Runout on brass after fired?

[Bradsb]

I am very new to BR shooting and learning as I go so please be patient with me.

Does anyone check their brass for runout after it's fired? I have been having problems with the concentricity of my loaded rounds for my 30BR. The best I can get is about .002 and some are as bad as .005. I started checking my brass at every stage of the reloading process and after I fire them all of my brass come right out of the chamber with about .002 runout. I think this is the where my problem starts. Has anyone else experienced this and is there anything I can do to improve it?

The gun is a 30BR with a Batt action and Krieger barrel, .330 neck and 250 rounds down the pipe. Brass is Lapua turned by Hoehn to .0098 and fired three times. All measurements are taken on a Sinclair concentricity gauge.

Just to make sure that I was not the problem I checked the runout on fired brass out of my PPC and they roll almost perfect. Loaded PPC rounds are almost all less than .002.

Any ideas on where I should go from here would be very appreciated.

 

[Shynloco]

Brad,
I'm no expert on this one, but why would you want to check your brass AFTER you've shot it? What is important is the concentricity of the casing after you've Full Length resized it and then again of the bullet runout once the entire cartridge is loaded. As you might know, the casing itself goes through an immediate expansion and contraction (to some degree) when the round is fired and that casing must be returned to it's original state (for ultimate accuracy usually for precision type shooting) which is done during the resizing process. For instance, if you measure the shoulders for a normal casing, you'll find that those shoulder have moved some .002 - .004 (depending on how tight or loose your chamber is). when that casing was fired. Again the resizing process takes those shoulders back to the orignal shoulder setting (the amount is set by how your FL Die is setup) so the bolt closes easily and without any resistance. But once those shoulder go too far, if not resized, you might reach a point where even the bolt won't close. That is why I measure each and every shoulder on the fired brass, but rely on my FL Die to resize the entire body of the fired casing. And from everything I've always been told and read about, a runout of .002 is your goal in any reloads. Anything better is just gravy, although some guys who use the "precision reloading" method strive for no more than .001 runout and those guys also usual have very closely cut FL Dies that match the chamber on their rifles.

Hope answer helps some.

 

[Steve Blair]

Significant case wall thickness variation can cause cases to "banana" when fired. No amount of sizing will completely remove the distortion. Creighton Audette demonstrated this problem many years ago. The solution is to measure case wall variation and sort those that exceed the significance threshold. I sort to .002" TIR, other folks use .003". Anything more than that is guaranteed to affect concentricity and point of impact.

 

[bozo699]

Brad,
I see your worries and disagree with some on this, I would be extremely worried if I measured .002 runout when I checked a fired case out of one of my match chambers.
I would only hope your smith cut a better chamber then that so with that said I would think as sleepygator said you have neck wall variations in your brass. with a good quality ball mic check your neck wall thickness, mark your case like a cut up pizza with a felt marker and measure each mark several times and write it down to see if you are measuring it correctly and consistently. The brass should come out of your chamber as about as perfect as your going to see it until the next time it's fired, if you have .002 out of the chamber I would imagine your seeing some .004-.005 out of spec once you have it loaded, ah,...I re-read your post and yes as bad as .005. Do you have a inside neck reamer? you mat need some new brass and some more tools if not. Your neck clearance may be more then you want but if your able to inside ream you may be able to fix the problem.
Wayne.

 

[kelbro]

Agree with Wayne. When I check runout after firing and before sizing, I expect to see almost none. What better baseline to gauge the quality of your dies?

 

[Bradsb]

Thanks to everyone that replied.
Synloco, I started to check runout on fired brass after I was having problems with the runout on loaded rounds. I started to check everything trying to figure how I could improve my runout on loaded rounds to get to that .002 or under. I concluded that it is nearly impossible achieve loaded rounds with low runout when the neck wasn't straight to start with.

Sleepygator and bozo699 I do have a mitutoyo ball mic and had previously checked a few cases ton the neck and all were very close to the .0098 in three places. I just got done checking 20 more out of 100 in four places on the neck, all were very consistant anywhere I checked. I do not have a neck reamer so that may be a next purchase on my list.

Sleepygator, how do I go about checking the case wall itself? My 1 inch ball mic doesn't seem to measure the actual case wall thickness very well.

And just to satisfy my curiosity I also checked runout of fired cases on my PPC as well as two of my factory hunting rifles. The PPC was almost perfect and the hunting rifles were both less than .0001 on brass that was fired months ago. Even the winchester brass (not turned) had very little runout after fired even though the neck walls were inconsistent.

I'm thinking I may have to try a different lot of brass and see if I get the same results.

 

[bozo699]

Thanks to everyone that replied.
Synloco, I started to check runout on fired brass after I was having problems with the runout on loaded rounds. I started to check everything trying to figure how I could improve my runout on loaded rounds to get to that .002 or under. I concluded that it is nearly impossible achieve loaded rounds with low runout when the neck wasn't straight to start with.

Sleepygator and bozo699 I do have a mitutoyo ball mic and had previously checked a few cases ton the neck and all were very close to the .0098 in three places. I just got done checking 20 more out of 100 in four places on the neck, all were very consistant anywhere I checked. I do not have a neck reamer so that may be a next purchase on my list.

Sleepygator, how do I go about checking the case wall itself? My 1 inch ball mic doesn't seem to measure the actual case wall thickness very well.

And just to satisfy my curiosity I also checked runout of fired cases on my PPC as well as two of my factory hunting rifles. The PPC was almost perfect and the hunting rifles were both less than .0001 on brass that was fired months ago. Even the winchester brass (not turned) had very little runout after fired even though the neck walls were inconsistent.

I'm thinking I may have to try a different lot of brass and see if I get the same results.

That is because the inconsistencies are pushed to the inside of the neck when fired, that is why I said you should have almost zero runout on fired brass, you may have to have your chamber checked, do you have the means to turn a new piece of brass and firing it in your chamber a couple of times and then check to see what the runout is?
Wayne.

 

[Steve Blair]

Sleepygator, how do I go about checking the case wall itself? My 1 inch ball mic doesn't seem to measure the actual case wall thickness very well.

I use a Neco Gauge, a derivative of the original Audette Gauge. [br]
http://www.neconos.com/category/Concentricity-Wall-Thickness--Run-out-Gauge-10 [br]
I happen to be sorting some 6mm Remington tonight and shot the two attached images. Neco_1 shows the mandrel that goes inside the case to a point ~.20-.25 above the case head. The case mouth fits over the appropriate step on the mandrel to the left. Note that the wiggler gauge is directly above the mandrel portion that contacts the inside case wall. Neco_2 shows a 6mm case in position and displaying slightly less than .0015 runout, a keeper. The case is rotated around the neck mandrel while keeping a light load against the internal mandrel and a bias to the left. Some folks invert this arrangement but I find the overhead approach works best for me. The measurement is repeatable and accurate after some "feel" is developed.

 

[markm87]

Brad,
I'm no expert on this one, but why would you want to check your brass AFTER you've shot it?

Because we're nuts. I've checked it too, and there should be none. I've checked runout every step of the way to see where it starts, where it's worse, etc.

 

[benjamin199]

I am thinking if all of your brass has about .002 runout after being fired and it is consistant, it is probably not the brass. Lapua brass is my favorite, but it is not super uniform I think the chances of all the brass having the same thickness variations would be very remote. I would expect some to come out very good, and others to show runout if it were a brass issue. I would be leaning toward the chamber causing your problem. You may be able to check this by marking some cases and inserting them into the chamber with the mark in the same orientation then shooting them. If the Runout is in a consistant location with regards to the marks on your case I would say your chamber may not be square.
Just my 2 cents worth.
Good luck.
Ben

 

[Shynloco]

Guys,
Let me ask you shooters who do measure the runout of their casings AFTER firing which as you have written should all the be the same. Are you guys talking about a "dedicated" chamber where the chambers of your rifles and dies have been cut to match? Though I tried to qualify my comments in the last line, a runout of .002 on casings shot in a general production chamber as opposed to a "dedicated" custom chamber rig, is acceptable. Now like bozo699 said, I too would be pissed if my Lapua brass showed a variance in runout of a fired casing having been fired in a custom chamber. But please clarify this issue because I perhaps made a bad assumption of the comment that was posted regarding use of what I thought was a general production rig, such as a Savage Model 12 Benchrest Target Series rifle, that I shoot. I can definitely see the issue of a fired casing showing a run-out difference as a concern (as another variable) if I were shooting a custom built target rig. Thx.

Alex

 

[Bradsb]

Thanks again to all who gave me some ideas.

This weekend I plan to shoot some more and I will turn some of my own brass from a different lot and see if my results are any different. At that point I think I will mark the brass and see if they come out with the runout in the same orientation. (thanks Ben)
I have contacted the gunsmith who built the rifle and he basically told me that my problems have to be a result of something that I am doing wrong. And while that is entirely possible what I wanted was info on what to check. I can't fix what I don't know!!
Another smith I have talked to has given me very good information and has given me a good checklist of things to try. He also said if I still can't find the problem to bring the rifle to him and we can check it over and find the cause of the issues I am having. I guess you get what you pay for with customer service as well as quality of work

Brad.

 

[bozo699]

Thanks again to all who gave me some ideas.

This weekend I plan to shoot some more and I will turn some of my own brass from a different lot and see if my results are any different. At that point I think I will mark the brass and see if they come out with the runout in the same orientation. (thanks Ben)
I have contacted the gunsmith who built the rifle and he basically told me that my problems have to be a result of something that I am doing wrong. And while that is entirely possible what I wanted was info on what to check. I can't fix what I don't know!!
Another smith I have talked to has given me very good information and has given me a good checklist of things to try. He also said if I still can't find the problem to bring the rifle to him and we can check it over and find the cause of the issues I am having. I guess you get what you pay for with customer service as well as quality of work

Brad.

Brad,
All good ideas but only turn maybe 3 or 5 at the most of your expensive brass to test, I sure hope it is your brass that would be the cheapest fix, unless you have a lot of them.
Wayne.

 

[Elkbane]

Another thing to check.......a long shot, but cheap to check.

It could be that your bolt face is not square to the chamber. Easy to check. We usually take this for granted.......

On my concentricity guage, the three index points are the two v-grooves the case body rests in and the pin/peg the casehead rests against. If your case head is not square, when you rotate the brass you will geat a slight forward/backward action which could indicate on the case neck as runout. To check, smear some lipstick or grease on the case head uniformly, put the case in the concentricity guage and make a full rotation. If the casehead is not square there will be a spot where the grease/lipstick is unbelmished.....

Think about it. If the high spot is at 12:00 or 6:00, it will contact the pin (either on the bottom or top). At 3:00 and 9:00 you'll have full contact on the pin on both sides. A low spot will never contact the pin if the pin is longer than the casehead diameter. The fix would be to face off the bolt to square - easier than replacing or setting back and recutting a chamber.
Elkbane

 

[Bradsb]

Thanks Wayne,

I planed on turning some more brass anyway. I have another 30BR that should be done in a couple months this one will be a LV the one that I am currently working with is a HV. I will just use the brass that is for the new rifle. And I am hoping for brass problems as well. The last thing I want to do is have to make the HV a LV with a new chamber and crown!!!!

Brad

 

[Bradsb]

Thanks Elkbane,

I will look at that and try it tonight although I don't think that is a problem because I have a PPC barrel for this rifle and those cases come out nearly perfect and I would think that if the boltface were a problem I would have noticed it on the fired PPC brass.

Brad

 

[bozo699]

Thanks Elkbane,

I will look at that and try it tonight although I don't think that is a problem because I have a PPC barrel for this rifle and those cases come out nearly perfect and I would think that if the boltface were a problem I would have noticed it on the fired PPC brass.

Brad

Not to knock elkbanes theory and I am not as I haven't actually tried that but in theory all that should do is make the brass go back and forth not up and down, which if your indicator was right where your bushing stops sizing the case then I could see a variance problem but you should be checking towards the mouth of the case not down by the n/k shoulder junction.
Wayne.