Help with a chamber reamer

[Frankr]

I want to have a chamber reamer made.
i been told to make a cast of my chamber,so i been planing on doing it and it seems after a few days the cast will expand .0025 over the dimensions of the chamber?
im very confused,,see it dont take much. lol
i want to have a reamer made to the exact chamber i have now and my main concern
is the throat and lead angles, wanted to get a idea of what was in there,that is why i was going to do a chamber cast.i have a few cases that have been fired @20 times or so and have only ever necked sized half the neck.
My plan was to send the chamber cast and a dummy round & a few fired cases away to have the reamer made.
can anyone advise me on what to do here?

 

[spencer313]

The expansion of CerroSafe is very well characterized. If you remove your casting from your chamber at 30 minutes (it shrinks first), then make your measurements at one hour, it will be at exact chamber dimensions. CerroSafe then continues to grow to a maximum value of, if I recall correctly, .0025 in/in. If you send your casting, AND identify the casting material and when the casting was made, your reamer maker should have no problem compensating for this growth. From the Brownell's site:

Unlike Woodsmetal which swells upon cooling and cannot be removed from a gun chamber, Cerrosafe shrinks during the first 30 minutes of cooling and then at the end of an hour, is EXACTLY chamber size. At the end of 200 hours it will have expanded approximately .0025". This factor is well known by all toolmakers and they will take it into consideration when making dies or reamers or gauges from your cast - if you will tell them the cast is of Cerrosafe. ​

 

[Frankr]

ok thanks for that,looks like my help is going to come from jgs.
lm sharpening up my mic's and calipers and angle gages.

 

[Dennis Sorensen]

I think more accurate measurements can be made by the reamer maker if they have an optical comparator as opposed to measuring with micrometers. That's what I was told once when I had some custom alterations done on existing reamers.

 

[Frankr]

still need help, they reccomend in a standard chamber that you taper the neck .001, so if you had .330 neck, you base of neck would be .330 and front of neck would be .229
i use a tight neck chamber and turn my necks so i dont think that would apply? im going to run a tight neck at .268 so it sould be a straight .268????
i have never filled out a chamber reamer chart before,this is all new to me.
anyone ever filled out a reamer print form ? have any tips?

 

[Dennis Sorensen]

It might help if you posted the cartridge and the make of brass you intend to use...

 

[Cheechako]

. . .they reccomend in a standard chamber that you taper the neck .001 . . .

I don't know who "they" are, but all of my reamer prints show a straight neck. Maybe Dave Kiff or Hugh Henriksen grind in a little taper but it certainly doesn't show on the print.

If this is your first reamer, send the grinder the chamber cast, a couple of fired cases, and a dummy round with a bullet seated where you will want it. Tell him you want a tight neck (and the dimension) and whether or not you also want a tight butt. Leave the rest to him. You're buying his knowledge and expertise in addition to the reamer.

JMHO

Ray

 

[jackie schmidt]

The vast majority of Benchrest Reamers have a straight neck........jackie

 

[Charles E]

I've used a .001 taper on the neck of several of my 1,000 yard reamers. I don't know why it works so well, but it does. Remember the T.J. Jackson neck turner? That put a taper in the neck when you turned them. That too worked well.

Having said that, my PPC and .30 BR reamers have a straight neck. But I've used the Jackson turner making cases for both, as well as a K&M. Seem to shoot about the same.

 

[Frankr]

Thanks for the replys. i got some e-mails into the reamer people and i guess i will see what they want.
i know this seems like a bunch of hupla but when you are trying to duplicate a short range benchrest chamber for a 6BR norma/lapua case
it seems to get alittle tricky.I mean im allready at a disadvantage,dont need a messed up chamber.lol
no guys a top benchrest gunsmith gave me this chamber(i wont mention his name,but if i told you,you would agree). the rifle has shot so well(i know barrels&bullets).
its been some years ago and the smith has no idea where the reamer went or what chamber it was.so im trying to see if i can duplicate the resualts.but i think this chamber has been great,really like it and would like to get as close as possible to it.its a .269 neck, but the reamer was sharpened and he said it was 2685 neck.so im going to tighten the neck up to .268 . the reamer chart reccomends the .001 taper in the neck. tryed to mic some cases that have been fired a bunch of times in the fired state and its just too hard to tell,looks like .003 taper.but one thing i like with necking half of that long neck is half the neck on a case that has been fired several times stays at chamber size.so my loaded round half the neck mic's at .2685,the other half that was neck sized to hold the bullet with fair grip and mic's at .266. all i can say is it works very well and if i do my part in good to fair condition,USUALLY will come real close to shooting down the same hole.hard to argue with that.
some targets so you can see im not full of BS.
very serious about this build,im trying to see if i can duplicate this rifle or if just a fluke.
this build will answer my question, can the 6BR be competitive in 100/200yrd group.
i know most shooters dont think it can, im not so sure. the .126 target was shot a long time ago when the barrel was new and groups in the low to mid .100's was allmost everytime
the rifle was fired, the other target group was shot this year at around 1,000 rounds when someone was questioning its accuracy. but at 1,300 round through it now it seems im chasing them kind of groups, i tryed to save this rifle for competition,thats why i have had it so long and ony has 1,300 rounds rounds on it. but the bug had left me. now i want to get back into it some so building a new one. we will see how it shoots.