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New Reloader Questions Regarding Headspace and Pressure

 
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  #1  
Old 01-16-2006, 01:55 AM
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New Reloader Questions Regarding Headspace and Pressure

The following pictures are of once fired brass from factory Black Hills 165 gr BTSP Match ammo, fired in a Tikka M595 Master Sporter in 308.












If you look closely at the pictures you can see a slight bulge or ring just above the case head (I think). Also, I am new to reloading but, the primer looks flat to me. These are factory loads out of a factory match chamber. I have shot 240 rounds of this ammo and every piece of brass looks the same. The 'ring' marks were definately not there before the brass was fired. They were also not visible on the once fired Federal GMM brass. There were no problems with a sticky bolt handle. No apparent accuracy issues (printed between 0.25 and 1.0 inches at 100 yards with about 0.60 as the average). No problems chambering the fired brass in my rifle at all. I took a metal clothes hanger wire and sharpened it with a dremmel tool and bent the last 1/8 inch of the hanger 90 degrees and ran it down the inside wall of the case and didn't feel any obvious hang-ups. Before I thought much about this I had already case prepped 200 rounds of the ammo (flash hole deburred, cleaned,neck sized, trimmed, weighed and sorted, primer pockets cleaned) so unless it is necessary, I don't want to just throw the brass out, but will do so if necessary for safety.

Additionally, when I started to prime the brass with Fed 210M primers it seemed like I had to exert more pressure than usual to seat the primers (remember though that I am new to this). When the primers felt like they had bottomed out they appeared to be (felt) slightly high in the pocket. When I applied substantially more pressure, I was able to get them to fit flush.

If anyone feels like pitching in and helping me out, here are some of my many questions:

1) Could this indicate a potential headspace problem with my rifle? Brass stretching and thinning above the matrix?

2) Could these BHA factory loads be 'hot' in my rifle for some reason?

3) Do I need to chuck this brass and start over with something else?

4) Does the primer look flat to anyone else, or am I just looking at it all wrong?

5) Will applying enough force with the priming tool to seat the primers flush (beyond where they seemed to bottom out) cause accuracy/reliability/safety issues?

6) What else can I do about the primers? Leave them slightly high where they bottom out in the pocket? try different primers? Use a primer pocket uniforming tool (already ordered the Sinclair tool)?

7) Am I worrying about nothing?

8) Anything else I should be aware of?

I appreciate the help in answering some or all of these questions.
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  #2  
Old 01-16-2006, 09:08 PM
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Re: New Reloader Questions Regarding Headspace and Pressure

IIRC, BH uses Winchester at least for their .308. Winchester .308 brass tends to be kind of thin and undersized.... if you measure the web area on an unfired case I'm guessing it probably measures somewhere around .463-.465"... unfired Lapua brass measures more in the .468-.469 region. I think the SAAMI spec measurement for your chamber is somewhere around .470", though it could be slightly bigger (measure your fired cases to get an idea). So in closing, no, I don't think there's anything wrong w/ your brass just because it has a little bulge there... it's just an artifact of the kind of brass being used and the plus/minus tolerances involved. FWIW, Winchester brass shoots just fine even w/ the bulge, and lasts a good while... maybe not as long as Lapua, but it costs about 1/2 as much or less.

HTH,

Monte
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  #3  
Old 01-16-2006, 09:24 PM
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Re: New Reloader Questions Regarding Headspace and Pressure

The same thing happens in my factory Rem 700 308, as well as 4ked Horn's factory Rem 700 308. 4ked asked about this a while ago and the consensus was that the factory rams the reamer into the barrel at Mach 3 and it is just the sloppy factory chambering that is causes this. Who knows how many barrels were reamed before your barrel.

The primers look like they just conformed to the bolt face, but in my rifles, all primers look like that. I figure as long as there is no primer flow or piercings then all is well.
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Old 01-16-2006, 09:48 PM
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Re: New Reloader Questions Regarding Headspace and Pressure

I'd pick your #7 and give you very high marks for your concern. You're asking all of the right questions and getting some good answers.

Flat looking primers are difficult to judge as some manufacturer's primers are softer than others. You mentioned that you had no extraction problems which is a better indication of pressures.

Createring on the primer around the firing pin indent, of which you have none, is another indication of pressure but is dependent on fit of firing pin to firing pin hole in the bolt.

Not exactly sure of what you mean by the first part of #6? However, the primer should never (as in Never) protrude above the case head. The bolt will press it in. If the bolt 'slams' as in a semi-auto you may have a whole nother problem. Not good. Think about it.

It may be that your chamber is a bit on the large size at the back end. If you full length resize with dies that are smaller than the chamber diameter you'll work the cases a bit excessively. Just another interesting thing to learn.

You're headed in the right direction, keep on truckin'
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Old 01-16-2006, 11:04 PM
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Re: New Reloader Questions Regarding Headspace and Pressure

The look of your brass is but one indicator of what happens upon firing. The look which you are agonizing over is important, as others have pointed out... you are doing well. Could be your headspace is just a slight bit large for that particular lot of brass, NOT A PROBLEM though. As to the primer pockets being tight and sort of shallow, that's good news as to pressure signs. I use and love the sinclair tool you ordered, because I believe that accurate reloads start with evenly seated primers. never use extra force to seat primers (from an accuracy standpoint.) Saftey is of course a different issue. From the size of your groups, and your attention to detail I believe you will do very very well at shooting/reloading. Enjoy the sport.
Dave
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  #6  
Old 01-17-2006, 12:19 AM
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Re: New Reloader Questions Regarding Headspace and Pressure

Hello Fishry.
Great pics and your explanation of your questions helps tremendously to diagnose the problem.

I hate to tell you, but you have a grossly oversized chamber and undersized case heads (normal in every way for Winchester brass) and that is what is making that big bulge ahead of the web. It is not a big deal for the most part, just unsightly. The only areas where it might be detrimental to your enjoyment are these:

A badly oversized chamber will allow the thick side of your brass (which is found in every brand from Lapua down to Lake city) to grow in it's direction every time it is fireformed and can stretch the brass to the point where it can "pull" the bullet release to one side. Then the next time you fire it, the fat side might not be in the same position in relation to your chamber and it will fireform to that side and pull the bullet in another direction. The only way to get around this is to "index" the cases. I found the best way to do this is to file a small notch in the case head on the thick side of the case and make sure to put it in the chamber with that mark up or out. It doesn't really matter where the mark is just as long as it is in the same place every time you chamber the round.

I had to do this on one of my own guns and it shot fine as long as I paid attention to the mark. But after awhile, I decided to just have a reamer made to my specs for a specific kind of brass in which there would be no "bulge" or "belly out". This solved the problem entirely and was less hassle. Or, you could measure several different brands of brass and pick the one with the largest case head dimension. Each brand has a different dimension despite SAAMI specs that say they should be .473" or whatever.

Doing this will help make up the slack if you don't want to spend $200 having a reamer made and then having a good smith rechamber.


One other problem that might arise from a "bulge out" is when you go to resize. If your particular dies are on the small side in the web area and your gun is in the big side in the web, then you might have Full length resizing problems down the road. This can be remedied by having a machinist "open up" the arse end of your die to a bigger diameter. THis can usually be done for $20.



As for your q's, here we go:

Q1 answer: Doubtful. Headspace is probably ok, just the diameter of the back end of the chamber is big. Headspace mainly deals with the length of the chamber from the bolt face to the datum line. And thinning will be minimal.

Q2: answer: They are definetly not mild but appear to be ok given the details you mentioned. One thing to remember is that BH uses ball powder which is sensitive to ambient air temperature and thus must be closely watched for pressure in changing environments. If those pics are of ammo shot in January, it may be too hot for your gun in July. Watch it closely from month to month.

Q3: answer: It is up to you. It can be made to work doing what I have detailed, but you might just choose to rechamber or use bigger brass.


Q4: answer: It's flattening but not terrible.


Q5: answer: I wouldn't recommend forcing the primer in. Use a good pocket uniforming tool and everything will be perfect.


Q6: answer: If you leave the primer above flush, it will slam back against the bolt face, and if there is enough pressure present, it will open up the pocket by force. All primers actually "pop" out of the pocket under firing and are in effect re-seated into the pocket but the ammo shouldn't be overloaded too bad or pocket enlarging will result. Leaving the primer above flush is to some degree is technically safe, but has terrible effects on accuracy. I would strongly recommend seating them flush or just below flush. Make room with the uniformer.


Q7: answer: Yes and no. Just be aware of what is going on. Everything is notable even if it may appear insignificant.

Q8: answer: none that I can think of at this time. You are doing good! [img]/ubbthreads/images/graemlins/wink.gif[/img]
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  #7  
Old 01-17-2006, 01:31 AM
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Re: New Reloader Questions Regarding Headspace and Pressure

fishry, In your third & fourth photo, I can see the radius on the edge of your primers. "Flat" primers will not show this radius. Also, as stated above, no brass flow from the striker is shown. when you get a reverse crater from your striker dent, then begin to worry. Sorry for the factory oversize problems. [img]/ubbthreads/images/graemlins/frown.gif[/img]
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