270 Ackley

[Bullwhacker]

Barrel length is 24" to the end of the brake, so it's approximately 22.5" barrel. I worked up pressure ladders with the top 3 powders out of Quickloads, RL26, 7828SSC, and N560. Both 7828 and 560 showed potential with near identical velocities. RL26 was crazy fast but the ladder looked like a shotgun. I'm working on seating depth this week and then I'll tweak powder charge. Below is an example of the groups it's shooting during the final rounds of breakin with virgin brass. Haven't seen anything over 1 moa yet.

 

[Mike Matteson]

I can some what relate as I feel there is a better selection of high bc bullets with the 7mm. But here's one possible caveat, ease of making an accurate load. I noticed that the 270 WBY Mag was really easy to work up an accurate load. I'm not sure why it just was. Might have been the neck, maybe the radius on the shoulder, or maybe just .277 bullet. Who knows. But maybe a 270-280 AI will have the same easy in load work up. Besides it's a 270, for some reason I just like 270's lol.

Longer case to the shoulder with the 280AI. Note the differents between the AI cases in 25/06 270 and the 30/06 to the 280AI case.

 

[xsn10s]

Longer case to the shoulder with the 280AI. Note the differents between the AI cases in 25/06 270 and the 30/06 to the 280AI case.

Yup I know. Just wanting to see his data.

 

[Bullwhacker]

I've worked with 3 custom 280 Ackleys and have never got them as close to a 7 Mag/7PRC as many say they are capable with a 180. The Berger 270 170 VLD has about the same BC as the 7mm 180 Berger and I'm currently getting about 100fps more velocity in the 270AI than I've been able to get in a 280AI. If that holds true I would have better trajectory, velocity and equivalent energy out past 1,000 yards. It is actually matching up better to the 7 Mag and 7 PRC from a ballistic perspective. I understand there are less bullet options and its not common as the 280AI but it's a fun and interesting project that is delivering some surprising results so far. It also has the nostalgia and cool factor of the 270 that many appreciate.

 

[xsn10s]

It's sounds like the rifle is a 270 AI. I mistakenly though he was building a 270-280 AI.

 

[VinceMule]

The N500 series of powders burn super hot and eat barrels, I know. H1000, N160, N165 are great alternatives to get increased barrel life. This was an expensive lesson learned in couple of calibers, and that was when replacement Hart barrels were $500 installed.

 

[Bullwhacker]

It's sounds like the rifle is a 270 AI. I mistakenly though he was building a 270-280 AI.

It is a 270-280AI. That made the most sense with brass options and ability to use a 280 AI die set with a smaller bushing.

 

[xsn10s]

It is a 270-280AI. That made the most sense with brass options and ability to use a 280 AI die set with a smaller bushing.

I agree it makes sense. My guess is it won't need fire forming. Or much of it.

 

[xsn10s]

Pretty amazing ballistics with a 22.5" barrel. I wonder how H4831 or IMR 4831 would do in your rifle. Probably slower but good accuracy and easier on barrels.

 

[Bullwhacker]

Pretty amazing ballistics with a 22.5" barrel. I wonder how H4831 or IMR 4831 would do in your rifle. Probably slower but good accuracy and easier on barrels.

I will finish testing 7828 since it showed promise. I'm guessing I'll have an accurate load between the two and probably won't test any further. If not I might look to H4831 as an option.

 

[xsn10s]

I will finish testing 7828 since it showed promise. I'm guessing I'll have an accurate load between the two and probably won't test any further. If not I might look to H4831 as an option.

That was David Bailey's got to powder for his 280 Rem in F Class. He said he found two nodes but chose the lower node because it was wide. He did say that the upper node was wide too but the lower node was wider.

 

[xsn10s]

Barrel length is 24" to the end of the brake, so it's approximately 22.5" barrel. I worked up pressure ladders with the top 3 powders out of Quickloads, RL26, 7828SSC, and N560. Both 7828 and 560 showed potential with near identical velocities. RL26 was crazy fast but the ladder looked like a shotgun. I'm working on seating depth this week and then I'll tweak powder charge. Below is an example of the groups it's shooting during the final rounds of breakin with virgin brass. Haven't seen anything over 1 moa yet. View attachment 462380

Yeah looks accurate lol.

 

[cajun]

I've worked with 3 custom 280 Ackleys and have never got them as close to a 7 Mag/7PRC as many say they are capable with a 180. The Berger 270 170 VLD has about the same BC as the 7mm 180 Berger and I'm currently getting about 100fps more velocity in the 270AI than I've been able to get in a 280AI. If that holds true I would have better trajectory, velocity and equivalent energy out past 1,000 yards. It is actually matching up better to the 7 Mag and 7 PRC from a ballistic perspective. I understand there are less bullet options and its not common as the 280AI but it's a fun and interesting project that is delivering some surprising results so far. It also has the nostalgia and cool factor of the 270 that many appreciate.

That seems strange given it's the same case just necked down .007.

 

[Mike Matteson]

It is a 270-280AI. That made the most sense with brass options and ability to use a 280 AI die set with a smaller bushing.

That's what I have done with a 6mm. I've set up and have a 6mm/280AI presently. Having a 25/280AI being built.