Is there a book or reference that teaches how to specify reamer dimensions for BR barrel chambers for competition?

[Tim Singleton]

The studying in reverse from existing reamer designs is about all you can do.
I started doing my own barrels almost 10 years ago. Started out with a ppc that was .440 at the 200 line and had .060 freebore length with .2433 freebore diameter which was nearly as the gold standard 1045 reamer
I fought that thing for two years. After speaking with other competitors and on this forum after two other versions I have gotten to a reamer with no clickers that works well with my bullets

It is an interesting process to work thru and is satisfying to get there. For the PPC there is no Robinette V2 so you do have to figure it out yourself.
Study the Robinette v2 as Al advised and learn what makes it work

 

[Tim Singleton]

Years ago when I was working on this some guys on BRcentral had compiled this on several ppc reamers of the day this information is probably 15-20 years old. It does show some of the thinking at the time. Some of it does not work the tight dimension at the 200 line was the WRONG trail to go down as Dave mentioned above.

PPC Reamer Dimesnion Comparisons — Postimages

postimg.cc

 

[AlNyhus]

One example of working with a proven reamer and tweaking it for a particular useage. The yellow highlighted are my changes.

 

[Cassidy]

Does anyone have the original 30Robinette (V1?) 30BR reamer print that they can post here. I would like to compare it with the 30RobinetteV2 reamer print (which I have; and I have the V2 reamer) to see what changes were implemented in the V2 versus the V1 and maybe learn from you all (and RG) why these changes were made.

 

[WSnyder]

see what changes were implemented in the V2

Everything is the same except the .200” line dimension (of course body taper will have a very minor change). Edit: The neck diameter went to .331" from .330" as well

There is a thread on here somewhere that talks about the dimension change and why. It’s the thread where RGRobinette introduced the V2 reamer. Before the V2 came along I had a reamer made with the same changes to the .200” for the same reasons and left everything else the same.

 

[ELR LVR]

I've got more than a few reamers where I got cute with tolerances. Like, hey if we tighten up the back end of the chamber the primer pockets will last longer. That shouldn't have even passed the first "Oh I have an idea" test.

Yep, I did that on the very 6x284 reamer print I posted here
asked for reamer to be .001" over head dia.
Ended up Getting bolt clicks
Had to enlarge the chamber .001" more in the head area.
------------------
It's fun to experiment if you have the means to rectify the problem
I was going to go .001" at a time larger there until things worked as they should.
I knew I spec'd it out tight there so also knew where to target the problem.
It was a good lesson not to get too tight just to save brass life but didn't hurt too bad as it only needed
.001" more clearance for the brass to balloon under pressure.
Kind of a neat realization actually
If you don't allow the brass to expand some, even in the web, weird things will happen.

 

[RGRobinett]

Does anyone have the original 30Robinette (V1?) 30BR reamer print that they can post here. I would like to compare it with the 30RobinetteV2 reamer print (which I have; and I have the V2 reamer) to see what changes were implemented in the V2 versus the V1 and maybe learn from you all (and RG) why these changes were made.

THE big issue with the dimensions on this print is the diameter at 0.200" ahead of the bolt-face.
For yours truly, this has never been an issue, as my original Redding Type "S" FL/Nk bushing die (a 7mm version, with the neck-port 'opened' to accommodate [no contact] passage of .30 Cal necks), is sufficiently 'tight' and sizes the .200" DATUM diameter enough to eliminate the [primary extraction] 'click'.

Of note, Ronnie Long made the first .30BRs (dimensioned/intended to use the SHORT/LIGHT thirty caliber bullets, for BR competition), including my initial barrel - I believe that the only alteration I made was the leade angle (1 Deg.-45 Min.), to 'better' accommodate 7 caliber ogive bullet configuration.
With a correctly positioned 'free-bore' - think longitudinally - the [free-bore] diameter is of little/no concern.
However, getting it 'properly' positioned must be somewhat 'tricky' - therefore, it is wise to specify a minimum of 0.0005" over nominal caliber, and 0.007-8" over is not bad - regarding diameters, more often than not, "bigger is better"! The bullet ogive should have FREE contact with the leade.

Hope this is helpful. RG

P.S. Sadly, there are numerous 30 BR reamers, 'out there' bearing my name, but dimensionally
excessively LONG OAL, and/or,with 'actual' free-bore, both of which may prevent being able to seat bullets in contact with, or, even near the lands!

 

[WSnyder]

Here's the original thread from RG:

Thread 'Here ya go folks - for a 30BR reamer, it won't get any better than this.'

Nov 18, 2021

Simply call, or, e-mail JGS, and order 30BR ROBINETT V2 (for Robinett version 2). Though this may prove neither better, nor worse, than reamers featuring other dimensions, it will certainly prove excellent! If wanting a new 30BR reamer, this is exactly what I'd order. No more messing about, exchanging dimensions: JGS will not let you down.

Note, this is a wild-cat (well, domesti-cat) - a chamber cut with this reamer will require trimming to 1.500" OAL! The .331" neck diameter will accommodate cleaning-up LAPUA 6BR-NORMA brass while allowing more than ample clearance with a...

• RGRobinett

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[SKWERLZ]

QMM on YouTube has a recent set of videos with the Manson reamer guy.