Consistent seating depth

sodak54 · March 10, 2013, 05:42 PM

Having trouble getting consistent coal, loading .223 rem in s&b brass. My oal goes from 2.197 to 2.205, i am shooting for 2.20. I'm thinking it has to do with swaging the primer pocket (rcbs second gen). Could it be a bulge so to speak on the face of the casing? I can't see anything but the case doesnt seem to sit perfectly when stood up on a flat surface. Tried some sandpaper but really can't see anything. Anyone have a thought?

Lucas McCain · March 10, 2013, 05:58 PM

The primer should be about > .005 thou below the primer pocket. You may have to prep your cases with a primer pocket uniforming tool.

jepp2 · March 10, 2013, 06:03 PM

Quote:

My oal goes from 2.197 to 2.205

How are you measuring OAL? If you are measuring from the tip of the bullet expect some variation. If you measure from the ogive of the bullet, you should see less variation and that is the OAL the rifle sees.

If you also have high primers from not seating them adequately, that can add to OAL measured either way, but that is a different issue to address. How are you priming your cases?

S&B brass tend to have very tight primer pockets. If you have any primers that aren't at least flush (at the very least) you need to address this.

pathdoc · March 10, 2013, 06:37 PM

S&B brass tend to have very tight primer pockets.

Aha, so it's not just me, then.

sodak54 · March 10, 2013, 07:00 PM

I am measuring oal from the tip, not sure how to measure ogive?
The primer is definitely seated below the shoulder.
I just tried the sand paper again and I think i can see a raised area around the primer pocket.
I'm not sure the brass even had a crimp to remove or if the pockets were just tight, once the primer started it went in fine without swaging, it just didn't seem right that it hung up right at the entrance but I had no trouble pushing them in with a hand primer. The funny thing is they still hung up even after swaging, only not as frequent or as much.

Lucas McCain · March 10, 2013, 08:13 PM

issue 1; OAL is the measurement you use to make sure the cartridge can fit in the magazine and feed properly. This measured from the tip of the bullet to the back of the cartridge case. Please note that all bullets from the same box may show a slight variation and when the seater contacts the bullet it is generally indexing on the ogive or close to it.
Issue 2; The ogive on the bullet is part way between the point and the base of the bullet on the curved portion of it. At this point the diameter of the bullet is the same as the distance between the top pf the rifling lands. Measuring the cartridge from the back of the case to the ogive is commonly called seating depth a,d a bullet comparator is needed to get this measurement. This measurement is used to seat the bullet close to the rifling in the throat of the rifle and help control how far the bullet initially moves before it comes in contact with the rifling. It has an effect on pressures and accuracy of the rifle. Each rifle is different and requires experimentation during load development. A bullet seating tool is required to determine how much free bore the chamber has.
Issue3; The depth that the primer is seated. Any protrusion of the primer will cause the above 2 dimension to be incorrect. Also if the primer is protruding you will have trouble closing the action because that protrusion is interferring with the head space.

ScottRiqui · March 11, 2013, 07:48 AM

Be careful you're not swaging too much. Since swaging doesn't remove any material, that displaced brass has to go somewhere.

When I first started using my Dillon swager, I set it so that it removed *all* traces of the crimp. The swaged cases looked beautiful, but then I had problems with cases not wanting to go into the shell holder, and if I set a swaged case upright on a sheet of glass, I could watch it "wobble". I even had a few primers pop out upon firing.

Now, I just swage enough to barely round off the edge of the primer pocket. The metal surrounding the pocket stays flat, and the cases don't hang up in the shell holder.

Bart B. · March 11, 2013, 08:19 AM

sodak54, the biggest cause of cartridge over all length (OAL) is bullet ogive shape. Even a production lot from the same set of forming dies, there'll be a couple thousandths spread in the ogive dimensions. That's caused by the lead core and jacket metal properties, dimensions and lube used in the process. So where that bullet contacts the seater stem will have dimensional issues with OAL. And hollow point shapes are not all exactly the same, either, so they'll make a tiny difference.

There's also a difference in the distance between a rimless bottleneck case shoulder and the bullet tip. As the distance between case head and case shoulder vary across a batch of full length sized reloads, the distance from case shoulder to bullet tip will vary by at least that amount; even with OAL being the same across all cases. This is the dimension that causes the greatest spread in the distance bullets jump to the rifling. Rimless bottleneck case shoulders are hard against the chamber shoulder when fired.

BoogieMan · March 11, 2013, 09:33 AM

You have a max variation from standard of .005". If everything else looks good, dont worry about it.

jlcrss · March 11, 2013, 11:56 AM

This is all new to me. I thought COAL was the tip of the bullet to the bottom of the case. I just measured a hornady round that I have downstairs and its close to 2.8 approximately. If I don't factor the ogive its gonna be shorter than what its supposed to be correct?

ScottRiqui · March 11, 2013, 12:05 PM

Quote:

This is all new to me. I thought COAL was the tip of the bullet to the bottom of the case.

You're right - It is from the tip to the base - that's why it's called "Cartridge OVERALL Length".

Measuring to the ogive is important if you're trying to consistently get the same gap from the bullet to the rifling, but any time you see a COAL figure, it's from the base to the tip, or at least it should be.

jlcrss · March 11, 2013, 12:44 PM

Awesome thanks for clearing that up.

Bart B. · March 11, 2013, 01:31 PM

ScottRiqui, one must measure from case shoulder to ogive reference diameter to ensure bullet jump to the rifling's the same for each round.

As rimless bottleneck cartridges have a small spread in head-to-shoulder dimension and the shoulder's hard against the chamber shoulder when fired, the gap between the bolt face and case head (called head clearance) will vary by that amount. So, the case heads across a batch of ammo will all have a few thousandths spread in head clearance when they're fired. That dimension's transferred to the seated bullet held in the case neck.

sodak54 · March 11, 2013, 01:53 PM

I'm fairly sure that my issue is over-swaging as I said earlier I don't think the S & B brass ever had a crimped primer, I sure can't see it if it did. I think the primer pocket is just very tight and when the primer starts its metal on metal, once it starts into the pocket it goes in fine, its just getting it started initially. So I'm not sure what I'll do with the 2-3,000 other S&B brass I have but next time I'll figure out the primer issue before I trim and prep them :-)
I have my fingers crossed that my bolt will close what I have but like Scott said above, when I put them on a flat surface the wobble for a couple seconds.

ScottRiqui · March 11, 2013, 01:55 PM

Bart,

I agree - I was just letting jlcrss know that his confusion was justified. Unless a specified dimension is measured from base-to-tip, it shouldn't be called "COL" or "COAL".

March 10, 2013, 05:42 PM	#1
sodak54 Junior Member Join Date: February 25, 2012 Location: Pierre, SD Posts: 14	Consistent seating depth Having trouble getting consistent coal, loading .223 rem in s&b brass. My oal goes from 2.197 to 2.205, i am shooting for 2.20. I'm thinking it has to do with swaging the primer pocket (rcbs second gen). Could it be a bulge so to speak on the face of the casing? I can't see anything but the case doesnt seem to sit perfectly when stood up on a flat surface. Tried some sandpaper but really can't see anything. Anyone have a thought?

March 10, 2013, 05:58 PM	#2
Lucas McCain Senior Member Join Date: March 7, 2013 Location: Callaway, MN Posts: 361	The primer should be about > .005 thou below the primer pocket. You may have to prep your cases with a primer pocket uniforming tool. __________________ If you have time to do it twice, then you have time to do it once right and put your name on it

March 10, 2013, 08:13 PM	#6
Lucas McCain Senior Member Join Date: March 7, 2013 Location: Callaway, MN Posts: 361	Oal problems issue 1; OAL is the measurement you use to make sure the cartridge can fit in the magazine and feed properly. This measured from the tip of the bullet to the back of the cartridge case. Please note that all bullets from the same box may show a slight variation and when the seater contacts the bullet it is generally indexing on the ogive or close to it. Issue 2; The ogive on the bullet is part way between the point and the base of the bullet on the curved portion of it. At this point the diameter of the bullet is the same as the distance between the top pf the rifling lands. Measuring the cartridge from the back of the case to the ogive is commonly called seating depth a,d a bullet comparator is needed to get this measurement. This measurement is used to seat the bullet close to the rifling in the throat of the rifle and help control how far the bullet initially moves before it comes in contact with the rifling. It has an effect on pressures and accuracy of the rifle. Each rifle is different and requires experimentation during load development. A bullet seating tool is required to determine how much free bore the chamber has. Issue3; The depth that the primer is seated. Any protrusion of the primer will cause the above 2 dimension to be incorrect. Also if the primer is protruding you will have trouble closing the action because that protrusion is interferring with the head space. __________________ If you have time to do it twice, then you have time to do it once right and put your name on it

March 11, 2013, 09:33 AM	#9
BoogieMan Senior Member Join Date: April 4, 2012 Location: South Jersey Posts: 2,217	You have a max variation from standard of .005". If everything else looks good, dont worry about it. __________________ Concentrated power is not rendered harmless by the good intentions of those who create it. Milton Freidman "If you find yourself in a fair fight,,, Your tactics suck"- Unknown

March 10, 2013, 06:37 PM	#4
pathdoc Senior Member Join Date: February 12, 2013 Posts: 669	S&B brass tend to have very tight primer pockets. Aha, so it's not just me, then.

March 10, 2013, 07:00 PM	#5
sodak54 Junior Member Join Date: February 25, 2012 Location: Pierre, SD Posts: 14	I am measuring oal from the tip, not sure how to measure ogive? The primer is definitely seated below the shoulder. I just tried the sand paper again and I think i can see a raised area around the primer pocket. I'm not sure the brass even had a crimp to remove or if the pockets were just tight, once the primer started it went in fine without swaging, it just didn't seem right that it hung up right at the entrance but I had no trouble pushing them in with a hand primer. The funny thing is they still hung up even after swaging, only not as frequent or as much.

March 11, 2013, 07:48 AM	#7
ScottRiqui Senior Member Join Date: January 27, 2010 Location: Norfolk, VA Posts: 2,905	Be careful you're not swaging too much. Since swaging doesn't remove any material, that displaced brass has to go somewhere. When I first started using my Dillon swager, I set it so that it removed all traces of the crimp. The swaged cases looked beautiful, but then I had problems with cases not wanting to go into the shell holder, and if I set a swaged case upright on a sheet of glass, I could watch it "wobble". I even had a few primers pop out upon firing. Now, I just swage enough to barely round off the edge of the primer pocket. The metal surrounding the pocket stays flat, and the cases don't hang up in the shell holder.

March 11, 2013, 08:19 AM	#8
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	sodak54, the biggest cause of cartridge over all length (OAL) is bullet ogive shape. Even a production lot from the same set of forming dies, there'll be a couple thousandths spread in the ogive dimensions. That's caused by the lead core and jacket metal properties, dimensions and lube used in the process. So where that bullet contacts the seater stem will have dimensional issues with OAL. And hollow point shapes are not all exactly the same, either, so they'll make a tiny difference. There's also a difference in the distance between a rimless bottleneck case shoulder and the bullet tip. As the distance between case head and case shoulder vary across a batch of full length sized reloads, the distance from case shoulder to bullet tip will vary by at least that amount; even with OAL being the same across all cases. This is the dimension that causes the greatest spread in the distance bullets jump to the rifling. Rimless bottleneck case shoulders are hard against the chamber shoulder when fired.

March 11, 2013, 11:56 AM	#10
jlcrss Member Join Date: March 7, 2013 Location: Lansing, MI Posts: 20	This is all new to me. I thought COAL was the tip of the bullet to the bottom of the case. I just measured a hornady round that I have downstairs and its close to 2.8 approximately. If I don't factor the ogive its gonna be shorter than what its supposed to be correct?

March 11, 2013, 12:44 PM	#12
jlcrss Member Join Date: March 7, 2013 Location: Lansing, MI Posts: 20	Awesome thanks for clearing that up.

March 11, 2013, 01:31 PM	#13
Bart B. Senior Member Join Date: February 15, 2009 Posts: 8,927	ScottRiqui, one must measure from case shoulder to ogive reference diameter to ensure bullet jump to the rifling's the same for each round. As rimless bottleneck cartridges have a small spread in head-to-shoulder dimension and the shoulder's hard against the chamber shoulder when fired, the gap between the bolt face and case head (called head clearance) will vary by that amount. So, the case heads across a batch of ammo will all have a few thousandths spread in head clearance when they're fired. That dimension's transferred to the seated bullet held in the case neck.

March 11, 2013, 01:53 PM	#14
sodak54 Junior Member Join Date: February 25, 2012 Location: Pierre, SD Posts: 14	I'm fairly sure that my issue is over-swaging as I said earlier I don't think the S & B brass ever had a crimped primer, I sure can't see it if it did. I think the primer pocket is just very tight and when the primer starts its metal on metal, once it starts into the pocket it goes in fine, its just getting it started initially. So I'm not sure what I'll do with the 2-3,000 other S&B brass I have but next time I'll figure out the primer issue before I trim and prep them :-) I have my fingers crossed that my bolt will close what I have but like Scott said above, when I put them on a flat surface the wobble for a couple seconds.

March 11, 2013, 01:55 PM	#15
ScottRiqui Senior Member Join Date: January 27, 2010 Location: Norfolk, VA Posts: 2,905	Bart, I agree - I was just letting jlcrss know that his confusion was justified. Unless a specified dimension is measured from base-to-tip, it shouldn't be called "COL" or "COAL".