280AI with too much head space...options?

[Hayudog]

My Montana rifle company .280AI didn't shoot great groups at first either. My best groups are from hand loaded 143 Hammer hunter bullets and factory 140 nosler accubond . My best loads have been with H4831SC.

I was very interested in your comment about misfires with 280 ammo. I too have problems with that but have never had an issue with 280ai ammo.

Good luck and enjoy your 280ai.

Warren

I think in my gun the factory 280 Rem ammo was being moved forward by the firing pin. This was where I began to think it was a head space issue. When I close the bolt on factory 280 Rem I feel no resistance, and I've read that there needs to be contact at the shoulder to hold the cartridge from moving at the firing pin strike.

 

[Weatherby Fan]

Ive built several 280AI, if you reuse the existing barrel I would insist the barrel be removed and rechambered with a new Sammi spec 280AI reamer, preferably a Manson Reamer, true and square the action while its apart.
its my experience that your better off grabbing a new barrel and starting from scratch but of course this is going to be another cost, but Im going to suggest you will much happier in the long run if you did.

I've used #1 #2 and #3 contour barrels, mostly Benchmark and one Bartlein, all 1-9 twist and they shoot.

 

[david g ranes]

Wouldn't it be possible for the new smith to ad a piece of scotch tape to the no go gauge until he gets resistance that might give an idea how much out of spec he is just a thought I've known people to head space guns this way in the past. David

 

[Seabeeken]

It closed on the no go gauge. Said out loud the name of his gauges, and said they weren't cheap. He name dropped, but it didn't register with me. I wouldn't know good/expensive to poor/cheap. Made a video to send to the other gunsmith, demonstrating his tools and technique. New gunsmith has said exactly that. Remove and turn down the current barrel. He also said there could be other tasks that could be needed, but we'd know more when he had looked into it further. Was just asking openly to get a variety in responses. And I had hoped that the headspace issue would have a degree of accuracy related Issues that would be cleaned up. Time will tell.

I had issues with new 280 Rem brass being loaded for fire forming, 4 of the first 30 did not fire. I do not have any resistance closing on factory 280 Rem ammunition.

As far as dies, started after fire forming with RCBS . The ones marked FL 280 Ackley Improved. Part number 17001. I had set them up to only size the neck. Brass after fire forming closed easily, and wasn't convinced that the shoulder needed to be pushed back if it wasn't fully forward.
Ive had positive results with Lee collet dies. I've picked up a neck sizing die for .280.
As far as the requested chamber to be reamed for, unless specified , I would think it would be the 280 AI saami. It's stamped on the side of the barrel now. 280 Ackley Imp.

Whether its SAAMI or traditional makes no difference. Both "versions" close snug on a 280 Rem factory case and if both have a 40* shoulder they must be the same. Nosler simply measures headspace at a different point than Ackley did which created this headspace myth. Ackley said the standard 280 Rem go gauge became the no go gauge in the ackley chamber. If your firing pin is driving the 280 Rem case forward enough to misfire, I'd say there is excessive headspace and it needs to either have the barrel setback and rechambered or rebarreled. My SAAMI 280ai closes on a 280 rem case without issue and forms nicely.Continuing to fire form brass in your rifle could result in a case separation. For those who believe that BS about there being 2 different 280 ai chambers, here is a video from a reamer maker to explain.

 

[Philward]

I've never had any rebarreling or rechambering done but I would think to ream a chamber out it would be best to remove the barrel. Didn't think a barrel could be reamed through the action. Probably should have the crown dressed up at the same time, but your rifle is pretty new...

 

[doggonner]

I've never had any rebarreling or rechambering done but I would think to ream a chamber out it would be best to remove the barrel. Didn't think a barrel could be reamed through the action. Probably should have the crown dressed up at the same time, but your rifle is pretty new...

you can chamber a barrel with it on the rifle some barrel makers sell what's called a short chamber then you buy the reamer and correct bushings for the receiver and start reaming very slowly doing checks, then when the go gauge drops your done,, this way you know exactly what you have not what someone tells you they done. I use only a go gauge when a screw on a new barrel..I set the barrel with a little feel on the go then i'm done..you can do this by knowing your shoulder datum., knowing your shoulder datum then checking your new brass and set to .002 growth, brass will last longer and not be worked as much,, I'm not a smith but I change out barrels alot. do my own throating. when running a improved chamber the bullet needs to be jammed or a false neck created, you can create a false neck on the 280 imp by necking up to 30 cal then neck down to 28 and leave the neck die short thus creating a false neck to hold the brass against the bolt face and letting the shoulder fill into the chamber..then set your dies to bump .001 or .002

 

[doggonner]

there's a lot of info missing here shoulder datum length and so on 280 need to shoot the heavy bullets what is the twist rate I would run 180 class bullets they will be more accurate at long range.. r u running a 1n9 twist or 1n8

 

[montana west]

yur problem is the chamber is a bit long-- easy to fix just load some very heavy bullets preferrably round nose and fire form your brass with a mild load.. with the bullet touching the rifles.. then set you die short about on turn up so the case will not completly resize. and if it will chamber you no longer have head space problems but you have to reload.. Once this is completed you can expect to get a bit higher velocity because you will probally be able to add 1 grain to your normal loads... I have this problem with a 35 gibbs. it is suppose to be 63 mm but the chamber is 64mm thus I had to go to 280 brass.. You do not have this option but you will never have to trim you cases once they are fired..

 

[Will Gray]

That is why I use barrel nuts to attach all of my barrels: set the headspace, tighten the nut. Send it back to Remington: they will fix it likely with a new barrel.

 

[Wv shooter]

there's a lot of info missing here shoulder datum length and so on 280 need to shoot the heavy bullets what is the twist rate I would run 180 class bullets they will be more accurate at long range.. r u running a 1n9 twist or 1n8

Anything over 180 would require 8 twist but you also lose velocity when going to heavy bullets it may not be what you are trying to achieve no free lunch's in belistic world

there's a lot of info missing here shoulder datum length and so on 280 need to shoot the heavy bullets what is the twist rate I would run 180 class bullets they will be more accurate at long range.. r u running a 1n9 twist or 1n8

 

[lancetkenyon]

That is why I use barrel nuts to attach all of my barrels: set the headspace, tighten the nut. Send it back to Remington: they will fix it likely with a new barrel.

Why would Remington rebarrel this rifle?

 

[25WSM]

Hayudog, I've been building 280AI rifles for 30 yrs. If your smith didn't set the barrel back any then he couldn't do a proper chamber. A 280AI original and new are set to the SAME headspace. It's . 004 shorter than the reg 280Rem. You can't have a reg 280Rem and just run the reamer in and make it . 004 shorter. Impossible. Everyone needs to get straight on the 280AI old vs new. They are the same length to the shoulder. You can use a go guage as the no-go for both. How do you think you can fire a reg 280Rem in either and it will fire form perfect. They both have a slight crush fit. The 280Remington Improved is different. But not the old and new 280AI. The reason people think there is a difference is because the prints show a different length. But look at where on the neck it's measured too. The measurements are from 2 different spots on the shoulder. That's why one print looks like it's longer. All the 280AI rifles I have built will fire a standard 280Rem or the new Nosler brass with no problems. Think about the fact that you use the same headspace guages for both. How can there be a length difference if you cut the depth to the guage. I talked with Dave Kiff about this when I got my new Nosler spec reamer. He said they are identical and interchangable. The problem occured when Nosler took the po Ackley version to Sammi. Sammi said Nosler had to use the datum line they use not the one Ackley used. This is why one looks to be longer. It's not. An AI chamber has a . 004 shorter body than the parent cartridge all across the cartridges. That is why you can fire the parent cartridge in all of them. They should have a slight crush fit on the parent case. Your chamber is not correct because your chamber never had a crush fit to begin with and you can't ream a current chamber smaller only bigger. It needed set back and then rechambered. I don't care what guages he used it was done wrong if he didn't set it back at least
. 004 before reaming. Ackley stated to use the go as a no-go and doesn't say anything about using a field guage. It an exacting chamber design for length because of being able to safely fire factory parent cartridges in it.
Shep

 

[Bob Wright]

I think in my gun the factory 280 Rem ammo was being moved forward by the firing pin. This was where I began to think it was a head space issue. When I close the bolt on factory 280 Rem I feel no resistance, and I've read that there needs to be contact at the shoulder to hold the cartridge from moving at the firing pin strike.

Within the correct headspace, yes, the firing pin will seat that cartridge into the shoulder. With too much headspace, fail to fire, nailing primers, brass stretch or worse, head separation. If you have zero headspace, you'll feel some drag on closing the bolt, like neck size only reloading will give you.
My preference is .002-.003" headspace created by bumping the shoulder in a full length die the same distance, from known fully fire formed cartridge brass dimensions.

 

[Hayudog]

Hayudog, I've been building 280AI rifles for 30 yrs. If your smith didn't set the barrel back any then he couldn't do a proper chamber. A 280AI original and new are set to the SAME headspace. It's . 004 shorter than the reg 280Rem. You can't have a reg 280Rem and just run the reamer in and make it . 004 shorter. Impossible. Everyone needs to get straight on the 280AI old vs new. They are the same length to the shoulder. You can use a go guage as the no-go for both. How do you think you can fire a reg 280Rem in either and it will fire form perfect. They both have a slight crush fit. The 280Remington Improved is different. But not the old and new 280AI. The reason people think there is a difference is because the prints show a different length. But look at where on the neck it's measured too. The measurements are from 2 different spots on the shoulder. That's why one print looks like it's longer. All the 280AI rifles I have built will fire a standard 280Rem or the new Nosler brass with no problems. Think about the fact that you use the same headspace guages for both. How can there be a length difference if you cut the depth to the guage. I talked with Dave Kiff about this when I got my new Nosler spec reamer. He said they are identical and interchangable. The problem occured when Nosler took the po Ackley version to Sammi. Sammi said Nosler had to use the datum line they use not the one Ackley used. This is why one looks to be longer. It's not. An AI chamber has a . 004 shorter body than the parent cartridge all across the cartridges. That is why you can fire the parent cartridge in all of them. They should have a slight crush fit on the parent case. Your chamber is not correct because your chamber never had a crush fit to begin with and you can't ream a current chamber smaller only bigger. It needed set back and then rechambered. I don't care what guages he used it was done wrong if he didn't set it back at least
. 004 before reaming. Ackley stated to use the go as a no-go and doesn't say anything about using a field guage. It an exacting chamber design for length because of being able to safely fire factory parent cartridges in it.
Shep

Shep- This ^ seems to make the best logic. Video that Seebeeken posted I watched last night. Just off the phone with gunsmith #3, Jim at Elite Rifle works here in Idaho. Our conversation went almost exactly down the line as your post above 25SWM.
thanks all for the input on this one. I have totally learned more about this process in the last week than I thought was needed, but in reality it was.