270 Thor's Hammer and 270 PRC and 27 Nosler

[James DeTorre]

I like all things AI, cost of fire forming seems prohibitive.

i keep going back to 280ai as my general purpose cartridge.

Brass not withstanding, 270ai is appealing.

 

[Idaho Hunter1]

New to the "create your own" cartridge game. I have always stayed with ones I could buy brass for. Very interesting!

How would this discussion of 6.8western/270 PRC/270TH/27 Nosler compare with if someone created a 270SAUM? That seems like it would be close to a 270 WSM or what is listed above…?

 

[rbTanzan]

In comparing items like the 270Win, 270AI, and 270TH, it would help to have some of the bare physics stated as well as any special effects like throat-changes and free-bore.

How many grains of capacity does the 270AI have over the 270Win? (My estimate: 3 grains)
And how many grains of capacity are provided by seating a 270TH forward an extra .29"? (My estimate: 6 grains)

For example, the 270AI seems to only have a 3 grain increase in capacity. That might be good for about 30-35fps, IF barrel, powder, bullet, primer, and case architecture remained the same.
When people claim 100-150 fps increases in a 5% capacity increase, they are doing that by switching to more optimal components and by allowing the loads to run up to higher pressures.
However, if a 270TH finds an extra 10-15% capacity by extreme seating out into freebore, then so be it. I would believe an extra 100fps with same pressures, or perhaps 100-200fps with higher pressures.

 

[can1010]

In comparing items like the 270Win, 270AI, and 270TH, it would help to have some of the bare physics stated as well as any special effects like throat-changes and free-bore.

How many grains of capacity does the 270AI have over the 270Win? (My estimate: 3 grains)
And how many grains of capacity are provided by seating a 270TH forward an extra .29"? (My estimate: 6 grains)

For example, the 270AI seems to only have a 3 grain increase in capacity. That might be good for about 30-35fps, IF barrel, powder, bullet, primer, and case architecture remained the same.
When people claim 100-150 fps increases in a 5% capacity increase, they are doing that by switching to more optimal components and by allowing the loads to run up to higher pressures.
However, if a 270TH finds an extra 10-15% capacity by extreme seating out into freebore, then so be it. I would believe an extra 100fps with same pressures, or perhaps 100-200fps with higher pressures.

just loading bullets like the 156 hammer hunter from 3.3 to 3.6 will gain you close to 6gr increase. the 100-200 fps increase is more from the high energy powders being used with the combination free bore compared to the saami spec with the old stand by powders.
bullet design and bearing surface contact will also increase speeds, the absolute hammer bullet design is a good example of that. the increase in velocity does not always mean increased pressure

 

[can1010]

New to the "create your own" cartridge game. I have always stayed with ones I could buy brass for. Very interesting!

How would this discussion of 6.8western/270 PRC/270TH/27 Nosler compare with if someone created a 270SAUM? That seems like it would be close to a 270 WSM or what is listed above…?

the 6.8W is basically an improved SAUM case. I use 7 SAUM cases fireformed in the 6.8 and the other wildcats i have on the 6.8 case. instead of doing a 270 SAUM just do the 6.8W and use better quality SAUM brass and save the hassles and cost of a custom chamber

 

[Muddyboots]

However, if a 270TH finds an extra 10-15% capacity by extreme seating out into freebore, then so be it. I would believe an extra 100fps with same pressures, or perhaps 100-200fps with higher pressures.

The advantage that I wanted to explore was using standard brass and other components readily available to maximize the performance of the high pressure design of the .270Win. It was a big leap of faith with 156HH with the COAL but I felt confident the concept would deliver. However, I did not expect what it delivered with RL26! Every bullet I tried surpassed expected velocities with RL26.

So many others have done this before which triggered my interest into this concept and intrigued me for a long time. @ButterBean and @FEENIX got my attention with .270AI but I wanted to see what standard would do with longer COAL. My next build just might be .270AI!

My first rifle in 1968 was a .270Win and it will always have soft spot for me and now the .270TH is my go to. And yes, I am that old.

 

[Alibiiv]

I like all things AI, cost of fire forming seems prohibitive.

i keep going back to 280ai as my general purpose cartridge.

Brass not withstanding, 270ai is appealing.

I cannot disagree that fireforming .270 AI or any AI cartridge is a bit pricey, however...I can find .270 Winchester brass fairly easy, where not so much for .280 Ackley Improved. This was on of the determining factors that prevented me from building a .280 Ackley when I was considering a build. I refused to be held hostage by Nosler to have to purchase "their" brass. I firmly believe Nosler moved away from the Ackley principle of straightening out the side of the case and blowing out the shoulder to 40 degrees so they could sell their brass. As for cost of brass, I can purchase .270 Winchester brass for around $1 per piece, it costs me a primer, 15 grains of Unique and some cream of wheat to fireform brass. I believe that presently .280 AI brass is running between $1.75-2.25 per piece and tough to find. And...I posted this to show that building and firing a wildcat cartridge isn't as costly as one might think. And...lastly that .280 Ackley is a great cartridge.

 

[rbTanzan]

. . .
bullet design and bearing surface contact will also increase speeds, the absolute hammer bullet design is a good example of that. the increase in velocity does not always mean increased pressure

Granted, of course design can produce dramatic increases of fps without higher pressure. The point is that those increases also occur with the other case, e.g., 270Win vs. 270AI. Both will dramatically increase with a special bullet and better matched powder. The difference between the little 3 grain AI expansion and the standard case is only minimal when both use the enhanced bullet combo or when both use a traditional combo.
As mentioned, I would expect the 270TH to produce a larger, more distinctive difference from the 270Win than the 270AI produces over the Win. And the 270TH can do that with a simple re-throating and with no need of fire-forming or special brass.

 

[Mcranch]

It appears the neck is just barely holding the bullet. What dies were used to set them?
At 3.67 that's close to where a 30 nosler with a .200 freebore with a 215 Berger sits at.
Who has data on what a 270 ai using a 156 or a 170 bullet would achieve as far as muzzle velocity?

 

[Muddyboots]

It appears the neck is just barely holding the bullet. What dies were used to set them?
At 3.67 that's close to where a 30 nosler with a .200 freebore with a 215 Berger sits at.
Who has data on what a 270 ai using a 156 or a 170 bullet would achieve as far as muzzle velocity?

There are actually three baring bands in the neck (>.277 diameter) which provides plenty of stability for bullet. Same with 170 EOL, 175 TGK, 165ABLR, 150 ABLR, 170BT, 150AB. These are very long bullets and provide sufficient bullet seating in neck. The .270 has another advantage with longer neck that lot provides a lot of stability.

I also would be curious to see comparable velocity test with the .270AI and RL26 and these bullets. I bet the .270AI will be a little better. How much? Don't know. My guess is 50-75fps? Watch it will be 150!!!

 

[Alibiiv]

New to the "create your own" cartridge game. I have always stayed with ones I could buy brass for. Very interesting!

How would this discussion of 6.8western/270 PRC/270TH/27 Nosler compare with if someone created a 270SAUM? That seems like it would be close to a 270 WSM or what is listed above…?

For me the .270WSM is a close runner up to the .270AI. With the .270 AI having a little more horsepower. I built the .270AI because I wanted a wildcat cartridge to add to the safe. I think I've owned rifles I just about every factory cartridge ever made and wanted something different. I also wanted something that would fill the gap for long range cartridge and under .30 caliber. I was seriously looking at the .280 AI, but at the time I could not figure out what Nosler was doing with their .040 thousandths difference from the parent.280 Remington cartridge. This was when the .280AI first hit the market. I went so far as to find a store that carried the cartridge and was very impressed when I saw it. But couldn't figure out what Nosler was doing and didn't want to get stuck having to buy their brass so went with the .270AI instead. My thoughts on the .270 SAUM are that if it's close to a .270 WSM, perhaps that would be the road to go?? However there's the bragging factor that goes with a .270 SAUM, and the custom reamer, the custom dies, and a rifle that is .270 SAUM compatible. These are all factors that can be worked on and made to work. I still believe that a .270 WSM with a 26 inch, 1:8 twist will make a great long range set up that would be capable of shooting the newest heavy, high BC bullets.

 

[Mcranch]

For me the .270WSM is a close runner up to the .270AI. With the .270 AI having a little more horsepower. I built the .270AI because I wanted a wildcat cartridge to add to the safe. I think I've owned rifles I just about every factory cartridge ever made and wanted something different. I also wanted something that would fill the gap for long range cartridge and under .30 caliber. I was seriously looking at the .280 AI, but at the time I could not figure out what Nosler was doing with their .040 thousandths difference from the parent.280 Remington cartridge. This was when the .280AI first hit the market. I went so far as to find a store that carried the cartridge and was very impressed when I saw it. But couldn't figure out what Nosler was doing and didn't want to get stuck having to buy their brass so went with the .270AI instead. My thoughts on the .270 SAUM are that if it's close to a .270 WSM, perhaps that would be the road to go?? However there's the bragging factor that goes with a .270 SAUM, and the custom reamer, the custom dies, and a rifle that is .270 SAUM compatible. These are all factors that can be worked on and made to work. I still believe that a .270 WSM with a 26 inch, 1:8 twist will make a great long range set up that would be capable of shooting the newest heavy, high BC bullets.

I have a 280ai that is not the nosler chamber. I was told that I couldn't shoot the nosler 280 improved because of the .040. Mine likes RL19.
But Rl 19 and 26 is nowhere to be found. I'm on all the sites maybe I will hit the lottery. I'm wondering if the 26 isn't as hot as the 19?

 

[Muddyboots]

But Rl 19 and 26 is nowhere to be found. I'm on all the sites maybe I will hit the lottery. I'm wondering if the 26 isn't as hot as the 19?

RL23 will be good to try. Lot more stable too.

 

[Deleted member 109523]

RL23 is my go to in the 280 AI. It should do well in the 270W or AI