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Ammo/barrel suitability

March 1 2015 at 9:08 AM
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Dave  (Login Dave1500)

 
Hi All

This is an urgent enquiry. Has anyone got the answer to this problem. I have a stainless steel 6 groove 1 in 10 twist 6 inch barrel, fitted to a S&W 686.

Testing it out at 25 metres produced lousy groups - 3 to 4 inch was common. I used a variety of powders Bullseye, Viht310, GM3 and 231. (Viht 310 is slightly faster than Bullseye) The ubiquitous loads of 2.7 or 2.8 of Bullseye and Viht310 used with a very finely produced 148gr swaged HBWC, and the same with the other two powders. FPS ranged from 680 to 750 across all the rounds fired. The best group actually came from some solid wadcutters, hard cast and cheap as chips pushed around 850 FPS. It could cloverleaf 3 rounds, the other 3 spread individually. I did get some spitting from those. In the past I have shot a sub inch one hole group with these loads so this is a mystery to me.

One clue I have is that the barrel was crudely slugged previous to fitting (bullet hammered down a bit of the barrel) which measured .355. A bullet fired from the revolver was recovered from the backstop and although mushroomed nice and evenly at the head, the skirt again measured at .355. Although I cannot 100% rely on these measurements being that accurate, could this be the reason?

I am due to test it again this Friday but have only .356 158gr SWC and .356 125gr round nose - not the best for a PPC. Can anyone solve this mystery.

Cheers

 
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AuthorReply
JPE0392
(Login JPE0392)

Re: Ammo/barrel suitability

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March 1 2015, 11:11 AM 

BARREL MAY HAVE DAMAGE FROM SLUGGING IT OR COULD HAVE UNEVEN CROWN ON MUZZLE DUE TO DAMAGE (DENT)AND MAY JUST NEED TO BE RECROWNED TO CLEAN IT UP DOESN'T TAKE MUCH TO EFFECT ACCURACY AND RECROWNING IS EASY TO SEE IF THAT IS THE PROBLEM. JPE

 
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Dave
(Login Dave1500)

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March 4 2015, 10:28 AM 

Thank you JPE JB and Jim C for your responses. I will check and try all things mentioned. The heads I use are triple swaged .357 by a private person, and in another revolver I have, produce sub inch groups all cloverleafing to one hole - 10 rounds - shot standing unsupported. I take from that it's not me or the ammo at fault.

The throat to cylinder is 3 thou and very even. The forcing cone is a precise 11 degree as is the crowned muzzle end. The crowning was hand finished. Aristocrat rib not loose. Forcing cone cleaned of any lead using both choir boys and girls (LOL!)

I'm in the process of making up some .356 and .355 to test out on Friday.

If it still shoots rubbish then the barrel is coming off in favour of a bit of DONNELLY .357 8 groove 1 in 14 I've had hanging round for years.

Cheers all

Dave

 
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JB
(Login x-cop)

BBL COMPATIBILITY

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March 4 2015, 4:12 PM 

Dave,
Slug and double check bore diameter if you can. You may need to be using larger diameter bullits then .355-.356, that is a 9mm size. That could be your problem. And make sure to check cyl. throat diameters for bullit match.
If you can get your hands on some larger bullits give um a test try, before you start changing out bbls. Try everything you can first-my suggestion.
wont hurt nothing. Where are you located?

 
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JB
(Login x-cop)

Ammo/BBl

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March 1 2015, 11:50 AM 

Dave,
You may have "several" problems facing you. Have you checked the cyl. throat diameters to see if tight or oversize for the bullits you are using. How about forcing cone angle(11 or 5 degree cut) and depth. Did you range the the gun(bbl align to cyl's). Is there a tight spot where the bbl is screwed into frame. Yes, check muzzle like JP suggests, is it cut square to centerline of bore and undamaged. "IF" bore is .355 diameter, the .356 bullits should work fine. What is the quality of the bbl.? What make? Make sure bbl not cobby and leading up badly.
Try the .356 bullits with the load you like and check the cyl throats and muzzle condition firs.
These are suggestions only and it could be one simple solution or multiple factors. Guns like women, can never figure um out and when you get a good one keep it.(lol)
You mention finely produced 148 grain hbwc's. Who made uM? What diameter are they?.357,.358,359?
With a 1:10 twist bbl. these should work fine.
Again, just some thoughts, hope this helps.
Stay safe

 
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Jim C
(Login jamesrchapman)

Re: Ammo/barrel suitability

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March 1 2015, 9:26 PM 



make sure you clean out the cylinder throats and barrel with a choir boy wrapped around your brass brush chucked in an electric drill to remove all the leading that may be present. or, use a Lewis lead remover.

I'm guessing you have a leading issue. or, the other problems already stated.

I had a model 14-2 that had similar issues. turned out the barrel/cylinder gap was .006 on one side, and .020 on the other. shot monumental groups until I had the barrel forcing cone recut and the barrel turned back a turn to give me a constant .003 gap.

good luck!.

 
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Jim C
(Login jamesrchapman)

Re: Ammo/barrel suitability

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March 1 2015, 9:28 PM 

that should be chore boy.... lol

 
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JB
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Ammo/barrel suitability

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March 10 2015, 3:13 PM 

jIM,
And you don't need to be in a choir to use the chore boy LOL

 
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Dave
(Login Dave1500)

Results

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March 15 2015, 9:48 AM 

Hi Guys. Well I tried a variety of .355 and .356 heads but still the same sort of grouping. A bit better but nothing startling. I did think I was onto something when my first 4 shots made one ragged hole but then had two fliers about 2 inches away in two different directions.

An interesting development though, I got in contact with Krieger Barrels - oh to get one of those - who gave me that according to the SAAMI the .357 should have a bore of .346 and grooves to .355. The question is that is this just for rifle barrels (mine is a Bergara rifle barrel) and should revolver .357 barrels be just that - .357 when shooting lead?

Krieger have offered to do me a barrel at .346 bore/.357 groove. Would that be too much groove and start shaving lead.

I note all your earlier comments. Although the forcing cone is 11 degree, should it be longer than the .075 it is now. The crown is also 11 degree cut straight to the rifling. Should I have a shallow flat recess around the exit hole or what?

Any ideas as your help is most welcome

 
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Unregistered Member
(Login JPE0392)

Re: Results

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March 15 2015, 10:29 AM 

There is an 11 degree depth gauge to set forcing cone depth if to shallow recut to correct depth. Concerning crown clean muzzle well fire several shots (6) then look at muzzle if fouling pattern is even and consistent all the way around muzzle, crown is square to rifling and bore and good to go. Should you find pattern inconsistent recut crown. JPE

 
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