LnL press varying shoulder bump
- Thread starter rebs
- Start date
If you're using cases fired in other rifles from unknown sources, you can expect some significant variation but 0.017" is a lot and I've never encountered that much variation when I used range brass which I do not do anymore for at least the last 20 years or so.
The two fixes I can think of are as follows:
1. (Preferred) Start with virgin cases, allow them to fire form to the rifle chamber before bumping the shoulder. In most cases, you will not have to bump the shoulder for several firings, set the FL die for zero to 001" bump and check in rifle for adequate chambering.
In most cases, because the FL die is also sizing the radial dimension of the case, that is all that is needed for several firings. However, the FL die must be set so it touches the shoulder to prevent extrusion, i.e., lengthening. Your datum line measurements (fired versus sized) will verify correct FL die setting.
I labeled this option as preferred because it minimizes problems. However, I realize that components are in short supply so you may need to use cases on hand, so I listed option 2.
2. If you insist on using once fired cases from unknown sources, then separate out the cases with more than .004" in datum line variation* from the highest measurement. Set your FL die as described above and allow all cases to achieve some head space equilibrium before bumping the shoulder.
Obviously, if a case will not fire in said rifle, it cannot be fired formed, so these have to be culled. However, you may be able to salvage enough cases to create a serviceable group.
*this is just an estimate - more or less may work or be required to fire in your rifle.
The two fixes I can think of are as follows:
1. (Preferred) Start with virgin cases, allow them to fire form to the rifle chamber before bumping the shoulder. In most cases, you will not have to bump the shoulder for several firings, set the FL die for zero to 001" bump and check in rifle for adequate chambering.
In most cases, because the FL die is also sizing the radial dimension of the case, that is all that is needed for several firings. However, the FL die must be set so it touches the shoulder to prevent extrusion, i.e., lengthening. Your datum line measurements (fired versus sized) will verify correct FL die setting.
I labeled this option as preferred because it minimizes problems. However, I realize that components are in short supply so you may need to use cases on hand, so I listed option 2.
2. If you insist on using once fired cases from unknown sources, then separate out the cases with more than .004" in datum line variation* from the highest measurement. Set your FL die as described above and allow all cases to achieve some head space equilibrium before bumping the shoulder.
Obviously, if a case will not fire in said rifle, it cannot be fired formed, so these have to be culled. However, you may be able to salvage enough cases to create a serviceable group.
*this is just an estimate - more or less may work or be required to fire in your rifle.
HandgunHTR
Gold $$ Contributor
1.459 and 1.442 are not "shoulder bump" measurements. Those are case length measurements to the datum line. What is the actual amount of bump (presizing measurement minus post-sizing measurement)?
I've done hundreds of thousands of 223 brass with LNL bushings on a Big Boss 2, and never had any issues with LC or ANY flavor of brass. I get brass from any and everywhere and cull it on loose primers pockets.
The LNL isn't perfect, but my money is on the issue being something else.
Oh The humanity!!!! Shoulder bumps again?
This has happened with virgin LC as well as twice fired LC. I checked the Die bushing and it is still tight tight to the bottom of the press. No wiggle or play at all. Could the shell plate be tipping enough to do this and if so why on only a some cases. I checked it for tilting and there is very very little almost none.
To clarify- You are sizing brass and a majority are 1.459 after sizing, and some of them are 1.442, correct?
What is the length of the short ones before you size? Has your sizing die been taken apart and completely cleaned? I've seen buildup in the die cause short lengths.
What is the length of the short ones before you size? Has your sizing die been taken apart and completely cleaned? I've seen buildup in the die cause short lengths.
The deck height may be different at each station. Think 5 different shell holders.
Attachments
If it is a LNL then I would go with 243winxb's theory.
Jam the bullets the first time you fire them so the case head is against the bolt face. Then they should fire and blow out to your chamber dimensions.
Added later: Are you seating the primers to the bottom of the pockets. Primers not seated to the pocket bottom and the firing pin having to push the case forward is asking for miss fires.
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I am using CCI benchrest 4 primers and after pulling the bullets out of the ones that did not fire, I found the primer did go off but not completely, it was slightly brownish and a bit of the powder was slightly brownish also. It is like the primer did not fire hot enough to properly ignite the powder. What would cause this? Seems to me I have some defective primers.
I had a similar problem and found it to be bushing failure; I've not heard of how your LnL AP bushings look in comparison to what you use in the big boss, only that you never had a problem on your big boss. I'm curious, check the bottom side of the quick change bushings in your AP press sizing station and see if they're looking crumbly.
Shell plate could be it too, but the bottom of the case is referenced to the top of the ram on sizing, so the plate is really for extraction only. It's a maybe, how do you set up your six ng die to start?
Could also be your process. What lube do you use, could too much be causing build up that causes a case flier?
Finally, I'm also curious as to what's your before and after measurements, do you have short shouldered cases to start with?
Are you running the sizing die with expander ball, if so; what height is your expander ball set to? Any chance you have it set high and a long case neck binds up and instead crushes the shoulder?
How often do you trim your brass; possible it's a long case neck?
We have more questions I'm sure. The significance of each question is variable, I don't think any one could be 0.017"; but I've heard worse before.
Final question, you shooting these from an AR? You say this happens with new brass, how are you measuring, after sizing, or after seating? What if the problem is in the seating operation?
-Mac
Shell plate could be it too, but the bottom of the case is referenced to the top of the ram on sizing, so the plate is really for extraction only. It's a maybe, how do you set up your six ng die to start?
Could also be your process. What lube do you use, could too much be causing build up that causes a case flier?
Finally, I'm also curious as to what's your before and after measurements, do you have short shouldered cases to start with?
Are you running the sizing die with expander ball, if so; what height is your expander ball set to? Any chance you have it set high and a long case neck binds up and instead crushes the shoulder?
How often do you trim your brass; possible it's a long case neck?
We have more questions I'm sure. The significance of each question is variable, I don't think any one could be 0.017"; but I've heard worse before.
Final question, you shooting these from an AR? You say this happens with new brass, how are you measuring, after sizing, or after seating? What if the problem is in the seating operation?
-Mac
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