robinett 30 br trim lengh
- Thread starter skeetlee
- Start date
C.L. Peterson
Active member
Reamer Blue Print
That happened to me--No Print with Reamer.
Called company and they apologized and e-mailed me the print.
Might be worth a phone call.
CLP
That happened to me--No Print with Reamer.
Called company and they apologized and e-mailed me the print.
Might be worth a phone call.
CLP
geo.ulrich
Member
Might help to know which one, there are a few variations...
Wayne Shaw
Active member
If you have a bore scope, you can drill out the primer pocket on a scrap piece of brass, size it, chamber it, and go look where it is in relation to the neck length.
Randy Jarvais
New member
Mine is supposed to be Robinette at 1.500 so I trim to 1.490. Many of the BR's are 1.520. I have never measured my chamber and my reamer is housed at my smith's shop. That's my story and I'm sticking to it. Randy J.
geo.ulrich
Member
Or you could ream a barrel stub and mill neck area and check against a piece of brass. this isn't rocket surgery
R.G. Robinett
"That'll never work."
Regrettably . . .
George is correct - there are many variations of the [so called] Robinett reamer out there.
If it is a true (original) version, the maximum case length should be 1.510" - and trim to 1.500". In my opinion, any reamer, ground with a single deviation from the/an original print, should not bear the same title - it's DIFFERENT.
Wayne points out a very good method for determining what you've really got. If you have, or have access to a bore scope, this is sure-fire. You can, assuming it was cut with the chamber reamer, also use your shoulder bump gauge, as opposed to chambering - then, you do not need to drill a hole - simply enter through the gauge-bore, and see what you've got.
Another, more complicated method: 1) trim a case (or two) only just enough to square the mouth(s) - something longer than 1.510"; 2) assure that the shoulder is short of the proper head-space length; 3) disassemble the bolt (remove the firing-pin & spring assembly) and chamber the empty, un-primed case, and see if the bolt will close of only the handle weight. If yes, your chamber longer. If no, your case is too long, and being held against the chamber-mouth chamfer: trim off another 0.005 and repeat, until handle will just close of its own weight. Once the maximum length is determined, trim to 0.010" shorter, then, moniter, and trim all cases when one reaches about 1.505" long, which will normally, be quite a few firings.
Sincalir International makes a "plug-gauge" which works in similar fashion, but the rim needs to be turned down to something smaller than the chamber neck-diameter. RG
George is correct - there are many variations of the [so called] Robinett reamer out there.
If it is a true (original) version, the maximum case length should be 1.510" - and trim to 1.500". In my opinion, any reamer, ground with a single deviation from the/an original print, should not bear the same title - it's DIFFERENT.Wayne points out a very good method for determining what you've really got. If you have, or have access to a bore scope, this is sure-fire. You can, assuming it was cut with the chamber reamer, also use your shoulder bump gauge, as opposed to chambering - then, you do not need to drill a hole - simply enter through the gauge-bore, and see what you've got.
Another, more complicated method: 1) trim a case (or two) only just enough to square the mouth(s) - something longer than 1.510"; 2) assure that the shoulder is short of the proper head-space length; 3) disassemble the bolt (remove the firing-pin & spring assembly) and chamber the empty, un-primed case, and see if the bolt will close of only the handle weight. If yes, your chamber longer. If no, your case is too long, and being held against the chamber-mouth chamfer: trim off another 0.005 and repeat, until handle will just close of its own weight. Once the maximum length is determined, trim to 0.010" shorter, then, moniter, and trim all cases when one reaches about 1.505" long, which will normally, be quite a few firings.
Sincalir International makes a "plug-gauge" which works in similar fashion, but the rim needs to be turned down to something smaller than the chamber neck-diameter. RG
there are many variations of the [so called] Robinett reamer out there.
Beware! There's one out there labeled Robinette that's 1.560".
R.G. Robinett
"That'll never work."
Yes - and THAT is a "KILLER" . . .
It amounts to 0.060" of excess free-bore, which is NECK diameter, as opposed to 'slightly' over groove diameter - unless one can make brass that long (it IS possible, using Jackie Schmidt's froming method), for most barrels, this is a REAL precision wrecker . . . RG
It amounts to 0.060" of excess free-bore, which is NECK diameter, as opposed to 'slightly' over groove diameter - unless one can make brass that long (it IS possible, using Jackie Schmidt's froming method), for most barrels, this is a REAL precision wrecker . . .
RGIt amounts to 0.060" of excess free-bore, which is NECK diameter, as opposed to 'slightly' over groove diameter - unless one can make brass that long (it IS possible, using Jackie Schmidt's froming method), for most barrels, this is a REAL precision wrecker . . .
When I was sent this print and saw the long dimension Jackie's BR and method came to mind. I'm also glad I caught the dimension before I ordered a reamer. The print said nothing other than "30 BR Robinett finisher".
BTW I have your original PS article filed in my drawer for reference. Thanks!
SGJennings
New member
Lee, you just have to make your brass by fire forming rather than necking it up over a mandrel. Requires a dedicated FF barrel, but you chamber your own, so that shouldn't be a problem.
The most consistent that I've found it to just let a cheapie 6mm bullet rattle down the barrel.
Greg J.
The most consistent that I've found it to just let a cheapie 6mm bullet rattle down the barrel.
Greg J.
Dusty Stevens
Hollow Point Dispenser
if you use a 6mm bullet dont worry about using a fireform barrel. I dont think you'll get any wear except for the heat.
Send it in and have it shortened. Get a print and mark the changes you want right on the print. Easy, been there and no problem. If you want PTG to do the work, call and they'll issue an RMA with a notation that the reamer is coming in for neck and throat rework.
JerrySharrett
Senile Member
Always, order the print, then order the reamer. The reamer grinder can't read your mind.
The original BR, made from the 308 Winchester was the 7BR. IIRC, this was called the 7mmCBR, a Jim Carmichel creation, and, again IIRC, 1.500" long.
Many later variants, the 6BR and 22 BR were 1.560" long. Some of the others, the 25BR, for example, were 1.530" long. A Clymer drawing for the 22BR
shows "base to case mouth" 1.570".
http://www.6mmbr.com/6mmbr.html
Again, get the print, then the reamer. The supplier and you have something solid to work from.
The original BR, made from the 308 Winchester was the 7BR. IIRC, this was called the 7mmCBR, a Jim Carmichel creation, and, again IIRC, 1.500" long.
Many later variants, the 6BR and 22 BR were 1.560" long. Some of the others, the 25BR, for example, were 1.530" long. A Clymer drawing for the 22BR
shows "base to case mouth" 1.570".
http://www.6mmbr.com/6mmbr.html
Again, get the print, then the reamer. The supplier and you have something solid to work from.
He's not shortening the neck, just the freebore, which is in front of the neck.
mwezell
Mike Ezell
As I read it, he would like to shorten the neck and keep the same amount of freebore, which will require re-grinding the neck and the throat. Yes, it can be and is done. If he only shortens the neck, there will be a longer area in front of the chamber, so the throat would need to be re-ground also, if he wants to maintain the same amount of freebore. As Randy stated, a short case in a long chamber yields a freebore area that is neck diameter, as opposed to generically, bullet diameter. I would consider that to be substantially less than ideal.