Problem forming 308 brass to 260

[ballison]

I had some Lapua 308 brass that I retired from my FTR rifle, and wanted to resize it to shoot with my 260. Everything seemed to go fine, but the bolt lift and ejection is crazy with the resized cases. I was hoping someone who has done this could shed some light on a solution. Here is the process I went through to resize the brass, and some pics. The only things I can think of is to use a cutting pilot when neck turning to clean up the ID. The necks thickness of the 260 brass is .016" and the 308 resized is .017". The headspace is the same for both.

1. Annealed the case
2. Used a 260 neck bushing die without a bushing to size half the way
3. Then used a 260 FL bushing die with a bushing to finish sizing
4. Expanded with a mandrel and turned the neck well into the shoulder
5. Ran everything through an ultrasonic cleaner
6. Loaded and fired

The pics are, in order, 260 fired case, 308 unfired case, 308 fired case.

 

[mytwo60]

My flow:

1/ run new 308 brass thru 308 expander
2/ Neck turn
3/ run thru 308 die w/o expander or bushing
4/ run thru 260 die with bushing
5/ done

Fits perfect w/o any issues.

 

[ballison]

Mytwo60,

I should also state that the 308 brass was turned as new, but not before resizing to 260. It was fired 8 times since. You think I should turn it again before resizing?

 

[LCazador]

You should be running that case through the sizing die after expanding and turning. You have that operation before turning and expanding. It's obvious that you have not pushed the shoulder back enough for proper headspace and fireform in your 260 chamber. Monitor the headspace with a headspace guage pushing the shoulder back .002" at time till the case chambers easily, then fireform. Since you fired these cases 8 times check your case length and be sure it isn't too long for your chamber. If the cases still measure the same neck thickness as before, why turn them again? Do they?

 

[ballison]

You should be running that case through the sizing die after expanding and turning. You have that operation before turning and expanding. It's obvious that you have not pushed the shoulder back enough for proper headspace and fireform in your 260 chamber. Monitor the headspace with a headspace guage pushing the shoulder back .002" at time till the case chambers easily, then fireform. Since you fired these cases 8 times check your case length and be sure it isn't too long for your chamber. If the cases still measure the same neck thickness as before, why turn them again? Do they?

The 308 necks were turned as virgin brass, but have been fired 8 times since w/o turning again. Also, I checked the headspace as various points on the shoulder, and it is identical between the 308 and 260 brass. The rounds chamber fine before firing, but are a bitch to extract.

So you're saying I should:
1. Expand and neck turn the case as a 308 again
2. Resize neck to 260
3. No need to expand and turn AFTER resizing to 260?

 

[jlow]

If it chambers just fine with the right headspace but the problem is in the extraction, maybe it is because your load is too hot?

What is your load?

 

[ballison]

If it chambers just fine with the right headspace but the problem is in the extraction, maybe it is because your load is too hot?

What is your load?

42.8 gr H4350 & 139 Scenars. Same load I've been shooting from my 260 brass. Ran both over the chrono and the 308 brass was about 20 fps faster (2830 vs 2810) than the 260.

 

[Albany Mountain]

Small base die for the body!

 

[ballison]

Not the case body. I have a custom Whidden FL die, and I measured the base on both cases. They were identical.

Maybe I should clarify what I'm calling heavy bolt lift. 90% of the bolt rotation is fine, but that last 10% is VERY sticky, and extraction can be tough.

 

[Laurie]

I imagine at least some of your problems arise from using fired brass. If your 308 Win rifle chamber was at all larger diameter at the rear end than that of your 260, the cases will be oversize even after FL sizing. Throw in cumulative case-head expansion from eight firings and you're asking for trouble.

 

[TikkaSporter]

Maybe I should clarify what I'm calling heavy bolt lift. 90% of the bolt rotation is fine, but that last 10% is VERY sticky, and extraction can be tough.

FWIW, I get the exact same kind of bolt lift on my 260 Remington starting at just a tad over 39.0 gr of H4350 which gets progressively more sticky as the charge goes up, but not showing any other pressure signs whatsoever... I've gone as high as 42.5 gr just to see if it'd show ejector marks or cratered primers and still just the bolt lift on the last 10%... This is with Lapua 260 brass, including virgin brass...

 

[LCazador]

If it chambers fine but is sticky after firing, your load is too hot. I'd back off 10% and start the load over. Are you seating into the lands? That will drive pressure up.

 

[jlow]

Agreed! Just because you can shoot this load in your 260 brass without a problem does not mean you can do the same with Lapua 308 brass that has been sized down. Have you checked the internal volume of your sized down brass and compared it to your 260 brass? Different internal volume means different chamber pressure.

 

[Sniper338]

Get a virgin 308 case and size it down... load it and see if that works... that will tell a lot...

 

[hothead]

I would try sizing it with a standard Fl die. NOT a bushing die. at least the 1st
time. a bushing die don't size all the way to the shoulder.
hh

 

[243winxb]

size it with a standard Fl die. NOT a bushing die.

<This. Then seat a bullet and check neck diameter. Should not be larger than .2970" If larger, neck turn. Dont turn into the shoulder, like in your photo. http://www.saami.org/PubResources/CC_Drawings/Rifle/260%20Remington.pdf

 

[ballison]

size it with a standard Fl die. NOT a bushing die.

<This. Then seat a bullet and check neck diameter. Should not be larger than .2970" If larger, neck turn. Dont turn into the shoulder, like in your photo.

My first attempt with this process was done with a FL 260 die, but even that never sized the neck the whole way to the shoulder. I think this might be causing the chambering issue, and I may have to grind the base of the FL die so I can lower it a hair. The reason I cut into the shoulder was to get rid of this radius, but I agree it may weaken the case.

 

[chkunz]

I am not being critical but am wondering why you would go to the effort to convert 308 into 260 since the 260 is now commercially available. When the 260 was still a wildcat that was the best (only?) option but now with the brass available it does not seem to be worth the effort. Again, not being critical, just wondering. Also, it seems like it would be informative to load some commercial brass to see if the problems go away, maybe it is not the brass. Good luck solving the problem.

 

[ballison]

I am not being critical but am wondering why you would go to the effort to convert 308 into 260 since the 260 is now commercially available. When the 260 was still a wildcat that was the best (only?) option but now with the brass available it does not seem to be worth the effort. Again, not being critical, just wondering. Also, it seems like it would be informative to load some commercial brass to see if the problems go away, maybe it is not the brass. Good luck solving the problem.

Short answer: because I can? 8)

Long answer: I shoot FTR w/308 and precision w/260. At precision matches, brass can be hard to track down. So if I lose Lapua brass that was already shot 10 times, no biggie. Cheap? Maybe, but I've got the time to do it, so why not?

 

[jlow]

It is certainly one’s preference, but if you lose that stuff, it is not just a 10x fired brass but also brass that you have spend considerable time changing over to .260 so a bit more valuable since your time is valuable.