Chambering questions for the Ultra Mags and Lapua's

T

TMR

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What techniques do you guys use to chamber the longer cases? I know with the shorter BR cases, preboring is the was to go...but the pilot will usually reach the bore with short cases.

Would a guy bore and taper the chamber to where the pilot would begin to engage and then use a reamer pusher?

Bore the chamber and hold the reamer on a center or a fixed style reamer holder like the GTR?

I watched the Gordy Gritters video and he drills, bores and then uses the GTR reamer holder. Just trying to get as much info as possible with the longer cases. Curious to what you fellas do.

Travis
 
Travis

Your are correct, longer cases do present a problem if you use the single point boring to get everything in line.
The longest case I have ever chambered using my method is a 30-06.
What you have to do is be sure that your compound is set on the exact taper as the reamer body, and be very careful. By boring with the correct taper, you can get the reamer 50 percent of the way in, which will allow the pilot to enter the lands.
It seems most shooters who wish to pre-bore after indicating the throat are simply boring the hole straight, being carefull not to take too much out. As the case gets longer, this has it's limitations. For the longer cases, you have to set the compound up to bore the chamber body on the correct taper.
This problem can be exasperated by the fact that many small lathes have compounds with very limited travel. If you have to re-catch the cut, you have to be very carefull that you match it up. I am fortunate in that my Pratt & Whiney Tool Room lathe has a generous compound travel.
This is another reason that when doing a barrel,the very first thing I do is establish as good of a chamber in the blank as I can, then following with all of the other operations, which are just straight forward machining........jackie
 
I reach as deep as I can with my indicator for set up and live with it ... they aren't exactly Benchrest cases...
 
Jackie,

That is what I was thinking....prebore with the body taper just enough to allow the pilot to enter. Figuring that I would indicate first, drill a hole, indicate the throat, and then taper the hole. Just not sure if I should use a pusher like you guys made or the more solid GTR style holder.

Dennis...I know these aren't benchrest cases, but I would like to get the accuracy. I always figured that if I did the chambers to my best ability that they would pay off on paper and animals.

Anyone else have any "special" techniques?
 
I just chambered a 300 win mag a few days ago and all I did was drill and bore the hole about .010 under the shoulder dia for the entire depth, and then I stepped it a little larger for about the first inch. It allowed about the full pilot to go into the rifling. After I was done the chamber only had .0003 runout.
 
For hunting rifle chambers, I have always simply roughed with a standard twist drill and continue to do so. If the barrel is set up perfectly and the bit is good, the hole will be straight and round.Never drill so far that the pilot will not reach. If the drill bit is crooked at all, I don't use it. Twist drill can work much better than many give them credit for. I have drilled a fifty five inch long hole 1/2 inch indiameter by drilling 28 inches from one end then switching ends and drilling from the other and had the holes meet within .005" of each other. This was done with a common twist drill bit silver soldered on to an extension.
If the barrel is well set up and the bore is straight, supporting the reamer on the center is just fine. If the bore is not straight or the setup imperfect so that the reamer has to float, the Bryant- style pusher is better.
I think the idea of boring a chamber prior to reaming is an excellent one and can work out very well providing the setup is perfect. I also think there is a point where any advantage to doing so is hard to see. I think the large magnum cartridges are well beyond this point. By the way, I also think, if the barrel is so crooked that setup is difficult, regardless of the length of the cartridge, it is a barrel hardly worth chambering. Good barrels shouldn't be crooked. Regards, Bill.
 
TMR Float the reamer

You'r right on the money, indicate, drill,re-indicate, taper within 0.1-0.15mm and float the reamer. If you'r 100% sure you have done everything right and you have a 100% straight tailstock you can run the reamer through it.

Shoot well
Peter
 
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