a quick 200 to 300 yard shot presents itself.
Still hunting these clear spaces give rise to a long, unhurried, silhouetted shot.
Moreover, the Davis Mountains are only 65 miles away.
Presenting another type of environment and set of shooting situations.

Quote:
Originally Posted by natman View Post
Your "goal" serves no useful purpose.
It all boils down to boosting 160 grain bullets to 2600 fps, so they will "fit" the scope.
If you want to use 160s for "brush busting", you won't need a BDC scope to do it....
Again, I agree. Which brings me to another conclusion.
One rifle ... two rifles can't do it all for me - properly.
The pencil barrel of my Remington Mountain DM, that I adore so much ,
has its limitations - to say the least.
I've decided to buy, yet again, another rifle - third and last centerfire for a lifetime.
(Need to get'er all done before I retire in five years from TDCJ - 10 years, CID, Alejandro O. Martinez)

It will be along the lines of a Remington Model Seven .260 REM.
Or, CZ 550 Full Stock 6.5mmx57 SE. This will be my brush rifle.
2600 fps be darned ... any heavy, round-nose bullet should work fine for my purposes.


Quote:
Originally Posted by natman View Post
BTW, I understand that you don't handload.
Unless you do, you will be far better off with a 260 Rem than a 6.5RM.
The 6.5mm was obsolete for years until Remington defibrillated it recently.
Ammo and brass availability will be much better for the 260.
Yes, handloading is in my future.
But, first comes the rifle(s), scope(s), case(s) and related accessories.
Then, comes the handloading equipment and related work area.
I can't afford to do everything at the same time.

One more thing, If Remington doesn't do more to promote the .260 REM,
it may, eventually, go the way of the 6.5 REM Mag.
Model 700
Quote:
6.5mm Rem Mag (1969 – 1973)
Remington's revival of the 6.5 REM Mag really misses the mark,
in actuality the 6.5 REM Mag needs to be marketed in a proper rifle - 24-inch CDL or BDL would be nice.
As opposed to the abbreviated barrels of the 600, 660 or 673.
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  #21  
Old 06-19-2009, 02:09 PM
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6.5x284 As Suggested by natman

Quote:
Originally Posted by natman View Post
If you feel compelled to make a change consider the semi-wildcat 6.5x284. No bolt head change needed.
Quote:
Originally Posted by natman View Post
"Here are the case capacities of our two cartridges.
  • 6.5mm-284 Norma = 68.33 grains of water
  • 6.5mm Rem. Mag. = 68.64 grains of water"
So I don't see how the 6.5-284 can be "over-kill" since its capacity is slightly less than the 6.5 RM.
natman ... I've been doing some research on the 6.5-284 cartridge.

I've looked very closely at the ballistics of some of the off-the-shelf loads available and I'm dumbfounded.
You were (are) right ... the 6.5x284 will perform, almost precisely, at the level I'm seeking.
Quote:
Bullet: 160 grain Sierra Spitzer Flat Base Pro-Hunter
Velocity: 2650 feet per second
Ballistic Coefficient:0.37
Required Twist:1:9 inches or faster
Use: Deer. Elk
Bullet Construction: Gliding Metal Jacket. Lead Core

Bullet: 140 grain Sierra Boat Tail Hollow Pont MatchKing
Velocity: 2760 feet per second
Ballistic Coefficient:0.53 Required
Twist:1:9 inches or faster
Use: Long Range Match
Bullet Construction: Gliding Metal Jacket. Lead Core

Bullet: 142 grain Sierra Boat Tail Hollow Pont MatchKing
Velocity: 2760 feet per second
Ballistic Coefficient:0.58
Required Twist:1:9 inches or faster
Use: Long Range Match
Bullet Construction: Gliding Metal Jacket. Lead Core
A few more elementary questions.
Is the 6.5x284 the same as the 6.5-284 Norma

Wildcatting the .284 Winchester
Quote:
The single complaint against the .284 is the rebated rim.
In some types of rifles, this can cause a bit of difficulty for the gunsmith.
It makes proper magazine lip configuration a bit more critical--poorly designed feed lips
can result in the bolt overriding the next round, rather than picking it up.
While a real consideration, it is the trade-off for allowing use of a 0.50-inch-diameter case
with the conventional 0.47-inch-diameter bolt face.
Moreover, this is not a serious problem when the gunsmith knows what he is doing.
What length action is needed for a rifle to function as a repeater with this round.
Considering the odd combination of short case length with long overall length.
What caliber detachable magazine will this case feed out of.

The Long-Suffering 6.5
Quote:
However, if you put a 6.5-.284 Norma, 6.5mm Remington Magnum or even a .260 Remington cartridge
into a .308-length action you do have concerns about bullets of 140 grains
and over intruding into the powder space.
And that's another reason we haven't seen, and probably will not see, a factory 6.5mm short magnum.
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  #22  
Old 06-19-2009, 06:33 PM
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Required Reading

The Long-Suffering 6.5
The caliber American hunters would love to love--but don't.
By Craig Boddington
Very good article.
Affirms much that has been said.
A great deal of insight into the state of 6.5mm cartridges.
Quote:
However, if you put a 6.5-.284 Norma, 6.5mm Remington Magnum or even a .260 Remington cartridge into a .308-length action
you do have concerns about bullets of 140 grains and over intruding into the powder space.
And that's another reason we haven't seen, and probably will not see, a factory 6.5mm short magnum ...

Of the many wildcats, the 6.5-06 is certainly one of the very best options;
with modern propellants it's another cartridge that can easily equal the .264 Winchester Magnum...

Unfortunately, if you choose any 6.5mm cartridge you are very limited in your choices in factory ammo.
There are currently four American factory loads for the .260 Remington, just two for the .264 Winchester Magnum
(Winchester and Remington, both 140-grain) and a single 6.5 Remington Magnum load...

To get the most out of almost any 6.5mm you probably should be a handloader.
I've played with both the 6.5-06 and the 6.5-.284 a bit. Both are excellent cartridges that come very close to .264 Winchester Magnum
performance, as does the 6.5mm Remington Magnum if you add a bit of length to both action and barrel....
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  #23  
Old 06-20-2009, 03:43 AM
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"My desire was to take advantage of the above 140 gr bullets
that promise an even higher ballistic coefficient. "

I hope we've established by now that over 140 grain bullets do not live up to that promise. However there are some 140 grain bullets that offer excellent BCs. I wouldn't be surprised if its possible to handload a 140gr 260 load that shoots flatter than the Leupolds BDC calibration.


"I've decided to buy, yet again, another rifle - third and last centerfire for a lifetime."

Ah, yes, the "last rifle ever" speech. I know it well. Only said it 40 or 50 times.

"A few more elementary questions.
Is the 6.5x284 the same as the 6.5-284 Norma"

Basically yes. There might be some slight angle differences in some of the wildcat versions, but conceptually they are the same thing.

"What length action is needed for a rifle to function as a repeater with this round?"

The 284 is designed to work with a 308-length short action.

"What caliber detachable magazine will this case feed out of?"

That's the rub. The 284 is fatter than a 308, but not as fat as a WSM. Your quote from Wildcatting the 284 about modifying the magazine is right on the money. Ask your gunsmith if he would prefer to open up a 308 magazine or tighten a WSM.
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  #24  
Old 06-20-2009, 05:28 AM
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Over-all Length of 6.5x284 to Function in Short Action

Quote:
Originally Posted by natman View Post
The 284 is designed to work with a 308-length short action...

That's the rub. The 284 is fatter than a 308, but not as fat as a WSM.
Your quote from Wildcatting the 284 about modifying the magazine is right on the money.
Ask your gunsmith if he would prefer to open up a 308 magazine or tighten a WSM.
Considering the over-all length of the 6.5x284 Norma ... 3.228 inches,
it doesn't look like a "factory" round will cycle-through a short action magazine.

Special Note:
Quote:
The 6.5mm-284 Norma ammunition is loaded to a longer overall length than the Winchester version
and will not feed through the magazine of a short action rifle,
though it may be single loaded.
However, it should be able to cycle in a 30-06 Springfield length action and magazine ... 3.340,
unless the bullets would be seated deeper into the case and limited by an over-all length of 2.800 inches.

Case Capacity of 260 versus 6.5x284?
Quote:
What is the case capacity of the 260 and the 6.5x284 in a short action?
What is the velocity difference?
I am not going to use the 140 grain bullets.
Quote:
The 6.5-284 runs about 11 more grains of H2O capacity the the 260, so an increase of about 20%.
20% of additional case capacity will earn you about 5% more speed, given equal barrels and pressures...

Also, I would recommend against building a 284 case rifle on a short action.
If you use the longer bullets, they will have to be seated so deep the
the ogive is INSIDE the case neck and this is not a good thing.
I just tried it with a couple of my favorite bullets.
The Sierra 142 MK makes a loaded round length of at least 3.00", the 130 Norma-2.88"
and my favorite, the 108 Lapua-2.85; all of which are longer than a short action (700) magazine box...

I punched my 700 Ti from 260 to 6.5x284 and picked up another 180 fps mv.....
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  #25  
Old 06-20-2009, 12:13 PM
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Quote:
Originally Posted by aom22 View Post
Considering the over-all length of the 6.5x284 Norma ... 3.228 inches,
it doesn't look like a "factory" round will cycle-through a short action magazine.

However, it should be able to cycle in a 30-06 Springfield length action and magazine ... 3.340,
unless the bullets would be seated deeper into the case and limited by an over-all length of 2.800 inches.
Action lengths vary slightly, but the 284 was developed for the Winchester lever action 88 and semiauto 100, which were definitely short actions. So the 6.5x284 Norma may be a tad long for the magazine of your Remington, probably because of the super long 6.5 mm bullets, but there is no point in putting it in a 30-06 action.

Don’t get preoccupied by bullet base intrusion into the case. If you have a case that is long enough to take advantage of the available magazine length and an extra long bullet it is going to intrude into the case.

You could shorten the case so the bullet doesn’t intrude, but that would lower capacity even more. Or you could move up to the next longer action. This would give you lots of room to seat the bullet out. So why not build a 6.5RM in a 30-06 length action? You now have a longer, heavier and less nimble rifle. The real problem is that you could just as well fit in a 264WM in the same action and get even greater ballistics. Of course long bullets would now intrude into the 264 case, so you could build a 264 rifle on a 375 H&H Magnum action and seat the bullets way out…..

I wish I had a dollar for every time I've heard someone advocating putting a short action cartridge in a long action rifle so you can seat the bullets out. Yes, it gives you maximum ballistics from the cartridge, but at the expense of less than maximum ballistics from the rifle. And since it's the rifle that you are going to be carrying over hill and dale while you are hunting, it should get top priority. Target shooters only have to carry the rifle from the car to the bench, so they don't care.


Last edited by natman; 06-20-2009 at 12:25 PM.
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  #26  
Old 06-20-2009, 06:15 PM
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6.5x284 NORMA ... Cartridge Over-all Length

Quote:
Originally Posted by natman View Post
Action lengths vary slightly, but the 284 was developed for the Winchester lever action 88
and semiauto 100, which were definitely short actions.


So the 6.5x284 Norma may be a tad long for the magazine of your Remington,
probably because of the super long 6.5 mm bullets,

but there is no point in putting it in a 30-06 action.
I just had an epiphany ... the over-all length of the .284 WIN is 2.800 inches.
Same as the .260 REM and .308 WIN - funny the .243 WIN is shorter.

So my next question ... "What cartridge over-all length does Norma specify for its 6.5x284 ammunition?"
Answer ... it varies according to specific bullet being loaded.

Reloading data: 6,5-284 Norma
Quote:
C.O.L = 2,913 " to C.O.L = 3,071 "
Note: There are at least three hunting loads specified.
All are significantly longer than 2.800 inches.
Very perplexing indeed - to say the least.

natman ... I'm not arguing against or trying to contradict what you are stating.
On the contrary, everything for the most part that you are advocating
is well reasoned, logical and practical.

However, it appears the factory information seems to indicate
the NORMA loads may not properly function in a short action rifle.
Unless they are to be singly loaded - very odd.

Quote:
Originally Posted by natman View Post
Don’t get preoccupied by bullet base intrusion into the case.
If you have a case that is long enough to take advantage of the available magazine length
and an extra long bullet it is going to intrude into the case....
And, considering the additional powder capacity of the 6.5x284, seating a bullet
deeper into the case certainly will be less of a deterrent on performance
as compared to the same bullet being loaded in a .260 REM case.
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  #27  
Old 06-21-2009, 11:54 AM
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Quote:
Originally Posted by aom22 View Post
However, it appears the factory information seems to indicate
the NORMA loads may not properly function in a short action rifle.
Unless they are to be singly loaded - very odd.
I suspect that due to the 6.5x284's popularity as a target cartridge, that most rifles chambered in it are customs built on long actions. Not so much of an issue on a target rifle. In your case it would mean buying a new 30-06 detachable mag rifle, throwing away the barrel, rebarreling to 6.5x284, modifying the mag, all in order to gain 200 fps over the 260 Rem you already own. Not worth it IMHO. Especially since it would be a LOT cheaper just to buy a new short action rifle in 270 WSM!

My advice would be to keep your 260 as it is. It's a terrific hunting rifle at any realistic distance. If you want it to shoot flatter, look into 120-125 grain loads, which still have plenty of sectional density for the game you plan to hunt.

I don't know how much hunting you've done, but in the real world, 350 yards is a long shot at game, despite the nonsense one finds on the internet.
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  #28  
Old 06-21-2009, 05:24 PM
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Extended Magazine and 2.800 COL Loads

I think I found out how a cartridge exceeding 2.800 inches can be fired from a short action repeating rifle.

Remington 700 6.5x284 Target Rifle
Quote:
Machine Receiver for Extended Magazine
Quote:
This 1/4-moa group was the first 200-yard target I ever shot with your Rem 700 Short Action
6.5-284 Norma Match rifle, a Gem-Tech TPR-S suppressor and my handloads....
Note the cartridge over-all length anotated on the target.

So how would a 6.5x284 loaded to an over-all-cartridge length of 2.800 inches potentially perform?
The following information most certainly contrasts with the CIP registered 6.5x284 NORMA.

The 6.5mm-284 Rifle Cartridge
Quote:
There are no standards for wildcat cartridge dimensions, but these are provided
for the 6.5mm-284 in the sixth edition of the Hornady Handbook of Cartridge Reloading:
Bullet diameter .264"; Maximum case length 2.170" (trim to 2.160");
Maximum cartridge overall length 2.80"; Rim diameter.473";
Base diameter .500"; Shoulder diameter .475";
Shoulder angle 35 degrees; Neck diameter .295".

Using Hornady's 140 grain bullets in front of 43.6 grains of WMR yielded a MV of 2400 fps.
And a maximum load of 49.7 grains of WMR gave the 140 grain bullets at a MV of 2700 fps.
Winchester cases and Federal 210 primers were used for all of these Hornady loads,
which were chronographed in a 24" rifle barrel.

It is interesting that the top velocities listed for the 6.5mm-284 are identical to the top velocities
for the .260 Remington (6.5mm-08) with the same bullet weights in the Hornady Handbook.
The 6.5-284 just burns more powder to get there.
The perfect long range round? - Post #9 and Post #13
Quote:
6.5 mm-284 reloading data is in the sixth edition of
Hornady Handbook Of Cartridge Reloading starting on page 281.
The Max ft/sec on the 140 grain bullet is 2700 ft/sec....

Bird Dog,The 6.5 284 is a great long range accurate round.
Ive had a couple,just sold one with a 24" Pac nor 1-9" twist.
Best I could get with 140 gr bullets was 2700 fps.
The benchrest shooters are getting around 3000 fps but thats out of 29 to 32" barrels....
6.5x284 info - Post #4
Quote:
Chuck Hawks does a good synopsis of the round:
http://www.chuckhawks.com/6-5mm-284.htm
His load data is a bit light, because I've run 140gr bullets right at 3000fps from a 6.5-284.
Load data closer to what I've used:
http://www.accuratereloading.com/65284win.html
natman ... all this data confirms your prediction of a 100 to 150 fps (at the most 200 fps) velocity increase in a short action.
Making a long action 6.5x284 Norma seem a reasonable necessity to achieve full potential.

This being said, for some reason the .260 Ackley Improved is beginning to look better and better.
No need to rebarrel, no magazine modification, retain short action.
Fire forming cases ... seems the biggest disadvantage.
Quote:
The main reason to go with an improved version of the .260 Rem, is velocity.
For most people, the standard .260 reaches pressure limits with 140gr class bullets
well before 2850 fps (with a 24"-26" barrel).
The .260 AI lets you drive those same bullets comfortably at 2930 fps or better.
The 139gr Scenars, 140 Bergers, and 142 SMKs all like to run in this higher speed range,
and the ballistics are clearly superior.
The Case for .260 Remington:
A Better Cartridge For Practical Long-Range Shooting
Quote:
My friend Chuck was seduced by the ballistics of 6.5-284 Norma
but wanted to stay with a real short-action cartridge.

The solution was 6.5-08 Ackley Improved, which is a .260 case blown out
to have a steeper shoulder angle and less body taper.
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  #29  
Old 06-22-2009, 12:42 PM
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Quote:
Originally Posted by aom22 View Post
I think I found out how a cartridge exceeding 2.800 inches can be fired from a short action repeating rifle.

Remington 700 6.5x284 Target Rifle


Note the cartridge over-all length anotated on the target.

So how would a 6.5x284 loaded to an over-all-cartridge length of 2.800 inches potentially perform?
The following information most certainly contrasts with the CIP registered 6.5x284 NORMA.

The 6.5mm-284 Rifle Cartridge


The perfect long range round? - Post #9 and Post #13


6.5x284 info - Post #4


natman ... all this data confirms your prediction of a 100 to 150 fps (at the most 200 fps) velocity increase in a short action.
Making a long action 6.5x284 Norma seem a reasonable necessity to achieve full potential.

This being said, for some reason the .260 Ackley Improved is beginning to look better and better.
No need to rebarrel, no magazine modification, retain short action.
Fire forming cases ... seems the biggest disadvantage.


The Case for .260 Remington:
A Better Cartridge For Practical Long-Range Shooting
Ackley wildcats show the most Improvement on cases that have a lot of body taper, like the 30-30. The 260 Remington has very little to begin with. The most significant sentence in the AI article:

"For most people, the standard .260 reaches pressure limits with 140gr class bullets well before 2850 fps (with a 24"-26" barrel). The .260 AI lets you drive those same bullets comfortably at 2930 fps or better."

So you have your rifle rechambered (flushing the resale value down the toilet), buy an expensive set of die$, fireform your cases and you get......a whopping 80 fps gain! Maybe 100 if your lucky. I suspect that most AI gains on modern cartridges are because the AI loads aren't pressure tested.

Last edited by natman; 06-22-2009 at 12:45 PM.
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Old 06-22-2009, 09:53 PM
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.260 AI ... Velocity & Pressure

Quote:
Originally Posted by natman View Post
So you have your rifle rechambered (flushing the resale value down the toilet),
buy an expensive set of die$, fireform your cases and you get......a whopping 80 fps gain! Maybe 100 if your lucky....
Yes, AI'ing rifles, most likely, will reduce the resale value.
But, for me it is a moot point ... my rifles, if they perform, are keepers.
Isn't re-chambering cheaper than re-barreling?
The chamber reamer and reloading dies maybe more expensive - but, not prohibitively ... I would think.
The task of fireforming cases is not an exclusive task.
The fireforming shots could be short range practice ammunition - maybe.
Good excuse, anyway .

I agree with the your potential velocity gain estimations - all things being equal.
However, I will be using a 24-inch barrel instead of a 22-inch one.
Hopefully, the additional barrel length may result in another velocity boost of, maybe, 50 to 70 fps.

Quote:
Originally Posted by natman View Post
I suspect that most AI gains on modern cartridges are because the AI loads aren't pressure tested....
I, once again, concur. I'm very skeptical of any velocity claims without attendant chamber pressure information.

260AI first results
Quote:
I am putting a new 8.5 twist Pac-Nor barrel on the tube gun in 6.5-284, and thought that I'd experiment with the 260AI...
It is now 26" long...
I got pretty good results with H4350 at 44.2 grains, yielding 2790 FPS, 48KPSI, with an SD of 3 and an ES of 11 over 5 shots.
The group was sub 0.5" at 100 yards.
I couldn't get to the next faster node with H4350 (about at 46.2 @ 2931 FPS ~60KPSI),
as the pressures started to get up there, and the primers were looking a bit cratered.

BTW, I used the PressureTrace module for all of this -*test*-('")ing.

I then tried Ramshot Hunter. This was my first time ever with any Ramshot powder, and I can say that I was quite pleased.
At 47.5 grains of Hunter, I got 2859 FPS, about 55KPSI, sub 0.5" groups, and a SD and ES of 11 and 27 respectively.
The Hunter was much easier on the cases than the H4350, and I was able to get more velocity with less pressure...
I measured the fired cases at 57.5 grains H2O capacity.
These bullets have never grouped better than 0.5" at 100 yards, but make about 0.3 MOA at 600, consistently...
I'll be trying the 260AI out at 600 soon. I figure about 47.5 to 48 grains Hunter ought to do it with fired cases...
It is within a hair of being the ballistic equal to the 6.5-284, and has much better efficiency.
Say hello to longer barrel life....
Right now, a Remington 700 BDL .264 WIN Mag is making, even better, ecomomic sense.
No re-barreling, no re-chambering.
The only hassle maybe conversion to a detachable box magazine.
And, this is possible to do with off-the-shelf parts.
The feed rails of the receiver may need to be milled.
But, for certain the stock will need to be modified (notched for magazine buttons).

Other than for the modification of the stock, installation of some detachable magazine related parts
and the need for downloaded ammunition ... not a bad compromise.
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