In his next article on what to look for in a custom rifle, John Stewart of Kiote Corp explains the right way and the wrong ways to cut a chamber and throat for a rifle…
The number one problem with most rifles both factory rifle and also some custom rifles as well, is the manner in which the chamber is cut.
Factory guns are made with reamers that get used on hundreds and hundreds of chambers. Over time, the reamers become dull, chipped, and dimensionally smaller due to wear. Scoring, gouges, too loose, too tight are all problems commonly seen in factory and less quality custom guns.
Just recently, I was asked to correct problems with chambers on two rifles that you’d expect to be near flawless: one Kimber 84L and one GA Precision HRT rifle. Both exhibited excessive scoring caused by chips not being removed during the reaming process. Both exhibited longitudinal gouging caused by the reamer being forced into the chamber. These are irreconcilable errors on guns that the owners paid in excess of $3000 for.
When I cut a chamber, I never use a reamer that has been used on more than 4 other rifles. Once that reamer completes its fourth rifle, it either gets sent back for re-conditioning or it gets tossed in the recycling bin. This ensures that my tooling is sharp and dimensionally sound before it ever cuts steel.
I also never cut more than 0.010” in depth in one pass. This ensures that I’m not overheating my tooling Even with oil or coolant applied, heat is generated which creates problems. More importantly, this ensures that I don’t have excessive chip build-up which could cause scoring or gouging inside the chamber while it’s being cut.
300 Norma Mag Chamber Cut Before Oil Removal and Honing (image courtesy of Kiote Corp)
My lathe does not have integrated coolant nozzles. Even if it did, it wouldn’t really work for chambering because I don’t want to push/flush chips into the chamber. I’ve found that using ISO 32 machine oil on my tooling allows for both proper cutting and ease of chip removal during the cut, allowing the chips to slide down the flutes of the reamer and out of the chamber. I also use a floating reamer holder from Manson Precision that ensures that my reamer stays inline and parallel with the bore. Even if my barrel were to be a half-thousandths out, the chamber would still be cut properly.
Once I’ve achieved proper headspace, I use a honing brush from Flex-Hone to ensure a near-mirror finish on my chamber walls. I don’t necessarily believe that a true mirror finish is necessary. In fact, I prefer not to have one because the walls should provide a slight resistance to the brass during expansion so that everything stays in line with the bore during the burn process of firing.
Properly cut and throated chamber after 1,000 rounds. (Image courtesy of Kiote Corp)
Another problem is that all factory rifles are chambered with a long throat. This is primarily done to ensure that no matter what brand of ammo the consumer is using, it will fit in their rifle. While it’s convenient, it’s also detrimental to both accuracy and life-expectancy.
Factory cut chamber after 1,000 rounds. (photo courtesy of Kiote Corp)
The longer the jump is between the ogive of the projectile to the start of the bore, commonly known as “free bore”, the bigger the chance is for that projectile to get off-center, commonly referred to as “sideways”, before entering the barrel. This is exaggerated by out of square, off-center chamber cuts commonly seen in most rifles.
The long throat also allows for quicker throat erosion. With the projectile essentially banging against the throat of the bore, it erodes microscopic pieces of the metal with forces in excess of 40K PSI found in most center fire rifles used for hunting or competition.
Several well-known custom have led the consumer to believe that they are required to have a longer throated chamber now so that they can set the projectile out farther to achieve greater velocity. Time and time again, history has proven that most calibers are more accurate and have longer life expectancy by setting the projectile a specified length off of the lands, typically 10-20 thousandths of an inch.
“Question of the Day: Pay Criminals Not to Commit Crimes?”
This program already exists all over the US. It’s called Welfare, and while it doesn’t help the people who receive it, it sure helps the Democrats who pay it with OPM (other people’s money).
For the sake of the discussion, exactly what is your definition of a “long” freebore? I’m at a loss how a bullet can be “banging against the side of the throat” unless the bullet has completely left the neck of the round, the chamber is cut so far out that it’s dangerous, and whoever loaded them never checked the case nor the load with concentric measuring gauges.
While I REALIZE this is about long range, precision rifles, the entire throat issue is of interest to me. I’m at a loss how a so called “properly” throated round can shoot great, but so do many rounds that used CIP specs and can have no freebore and as much as 1.10 inches of lead. When BOTH shoot 3/4 MOA with proper loads, both are getting velocities at the upper levels of the round’s expected levels (and not wimpy at all)………I’m ready to toss it all out the window and just throat my wildcat long enough to use any bullet I may use. (Hunting purposes).
Don’t confuse the “experts”. They don’t get that “freebore” and the “jump” are completely irrelevant as long as the bullet bearing surface “hits the lands” – which are nothing but the “regular bore” (non-free bore?) minus the “grooves” cut into that bore – before that same bullet bearing surface clears the neck/case mouth. They picture bullets actually “banging around” in that “freebore” even though the “freebore” of the throat in “commercial” cartridges made to “SAAMI SPEC” will A) only be the “inside diameter” to allow a “slip fit” of the “outside diameter” of the bullet which is “oversize” for the actual BORE “across the lands” and B) is only there so PROPERLY “LOADED” AMMUNITION WITH THE COMPONENTS AND VARIOUS DIMENSIONS BEING CORRECT BY “SAAMI SPEC” HAS ROOM FOR THE NECK TO EXPAND TO “RELEASE” THE BULLET and C) will always be “shorter” than the bearing surface of the shortest “commercial” bullet available in that cartridge’s caliber at the time the “SAAMI specs” ARE DETERMINED minus a significant “safety factor” in case somebody does the unthinkable and comes up with a LIGHTER AND CHEAPER AND SHORTER AND MORE CONSISTENT BULLET DESIGN.
THE “EXPERTS” CLAIM TO BE ALL ABOUT “ACCURACY” AND “PRECISION” BUT YET END UP WITH “PRECISION AMMUNITION” THAT’S TOO LONG TO FIT IN A “SAAMI-SPEC” CHAMBER/THROAT/MAGAZINE AND WON’T EVEN “CHAMBER” PERIOD UNLESS THEY “CUT DOWN” THE OD OF THE NECKS BECAUSE THE “GENIUSES” REFUSE TO “DAMAGE” THEIR “ACCURACY AND PRECISION” BY “FULL-LENGTH SIZING” THEIR BRASS. THAT THEY ONLY GET 4-5 RELOADS “MAX” AND FOR SOME REASON NEED TO TO “FIRE FORM” BRAND-NEW CASES SUPPOSEDLY MADE PRECISELY FOR A GIVEN “COMMERCIAL” CHAMBER AND AREN’T SMART ENOUGH TO “GET” THAT BOLTS AREN’T SUPPOSED TO “FLICK OPEN” AND “FALL CLOSED” AND DON’T IN GOOD RIFLES LOADED WITH QUALITY AMMUNITION PROPERLY LOADED TO “SAAMI SPECS” AND ARE ALL ABOUT TELLING THE REST OF US “NON-PRECISION SHOOTERS” HOW THE FUCK TO GET “SUB-MOA” ACCURACY/PRECISION OUT OF “CUSTOM” RIFLES/CHAMBERS/THROATS/CARTRIDGE DIMENSIONS WHEN MOST OF US “NON-PRECISION” SHOOTERS PRETTY MUCH EXPECT THAT KIND OF ACCURACY/PRECISION AS LONG AS QUALITY HARDWARE IS USED. ESPECIALLY SINCE $400 “BUDGET” MASS-PRODUCED RIFLE/OPTIC COMBOS THEY LOOK DOWN THEIR PRECISION NOSES AT OFTEN COME WITH “SUB-MOA” ACCURACY GUARANTEES THESE DAYS WITH NO STRINGS ATTACHED AND NO REQUIREMENTS FOR “PRECISION LOADED AMMUNITION” AT ALL. IN FACT, SINCE MOST “MASS PRODUCERS” OF “FACTORY” (THEIR “HIGH-END” PARTS AND COMPONENTS AND OTHER HARDWARE IS ALL HAND-MADE BY AGED, EXPERT “CRAFTSMEN” AND NOT IN “FACTORIES” APPARENTLY) RIFLES ARE ALSO IN SOME WAY, SHAPE OR FORM ALSO IN THE “AMMUNITION BUSINESS”, THEY SORT OF PREFER THAT “FACTORY AMMO” BE USED TO DEMONSTRATE THAT YOU DON’T HAVE TO BE AN “EXPERT” IN “BALLISTICS” AND “CUSTOM RIFLES” AND “PRECISION AMMUNITION” TO BE A “SUB-MOA SHOOTER”.
LIKE I SAID, DON’T CONFUSE THE “EXPERTS”. THEY EXIST IN A PARALLEL UNIVERSE WHERE “SKILL” IS FOR SALE EVEN IF THEY NEVER MANAGE TO FIND THE “STORE” SELLING IT.
Boy, if you don’t know that a REAMER is not a “drill bit” or “boring tool”, there’s not a hell of a lot of hope for you ever managing to get more than “4 rifles” out of a reamer before it needs “reconditioned”. And if you think its POSSIBLE to “recondition” a REAMER by “grinding” or otherwise removing metal from it besides “reconditioning” it down to a SMALLER CARTRIDGE/CHAMBER, there’s even less hope for you. Where did you go to “gunsmith school” and how many cereal box tops did your “degree” cost you?
Blah, blah, blah, blah, blah, blah… Look at me I’m an expert on everything in the history of everything… I know more blah, blah, blah than any blah-blahologist… And if you disagree with me I will call you names and TYPE IN CAPS to prove my superiority. And blah, blah, blah, blah!
Go gargle with broken glass and then fuck yourself in hell Mr. Blah Blah Blowhard
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I did my bit in 2017, purchased 6 firearms.
“She’s since added a few more — handguns, long guns, assault rifle…”
Wow, an assault rifle. Her husband must have left her some big bucks to be able to afford one (plus the transfer tax), Lucky her. /sarc
Just more clickbait.
Someone needs to contact Eugene Volokh.
“Question of the Day: Pay Criminals Not to Commit Crimes?”
This program already exists all over the US. It’s called Welfare, and while it doesn’t help the people who receive it, it sure helps the Democrats who pay it with OPM (other people’s money).
For the sake of the discussion, exactly what is your definition of a “long” freebore? I’m at a loss how a bullet can be “banging against the side of the throat” unless the bullet has completely left the neck of the round, the chamber is cut so far out that it’s dangerous, and whoever loaded them never checked the case nor the load with concentric measuring gauges.
While I REALIZE this is about long range, precision rifles, the entire throat issue is of interest to me. I’m at a loss how a so called “properly” throated round can shoot great, but so do many rounds that used CIP specs and can have no freebore and as much as 1.10 inches of lead. When BOTH shoot 3/4 MOA with proper loads, both are getting velocities at the upper levels of the round’s expected levels (and not wimpy at all)………I’m ready to toss it all out the window and just throat my wildcat long enough to use any bullet I may use. (Hunting purposes).
Don’t confuse the “experts”. They don’t get that “freebore” and the “jump” are completely irrelevant as long as the bullet bearing surface “hits the lands” – which are nothing but the “regular bore” (non-free bore?) minus the “grooves” cut into that bore – before that same bullet bearing surface clears the neck/case mouth. They picture bullets actually “banging around” in that “freebore” even though the “freebore” of the throat in “commercial” cartridges made to “SAAMI SPEC” will A) only be the “inside diameter” to allow a “slip fit” of the “outside diameter” of the bullet which is “oversize” for the actual BORE “across the lands” and B) is only there so PROPERLY “LOADED” AMMUNITION WITH THE COMPONENTS AND VARIOUS DIMENSIONS BEING CORRECT BY “SAAMI SPEC” HAS ROOM FOR THE NECK TO EXPAND TO “RELEASE” THE BULLET and C) will always be “shorter” than the bearing surface of the shortest “commercial” bullet available in that cartridge’s caliber at the time the “SAAMI specs” ARE DETERMINED minus a significant “safety factor” in case somebody does the unthinkable and comes up with a LIGHTER AND CHEAPER AND SHORTER AND MORE CONSISTENT BULLET DESIGN.
THE “EXPERTS” CLAIM TO BE ALL ABOUT “ACCURACY” AND “PRECISION” BUT YET END UP WITH “PRECISION AMMUNITION” THAT’S TOO LONG TO FIT IN A “SAAMI-SPEC” CHAMBER/THROAT/MAGAZINE AND WON’T EVEN “CHAMBER” PERIOD UNLESS THEY “CUT DOWN” THE OD OF THE NECKS BECAUSE THE “GENIUSES” REFUSE TO “DAMAGE” THEIR “ACCURACY AND PRECISION” BY “FULL-LENGTH SIZING” THEIR BRASS. THAT THEY ONLY GET 4-5 RELOADS “MAX” AND FOR SOME REASON NEED TO TO “FIRE FORM” BRAND-NEW CASES SUPPOSEDLY MADE PRECISELY FOR A GIVEN “COMMERCIAL” CHAMBER AND AREN’T SMART ENOUGH TO “GET” THAT BOLTS AREN’T SUPPOSED TO “FLICK OPEN” AND “FALL CLOSED” AND DON’T IN GOOD RIFLES LOADED WITH QUALITY AMMUNITION PROPERLY LOADED TO “SAAMI SPECS” AND ARE ALL ABOUT TELLING THE REST OF US “NON-PRECISION SHOOTERS” HOW THE FUCK TO GET “SUB-MOA” ACCURACY/PRECISION OUT OF “CUSTOM” RIFLES/CHAMBERS/THROATS/CARTRIDGE DIMENSIONS WHEN MOST OF US “NON-PRECISION” SHOOTERS PRETTY MUCH EXPECT THAT KIND OF ACCURACY/PRECISION AS LONG AS QUALITY HARDWARE IS USED. ESPECIALLY SINCE $400 “BUDGET” MASS-PRODUCED RIFLE/OPTIC COMBOS THEY LOOK DOWN THEIR PRECISION NOSES AT OFTEN COME WITH “SUB-MOA” ACCURACY GUARANTEES THESE DAYS WITH NO STRINGS ATTACHED AND NO REQUIREMENTS FOR “PRECISION LOADED AMMUNITION” AT ALL. IN FACT, SINCE MOST “MASS PRODUCERS” OF “FACTORY” (THEIR “HIGH-END” PARTS AND COMPONENTS AND OTHER HARDWARE IS ALL HAND-MADE BY AGED, EXPERT “CRAFTSMEN” AND NOT IN “FACTORIES” APPARENTLY) RIFLES ARE ALSO IN SOME WAY, SHAPE OR FORM ALSO IN THE “AMMUNITION BUSINESS”, THEY SORT OF PREFER THAT “FACTORY AMMO” BE USED TO DEMONSTRATE THAT YOU DON’T HAVE TO BE AN “EXPERT” IN “BALLISTICS” AND “CUSTOM RIFLES” AND “PRECISION AMMUNITION” TO BE A “SUB-MOA SHOOTER”.
LIKE I SAID, DON’T CONFUSE THE “EXPERTS”. THEY EXIST IN A PARALLEL UNIVERSE WHERE “SKILL” IS FOR SALE EVEN IF THEY NEVER MANAGE TO FIND THE “STORE” SELLING IT.
Boy, if you don’t know that a REAMER is not a “drill bit” or “boring tool”, there’s not a hell of a lot of hope for you ever managing to get more than “4 rifles” out of a reamer before it needs “reconditioned”. And if you think its POSSIBLE to “recondition” a REAMER by “grinding” or otherwise removing metal from it besides “reconditioning” it down to a SMALLER CARTRIDGE/CHAMBER, there’s even less hope for you. Where did you go to “gunsmith school” and how many cereal box tops did your “degree” cost you?
Blah, blah, blah, blah, blah, blah… Look at me I’m an expert on everything in the history of everything… I know more blah, blah, blah than any blah-blahologist… And if you disagree with me I will call you names and TYPE IN CAPS to prove my superiority. And blah, blah, blah, blah!
Go gargle with broken glass and then fuck yourself in hell Mr. Blah Blah Blowhard