Shoulder bump questions

[RemingtonAI]

I'm a little afraid to jump in at the cost of further confusing this gentleman needing help, but here it goes. I wont try to solve your problem as it seems like you have some good advice above but I do want to clarify thing that is certainly confusing.
Datum point: ill jump past the technical definition and straight to the fundamental principal. The tool has a hole that is large enough to fit the case neck and part of the shoulder through it, but stops at some point on the shoulder where it is just too large to fit through the hole. That point is essentially the datum point. Its just a point that the tool stops due to the shoulder being too large to slide in anymore, and it will always stop at the same point on every piece of brass. The numerical reading as far as the numbers go, really don't matter. All that matters is that you are able to get a reference number so you can then calculate how much you want to reduce it by and get that reading once you size it.
The reason why what the measurement reads doesn't matter is because everyone's tool may not read the same. When it is measuring in thousandths or less you may get differences between tools due to manufacturing tolerances. However, whatever the tool reads it will read each time consistently. So, for instance you and I wouldn't be able to match our cartridge base to datum point measurements up but we could verify that we are reducing the original number by say .002 and it would be accurate to say that even though we started out at different numerical numbers. Likewise, the readings you are used to seeing may be different if you replace the tool with the same exact kind in the future. So if you wanted to look up a reading you got some time ago in your data book when you were using a different measuring tool, and wanted to get the same measurement using a new tool, you might have to apply a 1 or 2% error to calculate what your new micrometer should be reading in order to get the same result.
It would be a hell of a lot easier if you could zero the tool out like on a run-out gauge on a lathe or something. I hope I haven't caused too many technical falsities in an attempt to shed some light as to why this in particular is so confusing to new reloaders. Jesse

 

[Dusty Stevens]

Good explanation jesse. If you were to want to zero something out you could use digital calipers and zero it on a headspace gage but as you said it doesnt matter. Take a fired piece of brass, measure it then size it and measure again. Or you could skip all that and test it in the rifle with firing pin removed, size til bolt handle drops about 90% down then all is right with the world. That may be .002 or .004 so thats why the rifle itself is my case gage

 

[Ringostar]

Do you know what the neck diameter of your chamber is? It's possible that you have a tighter neck and may need to turn your brass. That could explain your pressure signs and sizing problems.

 

[Cush]

I feel for you Cush, maybe I can be of help. You appear to have the tools needed, and an understanding of what they are for. Maybe just a basic suggestion of how to proceed will be of help to you. Start with your neck bushing size, and it will depend on your brass neck thickness and the amount of tension you wish to put on the bullet. You have a .308 bullet, plus a case neck of perhaps .015 thickness, so the formula is bullet size plus twice the neck thickness. .308 + .015 + .015 = .338 If I wanted to put two-thousandths .002 of neck tension on the bullet which is a reasonable starting amount, I would choose a neck bushing of .335 which will allow .001 of brass springback plus .002 of neck tension, leaving an outside neck diameter once the bullet is seated right about .336. If your brass is thinner, or you wish more/less neck tension, then take that into account when calculating the bushing size you will use.

For shoulder size, you now have some fired brass that you have measured as long as 1.582 at your shoulder datum-point and when chambered is giving you a stiff bolt close/open. That is a good case to work with. Back-off your sizing die, and feed-in this case. In very tiny increments, turn down your die by a thirty-second of a turn, very tiny amount, and re-measure that shoulder. When you get it to bump down by .001 which will be 1.581, take it back to your rifle and re-chamber it feeling for any bolt stiffness. If still stiff, go back to the press and turn down another thirty-second to 1.580 and repeat re-chambering. Continue until the bolt closes freely or with just a tiny amount of friction, at that point you know right where your shoulder (headspace) is as measured with your tools and dies. You would then turn the die down a further .002 and lock the die in place. That setting should give you smooth trouble free chambering of your rounds, and minimum case stretch.

At this point, you should measure your overall case length, and trim the neck if necessary. Your basic brass prep is completed, and you move to experimenting with powder and bullet seating depth!!! At some time in the future you may wish to go back to your neck tension settings and look into neck turning to establish exact neck thickness and further control your neck tension settings. Have fun!!!! Sorry to be so long winded.

Thanks for the input Irish Jim. That is exactly what I weas thinking ie just let the chamber be my guide. Thanks again

 

[fguffey]

It would be a hell of a lot easier if you could zero the tool out like on a run-out gauge on a lathe or something. I hope I haven't caused too many technical falsities in an attempt to shed some light as to why this in particular is so confusing to new reloaders. Jesse

It is possible to zero 'the tool' I make datum based tools, I drill round holes with sharp edges. I do not use a radius, the radius is used to make the tool case friendly. The Wilson case gage is a datum based tool, the datum in the Wilson case gage is case friendly, the datum has a radius.

F. Guffey

 

[Cush]

I feel for you Cush, maybe I can be of help. You appear to have the tools needed, and an understanding of what they are for. Maybe just a basic suggestion of how to proceed will be of help to you. Start with your neck bushing size, and it will depend on your brass neck thickness and the amount of tension you wish to put on the bullet. You have a .308 bullet, plus a case neck of perhaps .015 thickness, so the formula is bullet size plus twice the neck thickness. .308 + .015 + .015 = .338 If I wanted to put two-thousandths .002 of neck tension on the bullet which is a reasonable starting amount, I would choose a neck bushing of .335 which will allow .001 of brass springback plus .002 of neck tension, leaving an outside neck diameter once the bullet is seated right about .336. If your brass is thinner, or you wish more/less neck tension, then take that into account when calculating the bushing size you will use.

For shoulder size, you now have some fired brass that you have measured as long as 1.582 at your shoulder datum-point and when chambered is giving you a stiff bolt close/open. That is a good case to work with. Back-off your sizing die, and feed-in this case. In very tiny increments, turn down your die by a thirty-second of a turn, very tiny amount, and re-measure that shoulder. When you get it to bump down by .001 which will be 1.581, take it back to your rifle and re-chamber it feeling for any bolt stiffness. If still stiff, go back to the press and turn down another thirty-second to 1.580 and repeat re-chambering. Continue until the bolt closes freely or with just a tiny amount of friction, at that point you know right where your shoulder (headspace) is as measured with your tools and dies. You would then turn the die down a further .002 and lock the die in place. That setting should give you smooth trouble free chambering of your rounds, and minimum case stretch.

At this point, you should measure your overall case length, and trim the neck if necessary. Your basic brass prep is completed, and you move to experimenting with powder and bullet seating depth!!! At some time in the future you may wish to go back to your neck tension settings and look into neck turning to establish exact neck thickness and further control your neck tension settings. Have fun!!!! Sorry to be so long winded.

 

[Cush]

Jim, I removed the firing pin. With the firing pin removed, with an empty chamber, the bolt goes forward freely with zero resistance and simply drops down with no resistance. But when I put a casing in, there is always resistance no matter how much I reduce the shoulder.(I actually went down as far as 1.563) There is a spring loaded pin(not the firing pin) protruding from the end of the bolt. It is what is causing the closing resistance. Is this normal?
Once the bolt overcomes that pins resistance, then the bolt closes with very minimal resistance. Can you advise me on this? Thanks for your clarity thus far.

 

[Comrade Terry]

There is a spring loaded pin(not the firing pin) protruding from the end of the bolt. It is what is causing the closing resistance. Is this normal?

Yes, that's normal. That's your ejector, and when you close the bolt on a case you must overcome the resistance of the ejector spring. I suggest that you remove the ejector and its spring before you try to get a 'feel' of the bolt closing on a bumped cartridge.

 

[rmist]

That little pin is your ejector. You should feel very little resistance from that spring. Once your shell case is inserted into your chamber and you turn your bolt downward you will feel a little pressure but then the bolt handle should/will fall on it's own until almost 80-90 % closed then with a little more hand pressure from you to close the bolt all the way. If you're getting a lot of hand force to close your bolt then it may be you die isn't sizing the body of you case enough. Hope that helps

Must have been typing the same time as Terry

 

[ireload2]

You can check your FL resized cases for sufficient sizing of the body.
Measure a fired case diameter at the pressure ring and at the shoulder and record.
FL size the case as you normally would. Then remeasure it at the pressure ring and the shoulder. Both should be smaller.
Most dies will size a case body more than enough by the time you touch the shoulder.

 

[fguffey]

Jim, I removed the firing pin. With the firing pin removed, with an empty chamber, the bolt goes forward freely with zero resistance and simply drops down with no resistance. But when I put a casing in, there is always resistance no matter how much I reduce the shoulder.(I actually went down as far as 1.563) There is a spring loaded pin(not the firing pin) protruding from the end of the bolt. It is what is causing the closing resistance. Is this normal?
Once the bolt overcomes that pins resistance, then the bolt closes with very minimal resistance. Can you advise me on this? Thanks for your clarity thus far.

Again, I determine the length of the chamber first, I believe it is a bad habit to size a case until it chambers. Reason? There are control feed designed receivers and there are push feed designed receivers.


F. Guffey

 

[Dusty Stevens]

Again, I determine the length of the chamber first, I believe it is a bad habit to size a case until it chambers. Reason? There are control feed designed receivers and there are push feed designed receivers.


F. Guffey

Since he has a rem 700 and not a mauser we'll just keep on this track hes on

 

[fguffey]

Since he has a rem 700 and not a mauser we'll just keep on this track he is on

Again, no matter the design I check the length of the chamber from the shoulder to the bolt face and I believe sizing a case until the bolt closes is a bad habit. There are so many ways to determine the length of the chamber. With all the talent reloaders claim they have I am surprised they struggle with coming up with one, as in one way to determine the length of a chamber.

F. Guffey

 

[dmoran]

Again, no matter the design I check the length of the chamber from the shoulder to the bolt face and I believe sizing a case until the bolt closes is a bad habit. There are so many ways to determine the length of the chamber. With all the talent reloaders claim they have I am surprised they struggle with coming up with one, as in one way to determine the length of a chamber.

F. Guffey

Who's struggling with the length of the chamber?
I only see you claiming that others struggle.

​

 

[Dusty Stevens]

Who's struggling with the length of the chamber?
I only see you claiming that others struggle.

View attachment 978243​

Again I make it just fine as well as others that answered as well

 

[Cush]

Since he has a rem 700 and not a mauser we'll just keep on this track hes on

LOL, A mauser action will be on my 6.5 build

 

[IrishJim]

Jim, I removed the firing pin. With the firing pin removed, with an empty chamber, the bolt goes forward freely with zero resistance and simply drops down with no resistance. But when I put a casing in, there is always resistance no matter how much I reduce the shoulder.(I actually went down as far as 1.563) There is a spring loaded pin(not the firing pin) protruding from the end of the bolt. It is what is causing the closing resistance. Is this normal?
Once the bolt overcomes that pins resistance, then the bolt closes with very minimal resistance. Can you advise me on this? Thanks for your clarity thus far.

Hey ya Cush. As others have noted, that little amount of resistance that you are feeling is indeed normal, and it is caused by the ejector providing a small amount of tension against the case head. But you do not yet have a feel for what is normal, so…………

Since you pulled your firing-pin, if you wish to pursue finding your shoulder size by also removing the ejector out of your bolt, you can most definitely do that and will actually get a more sensitive feel. I believe Dusty suggested doing that, and if you do not mind removing the ejector, let’s take advantage and not only find your correct shoulder adjustment for your sizing die, but let’s also go ahead and find the maximum seating depth of your lands given the bullet you are loading. With a stripped bolt you can get two critical measurements at the same time, and save more work later.

First, holding the bolt in a ziplock-bag to catch flying parts, go ahead and push the pin out and remove the ejector and spring. Now with one of those fired cases that is too long and causing a stiff bolt when closing and opening, feed that case into your sizing die and adjust that die down a little at a time, each time checking that case in your chamber until the bolt closes and the handle JUST drops freely. Now use your shoulder-measuring tool (headspace/bump gauge) to record your Base-To-Shoulder measurement. Personally, I would then subtract another .002 from that measurement and turn down the die until your case equals that measurement. I believe in having .002 free-space for the ejector to do its work and allow for some expansion and springback of the shoulder when fired.

Second, you are going to want to know where to seat your bullet in relation to the lands. You are going to want a measurement of the Base-To-Ogive for the specific bullet you are using, which you mention is a Sierra 168 in either hollow point or tipped Match King. Take one of those now correctly sized cases and make a dummy round by seating a Match King, but seat it way out long. Now feed this into your chamber and GENTLY try to close the bolt. The lands are going to hit against a certain point on the ogive and prevent you from fully closing the bolt. Keep going back and forth seating the bullet a tiny bit deeper and trying the bolt, until the bolt handle JUST freely falls into the closed position. When the bolt handle falls without sticking or needing assistance, use your comparator to record your Base-To-Ogive measurement. With this dummy round you can check it in your magazine for fit, you will also be able to experiment with bullet jamming or setback for optimum accuracy, and in the future after many rounds down the barrel you can re-measure and compare to find throat erosion.

Re-installing your ejector can be a bit awkward the first time. You will need to simultaneously push the ejector inward against the spring, as you insert the retaining pin. With one hand take a spent case and slip the rim under the extractor then push the case-head against the ejector and hold it. This will push the ejector slightly into the bolt, and give clearance to insert the retaining pin with your other hand. Three hands would make it easier!

Have fun, and Happy Reloading! Jim

 

[Cush]

You can check your FL resized cases for sufficient sizing of the body.
Measure a fired case diameter at the pressure ring and at the shoulder and record.
FL size the case as you normally would. Then remeasure it at the pressure ring and the shoulder. Both should be smaller.
Most dies will size a case body more than enough by the time you touch the shoulder.

I assume by "pressure ring" you are referring to the diameter of the casing near the bottom just above the indented part.
Yes, the diameter at the shoulder of a fire case is .457, the pressure ring .470
After sizing we are at .........................................453 and .467 respectivley

Hey ya Cush. As others have noted, that little amount of resistance that you are feeling is indeed normal, and it is caused by the ejector providing a small amount of tension against the case head. But you do not yet have a feel for what is normal, so…………

Since you pulled your firing-pin, if you wish to pursue finding your shoulder size by also removing the ejector out of your bolt, you can most definitely do that and will actually get a more sensitive feel. I believe Dusty suggested doing that, and if you do not mind removing the ejector, let’s take advantage and not only find your correct shoulder adjustment for your sizing die, but let’s also go ahead and find the maximum seating depth of your lands given the bullet you are loading. With a stripped bolt you can get two critical measurements at the same time, and save more work later.

First, holding the bolt in a ziplock-bag to catch flying parts, go ahead and push the pin out and remove the ejector and spring. Now with one of those fired cases that is too long and causing a stiff bolt when closing and opening, feed that case into your sizing die and adjust that die down a little at a time, each time checking that case in your chamber until the bolt closes and the handle JUST drops freely. Now use your shoulder-measuring tool (headspace/bump gauge) to record your Base-To-Shoulder measurement. Personally, I would then subtract another .002 from that measurement and turn down the die until your case equals that measurement. I believe in having .002 free-space for the ejector to do its work and allow for some expansion and springback of the shoulder when fired.

Second, you are going to want to know where to seat your bullet in relation to the lands. You are going to want a measurement of the Base-To-Ogive for the specific bullet you are using, which you mention is a Sierra 168 in either hollow point or tipped Match King. Take one of those now correctly sized cases and make a dummy round by seating a Match King, but seat it way out long. Now feed this into your chamber and GENTLY try to close the bolt. The lands are going to hit against a certain point on the ogive and prevent you from fully closing the bolt. Keep going back and forth seating the bullet a tiny bit deeper and trying the bolt, until the bolt handle JUST freely falls into the closed position. When the bolt handle falls without sticking or needing assistance, use your comparator to record your Base-To-Ogive measurement. With this dummy round you can check it in your magazine for fit, you will also be able to experiment with bullet jamming or setback for optimum accuracy, and in the future after many rounds down the barrel you can re-measure and compare to find throat erosion.

Re-installing your ejector can be a bit awkward the first time. You will need to simultaneously push the ejector inward against the spring, as you insert the retaining pin. With one hand take a spent case and slip the rim under the extractor then push the case-head against the ejector and hold it. This will push the ejector slightly into the bolt, and give clearance to insert the retaining pin with your other hand. Three hands would make it easier!

Have fun, and Happy Reloading! Jim

Ok, excellent. I removed the extractor pin and spring (Baggie trick definitely a good idea)
The smallest shoulder length that had no resistance and dropped was 1.5705 so this is my base length
-.002 = 1.5685
I think my lands are so far away from the bullet that I cannot seat it out far enough to touch the lands ( I have heard this is true of some 700 5rs, but I will try anyway
Thanks again for help.

 

[Comrade Terry]

I think my lands are so far away from the bullet that I cannot seat it out far enough to touch the lands ( I have heard this is true of some 700 5rs, but I will try anyway

That's why I trim .308 cases to 2.010" for my 700 5R. It's a country mile from the bolt face to the lands. Regardless, the rifle is a good shooter.