Reamer sizing

Pete Wass

Pete Wass

Well-known member
If a person was going to order a reamer which would make chambers that were big enough for easy extraction but small enough to use "Off The Shelf" dies, how much bigger than the chosen case should the reamer be and what parts of the reamer should be larger?

Thanks, Pete
 
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Pete

I have been down this road with a couple of chamberings, mainly the 6PPC.

The really important dimension is the area about .200 from the bolt face, where the case is at it's thickest just before the solid web.

I would give Dave Kiff a call. He knows all of the dimensions of just about every chamber concieved. He has been a great help to me in every idea I have come up with..........jackie
 
Pete

When I order a matched set, meaning finish and resize reamers.

The finish reamer has to be a minimum of +.003" over unfired brass.
I order the resize reamer -.003" on the casehead and -.004" on the shoulder.

Now if you don't want to make your own FL dies the first question that needs to be answered is what size is the factory FL die. You can't go any further until you get that number.

Dave
 
Question Dave:

Dave Tooley said:
Pete

When I order a matched set, meaning finish and resize reamers.

The finish reamer has to be a minimum of +.003" over unfired brass.
I order the resize reamer -.003" on the casehead and -.004" on the shoulder.

Now if you don't want to make your own FL dies the first question that needs to be answered is what size is the factory FL die. You can't go any further until you get that number.

Dave
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In your opinion would +.006 be too big measured .200" ahead of the case head and +.0063 measured just below the shoulder? It seems quite a bit too large to me. I have the Standard die and a virgin case fits perfectly into it.

Thanks,

Pete
 
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Too big doesn't hurt anything. Maybe an unsightly bulge/lobe on the casehead but too small is what causes problems. If possible you want the sizing die to be close to the chamber so you don't over work the by excessive expansion and contraction.

What caliber/type rifle?
What does the virgin brass measure on the head and the shoulder?
What does your FL sizing die measure or what does a sized case measure after it comes out of the die?

Dave
 
reamer size

I agree with Dave Tooley to much is put into tight chambers. Having the correct chamber and the correct die is important in not exersizing the brass and allowing for expansion and spring back so extraction is not an issue.

It is easier to use a reamer that is on the tight side and polish out the web while the barrel is still in the lathe. I don't like seeing a bulge in the web area but I don't like stuck cases either. Extractors are expensive to replace.

Nat Lambeth
 
I had thought

.006 was excessive when one considers the kind of pressures we use in Benchrest. The plan is to be able to buy, say Redding dies and have a type s body die do the re-sizing. I have had my fill of custom dies. I'd rather spend the difference between a Redding and a custom on a barrel for instance. .006 is 100% larger than .003. It seems to me that .004 would be the maximum one would want to have to crunch every time they sized the cases.
 
Pete

I think there is something your not picking up on. Once the brass has been fireformed the only dimensional difference that matters is between the chamber and sizing die. Chamber pressure has nothing to do with the relationship between brass, chamber and dies. You're splitting hairs and the only way to do that is have a matched set of reamers or match your chamber reamer to your FL die.

How are you going to get this .004" fit without matching components.

Dave
 
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Thanks Dave

Dave Tooley said:
Pete

I think there is something your not picking up on. Once the brass has been fireformed the only dimensional difference that matters is between the chamber and sizing die. Chamber pressure has nothing to do with the relationship between brass, chamber and dies. You're splitting hairs and the only way to do that is have a matched set of reamers or match your chamber reamer to your FL die.

How are you going to get this .004" fit without matching components.

Dave
Click to expand...



I guess I have added too much in the way of comments in this. I simply want to know if .006 is too big, assuming the off the shelf die is exactly the same size as the virgin case. I would think .006 is a lot to have to push back in but don't know for sure. Is it too much to have to re-size every time?

I made the comment about pressure because I have experienced that as my powder charges go up, I must full length re-size vs when shooting lighter loads, neck sizing will often be fine for a few firings. Perhaps I am a bit like kathy, I don't know.
 
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Pete

.006" is a lot to compress each time. That doesn't mean that a chamber .006" over virgin brass is going to be sized .006" by a die. You're assuming the die is exactly the size of the virgin brass. That doesn't happen in the real world.

Until you know the dimensions of the brass, the chamber and the die you can't make an informed decision.

Nuff said

Dave
 
I measured both

I have both brass and die in hand so I measured the die and brass yesterday. The die was .001 larger than the virgin brass at the shoulder and exactly the same size measures .200 forward from the extraction groove. Don't know why I hadn't measured the die beforehand but I guess I needed a shove, eh ?
 
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