PDA

View Full Version : Robinett reamer?



skeetlee
10-11-2010, 05:07 PM
Fellas i was looking at a print of the Robinett reamer That dave kiff makes and it looks to me like that the max case length is 1.510? Im not exactly sure if i was reading that print properly so i was wondering if someone around here might know this for sure. Also if this is the case would a piece of brass that measured 1.513 cause accuracy issues? I ask this because i was under the impression that i could go out to around 1.520 with my brass length using this reamer? I am just curious and would like some more info on this subject. will long brass cause accuracy problems? I assume it would! Thanks Lee

Charles E
10-11-2010, 06:10 PM
It is a little cavalier to assume because somebody slaps a name, like "Robinett" on a reamer, you can assume they're all the same. Randy has had a number of reamers made up over the years. Usually the print has a date, but the date may be a manufacturing date rather than a design date. Or the other way around.

Reamer maker's differ too. I have a "Robinett reamer" from Hugh Henriksen, from when Randy shifted to having Hugh make his reamers. Case OAL on my print is 1.520.

BTW, I had Hugh make me a go-gauge too. So, if I chamber it at dead minimum on the gauge, and the gauge is right, I'll have a 1.520 chamber. But if I run the reamer in .005 short, I'll have a 1.515 chamber. And if I run it in .005 long, well, you get the picture.

Just for giggles, my reamer has a .075 radius on the neck/shoulder junction. Others may well have .0625. I'll bet your does. Usually we'd just allow that a an unremarkable variation, but a few people have thoughts on that, too.

Best of my knowledge, there isn't a SAAMI (US) or CIP (European) specification for the .30 BR. It is up to you to know the properties of the tooling you use, and to check the actual measurements.

If you have a print for the reamer actually used to chamber your rifle, and if it measures out, you have your answer. If the reference to the reamer is just a vague "Robinett" reamer, you don't really know -- it won't have exactly the same numbers as mine, for example. Dies may need to be different. Etc.

But aside from taking care of little details -- dies, trim-to length -- they'll shoot the same.

skeetlee
10-11-2010, 06:57 PM
Makes since! Thanks charles. I guess the best thing to do is cut all my brass at 1.500 and call it a day! Ill call jon up and see what the print shows. we have had this reamer for about a year and a half now. Thanks again! Lee

jackie schmidt
10-11-2010, 09:29 PM
There is sort of an "industry standard" it what has become a "Robinett Reamer. Basically, it features a .330 neck, a max case length of 1.510, and a "zero freebore" going into a 1.5 degree lead..

Keep in mind, there are tolerances on reamers. not every one is exactly the same, but basically, that is what constitutes a "Robinett Reamer".

Many shooters aske me about my version of it, the only difference is my overall chamber length is 1.550 instead of 1.520. I simply do this as a product of the way I make my brass........jackie

Bob Kingsbury
10-11-2010, 09:49 PM
my Robinett reamer gives a max case length of 1.528. this is the chamber, with correct Headspace

kiff
10-14-2010, 12:23 AM
The 30 BR reamers we make for Randy ,Jackie and many others have zero freebore and a .330 neck but differ in reamer case length . We stock the 30 BR Robinett reamer with the shorter neck per Randys design and also the longer version we call the 30 BR Schmidt . The 30 BR Schmidt has a very good neck length . I cant keep those babies on the shelf since Jackie broke the record . If any one would like one let me know as we are running a new batch of 25 thru. Jackie I sure thank you for all you do for the shooting sport and the help you give all us on this site. I always learn alot grinding reamers for Jackie he is not afraid to step out of the box. Thanks Dave Kiff

kiff
10-14-2010, 12:42 AM
I would also like to grind a few of the elips throats on the 30 BR. If anyone is interested call me. To date I have ground six PPC reamers and those boys are doing very well. I have also had many folks tell me the half degree is kicking butt also. Let me know if anyone would like to try the different throat grinds. Thanks Dave

Charles E
10-14-2010, 02:00 AM
I'm curious about the elips (ellipsis?) throat - I imagine you are talking about matching the throat to the ogive of the bullet? Or is that wrong?

As I'm sure most know, Randy makes two profiles in his .30s. Both are tangent ogives: a 7 and a 10, the latter which I think of as "mine," since the dies were the ones originally purchased to make the 187-grain bullets using 1.300 jackets. (All the 10-ogive bullets, including the 118-10 bullets on a 1.00 jacket, are pointed in the same die.)

But since the initial runs of light .30 bullets for BR, (Chism, Robinett, Fowler, and probably a few others), a fair number of people are now making competition grade light .30s. I imagine other profiles are used, perhaps even some with a secant ogive.

Does this have any bearing on the "elpis" throat?

* * *

Following a notion of Jeff Summers, I have a PPC with a 2-degree half cone angle (don't believe Jeff uses this anymore). This design was for use with the old Fowler bullets (6.5 degree tangent) There was also some thought that the throat would erode in a more forgiving manner. Hard to tell about the erosion notion. And in spite of tailoring the throat to the Fowlers, my rifle anyway, shoots these Fowlers and 8.5-degree tangent BIBs with equal aplomb. Well, Jeff Summers shooting would tell a far more interesting tale than my shooting, but my conclusion is the importance of throat angle is right down there in the noise level.

Just as a item of curiosity, I believe Ferris Pindell also made a reamer that cut a throat to the profile of his bullet. Think it was a 13-degree secant, but memory fades. I'd guess that erosion with a 13-secant would not be even. I forget who has that reamer these days. With the same fading memory, I don't believe that combination was particularly a world-beater, but anything Ferris Pindell comes up with is usually worth a look.

* * *

So what is the basis for the half-degree lead angle? How is throat wear with high-pressure loadings? And if anyone knows, wear with high-pressure loads in rifles chambered for much larger cases?

TIA,

Charles