Who can ai ream my 6.5x55?

3#cannon, you don't state which rifle you have chambered for the 6.5x55 Swede.

If it's an M38 or M96, you might be pushing its strength limits, if you intend to load the 6.5x55AI round to its full potential.

That potential isn't nearly as high as many would think, from looking at the cases side by side.

I bought a Danish converted K98 that had been chambered to 6.5x55, and then someone in Canada opened up the chamber to 6.5x55AI. (6.5 ARCH) ARCH did it before Ackley but only Ackley gave him the credit in his book.

I also had on hand another Danish conversion that was identical as far as barrel length, stock, and trigger. The only difference was my rifle was iron sighted and the new rifle was sans sights and had been D&T for scope mounts.

I was curious to find out how much advantage the Ackley Improved chamber would give, over the standard military round.

This particular AI had the shoulder cut to 50 degrees, the sidewalls straightened to a 3-degree taper, and the shoulder blown out to create a neck length of one caliber, or .264+-.

I was fortunate enough to have gotten several hundred Sierra 140 grain HPBT Match bullets with the AI, along with dies and fireformed cases.

I had several different powders on hand that were suitable for good performance as far as velocities and accuracy goes. Primers were CCI BR2

I started both rifles with the same powder charge, so I could see how much extra powder was needed to gain velocity.

Surprisingly, the original loads from the IMR7828 and H4831 showed almost identical velocities in both rifles, one was very slightly faster and it wasn't the AI so I credited that to the difference between barrels, which is normal.

Here's the good news.

With the AI I managed to gain between 50-100fps with the fastest powder I used, which was H4350 over CCI BR4 primers. 2900fps at best. Any faster, and I started to get badly flattened and pierced/cratered primers.

The powder charge for the AI wasn't significantly greater. I don't remember exactly because I gave all the data to the fellow who purchased that rifle.

Once the saturation point of a barrel is reached, it takes a lot of powder to eke out a few more fps. Way out of proportion to the rest of the load.

The AI made quite a difference in some cartridges, notably those with smaller, fast taper cases.

The 6.5x55 case design was decades ahead of its peers at the time it was released. Sooooo it's pretty difficult to improve it much.

The AI version may or may not give you what you're looking for, if it isn't just velocity gain.

Remember, original 6.5x55 was right on the edge of being over capacity because of the powders available at the time of its use to its retirement as a military cartridge.

In modern actions, even some 98s, the original cartridge can easily attain 2800-2900fps through a 24in barrel, SAFELY. I wouldn't attempt that velocity out of an M38 rifle.

If you want a 6.5x55AI, by all means, go for it. If you're hoping to add super powers to the cartridge, save your money an if you really insist on wanting significantly more velocity, go to the 6.5PRC or 6.5Weatherby, etc.
 
Last edited:
bearhunter said:
3#cannon, you don't state which rifle you have chambered for the 6.5x55 Swede.

If it's an M38 or M96, you might be pushing its strength limits, if you intend to load the 6.5x55AI round to its full potential.

That potential isn't nearly as high as many would think, from looking at the cases side by side.

I bought a Danish converted K98 that had been chambered to 6.5x55, and then someone in Canada opened up the chamber to 6.5x55AI. (6.5 ARCH) ARCH did it before Ackley but only Ackley gave him the credit in his book.

I also had on hand another Danish conversion that was identical as far as barrel length, stock, and trigger. The only difference was my rifle was iron sighted and the new rifle was sans sights and had been D&T for scope mounts.

I was curious to find out how much advantage the Ackley Improved chamber would give, over the standard military round.

This particular AI had the shoulder cut to 50 degrees, the sidewalls straightened to a 3-degree taper, and the shoulder blown out to create a neck length of one caliber, or .264+-.

I was fortunate enough to have gotten several hundred Sierra 140 grain HPBT Match bullets with the AI, along with dies and fireformed cases.

I had several different powders on hand that were suitable for good performance as far as velocities and accuracy goes. Primers were CCI BR2

I started both rifles with the same powder charge, so I could see how much extra powder was needed to gain velocity.

Surprisingly, the original loads from the IMR7828 and H4831 showed almost identical velocities in both rifles, one was very slightly faster and it wasn't the AI so I credited that to the difference between barrels, which is normal.

Here's the good news.

With the AI I managed to gain between 50-100fps with the fastest powder I used, which was H4350 over CCI BR4 primers. 2900fps at best. Any faster, and I started to get badly flattened and pierced/cratered primers.

The powder charge for the AI wasn't significantly greater. I don't remember exactly because I gave all the data to the fellow who purchased that rifle.

Once the saturation point of a barrel is reached, it takes a lot of powder to eke out a few more fps. Way out of proportion to the rest of the load.

The AI made quite a difference in some cartridges, notably those with smaller, fast taper cases.

The 6.5x55 case design was decades ahead of its peers at the time it was released. Sooooo it's pretty difficult to improve it much.

The AI version may or may not give you what you're looking for, if it isn't just velocity gain.

Remember, original 6.5x55 was right on the edge of being over capacity because of the powders available at the time of its use to its retirement as a military cartridge.

In modern actions, even some 98s, the original cartridge can easily attain 2800-2900fps through a 24in barrel, SAFELY. I wouldn't attempt that velocity out of an M38 rifle.

If you want a 6.5x55AI, by all means, go for it. If you're hoping to add super powers to the cartridge, save your money an if you really insist on wanting significantly more velocity, go to the 6.5PRC or 6.5Weatherby, etc.
Click to expand...

The Arch was slightly different than the AI version, as your measurements state. Both are good, useful cartridges, though neither gets turned into a 264 Win Mag. - dan
 
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