brass sizing/chamber fit issues

[AKDaddy]

Hey guys, I'm having fun playing with my new 260 Rem, but ran into the following issue.

I bought a shoulder bump guage from Sinclair, and am using it along with the ".308 family" insert. I used it to check the base-shoulder length on about 10 cases that were fired in my chamber, and they were all pretty much the same dimension, with .001" of each other. I set my Redding FL bushing die to bump the shoulder back .002", as measured with the same guage. However, after resizing and bumping the shoulder back .002" the cases are all still a "crush fit" in the chamber, meaning I can get the bolt to close on the resized cases but it's a sticky, tight fit. This continues to be happen until I bump the shoulder back by about .007". That seems like WAY too much shoulder bump. Am I wrong? As I understand it, more than .002 shoulder bump can lead to early case head seperation, and that many bump only 001".

Assuming there is something wrong, any idea what might be the problem? I'm using my 7-08 Rem Redding FL type-S (bushing)sizing die with a .288 neck bushing. The action is an Accutrigger Savage centerfeed short action. My barrel is a Brux barrel chambered with a custom 260 Rem match reamer with a .294 neck and .160 freebore. Brass is Win 7-08 brass necked down and turned to .013" thickness (.290 loaded round diameter) in case that helps solve the mystery!

Thanks!

 

[camac]

I would suggest you are bumping the outside of the shoulder back but the 260 (6.5mm) bushing is not bumping the neck /shoulder junction back until you go further down. The 7mm hole in the 7-08 FL die is leaving a 7mm neck. The 6.5mm bushing is not getting to the bottom of the neck (it can't). It is only the base of the neck that is causing the tight bolt whilst your shoulder is now a long way back from shoulder of chamber. Whilst you can use 7-08 dies with neck bushings for neck sizing, you can't really use them for bumping back the shoulder or a true FL resize. Unfortunately I think you will need to invest in a 260 bump die or FL die.

 

[AKDaddy]

I did form the brass using a regular (non-bushing) RCBS FL die, exactly because I wanted to make sure I resized the neck all the way to the shoulder before neck turning. I think you are probably right though. After firing the whole neck is expanded to .293, right down to the shoulder junction, and that little bit probably isn't getting squeezed back down by the bushing until I push the case way (too far!) into the die.

Unfortunately the RCBS die resizes the neck far too much (as most factory dies do), so I'm going to look back for that article a few days ago about having a Hornady die custom honed. I don't think anyone makes a bump die in 260 rem at this point. Please correct me if I am wrong!

 

[therifler]

Midway usa , bump die for 260 rem.$ 26.00 #483512 it is made by redding . hope this helps .The Rifler

 

[AKDaddy]

Here's an update: It's NOT the shoulder of the case, or the neck area. To test out what was happening I drew four lines, 90 degrees apart, the length of a case that I had pushed the shoulder back by .002 on. I inserted the case into the chamber...as mentioned it was still a tight fit. I opened and closed the bolt on it about five or six times and then took it out to see where the marker had been rubbed. The stripes were untouched at the neck and shoulder, but all the lines are rubbed about 1/2" above the head of the case, just above the webbing. It seems the problem here has nothing to do with the neck or shoulder, but is rather a chamber that is so tight that the case walls right above the webbing don't get squeezed down enough until the shell is so deep into the die so as to set the shoulder back by .007 to .008.

So now...is the answer to THIS problem to buy a "small base" body die? I see one made by Redding in the Midway USA catalog, and fortunately I see 260 Rem as one of the available calibers. Is that what I need to buy?

Now that I think of it, I may have this same problem on another rifle as well. I had to jam the casing all the way into the die before it would fit into the chamber without binding on that one too. I don't have a bump bushing for that, but I don't see a small base die of that caliber listed anyway.

Assuming a small base die is the ticket for my 260 Rem, what's the best thing to do if a small base die is not available. Custom dies or get the chamber honed a tiny bit wider? Maybe even polishing the chamber with Flitz, or even some lapping compund?? Anybody had to deal with this before?

 

[Laurie]

You do sometimes get this problem with custom rifles chambered with a 'minimum SAAMI' reamer. I have it with my 6BR - around half of the cases as they come from the box have slightly hard chambering and VERY hard extraction due to a tiny amount of interference fit at the rear of the case body. My gunsmith told me even the tiniest amount of mismatch will cause major problems. If this is your problem, I'm surprised you didn't mention hard extraction as this was a much greater problem with my rifle than chambering.

If it is the problem, the Redding small-base body die should cure it completely - it did for me. There are two things to note: (1) the die pushes the shoulder back if so set as well as reducing body diameter, so watch your die setting in the press (2) the brass 'remembers' its original dimensions and gradually returns to it over several firings and reloadings even with F-L sizing with a standard die, so you do need to reuse the S-B body die every now and then. I need to do it every five loadings, but it may be more or less with your brass.

Laurie,
York, England

 

[Old Navy]

Had the same problem with my 6BR. The small base die did the trick. Later! Frank