Is there and advantage in the 6.5-06 imp (40 degree shoulder) over the 6.5-06. The improved version seems to be too much of and overbore, and is no real advantage. The fps you get, verses the rise in pressure, does not seem to be worth the small gain you would get . Is there some one that knows about these two cartridges? Thanks.

While I have not worked with a 6.5-06, I have developed loads for 260 Rem and 264 Win as well as 30-06 and 30-06 AI. The AI version of the case allows you to squeeze an extra 3 to 5 grains of extruded powder into the case. With cases this close in capacity, muzzle velocity is very much a function of chamber pressure. To acheive more than 75 to 100 fps increase in muzzle velocity with the AI versions of 30-06 family, you must boost chamber pressure signifigently above the parent case.
While there has been a great deal printed,both good and bad, about Ackley's chamber designs, my observations support these theoreoms.
1 AI case gives the most improvement with the heavier bullet weights for the caliber.
2 AI cases work best with a powder which is slow enough to fill the case into the neck. I tap the side of the case with a teaspoon as I slowly pour the H 4831 into the powder funnel, many people prefer a drop tube.
3 I buy into the theory that the sharp shoulder acts as an impediment to powder movement at ignition, thus causing more of the powder to remain and burn in the case as opposed to flowing into the bore and burning there. This would explain the belief that the AI is a more efficeint design with slow powders and heavy bullets.
One can acheive higher velocities in larger cases without an increase in pressure compared to the smaller case. Take for instance the 260 Rem, 6.5-06, and the 264 Win mag, load them all with 140 gr bullets at 50,000 psi. You will get increasing muzzle velocities with increasing powder capacity.
If I were building a rifle or thinking of rechambering a current 6.5-06, I would go with the AI version for a large game rifle shooting 130 - 160 gr bullets and I would use H 4831, RL 22, RL 25 or H 1000 and a CCI 250 primer.
For a predator-varminter using 87 - 120 gr bullets, I would stay with the standard 6.5-06.
As you can see from the beginning of this post, I actually chose to go another direction. I use the 260 Rem for ground squirrels through mule deer with 100 and 120 gr balistic tips. And I use the 264 Win mag with 120 gr X's, 120 gr Bal Tip, and 140 partitions as a big game or long range rifle.
Even with the 264 mag, barrel life is good and chamber pressure is fine as long as you don't try for extreme MV with every shot.

I have owned all 3 and currently replaced my 6.5-06 AI with a 264 Win Mag. This is the best round with 140`s in my opinion, now that I think about it it`s the best with 120`s also. I started out with the 6.5-06 in 1991 and was astonished how accurate it was with Remington action and Hart barrel, the 6.5-06 AI also shoots great with RL25, I have yet to get enough range time in on the 264 but really looks promising, it has a 26" Krieger, w/Remington action. Idaho Shooter share some of your load developement for this round, I have lots of RL25, Retumbo, and an 8 pounder of H5010. I think H5010 might be good with the Sierra 140`s. 72 grains is a case full with no pressure. Another poster shared that load with me but I don`t remember who to give credit to.

[ 12-15-2002, 18:44: Message edited by: Tim in TN ]

I am looking at a 6.5mm cartridge also and have all but settled on the 6.5/06 as my choice.

Since I haven't shot either, I can only offer what I have read. According to Cartridges of the World (9th ed, Barnes/McPherson) most of the AI cases showed improvement, but *not* the 6.5/06. They theorized this was due to Ackley's limits on available powders. With the newer, slower powders, you might actually be able to get the better results typical of the other AI modified chamberings. Unfortunately, I didn't find anyone who has actually done that research.

Based on what I looked at, the 6.5/06 offers incredible accuracy, with less throat erosion. The 6.5-284 Norma might be slightly more accurate, but from what I have read, it erodes throats faster. Likewise, the 6.5-08 A Square (aka 260 Remington "we can buy SAAMI decisions") is very competitive.

If I didn't go with the 6.5/06, I would go with the 6.5-284 Norma.

Looking in the back of Precision Shooter, I noticed the 6.5/06 frequently makes an appearence in the winner's equipment lists. Admittedly, those lists are dominated by other cartridges (notably the PPCs), but I think the 6.5/06 is capable. Certainly more capable than I am.

I've been thinking of rechambering my .308 Win Striker to 6.5/308(260 Rem). Wanted to do this to up the velocities, since I only have a 15" barrel. Was going to keep bullets around 120grains. Anyone know if I'ld see gains going to the Ackley style instead? Maybe better efficiency would work better in a short barrel?

Does anybody know where I can get information on the 6.5mm Gibbs?

I have heard some people talking about it, as an improved version of the 6.5/06, but none of my manuals list it. I did find a 257 Gibbs - a 1930's era British sporting cartridge, but I don't think it is the same.

Thanks,
TGR

Tim
Here are the 264 Win loads I shot over the Chrony and recorded in my notebook.

case W-W Primer CCI 250

Bullet ------ Powder -- Charge Wt - M V
100 Nos BT -- H 4895 -- 50.0 -- 3200
------------- H 4350 -- 61.0 -- 3311 3295 3311 3298

120 Nos BT -- H 4831 -- 63.0 -- 3028

120 Rem ----- H 4350 -- 60.0 -- 3080 3085 3059 3059

120 X ------- H 4831 -- 64.0 -- 3267

140 Partition H 1000 -- 65.0 -- 3064
----------------------- 66.0 -- 3145
----------------------- 67.0 -- 3195
----------------------- 68.0 -- 3258
----------------------- 69.0 -- 3247 slightly flattened primer
----------------------- 70.0 -- 3270 flattened primer

140 Partition RL 25 --- 66.0 -- 3090
----------------------- 69.0 -- 3045 3188 3309 eratic performance and unpredictable pressure signs
----------------------- 71.0 -- 3231 3239 3239
----------------------- 73.0 -- 3268 Very flattened primer and brass flow into ejector cut

As you can see, RL 25 gave unpredictable performance in my rifle,while H 1000 gave good linear velocity increases with charge increase.
There really is not enough data here to draw any firm conclusions, except that my rifle does not like RL 25 in combination with 140 Partitions.
I can't predict if your rifle will shoot well with an even slower powder.
I am curious as to velocity acheived with 72 gr of 5010 behind your 140 gr Sierra.

[ 12-18-2002, 07:00: Message edited by: Idaho Shooter ]

I shoot a 6.5-06AI built on a win 70 action, Shilen SS select match barrel, 26 inch, 1-8 twist.

extremely accurate.

Load for the 142 smk is 56 grains of RL22, fed 210M primer at a chronoed velocity of 3070. I can make it go faster, but groups then start looking like shotgun.

I load to just a bit over 3200 for 129 grainers, again because that is the most accurate velocity.

Push the 95 vmax to almost 3500 which seems to work best for me.

Just because the above loads work for me doesn't mean they will for you. I will take the 6.5-06AI over a 6.5-284 anytime, mainly because the case cannot abe made from any other caliber. That was the main reason I went with the 6.5-06 in the first place, availability of cases, they were in short supply when I started to build this rifle.

Pecos

I have a 6.5-06 and a 6.5 Gibbs. The 6.5-06 has a 24", 1-9 twist barrel which is a bit fried at this point. The Gibbs has a 26", 1-8 barrel still in good shape. The Gibbs cartridge is slightly larger in capacity than the Ackley Improved version.
My best 6.5-06 load averages 2943fps with 140 Nosler's while my best 6.5 Gibbs load averages 3060 fps. Not much of a difference. I have gotten close to 3000 fps with the 6.5-06 but accuracy was lacking. At the same time, I know of people who have gotten over 3100 fps with the Gibbs, but I'm sure the pressure was high. My 26" 264 WM struggles to get much over 3100 fps without high pressures.
My advice? The 6.5-06. It gives you almost as much as the AI yet dies are cheaper, brass is easily made and data is out there. Now..... I've got to get busy ordering that barrel for my new 6.5-06 Ackley Improved!
John

Another member sent me an article talking about the 6.5mm Gibbs. In his work, he found the case necks would crack after 5-8 loadings.

That seems awfully quick. I would hate to go through the hassle of forming cases, uniforming pockets, weighing/categorizing cases, and then discard them a few shots later.

For those of you with 6.5 Gibbs, how are your case necks holding up?

In the article, he was forming them from 30/06 brass (as opposed to 25/06 or 270) with an intermediate step of a .264 WinMag die.

HEY TEXAS GUNRUNNER,
I HAVE A 30 GIBBS,AND A 25 GIBBS.IF I FIREFORM WITH PROJECTILES,I GET EARLY SPLIT NECKS.IF I FIREFORM WITH CREAM OF WHEAT,THEY DON'T CRACK TOO EARLY.SORRY FOR THE CAPS.
1geejay
www.shooting-hunting.com

Idaho Shooter, I should be getting to the range soon and I will chronograph this load, It looks like I might assemble a few with H1000 and give them a try also, Is the H1000 accurate enough for you?

I'm a big believer in annealing case necks on all my cartridges and especially the ones that go through radical changes (Gibbs). I haven't had much trouble with the Gibbs though. When initailly fireforming, I would lose about 1 case out of 20 due to cracking. I neck size with a Neil Jones die, so my cases don't go through a lot of stretching and forming like standard FL dies do and I don't load "hot".
John

posted in error

[ 12-18-2002, 20:36: Message edited by: TexasGunRunner ]

Idaho Shooter, I will return some data that I developed on a factory Rem 700 Classic, try RL25 with the 120`s, I was able to go to 70 grains with a velocity of 3450 with 24" barrel. This will give you something in return for your help. Tim. I will let you know how the trip to the range turns out.

Tim,
I purchased the H 1000 and RL 22 for load developement in a Ruger #1 7MM STW. In the STW I get 3200 fps with 86.0 gr H 1000 and a 160 gr Sierra spitzer bt or a Hornady 162 spitzer bt. Either bullet gives sub moa accuracy after some home style gunsmithing.
My Win 70 classic 264 will print the 100 or 120 bal tips into 3/4 in @ 100 yd with the 4350 and 4831 loads listed above. The 120 X and 140 partition grouped closer to 2 in with the above loads.
I am sure that both bullets are capable of much greater accuracy than this, I have not done enough load developement work to find it. I was mostly trying to develope charge vs velocity curves at that time. I think they would both shine with H 4831.
Since getting the 7 STW I have neglected the heavier bullet weights in the 264, it is simply such a pleasure to shoot with the 100's and 120's.

Idaho Shooter

The webmaster for Accurate Reloading (Saeed) send me an email saying that improved loas they used had a 35 degree shoulder.

Is anyone else using the 35 degree shoulder, or are they using the 40 degree shoulder?

In the end, I will likely follow JP's advice and stick with the normal 6.5/06...unless I decide to go with the 6.5 Gibbs.

Mine is a 40 degree shoulder. I developed my loads based on the loads on accuratereloader.com.

Pecos

Most of the AI's have 40 degree shoulders. The Gibbs line have 35 degree shoulders.

For Tim in Tn and Idaho Shooter,

I also use 70 gr. of H-1000 with W-W cases and 140 gr Partitions. Velocity is 3185 fps from a 24" barrel. The barrel is stainless with a 1-8" twist so accuracy with 140's is good, 3/4". Most of the old guys say H-870 is the only powder for a 264, but I can't stand the nasty stuff.

Saludos...Frank

Thanks Gringo, I surely will be trying that H1000 with my Sierra`s. I appreciate your input.