Revolvers/ barrels/forcing cones

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Post by Jerry Keefer on Thu 7 Apr 2016 - 23:14

This gun does not shoot well.. Inspection reveals a very poor forcing cone.. Forcing cones are poor when cut with some degree of precision.. This one has very little if any precision involved.. The bullet shows the point of engagement with the rifling.. See how much of the projectile is completely unsupported..Still in limbo between the cylinder and the bore.  Wonder why revolvers lead excessively.. ?? There's a clue..The last picture shows the barrel zeroed in the spider, and the Taylor Throat reamer doing it's job..more to follow...   
Revolvers/ barrels/forcing cones IMG_2858_zps8go8kvrf
Revolvers/ barrels/forcing cones IMG_2861_zpscppau3rx
Revolvers/ barrels/forcing cones IMG_2859_zpsg0fgba0n
Revolvers/ barrels/forcing cones IMG_2860_zpsiyb5ng1x
Revolvers/ barrels/forcing cones IMG_2862_zpsjadcsyg2
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Post by Fire Escape on Fri 8 Apr 2016 - 1:46

I am anxious to see the 'After' picture of that throat even though it will make me jealous. At least one of my S&Ws looks very much like your 'Before' picture.

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Post by s1120 on Fri 8 Apr 2016 - 11:00

Very interesting. Is this something you would now set the barrel back, to adjust the depth of the forcing cone?

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Post by Jerry Keefer on Fri 8 Apr 2016 - 17:13

Finished on this end..The projectile is completely contained and supported within the barrel before it begins to engrave. No chance to distort as a result of a forcing cone angle.. The angle/leade cut by the Taylor Throat reamer is a very gentle 1-1/2 °  Smooth gentle transition into the rifling.. Next, flip it to do the crown.. I still have reservations about this barrel, but will try all this as a last chance to salvage it.
Revolvers/ barrels/forcing cones IMG_2863_zps4a2y9src
Revolvers/ barrels/forcing cones IMG_2873_zpstdcrylmt
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Post by Virgil Kane on Fri 8 Apr 2016 - 22:16

Jerry,

I have to ask. Is the bullet your showing going into the barrel a WC or SWC ?

If I had to guess I would say WC but then would question why it went so deep into the barrel on the first picture (pre Taylor throat). The forcing cone doesn't look like it would be that deep to swallow up 1/2 of a solid base WC but the pictures can be deceiving. 




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Post by Jerry Keefer on Fri 8 Apr 2016 - 22:25

Virgil Kane wrote:Jerry,

I have to ask. Is the bullet your showing going into the barrel a WC or SWC ?

If I had to guess I would say WC but then would question why it went so deep into the barrel on the first picture (pre Taylor throat). The forcing cone doesn't look like it would be that deep to swallow up 1/2 of a solid base WC but the pictures can be deceiving. 




Virgil
200gr 45 swc
That revolver is a 625 S&W
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Post by Virgil Kane on Fri 8 Apr 2016 - 22:35

Oh, OK that explains the picture. I thought it was a 38 Special on a K or L frame.

Thanks Jerry.


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Post by HenryA on Sat 9 Apr 2016 - 1:27

I'd love to hear about the results on paper. (whenever that happens)

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Post by inthebeech on Sat 9 Apr 2016 - 8:27

I struggled trying to find the source of leading in a K-38 that was amazingly accurate but only until the leading started to influence performance. Bullet hardness, sizing diameter, lube type, and of course endless variations of velocity, crimp style and seating depth.  Literally a "years" effort.  Then I sent it off to a revolver smith for a Douglas barrel.  Now I can literally vary almost ALL of the above and get great accuracy with everything and no leading with anything.  When I inspected the forcing cone up close, I found out why.  Now I am spoiled and would have a hard time NOT rebarreling every additional revolver I might buy.  That's why I will probably always have my one revolver.  Sure opened my eyes.
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Post by Bigtrout on Sat 9 Apr 2016 - 10:46

Thanks for the prompt, Jerry.  I looked at my 986 forcing cone with a loop and found a burr on the face (that was probably perpendicular to the bore before firing) extending about .007-.010" into the cone.  The burr began a 7:00 and ended at 11:00.  I gently used a round jeweler's file under 3X mag to remove the burr leaving a .002" or so 15-degree chamfer where the burr had been.  I'm hoping this is the last quality issue I find with this gun.  I would not have inspected the cone if I hadn't seen your excellent thread.

 I would have sent it back to SAW but I just got it back for burrs on the lands at the muzzle that looked like an incomplete crown cut.  The burrs are gone leaving a shallow 90-degree chamfer but I did not get a new barrel (rough and scratched bore) because it "met the 25 yd. 3" group spec").  My riflesmith friend also said the bore was rough enough to justify replacement.  Needless to say, my confidence in SAW's warranty policy is shattered as is my choosing SAW for their quality reputation.   I'm thinking the rough bore is an artifact of cone face burr particles being blasted through the bore.

This will be my first and last SAW firearm.  Springfield, by comparison, has addressed all the deficiencies I listed on my RO, no questions asked.  I'm not asking for sympathy because there are thousands out there with worse SAW issues, but it really takes the fun out of being this gun's owner and operator.  

I did get one range session with 8 of 10 rounds 3/4" c to c off a manual rest at 25yds after it returned but the poor quality thought is kind of stuck in my head.  Live and yearn.
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Post by 243winxb on Sat 9 Apr 2016 - 11:33

The cylinder timing/alignment would also seem to play a major part in the accuracy.   Not just the perfect barrel?  Great photos, thank you.
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Post by Jerry Keefer on Sat 9 Apr 2016 - 12:02

243winxb wrote:The cylinder timing/alignment would also seem to play a major part in the accuracy.   Not just the perfect barrel?  Great photos, thank you.
Yes
Extreme accuracy of any firearm equals the sum of all the parts..but, as I have said before, we now  have superb machining and fitting methods, as compared to just 25 years ago.. That leaves the  barrel as the last frontier..It has basically remained unchanged for 100 years..Look at that forcing cone... Looks like it was carved out with a stone axe..It's an antiquated transition method to begin with..  The riflemen/smiths are light years ahead of the pistol game  because we are stuck on yesterday.. That's the way it has always worked..so it must be right..Right??
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Post by Jack H on Sat 9 Apr 2016 - 14:16

Jerry I understand has retired.  Who will do the cone on my 25-2?
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Post by Jerry Keefer on Sat 9 Apr 2016 - 14:26

Land to groove ratio... Factory (right)compared to a match grade Douglas..(left, narrow land)
Revolvers/ barrels/forcing cones IMG_2874_zpsxygdt8sb
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Post by Jerry Keefer on Sat 9 Apr 2016 - 14:30

Jack H wrote:Jerry I understand has retired.  Who will do the cone on my 25-2?
Jack, I don't know for sure..
Jim Stroh, the master of the Taylor Throat  has retired also... Pinnacle Guns in PA is operated by Mark Hartshorne.. He is a revolver competitor, master machinist, and a Guild member.. I would certainly consider giving him a call..
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Post by JIMPGOV on Sat 9 Apr 2016 - 16:03

"Land to groove ratio... Factory (right)compared to a match grade Douglas..(left, narrow land)"

AAAHHHH ! NARROW LANDS LIKE THE APEX BARRELS OF OLD. JP

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Post by troystaten on Sat 9 Apr 2016 - 16:51

Thanks for showing us what you did to the forcing cone, pretty appalling how bad it was, my S&W's from the early 70's look much better.

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Post by Jerry Keefer on Mon 11 Apr 2016 - 17:54

Results of the Taylor Throat and crown work..
A little more explanation in the ammo forum..24 shots.. 20 are inside of  1.710 X 2.00. All mixed practice ammo.. The circle is 3 inches. one low flyer..attributable to, the group gremlin..
I will test the other gun, hopefully tomorrow..
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Post by james r chapman on Mon 11 Apr 2016 - 18:46

I could make it shoot 5" groups, lol
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Post by rreid on Mon 11 Apr 2016 - 23:09

Jerry, would the Taylor throat be a good idea for a model 19?  Wondering if it would make the thin part of the barrel at 6 o'clock even thinner and more fragile. Or if by moving the point where the bullet contacts the rifling further in, where its supported by the frame, the barrel would be less likely to crack.
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Post by Jerry Keefer on Mon 11 Apr 2016 - 23:40

rreid wrote:Jerry, would the Taylor throat be a good idea for a model 19?  Wondering if it would make the thin part of the barrel at 6 o'clock even thinner and more fragile. Or if by moving the point where the bullet contacts the rifling further in, where its supported by the frame, the barrel would be less likely to crack.
When done correctly, the process does not change the tenon wall thickness from the original forcing cone.. It is a free bore... The lands are removed and approx. .0005 of the groove diameter.. The entire length of bullet should enter and seat against the 1-1/2° leade with finger pressure..
This is a common failure... Cones contribute to lead transfer..Lead build up increases the possibility of  cone breakage..Forcing cones are archaic.. The barrel cannot be merely removed.. Much of the damage must be machined away, and pressure relieved or the frame threads will be damaged/as in destroyed, removing the barrel.I do not see evidence of a frame crack on this revolver...yet..I'll clean it up more...
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Post by Jerry Keefer on Mon 11 Apr 2016 - 23:42

As Jim Stroh once stated.. "There has never been a revolver, that didn't benefit from a Taylor Throat."
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Post by troystaten on Tue 12 Apr 2016 - 0:36

Would you do a similar treatment on a .22 revolver?  My Model 17 is pretty accurate but would this make it better?

thanks

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Post by john bickar on Tue 12 Apr 2016 - 1:00

I feel like a Marksman must feel when squadded next to a High Master.

I don't even know what I don't know about what's going on here.

Wowsers. Thanks for sharing your craft, Jerry. Your photos are meticulous.
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Post by john bickar on Tue 12 Apr 2016 - 1:03

james r chapman wrote:I could make it shoot 5" groups, lol
Braggart  Very Happy
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