6.5x55 AI and the 6.5-06 AI comparison

[woodcr24]

Please forgive me if this has been discussed previously (I couldn't find anything using the Search feature), but I have a question regarding the external ballistics of the AI versions of the 6.5x55 and the 6.5-06. The question primarily has to do with how it is that I keep seeing references online to the MV being approximately equivalent between the two using the same projectile, barrel length, and ROT. What I don't get is how the AI 6.5-06 isn't producing a higher MV given the additional case capacity relative to the AI Swede. Pressures appear to be at or below the max CIP for the Swede and SAAMI for the 6.5-06. Is the AI version of the Swede just more efficient than the AI version of the 6.5-06?

This is not just a musing; I'm thinking of having my T3 Swede reamed for an AI, but also have a "donor" T3 in .270 that could be re-barelled in 6.5-06 AI.

Many thanks for your thoughts on this topic.

Best,

Chris

 

[Blacktail63]

Compared the 6.5x55AI and the 6.5x06Asquare in Quickload keeping all other variables equal. They were within 50ft of each other. the Asquare isn't quite an Ackley but it's close enough for comparison sake. The case volume is about 6gr apart.

 

[TMR]

Most 6.5x55 ai's top out around 3050 with a 140. All of the 6.5-06ai's I have built will run 3150 pretty easily with the same bullet. The extra case capacity helps out

 

[jakelly]

My thoughts:

• The A-Square is only a 6.5-06 not an AI, so 100+ fps slower.
• The 6.5x55AI is fatter, therefore the powder column has more surface area and burns quicker, so the cartridge more quickly creates velocity.
• This effect seems more dramatic because in general the powders used are too fast to demonstrate the velocity potential of the 6.5-06AI, while coming close to realizing the full potential of the smaller and fatter cases.
• The 6.5-06AI is significantly faster than the 6.5x284 or 6.5x55AI (which have identical capacity to one another), you're just going to have to use Retumbo, Reloader 26, H1000, et al before you really see it. (Think 3200-3300 with a 140).

And some non-ballistic thoughts:

• Neither the 6.5x55AI or 6.5x284 are at home in a short or long action.
• 6.5x55 brass is some of the cheapest Lapua produces, but fireforming is a big deterrent for me, YMMV.
• 6.5x284 Lapua brass is a big plus for me, I also think it may be slightly inherently more accurate than the 6.5-06AI, but that case has a design flaw that makes it very hard on barrels.
• Nosler 280AI brass is made for the new SAAMI 280AI which makes it usable for 6.5-06AI and is also pretty tough. Nosler rebrands various other manufacturers brass, so it's not all the same. This is a huge plus for me.
• The 6.5-06AI is a genuine LA cartridge, so conversion is completely painless.

The cream of this crop is the 6.5-06AI, (no flame to any happy owners of other 6.5s), especially for hunting rifles.

 

[ntg]

I understand you can make 6.5-06 out of 270 brass easily. Any issues with doing the same for the 6.5-06AI?

 

[jakelly]

I've made plenty out of 270 brass. You have to trim (about .050") and fireform. The 270 brass works well for leaving a false shoulder for fireforming.

If I had my way with redesigning the 6.5-06AI, I would grind the reamer to use 270 and 280 length brass and place the shoulder at the same place SAAMI put the 280AI.
Or... grind it to chamber tight on sized 270 brass and employ a 30° shoulder, either would add some nice upside.

I'm surprised this LA, 06 bolt face, and medium bore concept isn't more popular amongst hunters extending their range.

 

[TMR]

I'm surprised this LA, 06 bolt face, and medium bore concept isn't more popular amongst hunters extending their range.

It's actually pretty popular in the west. I build 25-30 of them a year for guys. It's one of my more popular calibers.

 

[ntg]

Nosler should just send in the request for the 6.5-06AI to SAAMI...or call it the 6.5-280AI....but I'm guessing they're too busy with their newer 26, 28, and 30 cartridges.

 

[woodcr24]

Interesting replies so far. Another reason that I struggle, if you will, with the decision of one vs. the other happens to be the cost of high-quality brass, and the point has already been made that 6.5x55 Lapua brass is extremely affordable relative to just about everything else that they offer for non-magnum rifle cartridges. Additionally, I have a ton of Norma, Swedish milsurp, and PPU brass already, which I'd be forming with a hydraulic press (e.g. Whidden). Not that brass for forming a 6.5-06 AI is hard to come by, but I don't already own it, and if all that we're talking about is a difference of maybe 100 fps, then it's probably not significant enough for me to justify going that route, in terms of cost.

Is there such a thing as an optimal barrel length for the 6.5x55 AI, at which it makes no sense to go with a longer one? I believe that Rich uses a 26" barrel with his 6.5 Sherman; wondering if that would be long enough to get the vast majority of performance out of the 6.5x55 AI (assuming the use of the appropriate powder). Can anyone speak to the performance of that cartridge with a high BC 140 out of a 24" barrel?

Rich - ever considered "Shermanizing" the Swede?

 

[elkaholic]

Interesting replies so far. Another reason that I struggle, if you will, with the decision of one vs. the other happens to be the cost of high-quality brass, and the point has already been made that 6.5x55 Lapua brass is extremely affordable relative to just about everything else that they offer for non-magnum rifle cartridges. Additionally, I have a ton of Norma, Swedish milsurp, and PPU brass already, which I'd be forming with a hydraulic press (e.g. Whidden). Not that brass for forming a 6.5-06 AI is hard to come by, but I don't already own it, and if all that we're talking about is a difference of maybe 100 fps, then it's probably not significant enough for me to justify going that route, in terms of cost.

Is there such a thing as an optimal barrel length for the 6.5x55 AI, at which it makes no sense to go with a longer one? I believe that Rich uses a 26" barrel with his 6.5 Sherman; wondering if that would be long enough to get the vast majority of performance out of the 6.5x55 AI (assuming the use of the appropriate powder). Can anyone speak to the performance of that cartridge with a high BC 140 out of a 24" barrel?

Rich - ever considered "Shermanizing" the Swede?

Hi Woods! I have too much going on already! I really do not see need to "Shermanize" the Swede, as you say. The 6.5 Sherman performs at a much higher level than the Swede, and you could load it down to Swede velocities and the barrel would last forever. The Swede is a good cartridge, don't get me wrong, but when I can reach 3300' with a 140, and get good barrel life at 3200', I just think I could better spend my time elsewhere. The Swede will not keep up with an '06 A.I. either. I shot an A.I. for years before I developed the Sherman......Rich

 

[woodcr24]

My thoughts:

• The A-Square is only a 6.5-06 not an AI, so 100+ fps slower.
• The 6.5x55AI is fatter, therefore the powder column has more surface area and burns quicker, so the cartridge more quickly creates velocity.
• This effect seems more dramatic because in general the powders used are too fast to demonstrate the velocity potential of the 6.5-06AI, while coming close to realizing the full potential of the smaller and fatter cases.
• The 6.5-06AI is significantly faster than the 6.5x284 or 6.5x55AI (which have identical capacity to one another), you're just going to have to use Retumbo, Reloader 26, H1000, et al before you really see it. (Think 3200-3300 with a 140).

And some non-ballistic thoughts:

• Neither the 6.5x55AI or 6.5x284 are at home in a short or long action.
• 6.5x55 brass is some of the cheapest Lapua produces, but fireforming is a big deterrent for me, YMMV.
• 6.5x284 Lapua brass is a big plus for me, I also think it may be slightly inherently more accurate than the 6.5-06AI, but that case has a design flaw that makes it very hard on barrels.
• Nosler 280AI brass is made for the new SAAMI 280AI which makes it usable for 6.5-06AI and is also pretty tough. Nosler rebrands various other manufacturers brass, so it's not all the same. This is a huge plus for me.
• The 6.5-06AI is a genuine LA cartridge, so conversion is completely painless.

The cream of this crop is the 6.5-06AI, (no flame to any happy owners of other 6.5s), especially for hunting rifles.

Wondering what barrel length you're using to attain 3200 - 3300 fps with a 140 out of the 6.5-06 AI.

 

[elkaholic]

Wondering what barrel length you're using to attain 3200 - 3300 fps with a 140 out of the 6.5-06 AI.

Not with the A.I., but with the Sherman! I had 2 6.5-06 A.I.'s with 26" barrels and you could hit a little over 3100-3150 if you pushed them......Rich
oops! I thought that was a response to my post! I agree with ALMOST everything that jakelly said except I don't believe 3300' is possible with an A.I unless you had a 32" barrel. Also, the Swede is only .005" fatter than an '06 so I can't see where that would make much difference, although the shorter powder column helps......Rich

 

[woodcr24]

Rich - what projectile, and what was the approximate velocity of your most accurate load?

Best,

Chris

 

[elkaholic]

Rich - what projectile, and what was the approximate velocity of your most accurate load?

Best,

Chris

Are you asking Sherman or A.I.? If A.I., You had to keep it under 3100' and probably closer to 3050' to get top accuracy. I used a lot of RL25 and 7828 at the time and mostly Nosler partitions because I was shooting elk a lot. You have to keep in mind that bullet and powder selection were not nearly as plentiful as today. My elk load was not the MOST accurate, but was accurate enough for the 600 yard shots I was making. I think it was 59 grains of RL25 at around 3100' which was getting very close to max. Accuracy was better at a couple grains less. 4831 was always accurate, but velocity was limited to about 3050'. The 140 A-max was very accurate and I used it right at the tail end before I built the Sherman. If I were loading for the A.I. today, I would definitely try RL26. It is more consistent than 25 and gives even better velocity. It is also way better for temp swings. I have gotten the lowest es with it of ANY powder I have ever used. N570 might be a good choice also (with 140-160 grainers.
Having said all that, I would just build a Sherman I have shot both of them a lot. In order to form GOOD A.I. brass, you have to use 270 or 280 anyway so if you want to be a bear, WHY NOT BE A GRIZZLEY! .......Rich