I've looked everywhere online and can't find anything regarding grinding a barrel throat.
I plan to use a tool post grinder holding a die grinder with a small diamond bit in a lathe to throat a hardened barrel
Am I way off? Am i missing something as to why this wouldn't work well?
Any input is much appreciated!
What gun what caliber?
Got a .22 .30 .32 .357 .38 .40 .41 .44 .45 .480 or .500 S&W cylinder that needs throats honed? 9mm, 10mm/40S&W, 45 ACP pistol barrel that won't "plunk" your handloads? 480 Ruger or 475 Linebaugh cylinder that needs the "step" reamed to 6° 30min chamfer? Click here to send me a PM You can also find me on Facebook Click Here.
I’ve always heard about reaming the throat. Is there a specific reason for grinding it? What exactly is your project?
That same shadow 2Originally Posted by DougGuy
The reason for grinding is it is hard as woodpecker lips. A carbide reamer wouldn't do it.
If the steel is that hard there is an issue with it being brittle. Even in a 45 cal barrel by the time you get past the case section the wheel is going to be out along ways unsupported and vibration chatter will be an issue
Most barrels arent that hard even stainless most cut very well with a HSS reamer ran slow and with lots of oil. I know of reamers that have cut a lot of chambers before needing a touch up to sharpen the edges.
If the barrel is actually that hard then there is something causing it. What gun whose barrel and more info may be needed here.
M14 and M16 barrels were sometimes chrome lined as were some machine gun barrels. Black stars billed to be harder but still cut with HSS. Chrome is hard ( around 70 RC) and would require grinding or lapping.
I believe before I tried grinding I would turn up a brass lapp or a lead lapp and a bushing for the chamber and lapp it in by hand.
What is the goal for doing this. moving throat forward to allow a longer load OAL? clean up a worn/ burnt out throat? reangle it for a certain bullet?
The a couple of reasons that a barrel would be that hard is it's Melonite treated, chrome plated or is a machine gun barrel with a Stellite liner. Carbide will cut Melonite treated barrels. Several issues with throating a chamber using a tool post setup using a die grinder. First is the length of the diamond bit. In a 45 ACP chamber this may not be a problem but in a .223 chamber it's going to be a huge issue. Same for surface finish. Die grinders normally don't use high precision bearings.
Without knowing what cartridge the barrel is chamber in answer will range from not very doable to very doable.
Last edited by M-Tecs; 10-15-2020 at 02:46 AM.
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The goal is to make some amount of freebore.
My understanding is it acts as if its case hardened. And it is about impossible to get through the first few thousandths and once a reamer breaks through it will cut easily so the groves aren't cut at all and the lands cut deeply if that makes sense.
It's a 9mm
I also have a 9mm ar barrel I can attempt first, just incase it doesn't work I will not be out too much money for a replacement.
Last edited by Flailguy; 10-13-2020 at 10:17 PM.
Normally the reamer has the throat, free bore and lead ground into it and its all cut to saami specs or what was specified when the barrel is chambered. Most barrels Ive worked with dont work harden that much.
Have you tried turning the reamer by hand slow with a heavy dose of cutting oil. Reamers are meant to run at slow RPMs and more pressure. If your set up in the lathe already try a center in the tail stock and insert reamer in to chamber then while holding tension with the tail stock hand wheel turn the reamer with a wrench. Lock the spindle in lowest gear. The center will keep reamer centered and the tail stock will give straight even pressure. The slow turning will give the reamer a chance to cut.
Considering a carbide reamer did a poor job on this barrel I didn't want to destroy my hss reamer I could try but from what I was told it would ruin it.
Diamond does a poor job grinding steel.
Are you using an actual throating reamer or a machine reamer. They are different. as to geometry and angles they cut.
Why do you want to do this ?
Free bore is not all ways a good thing
I have a Manson hss throating reamer I have used on other barrels but not this one. I already had this barrel reamed professionally with a carbide reamer but it will still not chamber the .358 boolits I use in all my other 9mm's. My entire goal is to be able to shoot the same boolits in all of them.
Die grinder would not be capable of doing a semi-adequate job at all, for the reason given above. An ID grinder might do a semi decent job, but a good one would cost $250,000 or more.
Spell check doesn't work in Chrome, so if something is spelled wrong, it's just a typo that I missed.
How much runout would you expect from a die grinder on a lathe? .001-.002"?
How much runout would you expect from a die grinder on a lathe? .001-.002"?
Are you trying to increase the lead/throat length or increasing the chamber size? Some tight 9mm chambers won't accept .358" diameter bullets due to increased the brass size from the .358" bullet.
Not sure we are all using the same terms. https://bisonballistics.com/articles...rifle-chambers
SAAMI 9mm chamber specs on page 27 https://saami.wpengine.com/wp-conten...sting-Copy.pdf
Last edited by M-Tecs; 10-14-2020 at 02:02 AM.
2nd Amendment of the U.S. Constitution. - "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."
"Before you argue with someone, ask yourself, is that person even mentally mature enough to grasp the concept of different perspectives? Because if not, there’s absolutely no point."
– Amber Veal
"The Highest form of ignorance is when your reject something you don't know anything about".
- Wayne Dyer
I'm trying to increase leade/throat length. The chamber is fine.
Why would a 9mm barrel be hard at all? Something here does not compute.
If it's surface treatment (again...why?) cutting through it will expose softer metal underneath, right where it will do the least good - in the leade.
Straight flute reamers are very bad at handling interrupted cuts. If it absolutely must be reamed, you'll need a spiral flute reamer. Good luck finding one except at a price reminiscent of the national debt. Remember it's gotta cut not only the freebore but the leade taper, too.
Might try making a brass lap with a pilot to keep it centered?
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