GP100 Forcing Cone Wear

[Chuck 100 yd]

Ruger will take care of you...

 

[Laserbait]

I've been tempted to send it back, however, it's shooting so well I really don't want to change it. And yep, she does spit, but I only get powder burns on my face 4 out of 6 shots. :lol:

Eventually I'll get in in to Ruger...

Are the 1/2 lug models more desirable/collectable? Maybe I can ask Ruger for the barrel back if they do replace the barrel.

 

[David Bradshaw]

Laserbait.... suggestion of Wild Weasel to return GP-100 to Customer Service offers the most direct therapy. Call service manager, requesting----as you prize accuracy of present barrel----that they set back the barrel. They may only replace barrel. Your forcing cone is deep, and rough. Appears concentric. These things difficult to judge accurately from photos. The deep cone is easily seen. For best accuracy, the best way to clean a deep cone is to set back the barrel, which requires trimming the barrel shoulder. Correct thread timing is based on lathe-turning enough should to hand tighten barrel to 10-12 degrees BTDC.

When it comes to the revolver barrel, the torque wrench is for an amateur. THREAD TIMING is for a pro. How else do you think those beautiful 19th Century Colt and Smith & Wesson frames weren't buckled, and they shot so straight?
David Bradshaw

 

[Carry_Up]

Your Ruger needs the forcing cone cut. This is a touchy subject as factories don't really do this as best needed. I have my own cutter and cut all mine with the 11 degree cut which works best for cast bullets. I believe Ruger does an elementary cut on some revolvers at 9 degrees, which is supposedly better for jacketed bullets. However, many forcing cones on NIB guns appear to me to have no cut at all. Find a local gunsmith who can do this for you. They charge approx. $20.00 or so.

The actual forcing cone on the op's gun looks exceptionally smooth - someone may have already done a clean up because the factory rarely does the job this well.

Changing the forcing cone angle - perhaps this what you were suggesting - will not limit or prevent forcing cone erosion. The angle change in combination with throat reaming will improve accuracy with lead, however. Cutting the face of the forcing cone, which I call facing (since that's what it is), will increase the b/c gap. You don't want to increase the b/c gap arbitrarily. That cut should be done once at the factory, or once if the factory forgot to do it.

Obviously if the barrel is set back, the b/c gap once again has to be checked and re-cut if necessary.

 

[David Bradshaw]

FORCING CONE is not a touchy subject with me. I've studied it long and hard. Pretty well bled dry of opinions on the matter, as experience at long range with a nearly infinite variety of tolerance combinations replaced opinion and conjecture with graphic revelation on target. The term "forcing cone" includes two technically separate areas----forcing cone and barrel face. When we speak of "forcing cone erosion" we refer to the barrel face.

With multiple chambers separate from the barrel, accuracy from a revolver depends on certain of those relationships supporting one another. as the link between chamber exit----throat----and rifled bore, the forcing cone guides the bullet into the rifling. Either the bullet seats straight and balanced or arrives obturated----deformed out of balance. A bullet under pressure yet not spinning, has no grip on stability. Only a spun bullet has a chance at stability. A bullet deformed passing though an oversize forcing cone, or manufactured out of balance, cannot fly straight.

PERFECT REVOLVER
A perfect revolver has perfect chamber-to-bore alignment. Theoretically it should not need a forcing cone at all. However, a very short forcing cone does wonders to guide the bullet into the rifling. The chamber supports the bearing surface of the bullet to hold it straight and maintain bullet base square to bore axis, as shoulder of bullet enters the rifling. A perfect forcing cone lines concentric to bore SMOOTH----without tool marks----especially absent a hideous a ring where cone meets rifling. A perfect bore exhibits uniform lands and grooves----no tight or loose spots.

Brief description paints forcing cone as vital link between throat and rifling. The forcing cone can perform a minor miracle correcting chamber-to-bore misalignment----providing it is shallow and chamber throats are not oversize. For ay least two generations the "11-degree included angle" forcing cone has been an industry standard. One degree more or less is irrelevant. The problem got out of hand in the early 1980's as, in answer to product quality issues and a surge in magnum ammunition consumption, spurred by silhouette, S&W and Ruger resorted to hogging the forcing cone. Spitting follows from forcing cone erosion and chamber misalignment. In error, the fat forcing cone answered. Accuracy fell. Shooters bought and sold revolvers in search of an accurate wheelgun. Which caused shooters to leap on Dan Wesson, Seville, and Freedom Arms revolvers,in pursuit of accuracy at first purchase.
David Bradshaw

 

[G. Freeman]

Hi Dogmax,
Even if Ruger replaced the barrel, you may see the same forcing cone wear after another 1200 rounds. Forcing cone wear is normal when using magnum loads. But certain powder & bullet combinations can accelerate this wear.

If I were you, I'd just keep shooting it. When it begins to look like laserbait's pics, then it's really time to replace.

 

[DGW1949]

Hi Dogmax,
Even if Ruger replaced the barrel, you may see the same forcing cone wear after another 1200 rounds. Forcing cone wear is normal when using magnum loads. But certain powder & bullet combinations can accelerate this wear.

If I were you, I'd just keep shooting it. When it begins to look like laserbait's pics, then it's really time to replace.

T
Yep....that's perty-much the bottom line.

DGW

 

[dogmax]

Got my revolver back today. Repair notes say they replaced the barrel. Hopefully it will shoot as good as it looks!

 

[Laserbait]

Got my revolver back today. Repair notes say they replaced the barrel. Hopefully it will shoot as good as it looks!

Got a chance to shoot it yet?

 

[GP100]

Funny thing is, on all my gp100's, I shoot magnums in the 125gr range. Have shot thousands of them. No errosion to forcing cone at all. Not sure why.. Could it be the powders I use? I run a 125gr hornady XTP-HP With 19.7gr of H110 powder. For my 38's, I go 125gr lead round nose with 5.5gr of HP-38 powder. Never had any issues with any of my revolvers with these loads.

Anybody might be able to explain? Would appreciate it since I have never seen these issues crop up.

 

[dogmax]

Got my revolver back today. Repair notes say they replaced the barrel. Hopefully it will shoot as good as it looks!

Got a chance to shoot it yet?

Yes. I put 50 rounds through it. Preformed as expected.

 

[GP100]

Glad your gun shoots fine dogmax.

As to my questions, thanks for all the answers guys..

 

[kobs57]

Hi new to the forum but not to this gun, sorry to resurect an old thread but looking for this problem on the internet i've come to this place. I've had a GP100 for nearly 2 years been shooting mostly 158Gr. plated bullets with 8.4Gr. of hodgdon longshot according to the conservative Hodgdon site this is a max load, but I've shot store bought rounds with a lot more kick and flames... Any ways this is a close up picture of my forcing cone after not even 1500 rounds through. No top strap burn so I'm ruling out "abuse" from hot loads.I've always been taking extra good care of my guns as you can see from the picture. I'm calling a Ruger service center today (lucky for me it's like 20 minutes away from where I live) I just hope they're not going to tell me "normal wear" Thanks to all for the pointers I didn't know what to think of this

 

[Jimbo357mag]

kobs57 that looks pretty bad, not terrible yet though. ---- I think the reason some barrels show more barrel face erosion than others has to do with how well they are heat treated. Good luck, I'm sure they will take care of it.

 

[22/45 Fan]

For my 38's, I go 125gr lead round nose with 5.5gr of HP-38 powder. Never had any issues with any of my revolvers with these loads.

That a pretty hot load for a .38 Special. The Hodgon load data center for HP-38/WW231 powder with a 125 gr lead bullet recommends 4.8 gr max for a standard pressure .38 Special load and 5.5 gr max for a .357 load. You are certainly running +P pressures and perhaps a bit higher.

Obviously the GP will tolerate way above .38 Special +P pressures but that's a stiff load you are using.

 

[mike campbell]

Note that the "5.5 grain maximum" for 125LRN in .357 is actually a bit below 38+P pressure.

It's typical for powder manufacturers to set lead bullet maximums in magnum cartridges based on velocity rather than pressure.

 

[Onty]

This is the forcing cone on my 6" half lug stainless GP100. It has a had a steady diet of 158 grain plated bullets on top of 16.5 grains of Lil'gun, and the accuracy is phenomenal.

I've had a GP100 for nearly 2 years been shooting mostly 158Gr. plated bullets with 8.4Gr. of hodgdon longshot according to the conservative Hodgdon site this is a max load...

This clear indication what double base powders could do to revolvers. I remembered event when shooter was loading (top loads) for FA83 353, using H110 and 296, and had similar problem. Once he switched to IMR4227, further erosion stopped.

I do not have 357 revolver now, will probably go for 686 Target Champion (or DX, if I can locate it), and single base, nitrocellulose, powders will be the only one I will use.

 

[Dienekes]

As noted way above, I had this problem with two Sixes years ago. Nowadays there are no more replacement barrels for those guns, older K frame Smiths, and Lord knows what else. At least GP barrels will probably be around for a good long while.

I don't shoot many hot 125s anymore, partly because the blast and recoil are substantial (I'm not as tough as I once was) and my wheelguns are used for recreational purposes nowadays.