1) Is 6.5x55AI and 6.5x55 BJAI same improved version? What stands BJ for?

2) Norma factory load in 6.5x55 with 140grains Partition has MV 2689fps. How much increase in speed can I get with the 6.5x55AI over the original 6.5x55, both with 140grains Nosler Partition?

3) Is there risk I will get feeding problems if I change to 6.5x55AI? And have some rifles better feeding with AI cartridges then other?

I agree with Paul H....

If the action is a CRF it WILL NOT feed as well as it did before the "improvement" without extensive work.

It's certainly not worth the cost and trouble unless you just *want* one.......then I'd reconsider before doing it, especially if the action is nice and best left without the changes the had to be made to give it enough width to feed the more "square" cartridges.

Jamt,
I did a search of the AccuLoad and ECRA databases, but had no hits on the 6.5x55BJAI. A Google search didn't turn up anything either. All I can say for sure is that it isn't a Barnes-Johnson. Barnes only made one 6.5 that I know of and that was the 6.5mm Barnes QT, based on the .264 Winchester Magnum case. If you find out about this cartridge, I'd appreciate the info.
Regards,
Ed

[ 05-09-2003, 05:02: Message edited by: HockeyPuck ]

Good thing Bill C. doesn't post here. He knows what those initials stand for. So does Monica!!





[ 05-09-2003, 06:53: Message edited by: HBL ]

Common guys where you been for the last decade? Google shmoogle. Bob Jourdan (BJ) is a field editor for Precision Shooting magazine, and is INTO the 6.5's. He wrote several excellent articles and a chapter in one of the older PS annuals several years back about the 6.5's, and his creation the 6.5X55 BJAI is another "improvement" on the parent case. I'll try to check back issues tomorrow to see if i can locate the info., that is, if my fiancee gives me the time. She thinks this hunting forum stuff is a bunch of crap-- blasphemy, i say!

[ 05-09-2003, 11:37: Message edited by: sscoyote ]

Well I have a Carl Gustaf 63 ( = Competition rifle on M96 action) and it has CRF. I suppose I will get feeding problems if I rechamber to 6.5-284 Norma also, plus losing magazine capacity I suppose. You who have wildcat 284:s is the feeding working fine? And do you have any problems with the magazine?

When I'm asking witch is the better one of 6.5-06 and 6.5-06AI? Plus and minus with respectively?

To answer some questions on the 6.5x55 BJAI...
1. BJAI = Bob Jourdan Gun writer.
The bjai is not a .455 diameter shoulder, but .465....
2. 140 grainers have seen the 2900 fps envelope.
3. I am still building mine, and may or may not see any feeding problems. My dummies have been feeding pretty good so far.. Had to do some extracter polishing, etc.

A few more comments on the 6.5x55 BJAI.

A few of the Ackley Improved cartridges did show substantial improvement over factory offerings.
P O Ackley himself said that many were just a waste of time. However the ones that faired well were the .250 Savage AI,257 Roberts AI and the 7mm Mauser AI. However, P O never did any work on the 6.5x55 Swede. Bob Jourdan, using the Ackley Improved perameters, did put it together and it very definitely was an improvement. The 'hottest' available factory advertised loading is the Hornaday Light Magnum @ 2750fps with a 129gr bullet. (my own chronographed test didn't bear this out, 2605fps was the highest velocity I obtained using a CZ550 with a 23.8" bbl.) Bob Jourdan is very definitely not a high pressure loader and is a real gentleman and a scholar. When he lists data, you can go to the bank on it. The 6.5x55 BJAI is a very definite improvement over the standard round. The 2900fps with the 140gr is achieveable without running the pressures thru the roof. The dummy rounds I have run thru a 98 Mauser action have worked without a hitch using US made brass. A cartridge really worth considering.

Ol' John

You know, i remember when i was reading about the BJAI, that he was quite impressed with his creation. I actually spoke with Bob several years back, and i agree, he is quite the gentleman scholar, very much taken with the 6.5's.

[ 05-10-2003, 14:49: Message edited by: sscoyote ]

There was also the 6.5 Improved Arch, basically a 6.5 X 55 Ai as near as I can tell. 140 gr bullets at 2900 fps according to Ackley, but who knows? - Dan

Dan, I read on the 6.5 Arch, and from what I can tell, is it was created for higher-pressure firearms. Instead of having less taper in the case, it actually had an arch in its shape (hump). I have not seen one, or how the arch would be built into the case. I kind of got the impression it was shaped like a key... Load data was also very limited at that time.
Then again, I could be wrong>>>>> (lack of information)

I thought the 6.5 Arch was named after a Dr. Arch who did the cartridge development. Anyone else out there have info on this one? - Dan

As I understand it, the 6.5 Arch Improved required that the shoulder be set back slightly and the case shoulder angle was 45* rather than 40 in the Ackley design. Using this procedure the standard 6.5x55 cartridge could not be fireformed to the chamber as the base to the shoulder/neck junction was too long. The Arch required the cases to be formed first and then fire-formed to the new chamber. I am relying on memory here so there might be an error in what I posted. But I believe this to be correct.

Ol' John

Thank you John. - Dan

Here is a cool link, the Arch is not there, but lots others are.... http://www.reloadbench.com/cartspec.html

Look at the difference in the SKAN vs MAUSER....

[ 05-11-2003, 22:13: Message edited by: Mauserkid ]

There is not much improvement between 6,5-06 and 6,5-06imp than in mussle blast!
An other improved 6,5 is 6,5*55 scandinavian just abit longer so it cant fit 6,5*55 chambers for actions that can take higher pressure.

MVH Kimmo

I have two rifles that are Ackley Improved, a 03a3 30-06AI and a .35 Whelen AI, both perform very well and fee dperfectly. The 03AI did require a second trip to the shop regarding the feeding, they had to do some work on the extractor.

I do think they increase the performance, and if you have a perfectly good rifle you want to bump just a little without rebarreling or rechambering I don't see a problem with it. As one of the other gentleman has already written, some cartridges benefit from it, some don't. My stepfather and his brother both have .257 roberts AI's, and they perfrom FANTASTICALLY.

My 06ai goes 165g bullet at 3040 out of the 24" military barrel, the whelen throws a 225g Sierra at just over 2800 out of a Douglas 26" barrel. Both are chronographed, not paper calculated.

As far as the factory ammo thing goes, well, yes they shoot it no problem however point of impact is changed from where the rifle is sighted in. On my 06 it is a couple of inchs difference. just something to remember about that.

Red

Thanks for the answers guys!

I went to the range and cronied five rounds for a neighbor who builds custom mausers lastyear. This rifle was a 257AI, and the five averaged 4030fps.This was a one time deal, as he does not load that normally. His 9 year old grandaughter killed a 9 point white tail this past season with this rifle. I have a 6mm-284 and it is outstanding. I had to open the rails slightly and polish them

I've owned a .257 AI for 32 years and have nothing but praise for it. I've shot whitetails, mule deer, and antelope with it to my complete satisfaction. Mine is built on a pre-64 Model 70 Winchester with a Douglas Premium barrel. Excellent accuracy and performance have been realized with 100 gr. Nosler Partitions. I have also shot prairie dogs with the 75gr. Hornady bullet. It's a great performer on deer-sized game.

I think that what is being missed is the fact that alot of the calibers that P.O. Ackley considered to be "overbore capacity" were because of the burn rate of the powders available to him when they were tested. One thing I have noticed is a modest increase in velocity but also an increase in accuracy potential. This I figure to be because of the sharper shoulder angle and lesser body taper (short fat case) contributing to more positive powder ignition. Especially with the slower burning stick powders. Some of the advantages are more magazine capacity over the bigger magnum cases, more efficient case design, less perceived recoil, and less brass flow into the neck, and ability to shoot parent round in a pinch. On the down side are trickier feeding, more expensive dies, and almost non existant pressure signs until they become very high (over 70,000 psi).

I've tested pressure in 10 different rifles extensively with various shoulder angles up to 30 degrees since I've had my Oehler 43 and the one thing I've found accross the board is... NO pressure signs until I was over 70k PSI on all but two loads, and those were in my 300 Ultra using Retumbo powder with a 220gr SMK and a 178 A-Max. Both caused heavy bolt lift and slight ejector marks at a meere 62-63k PSI. Velocity was about equal to RL25 at the same PSI too. FWIW.

Ole man Ackley was a man ahead of his time!!! He had a vision and sought to acheive it! He created the first "short and fat" cartidges! Although some of them weren't all that short!! Then 30 years later someone shortened them further! I wish I could sit down and have a talk with Mr. PO Ackley today!! Ask him what he thinks about what has happened in the last 30 years to cartridge making!!! He'd probably reply that "If you changed this shoulder to .....and shortented the neck to ..... I COULD "IMPROVE" it!!!! GHD

I think the 6.5X55 BJAI is a fine wildcat for the same reason that the 257 Ackley was...the parent cases have similar capacities and the bullet diameter is only a difference of .007 inches. The 6.5 has the fast twist rate and can stabilize much heavier bullets. In addtion, the 6.5X55 case is very strong in the web and only 1 or 2 grains lighter than the much bigger '06 case.

The previous comment regarding the modern slow burning powders is right on. The standard 6.5X55 is an R22 case with 140 gr bullets...you get 2700 fps at 45,000 CUP (SAAMI specs) all day long in a 24 inch bbl, and 2800 fps if you go up to 50,000 CUP. This is a very safe pressure in the strong case in a new bolt rifle.

Taking the shoulder from .435 to .465 alone gives a 7.1% increase in case capacity, and the increased shoulder angle adds another 3%, so we are talking about a 10% increase, translating to 2881 fps with the 140. Go to 52,000 CUP and you get 2938 fps.

The increased case capacity graduates us from R22 to IMR 7828, AAs Mag Pro and even R25. If you go to a 26 inch bbl with these powders, there is another 60 fps available with lightly compressed loads. If you seat a flat based 140 one caliber into the BJAI case, you have 61 grs of water capacity left over and a 3.1 COL. Hey... that sounds like a short version of the...

6.5-06!!!

Many of these discussions about the effect of improved cartridges can be helped by using the basic internal ballistics equation:

V2 = ( C2/ C1)^0.30 X V1

Where C2 is the new usable case capacity, C1 is the original usable case capacity, V1 is the original muzzle vaeloity and V2 is the new muzzle velocity. The term ^0.30 is a power applied to the value in parentheses. Case capacity is in grains of water.

It assumes that chamber pressure remains constant and that C1 is close to a max velocity load using the propellant giving the highest velocity for the case.

The 6.5 BJAI C2 divided by the 6.5X55 C1 is quite close to 1.1, and 1.1 to the 0.30 power is 1.029, indicating a 2.9% increase in velocity.

So, if we can get 2800 fps with a 140 gr bullet in C1, we can get 1.029 times 2800 or 2881 fps from C2. This example is working at a constant pressure, right around 52,000 CUP.

Now, if we started with the 45,000 CUP version of the 6.5X55 we would go from 2700 fps to 2881 with the BJAI, but 100 fps of the gain is due to higher pressures.

The equation is even more useful when we solve for C2:

C2 =( V2/V1)^3.333 x C1

Say we want our 140 gr 6.5 to do 3120 fps...what case capacity do we need?

V2/V1 is 3120/2800 or 1.1143, and raising this to the 3.333 power gives 1.4345. Since the usable case capacity of the 6.5X55 was about 55 grs for C1, the required case capacity is 1.4345 times 55, or about 79 grains. We just invented the 264 Win Mag!!

Now the part I left out is that the 264 needs a 27 inch barrel to do this and the Swede needs a 24 inch bbl. Also the propellant giving max velocity has gone from R19 to H870. The formula assumes that you can find the best propellant and will adjust barrel length to use it effectively.