Shoulder Bump Inconsistency on Co-Ax

[LRPV]

Use Custom shell holders made by Redding. Shell holders for complete control of shoulder bump.

My custom chambered barrels are set to minimum headspace so my problem is getting a die to short enough. I wish that someone would finally make a competition set that went shorter instead of taller. IE, letting the die come down farther to bump the shoulder more.

I have tried many different presses, CoAx, Rockchucker, Big Boss 2, MEC, Lyman turret, T7, and zero. The zero being the most expensive and theoretically the strongest AND using their modular shell holder system. When attempting to size brass that could be considered problematic, the shell holder will not make contact with the die when trying to size the brass. It very well may be because of over pressured brass as I do run a lot of it on the upper end. Maybe I should have my gunsmith chamber my barrels deeper? Maybe I should have true custom dies made?

 

[jelenko]

My custom chambered barrels are set to minimum headspace so my problem is getting a die to short enough. I wish that someone would finally make a competition set that went shorter instead of taller. IE, letting the die come down farther to bump the shoulder more.

I have tried many different presses, the zero being the most expensive and theoretically the strongest. When attempting to size brass that could be considered problematic, the shell holder will not make contact with the die when trying to size the brass. It very well may be because of over pressured brass as I do run a lot of it on the upper end. Maybe I should have my gunsmith chamber my barrels deeper? Maybe I should have true custom dies made?

FYI.
For my 223 brass using a COAX [i.e., built in shell holder] and Forster, RCBS or Redding dies, I can easily get the headspace below SAAMI min.

 

[BoydAllen]

My custom chambered barrels are set to minimum headspace so my problem is getting a die to short enough. I wish that someone would finally make a competition set that went shorter instead of taller. IE, letting the die come down farther to bump the shoulder more.

I have tried many different presses, the zero being the most expensive and theoretically the strongest. When attempting to size brass that could be considered problematic, the shell holder will not make contact with the die when trying to size the brass. It very well may be because of over pressured brass as I do run a lot of it on the upper end. Maybe I should have my gunsmith chamber my barrels deeper? Maybe I should have true custom dies made?

Two things: First of all, I do not think that chambering to absolute minimum headspace is necessarily a virtue, especially for reloaders. Secondly, I often run into posters who are trying to bump shoulders after a single firing of a case. Typically, if you size a one time fired case so that the shoulder is in the exact same place that it was after firing, it will chamber freely, In the past, since I commonly had my loading gear at the range, with a new barrel or rifle I would reload a single case, neck sizing only, with a safe but hot load, until the head to shoulder measurement stopped growing, and set my die to bump back from that measurement. If I am forced to come up with a proper die setting using once fired brass, I decap and cover the head of the case with Scotch tape, which leaves me with a case that is too long to chamber, that I can use to work down to the fit that I want.

 

[RabbitSlayer]

FYI.
For my 223 brass using a COAX [i.e., built in shell holder] and Forster, RCBS or Redding dies, I can easily get the headspace below SAAMI min.

Me too. I have a tikka that must be set to min or even below. It barely closes on a go gauge. I have another tikka that 1 layer of scotch tape it barely closes on the go gauge. I am able to bump > .002 with forester dies.

 

[SSchnd]

Have you have poor results using non-Forester lock rings? I have used Hornady rings (and Forester) and they seem OK but I haven't done any comparative tests on them.

Forster Die Lock Rings are thicker, I am not home to measure but my reason for only using Forster rings is they fit the slot in the press properly. Others will allow movement up down.

 

[tdogg]

Ran across something last night that I hadn't been tracking as I started using my new Giruad for the first time. I was noticing that my cases were coming out varying case lengths after trimming. That got me to exploring my shoulder bump's to see if I was standard across all the cases. What I found was that I had varying shoulder bumps on some of the cases that had ejector swipe marks on them (hotter load). After rechecking my Micron sizing die in my Co-ax I had all the non-swipped brass consistently at 1.6080 on my comparator. Regardless of how many times I did the sizing die on some of the ejector swiped brass I could not get the comparator to read less than 1.610. Thought that was really strange and then I started looking at the bottom of the brass and noting that the distance between the case rim and the bottom was wider on the ejector swiped brass. Nothing I could do on the Co-ax could get these to standardize with the other cases. Assuming that is because of the way the jaws grip the case in the ejector groove. Has anyone experienced this issue. I am culling those brass out as they are not at the same case length, but wanted to see if this is common or a way to be able to reform to get common sizing.

I have run into this with my reloads in both 7PRC and Dasher. I think it has to do with a mismatched die and chamber. If the base of the case gets blown out with a "hot" load, the die cannot resize it properly and it will spring back. I think the base of the die is actually too small and the work you put into the case goes into trying to size the body vs bumping the shoulder. The die body grabs the case and it compresses it and thus the shoulder doesn't get bumped. When you lower the case out of the die the case body springs back.

I think the solution is to the roll size the case prior to attempting full length sizing. This will allow the case to slip into the die body with less effort and the shoulder will be properly bumped/sized.

The work around is to lube the case with good lube (imperial wax), size the case, relube the body again, and size the case. It generally only takes two-three lube sizing cycles to get the shoulder to bump properly. In my experience, you can't just run it back up into the die again without applying lube again. Don't ask my why, but spinning it in your lubed fingers between cycles is key to getting it to size fully. Once the case is free to "slip" in the die, it will properly bump the shoulder. You will most likely need to back off the sizing die to not over bump the shoulder.

I don't have a universal rollsizer yet but do rollsize pistol brass. It really does bring the case back into spec as most pistol cases are too short post firing and generally only get shorter with age. Roll sizing brings them back into spec length wise (almost to a fault as some come out too long in the process).

Post up if the lube cycle process gets your shoulder bump to happen more consistently.

Cheers,
Toby