My .280 AI puzzle - looking for suggestions

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cowboybob

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I've got one that has me puzzled. I've got a Cooper .280AI for which I've been handloading. Up to now I've been using fireformed Remington .280 brass. Accuracy is wonderful but the full length sized cartridges chamber very tightly - takes a little pressure to turn the bolt down. Everything seems to mike to spec but they are tight. Recently purchased some Nosler .280 AI brass from another CGNer and they chamber smooth as silk. Haven't fired and sized them yet but I can't detect a difference in specs from the Remington brass. Whatever the difference is, it is very subtle. Have been using Hornady dies. Anybody got any ideas as to what the issue might be?
 
The AI chamber is 0.004" shorter to the datum line on the shoulder of the cartridge then the parent cartridge. Try resized 30-06 cases (check the neck thickness after necking down) and see if the problem goes away. You may have to bump the shoulders back a bit on your 280 brass. - dan
 
.280 ai

Funny you should mention this. I just finished reading an article in the latest ( July/August) Outdoor Edge magazine titled, The Ackley Improved. One of the sub-sections in the article is the .280 Remington Controversy. It is an intersting read that talks about 2 different headspace specifications with the 280 AI chambering. Those 2 are the original Ackley spec's and the Remington ones that were approved by SAAMI. According to the article there are issues with using brass from manufacturers that is sized for one spec and then fired in a rifle with the chamber reamed to the other spec.

It might be worth a read for interest anyways...

Cheers,
hf
 
You might not be able to detect a difference in specs, but there is obviously some small difference. I use the Nosler brass in my 280AI, and it chambers very easily when new, and after being fired and resized in my Redding dies.
 
After firing and resizing the new brass the problem still exists with properly setup dies I would suspect the dies. When I worked at WSS:redface: I had to return quite a few Hornady dies for similar problems. Hdy was good to deal with but had some QC issues.
 
Thanks for all the input guys. Dan was correct. The shoulder was too far forward. The dies proved to be the problem. Some careful filing of the sizing die to reduce its length resulted in bumping the shoulder back a few thousands and that was all that was needed. Chambers the brass no problem now. I admit, I had concerns about potentially messing up an expensive set of dies but it filed surprisingly easy. Thanks again Bill for the suggestion.
 
cowboybob said:
Thanks for all the input guys. Dan was correct. The shoulder was too far forward. The dies proved to be the problem. Some careful filing of the sizing die to reduce its length resulted in bumping the shoulder back a few thousands and that was all that was needed. Chambers the brass no problem now. I admit, I had concerns about potentially messing up an expensive set of dies but it filed surprisingly easy. Thanks again Bill for the suggestion.
Click to expand...

Glad to hear that you resolved your problem. But if it was me, I'd have thinned down the $5.00 shell-holder rather than messed with an comparatively expensive sizing die.
 
I admit, I had concerns about potentially messing up an expensive set of dies but it filed surprisingly easy.
Click to expand...

The fact that it filed so easily makes me wonder about the quality of the die. Of course the fact that it required filing is also a concern. I will stick with Redding and RCBS dies myself.
 
i have a cooper in 280. i would guess cooper cuts the camber on the tight side. even after full lenth resizing with hornady brass it still requires a little downward pressure on the bolt.
 
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