Small bulge in 30-06 brass

[pyrolater]

I know 6mmbr is more of a precision shooting kind of place and my question pertains to a deer rifle but I figured I would get some good info here.

I have a 1956 vintage Winchester model 70 in 30-06. I shot some Federal 150 grain ammo and some Winchester 150 grain ammo through it. I wanted to reload the brass for the Model 70 and for highpower in my M1 so I tumbled, polished, sized trimmed and all that. When I was getting ready to actually put powder and a bullet in the brass I noticed a slight bulge at the bottom of the case. If any one is familiar with the bulge you get with 40 S&W the bulge on the 30-06 brass is pretty similar.

It looks like all the brass shot out of that rifle has that little bulge. If you have a nice clean case and hold it under a desk lamp and turn the brass in your hand you can see the case is just slightly deformed mostly on one side or about a third the way around just above or right even with the web.

My question is: what the heck would cause that?

I have no signs of over pressure. The rifle came to me used but looks like it has not been shot very much. I get about an inch and a quarter or so groups with it.

I really wanted to reload the brass that went through that rifle but I’m afraid if I reload brass with a bulge in it the brass has already been weakened and If I make up a nice concentric round as soon as I stuff one in the chamber the round will be out of alignment.

Any suggestions?

 

[Johnboy]

it may be a bad batch of brass.but from what you have said it sounds like a pressure sign that will lead to case separation.take a paper clip and straighten it out and put a bend in it.just about 1/4 of an inch at a 90 degree.then run it down the case from the inside of the case.if there is an inside crack in the case at the spot you can see from the outside of the case.then don't reload it.another thing you can do is waste a case by cutting it open and looking at the bulge area.the safest way of doing this is to open it up with a milling machine just by removeing away half a the case.but not the half you want to look at.hope this helps.Johnboy

 

[Steve Blair]

You probably have an oversize chamber. The brass tends to lie at the chamber bottom and bulge upwards.

I bought a 1958 Winchester Model 70 in .30-'06 that had an oversize chamber. It would fire OK and had reasonable accuracy but would bulge the cases like an M60. They would resize only with effort and have a frosty appearance after sizing. I took the rifle to a gunsmith and was told the chamber was oversize.

Measure a fired case against a chamber drawing and I think you will find the body dimension is over spec.

 

[GermanS1]

In my experience, that small bulge is very common, even in perfect match chambers. It is caused by the varying thickness of the case wall which causes the case to stretch in the direction of it's own thin side when fired. My article about case wall concentricity here covers that topic.

http://riflemansjournal.blogspot.com/2009/07/reloading-audette-neco-case-checker.html

The bulge itself doesn't appear to cause any harm and it is lower on the case body than the line at which cases will separate from excessive sizing.

 

[Steve Blair]

Mr. Salazar is likely correct. My Model 70 did not show what could be described as a small bulge and it covered about 270 degrees on the case. The chamber cast was clearly oversize and the bulge evident from the first shot. It was, however, always oriented to the chamber top.

Not all chambers show the effect. I have a 6mm Remington 40-X with a tight chamber that displays no bulging at all. The chamber was cut with a custom-ground reamer that was also used to create the sizing and seating dies. No expansion forward of the web is evident, even under magnification. One lot of Remington brass would not chamber in the rifle until sized. This would not be a good choice for either a match or hunting rifle but has been very effective on San Diego crows.

 

[pyrolater]

How common is this??

If the bulge is a normal thing how will that effect my reloads? If I make up a nicely aligned round wont the bullet go in the barrel crooked if the bulge pushes everything to one side when the round is chambered?


Is there a resizing die that will resize all the way down to the base of the brass to get rid of the bulge?

 

[GermanS1]

How common is it? 100% - but in many cases it's hard to detect because it can be very small. The magnitude of the bump depends on the magnitude of the case wall runout, so the better the brass, the smaller the bump. Almost any die will size down in that area but what we're dealing with is the springiness of brass and that's why it pops back, the brass is somewhat banana shaped due to case wall eccentricity and you can't get rid of it.

The good news is that you can minimize the effect by orienting the thin spot to align with one of the locking lugs as I described in the article. This is one of those small details that most people overlook and can be a source of improvement by minimizing random error. The effect is small, however. By deliberately orienting the worst bump I could find to the worst orientation,90 degrees from the lugs) I shot a wide 10 at 500 yards when the properly oriented cases shot center X's. For Garand shooting, I wouldn't have any concerns about it.

 

[pyrolater]

I read the article and it all made sense. I'll try loading the bulge in line with a lug.

It just seems to me that there shouldn't be any bulge and that after the case is fire formed it should be as round as the chamber. I get really anal about this stuff and I can drive my self crazy. ,Short trip)

I'll just have to accept an imperfect case and deal with it.

Thanks for the info

David

 

[Innovative]

Pyrolater .........

I've seen bulged cases caused by shooters that don't measure their headspace,at the shoulder). If you adjust your resizing die,according to the instructions) it's possible to push the shoulder back too far. The shoulder does need to be pushed back, but no more than -.002' at the most.

When it gets pushed back more than that, the case stretches to fill the chamber when it's fired. This thins the brass just above the web of the case. Your case then bulges when ANY downward pressure is applied during reloading. I suggest measuring your headspace, and setting the height of your resizing die accurately.

- Innovative

 

[pyrolater]

This brass is new federal and Winchester brass. Its only been fired one time and then prepped. I noticed the bulge before I had a chance to reload the brass and fire it a second time.

The only way I can check the chamber size is to go off of the fired brass. I try to just bump the shoulder bank a few thousandths. I'm using a Stony point head and shoulder gauge

 

[Innovative]

Pyrolater .........

I assume you're using a good FL die, and it sounds like you're watching your headspace. I have seen chambers with huge body diameter, and they will leave your brass looking bulged no matter what you do. I've also seen brass with undersize case heads,this is very rare), but it has the same effect. Compare the case diameter of different brands of brass,at the web), and see if they all measure the same.

- Innovative

 

[pyrolater]

My chamber could be huge but I won't be able to check that until tomorrow.

I'm using a Hornady resizing die so I don't think thats a problem. I'm going to some comparative measuring between new factory ammo, once shot brass and SAMMI specs.

I'm also going to fire off a couple of rounds in the morning. I got a few ideas for Germans1 so I'm going to mark my shells on the base and try and orientate the marks to 1200 and see if the bulge appears in the same or different spots.

Not sure what that will tell me just yet but I'm sure it will mean something.

 

[Innovative]

pyrolater .....

Check out this new tool for measuring different locations on a tapered case. Visit www.larrywillis.com

- Innovative

 

[BoydAllen]

Your cases are not the same thickness all the way around. The thinner part yields under pressure more than the thicker, giving the asymmetrical bulge. One of the reason that some target shooters use some brands of foreign brass, Lapua, RWS, Norma) is that they have superior uniformity in thickness around the case. To sort new brass NECO sells a concentricity gauge that can be set up to measure case thickness near the back of the case. For once fired brass, you can visually sort by picking cases that have the most symmetrical expansion at the back. Before you do anything too radical or expensive, you should do a blind test with your best and worst cases, to see if there is a problem that you can see on the target. If there is not, don't worry about it. Things that matter for highly accurate Benchrest rifles may get lost in the noise on a factory or military rifle.

 

[Innovative]

I agree with Boyd. Too many shooters worry about things that only apply to the needs of benchrest shooters, with no benefit at all to hunting rifles. If your rounds don't chamber properly that's a different matter.

RCBS also makes a handy case measuring tool - the Case Master. It serves several different measuring jobs, including measuring brass thickness all the way back to the web. That's a very useful tool for any handloader.

- Innovative

 

[pyrolater]

I agree with Boyd. Too many shooters worry about things that only apply to the needs of benchrest shooters, with no benefit at all to hunting rifles. If your rounds don't chamber properly that's a different matter.

I agree with Boyd too and with what Germans1 said but now I want to know more about whats going on inside the chamber. I can get pretty anal about this stuff. In this rifle none of this may really matter in the long run but like most of you guys I'd like to get some smaller groups. It seems most of you guys know more than me so thats why I find this 'problem' so interesting.

I figure all this info will carry over to my next rifle which will most likely be some sort of tactical/F class/Highpower/bechrest type of rifle. Uh Oh, I may need more than one more new gun.

Being able to just look a the brass and see a bulge should make the 'trouble shooting' or figuring out whats causing what easier to do now that I have an idea of what to look for.

When I do get something that shoots little bitty groups I think I'll be a head of the game when I reload for an accurate gun.

 

[BoydAllen]

If you want to shoot smaller groups, make sure that you have something,actually, several things) in front of you, so that you can see what the wind is doing. Also, don't bother with the old 'I only shoot when the wind is not blowing' thing. Wilbur Harris answered that best when he said that it is amazing how just setting up a few wind flags can make the wind start to blow. It's not all the rifle and the load. Also, there are some basic mistakes in rest setups that I see almost every time that I go to the range. The rifle needs to be supported in the right places, be able to slide easily, and be stable enough, on the bags, that holding it perfectly still is not a big issue.

 

[pyrolater]

I have a Lead Sled and I put a small towel in the butt rest to help cusion the rifle and it also helps to steady it some.

When I shoot for groups I like multiple 5 shot groups and I don't worry about the wind to much. First thing in the morning around 0700 on a nice calm day I feel the wind isn't really an issue out to 300 yards. The range is up against a hill with berms on both sides so is kinda protected

If I can get an inch moa with my AR and an inch and a half moa with my 06 I think thats about as good as those guns are going to shoot., factory ammo with the 06)

I have an Fulton Armory Titan,AR10) heavy barrel I still need to break in so I don't know what that gun will do yet but I think all this brass/ammo info will help me with the 308 too.

 

[pyrolater]

I finally got out to shot a few rounds and this is what I found.

I marked 5 rounds with a sharpie where it says FC on the Base of the case and orientated the mark to the 12 o’clock position. If it moved when I closed the bolt I don’t know It sorta looked like the bulge developed in the same general direction. ( this is assuming the cases are drawn and stamped at the same time and any weakness would be on the same side or the chamber is over sized on one side ) Nothing conclusive,


Once shot brass diameter measured just up from the base of the case by the bulge is about 5 thousands over factory brass diameter

Head space on once fire brass was also about 5 thousands longer than factory brass.

The Bulge as best as I can tell is only about 1 to 2 thousands high. I did a little filing on my Sinclair run out gauge so the 30-06 brass would fit on it back wards. Any way I ran the gauge length wise over the case and my best guess is the so called bulge is only a .001 or .002 high.

I do not have the equipment to check the in side of the case.

I’m not sure what this is telling me other than I got a little bitty bulge on the side of the case. Next question is how will that little bulge affect the accuracy of my reloads??

The bullet be slightly of center when I use this brass but how much difference will that make?

Last but not least the LC brass I shot shows no signs of any deformities.