Another reamer question

J

Jim Gartrell

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I am planning to switch from shooting the 6BR to the 30BR sometime this year (2012). 30 BR Robinett Chambering Finish Reamer

Would this reamer get me started or are there better choices? I will probably start with Berger bullets to get off the ground and have read about jacket length possible being an issue. This will be used for 1-200 yd. score shooting.

Thanks, Jim
 
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That's The One.

The only other reamer that has a significant difference is my grind, which is a product of how you make your brass. If you are necking them up in the traditional manner, then the Robinett with it's 1.505, (I think), trim to length is great. If you are making your cases the way we down here in Houston do it, by blowing them out, then my reamer that features a 1.540 trim to length is the ticket. Aside from that, the reamers are identicle.
 
Your reamer should do fine. It's probably the standard for the 30 BR across a wide array of good builders. With a some bullets and a 7 ogive, it's a little shorter for freebore than my next one will likely be. I think about .020"-.025" freebore would be more versatile in terms of bullet selection and in terms of more powder room for less compression of the powder charge.. This is just what I believe to be about ideal. Not really much different than what you have.---Mike Ezell
 
I too am among the legions who uses the Robinett pattern. As to the freebore: if you are never going to shoot anything aside from a .30 BR, with bullets from 110 to 118 grains (.925 to 1.00 inch jackets), and conventional ogives (7-9 tangent), then zero freebore is correct. Actually, I've talked to Randy about this, and he said either .010 (or maybe .020) would be fine. (He only used one number, it's my memory that required me to give two numbers.)

Whatever you wind up using, you want to be able to test the BIB 112-grain, 7-ogive bullets. They shoot so well in so many rifles. That's why the zero or .010 freebore length.

BUT:

Down the road, you might change your mind about the range of bullets you want to try, or decide to get another .30, or, or, or. That's where the beauty of a throating reamer comes in. I shoot more than one .30. For each chambering, I have the chambering reamer ground for the shortest bullet I might use. Then, if I have a barrel with a different twist & want to use a longer bullet, I can simply throat out that barrel.

Get the kind that can be driven with a T-handle as well as a lathe. I also like spiral flutes on throating reamers. Probably like so many things, this doesn't matter. Jackie could tell you better. They sure cut easily though, and I often throat out my barrels by hand, with the barreled action still in the stock.

Theoretically, I suppose it is "better" to have the freebore built into the reamer. Just one tool, one setup. But I've used throaters a fair bit, with chamberings all the way from .30BR to a .30 on the .404 Jeffrey case -- & several in between. After using a throater, we do check the work; it is always fine. I think you can do this visually, with a borescope, but would also defer to Jackie or any real gunsmith. The real test for me is the target; they have all shot fine.

Just my $0.02

Edit:

Forgot to mention. This system works best if you keep your freebore diameter constant. All your .30s should use the same diameter, anywhere from .0005 to .001 over nominal bullet diameter. I use .001 over. The same with the forcing cone angle. Again, I use 1.5 degrees half cone angle. Pretty conventional stuff.
 
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Schmidt 30 BR reamer

Hi Jackie. I just got a 30 BR reamer with your grind. Never shot a 30 BR. Would you give me some info on how you size and trim you brass? Thanks Don
 
Charles E said:
Forgot to mention. This system works best if you keep your freebore diameter constant. All your .30s should use the same diameter, anywhere from .0005 to .001 over nominal bullet diameter. I use .001 over. The same with the forcing cone angle. Again, I use 1.5 degrees half cone angle. Pretty conventional stuff.
Click to expand...

Now, how do I specify freebore diameter with a zero freebore? I ask Hal Drake the same question. I can't put his answer on a family read forum!!
 
JerrySharrett said:
Now, how do I specify freebore diameter with a zero freebore? I ask Hal Drake the same question. I can't put his answer on a family read forum!!
Click to expand...

Jerry, read more closely. I said I use the throater for multiple chamerings in the same caliber. I'd never have a .30 on an 8x68 case with zero freebore. But I (or someone) just might set it up for 155s. Then they want to try 210s with a different barrel.

I don't want to buy multiple throaters any more than I want to buy multiple reamers for the same chambering, so you pick a diameter & run with it.

Or are you suggesting a better performance compromise is to have all the basic chambering reamers set up with zero freebore, and get a throater for each? More cost, but cheaper than all new chambering reamers every time you want to significantly change bullets. I guess it gives a little more flexibility, but I don't think it justifies the cost.
 
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Charles E said:
Or are you suggesting a better performance compromise is to have all the basic chambering reamers set up with zero freebore, and get a throater for each? More cost, but cheaper than all new chambering reamers. I guess it gives a little more flexibility, but I don't think it justifies the cost.
Click to expand...

Ream chamber then throat? If a person is a gunsmith doing many barrels and has a proper setup to throat (and control that throat depth) then that might be a way to go. That gunsmith will have a mix of customers with their own reamers and customers that want non-standard throats.

As to zero freebore, seeming to be popular with the 30BR, and stating I don't shoot that monster, if there is not at least a trace of freebore it would be more difficult to inspect the finished concentricity of the chamber-bore relationship. I had a 30BR reamer ground that had 0.010" freebore and it looked far more comforting just to see a small cleanup than if there was just the leade ramps to inspect. BTW, I got rid of that entire setup after shooting beside someone with a 10.5# 30BR!!
 
Jim, the .330 neck 30BR 'Robinett' reamer is the Gold Standard. As to freebore, anything from a 'zero' freebore to .025-.030 freebore length will be fine. Quite honestly, even a 'zero' freebore chamber has a skosh of freebore length after a few firings. If there was one change I'd suggest, consider making the back end of the reamer just a smidge bigger...on the order of .4715-.4720.

Add a Harrel's #2.5 f.l. bushing die, a Wilson standard seating die, neck bushings in .324, .325, .326 and .327 and you'll be in good shape. Neck clearance of not less than .002 (measured over the pressure ring of a seated bullet). More neck clearance won't hurt performance. Anneal before firing the first time, if only obviously...;)

Have fun and good shootin'. :D -Al
 
Al,

Does that mean the necks may need to be cleaned up to achieve the proper clearance? Is there a preferred amount of neck tension? Also is a 17 or 18 twist preferred by most?

Jim
 
Thanks for all your help. I'm sure there will be more questions in the near future.

Happy New Year.

Jim
 
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