How do I fix case head separation for 6.5x55 swede

[chutestrate]

I'm out of my element on this question. I have a Tikka T3 Hunter in 6.5x55 swede. When I first picked it up I and reloaded with a pile of brass I had on hand I experienced a couple of instances of case head separation. I didn't have history on the brass so I scrapped it, and picked up new brass from PMS and PPU. I started working up a load for it last week and I'm seeing that little line around the base again. Not sure what to do about. I do have a neck resizer so maybe that is the way to go?
My current reloading steps are using a 2 die steel rcbs set and full length resizing die. I adjust the resizing die until the bolt of the tikka closes easily on a sized case. I adjust down in tiny increments until I get that easy close. From what I can glean from youtube that is probably the issue. I also see that measuring the shoulder setback is recommended for a certain range, but so far haven't picked up why, and what my goal for doing that is. Probably haven't found the right video yet if it exists.

Would anyone mind giving me a little guidance, and big bird it down for me.

[Delkal]

A line around the case is normal and doesn't always mean case separation. Get a good flashlight and look inside the case and inspect the sides above the web. You will clearly see a darker line going around the case if you are getting incipient case separation. You can also use the paper clip trick but actually looking is better.

For setting up your die do not use the rifle. Get a dry erase marker and blacken the neck and shoulder. Then slowly lower the die till you see it barely bumps the shoulder. I use standard reloading dies for neck sizing (just don't touch the shoulder). RCBS also sells a gauge but checking some of my old setups using this method gave the same results.

[garandsrus]

What you are doing and what Kelkal is suggesting is about the same thing. The ring you see could be from the sizing die, but it is not indicating case head separation.

[Jhon]

Indeed, the bright line appears on many cals. Worst and one I pay most attention to is old brass in 303B..but the line is only a hint. I use a straightened paper clip with a tiny hook bent on one end. Insert into case and drag the inner wall from head toward neck. If it catches in a groove opp the shiny ring you have a problem- imminent case head separation.

[chutestrate]

Thank you for that. Maybe too far down the rabbit how, but where on the shoulder am I looking for a mark? Is it somewhere in the middle between the angle of the shoulder at the case body or closer to the neck. I way out of my experience depth on this one.

[chutestrate]

I should add that this is new brass with only one firing. Maybe it's nothing.

[M-Tecs]

[triggerhappy243]

I should add that this is new brass with only one firing. Maybe it's nothing.

I have extensive experience with this subject. So, a few questions: is this rifle new to you? did you buy it new? If not, I can help with a few solutions for you.

[chutestrate]

The rifle is only a year old. Bought it new from Tikka.

[chutestrate]

M-Tecs you must be a numbers guy. I'm lost on that video. I watched it a couple of times and it leaves me scratching my head.

[M-Tecs]

M-Tecs you must be a numbers guy. I'm lost on that video. I watched it a couple of times and it leaves me scratching my head.

Actual case head separations are caused by excessive clearance between the chamber shoulder and the cartridges case shoulder during firing. Most common cause is pushing the shoulder back to far via oversizing. This results in the case being pushed forward by the ejector spring or firing pin as it hits the primer. As the front of the case expands to adheres to the front of the chamber while the thicker case head it pushed back resulting in excessive metal stretching above the case head leading to a separation.

[chutestrate]

Ok, I did get that from another video. Now my question/s are the tools show before and after, I'm not real clear on that. And if it's important how do I apply that to my situation?

[M-Tecs]

Ok, I did get that from another video. Now my question/s are the tools show before and after, I'm not real clear on that. And if it's important how do I apply that to my situation?

For the most basic method you fire a round in that chamber. The case will fire formed to the chamber. You than measure the fired case at the shoulder and adjust the die for the amount of shoulder setback you want. In a bolt gun I like .001" to .002" The instruction that come with dies are the most basic possible to work with all combinations. While this will normally work it is less than optimal. Due to tolerances this can lead to excessive shoulder bump that will produce head separations. Dies also can be out of tolerance. I’ve seen two new factory dies the pushed the shoulder back over .030” when adjusted to touch the shell holder per the manufacturers recommendations.

[chutestrate]

Ok, conceptually I get it, but so far what I'm watching is starting at a point I'm not at. I really need a dumbed down video which I'll try to find. I just don't get the chamber dimensions in relation to the shoulder bumping distance, and look at this measurement in the book and it means that you want to do that. Nope. Not there. This seems to be very technical, and I'm just not picking up the whys and having an idea of where to start. I appreciate your links though. thank you

[M-Tecs]

Ok, conceptually I get it, but so far what I'm watching is starting at a point I'm not at. I really need a dumbed down video which I'll try to find. I just don't get the chamber dimensions in relation to the shoulder bumping distance, and look at this measurement in the book and it means that you want to do that. Nope. Not there. This seems to be very technical, and I'm just not picking up the whys and having an idea of where to start. I appreciate your links though. thank you

My guess is you are over thinking this. Once you understand it this becomes very simple. For your purpose the only numbers that matter are the shoulder measurement on a fired case followed by how much you push that shoulder back when you size the case.

[chutestrate]

Yeah....one of my many faults. I find the unnecessary rabbit holes. So is that the difference these guys are talking about? Measure a fired case, measure a sized case and subtract the difference? How do you make the decision of one measurement vs another? What determines what is right for my rifle?

[M-Tecs]

Yeah....one of my many faults. I find the unnecessary rabbit holes. So is that the difference these guys are talking about? Measure a fired case, measure a sized case and subtract the difference? How do you make the decision of one measurement vs another? What determines what is right for my rifle?

Rule of thumb is

.001" to .003" for boltguns.

.002" to .004" for semi-auto or lever guns

Minimum will give you the best case like and accuracy.

For a dangerous game rifles you can do more since case life is the least of your concerns.

I do everything at .001" to .002" on everything but to hold that you need to anneal your brass every couple of firings. Difference in work hardening of the brass tends to give inconsistent spring back so it's not uncommon to see .002" variations due to that.

[chutestrate]

Ok what does this mean? Difference in work hardening of the brass tends to give inconsistent spring back so it's not uncommon to see .002" variations due to that.

[Bad Ass Wallace]

Nobody has described the real problem. The cartridge dimensions for the 6.5 require a head diameter of 0.476" and are exact for brass from Lapua, Norma, CA and military. Nearly all commercial brass (Rem, PMC, PPU etc. has a head diameter of 0.472" a 0.004" difference. That is the reason you are getting head seperations!

My best accuracy comes from military brass and berdan primers. Some of these cases would have been fired 10-12 times with no problem.

[M-Tecs]

Ok what does this mean? Difference in work hardening of the brass tends to give inconsistent spring back so it's not uncommon to see .002" variations due to that.

It means when you size 20 cases with different levels of work hardening and you measure them they will have inconsistent measurements whereas annealed will be more constant. It just if you are not annealing on a bolt gun .003" shoulder bump back will likely be a better option than .001”.