A Cautionary Chamber Tale
Posted: Thu Dec 20, 2012 11:00 am
Good Day,
Back in January a fellow wanted to sell a 6.5-284 takeoff-barrel for a very good price. He said it only have 600 rounds through it. A $60, Krieger, take-off barrel was tempting since it had a 30" Palma-taper with long shank. I figured I could have it cut back to 27" and have quality lands in front of the chamber. The guy said he just couldn't get it to shoot up to his expectations. I appreciated his honesty. My initial guess was that he had a badly designed chamber or maybe a bad crown. Temptation got the best of me; what the heck, a $60 gamble on a stainless steel Krieger with a great taper for a HP silhouette rifle, what's not to like???
At home the barrel was bore-scoped and pin-gauged. Everything looked good. Cutting 3" off the back of the barrel along with a 2" long 6.5-04 chamber will put nice looking lands at the front of the new chamber's freebore. But, this morning curiosity got the best of me, so I Cerrosafed the chamber. OMG, no wonder his rifle wouldn't shoot. The 1/4"-long freebore is 0.268" in diameter, 0.004" over bullet and groove diameter. Bullet-to-bore alignment will not be consistent, due to such a sloppy free-bore, when the light turns green That is typically the road to less than stellar accuracy. But, not only that, the chamber's neck-diameter is whopping 0.3045" in diameter, WOW!!! A loaded round's neck-diameter is 0.290" with unturned WW brass, 0.292" with unturned Lapua brass. A gunsmith somewhere has "got some splainning to do" on that one because this was supposed to be an F-Class, match rifle. A cartridge neck-clearance of 0.007" per side further drives accuracy into the proverbial toilet. No wonder that guy couldn't get his rifle to shoot. My 6.5-284, Krieger-barreled Palma/F-class rifle has a 1/4" long freebore also, but it is 0.264" in diameter and the chamber-neck diameter is only 0.292". My Lapua brass is neck-turned so that there is only 0.002" total clearance. The rifle shoots such small groups off the bench at 100-yds it boggles the mind.
Bottom-line; never have a rifle chambered if you don't know the reamer dimensions. Several friends over the years have run into the same problem, diagnosed by Cerrosafing their chambers.
Back in January a fellow wanted to sell a 6.5-284 takeoff-barrel for a very good price. He said it only have 600 rounds through it. A $60, Krieger, take-off barrel was tempting since it had a 30" Palma-taper with long shank. I figured I could have it cut back to 27" and have quality lands in front of the chamber. The guy said he just couldn't get it to shoot up to his expectations. I appreciated his honesty. My initial guess was that he had a badly designed chamber or maybe a bad crown. Temptation got the best of me; what the heck, a $60 gamble on a stainless steel Krieger with a great taper for a HP silhouette rifle, what's not to like???
At home the barrel was bore-scoped and pin-gauged. Everything looked good. Cutting 3" off the back of the barrel along with a 2" long 6.5-04 chamber will put nice looking lands at the front of the new chamber's freebore. But, this morning curiosity got the best of me, so I Cerrosafed the chamber. OMG, no wonder his rifle wouldn't shoot. The 1/4"-long freebore is 0.268" in diameter, 0.004" over bullet and groove diameter. Bullet-to-bore alignment will not be consistent, due to such a sloppy free-bore, when the light turns green That is typically the road to less than stellar accuracy. But, not only that, the chamber's neck-diameter is whopping 0.3045" in diameter, WOW!!! A loaded round's neck-diameter is 0.290" with unturned WW brass, 0.292" with unturned Lapua brass. A gunsmith somewhere has "got some splainning to do" on that one because this was supposed to be an F-Class, match rifle. A cartridge neck-clearance of 0.007" per side further drives accuracy into the proverbial toilet. No wonder that guy couldn't get his rifle to shoot. My 6.5-284, Krieger-barreled Palma/F-class rifle has a 1/4" long freebore also, but it is 0.264" in diameter and the chamber-neck diameter is only 0.292". My Lapua brass is neck-turned so that there is only 0.002" total clearance. The rifle shoots such small groups off the bench at 100-yds it boggles the mind.
Bottom-line; never have a rifle chambered if you don't know the reamer dimensions. Several friends over the years have run into the same problem, diagnosed by Cerrosafing their chambers.
