Reply with quote #1
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.
Reply with quote #2
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
Reply with quote #3
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.
Reply with quote #4
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.
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.
Reply with quote #5
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.
Reply with quote #6
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?
Reply with quote #7
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.
Reply with quote #8
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