Forming .260 Rem brass from .308 Win


August 2, 2011, 12:30 PM
How much of a time investment should I expect when making .260 Remington from 1000 pieces of .308 Win brass? I have never neck-turned my brass before, but it seems like it's a required step in this conversion, as the extra brass has to go somewhere.

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August 2, 2011, 03:36 PM
It is easier to reform .243 brass to .260Rem, but, if you already have the .308 brass, go ahead with the project. It ain't that bad.

You piqued my interest with your question, so I went downstairs to the "arsenal", and formed 6rds and loaded them, measured them, and chambered them in the rifle. After I get off here, I'll test fire them.

For a "worst case scenario", I reformed 6 pieces of WRA-66 Nato headstamped cases. This is mil-spec brass and is thicker than commercial stuff.

There were no "issues" with the reforming. I used a set of Lee .260Rem dies and set them to the same "full length" setting I'd previously determined to be just enough sizing to easily chamber in my Remington M7. After the first case was formed by shallow, progressive insertion, I subsequently just smoothly with a full stroke sized the subsequent 5 cases.

I reamed the primer pockets to remove the primer crimp. This was the most time involved step, but was easily accomplished.

According to the drawing in the Speer #14 manual. The neck out-side spec is .297". These with a PPU 139gr BtSpt seated to 2.800" measured with a vernier caliper .2975-.2985". They chamber easily with no rubbing. However, the case oal is 2.012" which is .010" longer than SAAMI max of 2.035" with a trim too length of 2.025" Hence they WILL need to be trimmed shorter.

Hope this helps.

Sorry: I misread the caliper. The brass is .020" shorter than the SAAMI oal. Length therefore is acceptable, though a tad short....

August 2, 2011, 03:41 PM
The brass I'd be using is LC brass that I've already reamed and prepped for .308. So no worries there. But you didn't have to turn the necks? I thought that was SOP for going down that far. Where'd your extra brass go? :)

August 2, 2011, 04:05 PM
Brass probably wasn't there to start with!

I was loading some .270's for a friend this morning. I was using an assortment of range pick-up R-P brass from over 15yrs accumulation. Only about 8 of the 50 needed trimming, and many were as much as .015" short.

The only time I've ever needed to neck ream brass, even making .257Roberts from 8mmMauser, was with some factory PMC 7mm08 that came in a trade I made in '04 for a NIB Remington M7 in 7mm08. The factory ammo chambered "stiff", and reloaded with identical bullet (Hornady 139gr) wouldn't but barely chamber and was over-pressure as was factory ammo. I bought a Forster hand neck-reaming set up and reamed the brass to fit. It is the most accurate brass I have for that rifle. However, even forming some 7mm08 from .358wcf had necks thinner than the reamed PMC........

If it ain't there, it ain't there. Therefore no reaming neccessary, for MY RIFLE. Yours may have a tighter neck and therefore need the necks reamed.

However, count that as a "positive" rather than a negative. I suggest using the Forster hand reamer and use a Lee case spinner that comes with their trimmer set and a cordless drill. It makes the neck reaming much, much faster......

August 2, 2011, 04:28 PM
I've formed 243 from 308 before, with zero issues. I just lubed it, sized it, and trimmed it to length.

It is a good idea to anneal first, to make sure the brass will form easily.

August 2, 2011, 04:31 PM
Those that do not measure before and after make it up, they believe the neck gets thicker and or thinner when necking up or down, they never consider the neck gets longer and shorter as when necking up a 30/06 case neck to 35 Whelen, the neck shortens .035 thousands, had the neck thinned after necking up the sizer ball would not touch the inside of the case mouth, then there is that other bit of advise that is made up for the lack of anything else to say, "the case lengthens when the sizer ball is pulled through the neck when the ram is lowered", and for those that do not measure before and after that advise seems reasonable to believe and worthy of repeating, a lube inside the neck and on the top of the neck expander ball will eliminate that 'chatter/squeak' sound.

Then there is no qualifying statement as to how many times the case has been fired, some believe the case can be fired to form then neck sized 5 times and THEN full length sized to stat over, I can not do that, after firing a case 6 times, it has been fired 6 times.

Reaming necks, I have formed 308 W from 30/06, forget the neck, I cut it off with a hack say, part of the shoulder became part of the neck and the shoulder was erased and part of the case body became part of the neck, back to reaming the neck, the neck in military 7.62 NATO chambers are generous (larger in diameter than commercial 308 Winchester necks), meaning it is not required to ream the neck even though the neck is thicker because the neck was formed from the case body, but when forming 308 W from 30/06 case it is necessary to ream the neck, again because the neck is formed from a thicker part of the 30/06 case, again, the shoulder did not move back, the shoulder was not bumped? back, the shoulder of the 30/06 was erased and the new shoulder was formed from the case body.

I am a big fan of measuring before and after.

F. Guffey

August 3, 2011, 03:19 AM
Save yourself a lot of grief. Buy a box of Lapua .260 brass. It will last forever relatively speaking, and is excellent.

August 3, 2011, 11:23 AM

I am a big fan of forming dies, I could purchase Lapua brass, 100 of them for $90.00, or I could order the forming die (58121 Page 9) for $90.95 from RCBS, with the forming die I would never run out of cases as long as I had 308 W cases, I could even form cases for other shooters, if I purchase the cases from Lapua I have cases, and Shmakey said "260 Remington from 1000 pieces of .308 Win brass?" Shmakey has 1,000 cases, if he purchase the forming die and used it to form 100 cases, the die is paid for and he has 900 cases left, if he purchased 900 Lapua cases he would be looking at $800.00 plus. if he formed all 1,000 cases the cost of the cases would be .09 cents each.

If I had $90.00 to spend I would not spend the money for cases, there is new/unfired, then once fired/fire formed/ and neck sized 5 times and the illusion the 6 time fired case can be full length sized to restore for starting over.

And if going from 243 to 260 part #09824 for $8.94 is to be used with the 260 die.

Remember, the 260 has a pedigree, 6.5-08 and 260 Remington.

F. Guffey

And he does not have to get into mortal combat with the press and form all the cases at once, he could start with 40 cases, make a trip to the range, road test them.

With the 2 part numbers and a 260 RCBS full length sizer die he can form 243 or 308.

August 3, 2011, 11:58 AM
Ah, so I'd need a specific case-forming die (e.g., part 58121). Didn't realize that.

August 3, 2011, 04:45 PM
As Denton pointed out, the 243 case can be necked up to .260 with a 260 full length sizer die. when necking up it is advise the sizer ball is designed for necking a case up, thus the additional tool for necking up 243 to 260. When going the other way according to RCBS it is recommended a case forming die is used, meaning if forming 308W to 260 was recommended there would be an '*' in the price column, the * indicates no forming die required, to form cases with the * use a full length sizer die to form that case.

So the answer to your question is yes, RCBS does not list another option, but, that does not mean it will not work and the good news they do not list a reamer with the kit. If you have a 280 full length sizer die, lube the inside of the neck and case body then try the 260 die when forming the 260 cases.

And for all the reasons listed I would choose the case forming die.

I have formed 7.65mm53 B. M. from 30/06 cases with a full length sizer die, it worked, but with the forming die #14365 failures were eliminated and when finished the cases were close to store bought.

F. Guffey

August 3, 2011, 08:49 PM
.243 or better yet, 7mm08 brass is cheaper and easier to re-size to .260Rem. If you make a chamber cast there may be an advantage of using the thicker .308 cases if there is enough "room" for non-neck-turned brass loaded with correct sized bullets. Sometimes the best accuracy occurs when the loaded neck diameter is about .001 to .002 under the chamber's neck diameter. Not only does brass get worked less but bullets get started straighter into the bore.

August 3, 2011, 09:26 PM
I've shot hundreds of 260 formed from 308 brass. My procedure is to small base size the 308, followed by a full length 260 die. I use Hornady one shot for case lube, and bought a used turret press expressly for this forming operation. I have had ZERO issues with chambering, and see no need for neck turning.

Several dozen of my first neck downs are on their sixth firing(not including the original 308 firing) and are showing no signs of any work hardening or lack of neck tension.

While 7-08 would be great for forming 260 brass, I got a thousand 1x 308 Federal range pickup from a police range for $65, so I figured what the heck. The neckedd down 308 works very very well.

Be very careful if you also reload for 308. I use Dykem red on the bases of my neckedd down brass. It lasts 3-4 tumbling cycles.

August 3, 2011, 09:37 PM
I just formed some .260 into .243 a few month ago because I couldn't find anyone who wanted them. Same with some .308.

August 3, 2011, 09:59 PM
I made mine from 7mm-08 brass. A neck turner is a good investment anyway.

August 4, 2011, 03:36 PM
The factory 260 Rem chambers are typically .299" neck.
The factory 260 Rem full length sizer dies are typically .284" neck.
The factory 260 Rem brass with a 6.5mm bullet are typically .292" neck.
The military 308 LC97 brass with a 6.5mm bullet are typically .299" neck.

The brass used for 260 is 7mm-08, 260, 243, and 308. Which brass is going to be used drives what diameter to have the sizer neck honed.
The stock Forster full length sizing die has a neck that will go with a .284" pin gauge.
The 260 SAAMI drawing tolerances for the chamber neck are:
a) .299 - .301" at the rear of the neck
b) .298 - .300" at the front of the neck

As best I can measure with pin gauges, my 260 [long chambered at Douglas] is:
a) .299" at the rear of the neck
b) .298" at the front of the neck

I have used 308 brass, 243 brass, and 260 brass in my 260.
My experiences are consistent, but not a complete verification of the synopsis I offer here of internet folklore mythology I have read about the 260:
1) 7mm-08 brass is the best, good fit between chamber neck and ammo neck
2) 260 brass is second best
3) 243 brass is third best. It gets a donut formed at the base of the neck
4) 308 brass is 4th best. Commercial brass will work. 10% of the time there will be a nasty pressure spike from a pinched bullet. These misfits can be sorted out, turned, or reamed.

The Douglas long chambered 98 Mauser barrel is .299" rear of the neck and .298" forward.

The stock Forster size die is .284"

The 308 brass comes out of the 260 die with .277" neck with a bell at the mouth.

after using Expander ball after sizing, .297" od neck, .260" id neck, .016" neck wall measured, .0185" calculated, concentricity at neck od .003"

This means that a .264" bullet would bulge the neck od .297+ .004" = .301", which should chamber with .298 - .301" = .003" interference

Seating a 140 gr at 2.925", there is some lands engagement.
The neck measures .297" with the LC97 brass

What does it all mean?
308 brass is the worst of the above 4 options

August 4, 2011, 04:35 PM
Reformed necks do get thicker/thinner when we change the diameter. Thing is, most cases necks are much thinner than they need to be so sizing down still leaves most finished necks thin enough. (And the 'dreaded donut' doesn't happen when necking down.)

August 4, 2011, 05:04 PM
I measure before and after, others assume, again, necking down causes the neck to lengthen, necking a case up causes the case to shorten, again, I have formed 308 Winchester using 30/06 cases, for those that have the ability to keep up with two thoughts at one time, I cut the neck of the 30/06 off with a hack saw, the case body became the shoulder and the neck and there was nothing about that procedure that had any similarity to 'shoulder bump' I then full length sized the case, loaded and chambered it in a 7.62X51 NATO chamber and still there are those that tell me I have to ream the neck or trim the outside of the neck or the chamber will not allow the bullet to be released.

I am a big fan of measuring before and after....and bullet hold, yes, I am a big fan of bullet hold, I can measure bullet hold, neck tension measured with a pin gage does not measure neck tension. But just in case I have an in-line, butt and angle grinder. just in case I need a pin gage, when measuring holes I find a tapered gage more useful, one needs to know how to make them and then be able use them.

I can not ignore the fact RCBS sells a forming die for the 6.5-08, if in their opinion the process of forming 308 W to 6.5-08 required a reamer they would include the neck reamer, for more money. I can not ignore the fact that other responders have successfully formed 308 W to 6.5-08.

Measure before and after, the other one, pulling the sizer ball trough the neck after sizing stretches the case? Neck? Shoulder? or something. I measure before and after.

F. Guffey

August 4, 2011, 07:03 PM

Join Date: December 3, 2006
Posts: 2,801
Reformed necks do get thicker/thinner when we change the diameter. Thing is, most cases necks are much thinner than they need to be so sizing down still leaves most finished necks thin enough. (And the 'dreaded donut' doesn't happen when necking down.)

I am no expert, but I just did a search on what causes donuts, and one poster says it is caused by shoulder brass being thicker than neck brass... which could happen when necking up.

This, then explains how the thin 243 neck gets a bullet blocking doughnut at the base of the neck when necked up to 260.

I have a 6mmBR reamer designed for a bullet so that the bullet will not touch the doughnut. How was I supposed to get a doughnut in 6mmBR?

August 4, 2011, 09:30 PM
Brass flowing up from the thicker shoulder into the neck. If you neck turned them you get it from not turning down far enough.

August 4, 2011, 10:09 PM
We get no shoulder brass in the necks when reforming them down, ergo, no doughnut.

August 4, 2011, 11:29 PM
Ranger335V, there was a thread on another forum about the dreaded donut, I was not going to get involved because the discussion was between those that I have never heard say OIC, as in OH! I SEE, then I got the feeling they were making it up, sure enough, all the donuts they were creating were the results of bad habits and cute dies.

I am a big fan of forming dies.

F. Guffey

August 5, 2011, 01:08 AM
I am now officially more confused than before I asked. :)

August 5, 2011, 07:34 AM
Two or three posters said they have done it with no problems and no need to ream or neck turn, only trim to length. I would ignore the rest and try a few cases and see how it does for you.

Load one of these formed brass and see how fat you are where the bullet is seated in the case. If that is OK, you will be fine. If it is too fat, you will need to ream or turn the necks. A chamber cast is a good way to do this, or, assuming the loaded round fits the chamber easily with no resistance, fire a light load with one and then see how easily a bullet enters the neck area on the fired case. It should slip right in. If there is any resistance, the necks are too thick and need to be reduced.

August 5, 2011, 09:45 AM
"How much of a time investment should I expect when making .260 Remington from 1000 pieces of .308 Win brass? I have never neck-turned my brass before, but it seems like it's a required step in this conversion, as the extra brass has to go somewhere"

Again, there are those that do it and there are those that talk about it. The RCBS listing for a forming die does not list additional parts with the forming die, if you will look through the dies available on page 8 and 9 etc., you will notice some kits cost $300.00 +, the high cost of the kit is necessary because multiply dies and reamers are required, you will also notice dies are listed in groups, when looking for a forming die I want the die I am looking foor group A, there are more times than not the die will be in group G, that is about $90.00.

RCBS also has reamer dies, about $100.00 for the die and $70.00 for the reamer, this set is not for everyone, just the most serious. You started with the assumption neck turning or inside neck reaming was required, If you have a set of dies, shell holder, press and 1,000 308 W cases lube the cases, do not lube the neck or shoulder, lube the inside of the neck and remember the sizer ball will be used as an expander, a sizer ball with a long taper is desirable.

It does not get better than new cases, then comes once fired after that the frequency of neck splits increase and if not then expect neck splits when fired.

Military brass? It is thicker, they say that over and over and over, it is only half true. As with the military 30/06 case, it is heavier unless it is Winchester, the case heads are thinner by .060 thousands, that leaves the additional weight in the case body, if the case body is where the weight is then the case body is thicker, and I say I measure before and after, and there is nothing wrong with seating a bullet in the necked down case to determine the outside diameter of the neck when loaded, and if you have fired cases you can compare the outside diameter of the fired case with the outside diameter of the loaded case, the difference will tell you the Clarence between the neck of the case and the chamber neck.

F. Guffey

August 5, 2011, 09:54 AM
"brass has to go somewhere"

Again, an example, necking up a 30/06 to 35 Whelen shortens the neck (not the case body) .035 thousands, not easy to get someone to think.......about it, the neck got shorter, if the neck got thinner why did it get shorter, could have gotten a little of both, but, how difficult is it to provoke someone to measure before and after.

And still there is the pulling of the sizer ball through the neck and those claiming the case gets longer because the sizer ball is pulled through, and again who measures before and after.

F. Guffey

August 5, 2011, 10:10 AM
"I am now officially more confused than before I asked."

Yeah, guess I can understand. As Walkalong suggests, just form a new case, seat a bullet and measure the loaded neck diameter. If it's any smaller than a normal fired case from your rifle you are good to go. It it's larger than your fired cases you need to turn the necks to make it so. All the rest is meaningless trivia from web 'wannabe' gurus.

I only mentioned 'donuts' because that often gets tossed into the trivia conversation but it has no meaning for what you want to do.

Good luck!

highlander 5
August 5, 2011, 10:27 AM
Yeas ago I had a Ruger M77 in 7 mm Mauser wanted to shoot the rifle but no one had brass or ammo in my neck of the woods. So I got me a set of 7 mm Mauser dies and a file and trin die,some 30'06 surplus brass and a hacksaw and went to town. A few days later I had several hundred 7 mm Mauser cases and they shot fine no neck reaming needed. I read most of the post and I would like to make one suggestion,get a carbide expander ball. Hornandy makes them for RCBS dies and Saeco has them for their dies.
The carbide ball will save your elbow,trust me on this. I reformed 1500 223 cases to 300 AAC and the carbide ball saved me a lot of work.

August 5, 2011, 11:04 AM
A logical conversion was believed to be the 280 Remington, 7mm57s were chambered to 280 Remington, when fired the 280 cases were ejected with two neck diameters about .055 thousands of the 7mm57 chamber (neck) was/is not cleaned up by the 280 Remington reamer, meaning the neck of the 7mm57 chamber was/is generous? (larger in diameter) again measuring before would have avoided the two different neck diameters later.

For some going from 308 W to 30/06 was a no brainer, when fired cases were ejected the shooter discovered a ring around the case where the 308 case body shoulder juncture was on the 308 W meaning the shoulder of the 308 W is larger in diameter than the 30/06 case body when measured from the bolt face to that juncture on both cases.

Those I know that did the conversions have no problem with continuing to fire the rifles, and it is a good way to sort brass for them.

F. Guffey

August 7, 2011, 02:22 PM
I have necked 8mm brass down to 7mm with Wilson vise die, and then necked it down to 257 Roberts with another Wilson vise die. Then I fire form to 257 Roberts Ackley.

This works very well.

308 -> .243 not so good... a guy could get killed.

I have some Lapua 308 brass with small primer pocket.
I plan on making some very high pressure 260 ammo with it.
But that brass costs too much to screw around with.
I have more than 100 pound of other 308 brass lying around I will practice my neck turning. I have the little Forster unit, but I want to do it on the lathe like Mike Bryant. I have been using his chamber reaming method for 10 years, time for me to learn a new trick.

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