Throating Hardened Barrels With Carbide

[DougGuy]

A LOT of current handgun manufacturers are turning to various means of heat treating barrels to increase the life of the barrel (and reduce warranty claims) these processes known as Tenifer, Melonite to name two that use the salt bath for treating, and nitriding as well. The salt bath hardened barrels are put through a much more thorough process than the surface treating like case hardening, they take a dip in a 1500F bath and are soaked in it for a specified amount of time. This often results in a barrel that's hardened all the way through, not just the surface.

Suffice it to say that carbide reamers are the only tooling that will successfully "throat" one of these barrels, that is to cut some smooth freebore ahead of the chamber, and push the leade-ins of the rifling farther forward to allow for chambering boolits seated to the published COA in load data, instead of being forced to seat down farther in the case so the gun will function.

The downside of using carbide for this is that the carbide reamers wear VERY quickly, and after only 10 or 12 barrels they start cutting slower, cutting smaller, not as smoothly, and they need resharpening. Let's say you custom order a throating reamer and you wait 6 months for delivery, and cost is 3x what a HSS reamer costs, and it only does 10 barrels before it's time to have it sharpened, you come to the realization that every time you use that $300 dollar reamer, it eats up roughly $30 worth of the cost to throat a single barrel. You send it out to have it sharpened, it costs in excess of $200 for this, plus a 6 month wait, only to get a new edge on the flutes that will be toast again after 10 or so barrels.

It is an expensive and time consuming game to stay in, in some cases it is cheaper and much more practical to source an aftermarket stainless barrel that can be throated to your heart's content with HSS tooling, for not much more than the cost of having a hardened barrel throated. It also gets you out of voiding a warranty by modifying the factory hardened barrel.

There is no winning this battle, carbide vs. salt bath hardening, you can't even break even. And there are some barrels that the carbide reamer won't cut, you can and will seriously ruin the cutting edges trying to throat one of these case hardened barrels, which in fact is MUCH harder on the surface than salt bath hardened barrels.

To meet the need for throating these barrels, I would have to invest in 2 or 3 carbide reamers so that I would have one while the others are out getting sharpened, the cost now hovering around $1,000, I could not offer the service at an affordable price point, as the cost for labor would be as much as the cost of a stainless barrel.

After wearing out several carbide reamers, not willing to forego the cost and time involved in getting them sharpened, I have been forced to back away from throating the hardened barrels, too much of an uphill battle.

[P Flados]

You make a very good point.

I had a 300 BO barrel that I wanted to make more cast friendly, but found the treatment (melonite as I recall) made any improvement impractical. Coincidentally, the fix involved purchase of a stainless 300 BO barrel.

If the goal is only a small amount of material removal, an abrasive approach (lapping, honing, etc.) with diamond grit might be able to remove the material. However, I see reliably controlling the final shape as very challenging.

[littlejack]

I had Doug throat three of my 9mm barrels a couple months back. One of them was purdy tough on his carbide reamer. He did manage to get the job done, but he did have to get his carbide reamer sharpened. I felt bad, because others were having to wait for Doug to get his reamer back to have their barrel done. Thankyou Doug for your lengthy explanation of what it take to throat one of the hardened barrels. I hope that the members here on the CastBoolits do understand.
Regards

[DougGuy]

I had Doug throat three of my 9mm barrels a couple months back. One of them was purdy tough on his carbide reamer. He did manage to get the job done, but he did have to get his carbide reamer sharpened. I felt bad, because others were having to wait for Doug to get his reamer back to have their barrel done. Thankyou Doug for your lengthy explanation of what it take to throat one of the hardened barrels. I hope that the members here on the CastBoolits do understand.
Regards

That was my 35 caliber rifle throater, High Speed Steel, it's what I use to throat autopistol barrels. I called the SAR customer service tech, who assured me the barrels were not salt bath hardened, so I used it in the one barrel that did not cut at all, it wiped the cutting flutes so bad I had no choice but send it out to be sharpened. The tech obviously was reading from a text describing one of their models, and assumed the other model I was asking about was also not hardened. He was definitely wrong in his assumption.. I was barely able to finish the throating job with one of the well worn carbide reamers I have.

[FergusonTO35]

Hey Doug, you ever throat the barrel on an S&W SD9 series? They look like just regular stainless to me.

[littlejack]

I stand corrected. Thankyou again Doug, it worked. I can now seat my boolits out farther to the proper COL.

[DougGuy]

Hey Doug, you ever throat the barrel on an S&W SD9 series? They look like just regular stainless to me.

I could have without knowing which gun it came out of but yes it is SS. Would be a typical throating job for a HSS reamer.

[kenton]

I will preface this with I know nothing about the throat shape, but

Could you cut the throat profile with a solid carbide boring bar? The interrupted cut on the rifling might be hard on the boring bar but I was curious if it was something that could be considered.

https://www.mcmaster.com/3301A54/

[FergusonTO35]

I could have without knowing which gun it came out of but yes it is SS. Would be a typical throating job for a HSS reamer.

Thanks, I'm probably going to get one.

[alfadan]

I guess the 30,000 round barrel life wasn't good enough /s.

[DougGuy]

I will preface this with I know nothing about the throat shape, but

Could you cut the throat profile with a solid carbide boring bar? The interrupted cut on the rifling might be hard on the boring bar but I was curious if it was something that could be considered.

https://www.mcmaster.com/3301A54/

I would be difficult. You'd have to index the barrel off the lands and I have thought about the possibility of a miniature internal tool post grinder doing the actual throating work but by the time you figure all this out and come up with the tooling, you would either be doing it for minimum wage or you would be more expensive time wise than buying an aftermarket barrel.

[M-Tecs]

I will preface this with I know nothing about the throat shape, but

Could you cut the throat profile with a solid carbide boring bar? The interrupted cut on the rifling might be hard on the boring bar but I was curious if it was something that could be considered.

https://www.mcmaster.com/3301A54/

For hardened materials there are better choices than carbide but when you move into using a lathe the setup time and machine/tooling cost is significantly greater.

https://www.mmsonline.com/articles/i...cult-materials

[DougGuy]

For hardened materials there are better choices than carbide but when you move into using a lathe the setup time and machine/tooling cost is significantly greater.

https://www.mmsonline.com/articles/i...cult-materials

Exactly what I was saying earlier. The majority of these modern poly framed guns are compacts, and the barrels are short enough that you'd play hell getting them chucked up and zeroed in a lathe, THEN you gotta more or less invent some tooling that will reach into the chamber and throat the barrel. Accurately. Concentric to the bore. And make it affordable. I don't see it happening in that order.

I will say this about the industry. They DO NOT want you to use handloads, they DO NOT care if their barrel will only accept the majority of factory ammo, this is how they deter you from shooting cast handloads and they along with the ammo manufacturers are good with that.

[HWooldridge]

Could you jig grind a barrel (on the right piece of equipment)?

[M-Tecs]

Could you jig grind a barrel (on the right piece of equipment)?

Yes, I can be done with a variety of methods. The issue is, not if it can be done, but can it be done cost effectively?

[charlie b]

A good machinist could do this, but, the job will probably cost more than a new barrel

[Moleman-]

I don't blame you one bit. I have a AR-223 pistol barrel with a tight neck. Wish I would of caught it in time to return it, but it was well past the return time by the time I installed it and found the defect. It has the nitride finish and isn't worth ruining my 223 reamer on or buying a carbide reamer. I also have no interest in trying to lap the neck out at least .002". GMB had a sale on blanks, so it's getting the barrel extension pulled and a new barrel made for it.

[contender1]

This is a very interesting post.

Doug,, can you share info on what manufacturers are using the Tenifer or Melonite methods? And is it just handguns or in rifles too?

[DougGuy]

This is a very interesting post.

Doug,, can you share info on what manufacturers are using the Tenifer or Melonite methods? And is it just handguns or in rifles too?

A BUNCH of manufacturers are using hardening methods from salt bath to nitride coating, basically if it's a flat black finish, it's hardened. Glock uses tenifer, plenty of others use melonite, ALL of the poly framed Springfields have salt bath hardened barrels

AR barrels are often nitrided, probably salt bath hardened as well. Milsurp barrels are often hardchromed in the bore, both rifles and handguns.

You can always go to the mfgr's site and look or call their customer service and ask.

[Silvercreek Farmer]

Are you running into hardened revolver cylinders? If so, any problems with the hone cutting them?