Model 27-2 forcing cone erosion

[D1911]

I picked up this 5" 27-2 from the original owner a while back. He said he bought it new in '73 (S/N N166164) and only put 200 rounds through it, but didn't say which rounds were shot (and I didn't ask). I noticed the gun was a bit dirty when I bought it, but didn't think much of it as the gun was overall excellent. I did a detail strip of the gun and while cleaning, noticed the erosion at the forcing cone. I've had a number of 27s and 28s (still have two 28s) over the years and shot them a bunch, but never had one with this type of erosion.

So, would this have been caused by hot Magnum rounds, timing (timing is fine), or something else? Although the gun shoots fine (I've only put 25 rounds each of factory mags and .38 Specials), I was thinking of taking it to my smith and having him set the barrel back. Or, I have a mint 3 1/2" barrel that would look mighty sweet on this gun. The wear just bugs me. What do ya think?

 

[ken158]

Looks like lead to me…

 

[Vtgw938]

I would have to look at all mine to see how sharp they are. Yours looks the same all the way around. I wouldn't bother with it but I know what you mean about bugging you. I had a leaf screw I couldn't get out and I had in drilled out just because I want every screw to be able to be removed.

 

[D1911]

Looks like lead to me…

Nope, scrubbed it and used a lead removal cloth. Made no difference.

 

[Farmer17]

How is the barrel to cylinder gap?

 

[Mike SC Hunter]

I'd forget it and shoot it.

 

[tennexplorer]

I would say you have a barrel cylinder gap that exceeds .006", and it has been fired with magnum loads. When Little Gun first came out there were a lot of complaints that it cause wear like that due to flame temperature. I had a Model 27 barrel with wear like that but more severe. I set it back one turn and used it in a project.

 

[Yendor357]

Yeah, that thing is shot, toast, junk. There is only one way to recoup some of your loss is to sell it to me. Im always there to help out a buddy.


Seriously, just shoot it. Take it to the range. Let the gun talk. If it shoots good and chronographs well, forget about it. Just about everything I own has a tiny or not so tiny flaw. I just don’t point it out to anyone.

Those old 27s were great guns; way overbuilt for the .357. I’ll bet there’s nothing wrong with your gun. To me, it looks like that a bevel machined into the end of the barrel.

 

[6string]

Yes, that is forcing cone erosion. Been there, done that.
(Additionally, it looks like you’ve got some rough file work on the flat of the barrel breech.)
I bet the B/C gap is on the large side (.008”-.010”). The large gap just accelerates this wear, for some reason.
Combined with few hundred magnum rounds and that’s what happens.

2400, 296, H110 are a few of the powders that I’ve associated with the problem.

Yes, by all means, have the barrel set back one turn. It’ll give the opportunity to reset the B/C gap and clean up the erosion and tooling marks.
This is a process that can be done more than once to freshen up a barrel.

PS: I have personally observed improved accuracy by doing a barrel set-back, at least in the case of Model 29s.

 

[stansdds]

It might have seen only a couple hundred rounds fired, but I'd wager all of them were 125 grain jacketed full power factory loads or reloads using H-110/W-296 as the powder. Given that it is an N-frame and the barrel shank diameter is far larger than it ever needed to be for the 357 Magnum cartridge, I would not worry about it. The fix would involve removing the barrel, turning down the barrel shoulder, reinstalling the barrel, adjust the barrel shank to obtain correct barrel-cylinder gap and maybe re-cut the forcing cone. More work than it's worth, in my opinion.

 

[steelslaver]

First question is how well does it shoot. Everything else is really secondary.

IF the barrel is set back one turn, that is .02777. Not only will the barrel shank face need trimmed to remove the erosion and adjust the gap, who ever does it also has to file back the pin notch in barrel threads and shorten the ejector rod and center pin that same .02777. Neither is a big deal or noticeable.

A good smith should be able to set it up with a .004-006 gap. It won't show except a barrel thread might be exposed behind the frame and the face of the barrel will be in the white until a few rounds scorch it black. Will it be more accurate? Maybe. Will it get more velocity? Maybe 10fps tops.

Its only money.

 

[RKmesa]

Your barrel looks like brand new compared to this pre-war Magnum barrel

 

[Pine_Worker]

I'd forget it and shoot it.

What he said ^^^ Just shoot it and enjoy it!

 

[Piwo]

I have a few magnums with more erosion than yours. They shoot fine with no accuracy issues. Two of them are K frames and I restrict them to 38 spl. ammo for the most part due to the encroachment to the "6 oclock" flat spot. On my L frame and N frame I don't worry at all.

 

[Hair Trigger]

I picked up this 5" 27-2 from the original owner a while back. He said he bought it new in '73 (S/N N166164) and only put 200 rounds through it, but didn't say which rounds were shot (and I didn't ask). I noticed the gun was a bit dirty when I bought it, but didn't think much of it as the gun was overall excellent. I did a detail strip of the gun and while cleaning, noticed the erosion at the forcing cone. I've had a number of 27s and 28s (still have two 28s) over the years and shot them a bunch, but never had one with this type of erosion.

So, would this have been caused by hot Magnum rounds, timing (timing is fine), or something else? Although the gun shoots fine (I've only put 25 rounds each of factory mags and .38 Specials), I was thinking of taking it to my smith and having him set the barrel back. Or, I have a mint 3 1/2" barrel that would look mighty sweet on this gun. The wear just bugs me. What do ya think?

I think you have a 50+ year-old revolver that has been shot a fair amount; it also has moderate flame cutting under the top strap. My guess is a slow, hot powder with lighter weight bullets (110 and 125 grain). The erosion is there, but doesn't extend far on the back surface. I wouldn't worry about it, keep shooting it if it's mechanically sound. Refrain from lightweight bullets. They are shorter than heavier ones and even a fast powder is still burning when the back of the bullet passes the B/C gap. The flame front hits the rear of the forcing cone and top strap above the B/C gap. Measure your gap and check the cylinder for end play. Excessive end play can widen the gap.

 

[H Richard]

I just can't understand how so many people still use the Hot 125 gr. bullets. They have caused nothing but trouble. As long as it shoots good (With 140 Gr or longer bullets), Continue to shoot it. When it loses accuracy, set it back.

 

[BigMuddy]

I too have been there done that with a FA gun and Lil Gun powder. I too couldn’t leave it alone. If I was going to have it fixed I would be very tempted to use that 3 1/2” barrel.

Dan

 

[Alk8944]

OPs photos show perfectly normal erosion of the breech of a magnum barrel, nothing to worry about. The only other comment I have is the gun has probably been fired well more than 200 rounds! What does amaze me is that magnums erode the breech of the barrel so little! Think of the heat and pressure of the gasses escaping through the barrel-cylinder gap and it is a wonder that they wear so little from erosion.

 

[steelslaver]

It would be interesting to know the temperature and velocity of the gasses as they escape

 

[pantannojack]

I'd recon the lil ol lady only drove it to church on Sunday shot it 200 times on the way home. Check the road signs for holes.

Otherwise I think it looks brand new for a magnum.