Excessive Shoulder Bump

[Martin52]

Having a problem with a new 0.308 Redding Type S FLS bushing die, resizing lapua cases with turned necks, .335 bushing.

Previous FLS was a standard Forster and that worked fine.

The new Redding either does not bump the shoulder or it bumps it back too much. Spent hours fiddling around with the settings, the minimim shoulder setback this die will produce is 1.557 inches, my fired cases measure 1.560 and I'm trying to bump to 1.559.

Anyone had this problem before and knows a solution ? Otherwise I think there's a problem with the die.

Thanks

Martin

 

[Martin52]

With my +.010 Redding comp shellholder and with the die backed out of the press about half a turn I get about 2 thou shoulder bump. The base of the case is not getting sized but it's a better result. Still, I think the die is short. May go back to Redding on this one.
Martin

 

[jo191145]

If the die is capable of sizing down to 1.557" then I see no logical reason it can't be set to 1.559". I'm confused.

Whether it sizes the web enough to fit your chamber is a different matter.

There is a "gray area" in setting FL dies that can cause strange numbers.

If you start well above "shoulder bump" settings and slowly work down you should notice your headspace measurments begin to grow above 1.560. (NoteAlways remove the entire decapping stem after the first initial size and primer removal. Let if function as a body die for setting headspace. In your case the bushing as well.)

As the body of the brass is constricted the shoulders move forward beyond the 1.560 you started with. Have you noticed that?
This is usually a good indicator your getting close. In very small increments continue adjusting the die down. You should be able to feel it contacting the shoulders during sizing. Then its just a matter of getting it to 1.599"

Older brass and brass used in load development may show varying headspace measurments in this gray area. Just a thought.

 

[bozo699]

If the die is capable of sizing down to 1.557" then I see no logical reason it can't be set to 1.559". I'm confused.

Whether it sizes the web enough to fit your chamber is a different matter.

There is a "gray area" in setting FL dies that can cause strange numbers.

If you start well above "shoulder bump" settings and slowly work down you should notice your headspace measurments begin to grow above 1.560. (NoteAlways remove the entire decapping stem after the first initial size and primer removal. Let if function as a body die for setting headspace. In your case the bushing as well.)

As the body of the brass is constricted the shoulders move forward beyond the 1.560 you started with. Have you noticed that?
This is usually a good indicator your getting close. In very small increments continue adjusting the die down. You should be able to feel it contacting the shoulders during sizing. Then its just a matter of getting it to 1.599"

Older brass and brass used in load development may show varying headspace measurments in this gray area. Just a thought.

Your spot on Joe, if it will do 1.557 than it will do 1.559, something else is wrong, possibly the neck is to long and the mouth is hitting and shoving the shoulder back before the bump part of the die ever touches the datum of the case?
Wayne.

 

[BoydAllen]

One thing that could contribute to the problem is variability of bump with the same die setting. If you leave the die alone, and size several fired cases, how much does the bump vary from case to case, in say 20 cases?

 

[bozo699]

One thing that could contribute to the problem is variability of bump with the same die setting. If you leave the die alone, and size several fired cases, how much does the bump vary from case to case, in say 20 cases?

Boyd,
What do you think could cause the variability you are speaking of ?
Wayne.

 

[BoydAllen]

I have seen it with once fired brass. I think that the major reason is the differences in the annealing, from case to case. Such things as inconsistent lubing, can also contribute to the problem. The magnitude of the problem is reduced when the shell holder contacts the die, at the top of the sizing stroke. Ultimately, a problem of this sort that came up with magnum cases in a couple of calibers (7 mm WSM, and .338 Lapua) was resolved by annealing to less than a fully softened state, down past the cases' shoulders. (Annealing is a subject that seems to have more bad information available than good. I subscribe to Ken Light's idea that if a case gets hot enough to glow, even slightly in a darkened room, it has been over heated, and will thereby be over softened in the area that glowed)

 

[bozo699]

Boyd,
Thats very interesting, I am being serious and not a smart alic, why is it important to have the shell holder touch the die, I mean what affects would you have touching VS. not touching and why in your opinion. And I agree with you on the annealing, a lot of misleading info out there. Just for the record how often do you anneal your match cases? Thanks again for all the insite.
Respectfully Wayne.

 

[BoydAllen]

Some of the variance in shoulder bump has been demonstrated to have been reduced ,by actual test, by using a shim, or the appropriate Redding Competition Shell Holder to create a solid connection, with a small amount of toggle, between the shell holder and the bottom of the FL die. I believe that this is because this toggling takes some of the slack and/or spring out of the press linkage and frame. Large differences in the amount of lube applied, and dwell time at the top of the sizing stroke can also influence the amount of bump. I did these experiments a long time ago, before the internet, when we had to figure out these sort of things on our own, or do without an answer. Luckily, I like doing experiments.

 

[bozo699]

Thank you Boyd.
Wayne.

 

[Martin52]

Thanks all for your comments. The die will now size to 1.559 using a 0.010 Redding comp shell holder but the die is backed out about half a turn and the web of the case is not getting sized. Screwing in the die pushes the shoulder back as you would fully expect to happen. The case length is ok at 2.005 so I don't think the cases are causing the shoulder not to seat inside the die, the die chamber just seems a tad short.
Will have to send it back.
Martin

 

[bozo699]

Good luck Martin, its been a good thread,I learned a thing or two.
Wayne.

 

[Martin52]

You're welcome Wayne, it has helped me work through the problem.
Martin

 

[dantiff2]

Very interesting you mentioned dwell time in the die, Boyd. After some testing of my own I came to the same conclusion, now I do a three count when the ram is at it's up most position. I also had very inconsistent shoulder bump before I started annealing brass but now I have no problem keeping it too one thousandths of an inch.

Dan

 

[BoydAllen]

Another fellow with too much time on his hands

 

[Webster]

How do you measure setback?

 

[bozo699]

Webster,
That is a very good question, There are bump insert tools for vernier calipers that will take different shoulder bump inserts, these are probably the most common and there are caliber specific tools like the Redding instant indicators and several other tools available to measure the amount of shoulder bump you are getting.
I personally like the Larry Willis Digital headspace gauge for measuring your amount of shoulder bump. Once you have determined your length, you set your die size a case and measure turn the die in a little and measure again continue this process until you get your desired bump, I like about .001, in the old days you would do the steps above with your die then chamber your case in your rifle and gauged your bump by the feel of the bolt closure and many people still do it that way. hope this helps.
Wayne.

http://www.larrywillis.com/

http://www.midwayusa.com/viewProduct/default.aspx?productNumber=191549