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280 rechamber suggestions

3K views 12 replies 9 participants last post by  WildBill 
#1 ·
so i just got a NEF 280 in a trade that i intended to trade again, but im kinda obsessed with these rifles now. Ive got a gunsmith buddy who does rechambers so i think i want to rechamber this barrel and build a super long range bench gun, what i need is caliber suggestions off of a .280 bore. I don have reloading equipment, so its going to have to be in caliber that i can purchase ammo for.
 
#8 ·
Lots of luck rechambering it to a 280 Imp.

To "Correctly" rechamber the parent rimless bottle neck cartridge to a TRUE improved the barrel needs to be setback to clean out the existing chamber. A threaded barrel is easy, a NEF would be a semi major under taking.

Since headspacing-head clearance is established from the breach face to datum (shoulder) one would have to remove the lug, ejector-extractor, shorten the tenon, ream, re-cut the extractor-ejector mortise and finally re-attach the lug.

With that type action its a bit more involved than just hogging out a chamber!

Bill
 
#11 ·
outofstater said:
is it true on an ai chamber job you use the no-go gauge for go?
Ya have it backwards, for a bottle neck rimless cartridge the GO become the NO GO.

Pictures are worth a thousand words.



Another showing how in real life the parent and the formed improved versions. The ring on the junction indicates where the parent makes contact. L-R, a 22-250, 250, the wildcat 270-08 and their improved versions.



An improved chamber is .004" shorter than the parent at the neck-shoulder junction. The typical GO gage would act as a NO GO at that point, not on the shoulder as normal. In fact looking at the pic you can see how the parent cartridge head clearance is established with a.004" crush fit in a improved chamber for firing. Why they're called improved and not wildcats. Take notice the entire shoulder of the parent is hanging out in the wild blue yonder.

For example, a 280 REM GO gage (if correct) measures 2.099" on a .375" datum. However, that same gage is .004" longer at the neck-shoulder junction, so it becomes the NO GO for the 280 Imp.

If you look at gages you'll see for standard cartridges many are interchangeable. For example, gages for the 308 are the same for the 243, 260,7-08, my 270-08 and the 338 Federal. The same applies for the '06 family. But, although having the same parent improved gages are unique. The breach to neck-shoulder junction lengths are different,hence different gages.

It also why you can't simply neck down 308 brass for a 243 Imp without forming a false shoulder. The breach to junction lengths are different.



Clear as mud huh?


Bill
 
#13 ·
outofstater said:
backwards was still close, you know where i was going.

so how do you know when correct headspace is obtained?
Yeah, I think I know what you though you meant!


I assume you asking about Improved cartridges.

Well, a couple ways. One, buy or make gages or use the parent cartridge and chamber for +.004" protrusion. In other words if you need .150" ream for .154". When the parent is chambered you will have the .004" crush fit your after.

Gage are far easier. After measuring the action you simply chamber to the GO gage protrusion you need for the action dimensions. In the case of an improved the .004" crush is taken into consideration when the gage is made, it will be .004" shorter than the cartridge based on the casehead to junction length of the parent.


Bill
 
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