extreemly tight Colt bore

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  • Last Post 25 August 2011
inthebeech posted this 10 October 2010

I just slugged (twice as well as confirming the results with inside callipers and a vernier mic) my recently acquired Colt Officers Model Match 38 revolver.  The groove is .354.  I couldn't believe the numbers.  I am getting marginal results with .358 and .359 flat points (commercially cast and the supplier advertised “hard cast match grade” whatever that means).  Accurace off hand is about 4 inches at 25 yards which, with other guns, I've done better.  I spent 30 minutes scrubbing lead from just past the forcing cone tonight.  So with the leading and the super tight groove, I am pretty bummed and ready to send this beautiful target revolver on its way.  The throats by the way, are .3594.

Is this bore typical of dedicated target revolvers?  This is my first.  What did owners from the days when this model was popular, do to obain highest degree of accuracy?  Is this a jacketed bullet-shooting gun exclusively?

Any advice, experiennces would be very much appreciated.

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hunterspistol posted this 10 October 2010

     Were it me, I'd just get out the 9mm mold and grab up the sizing die for it.  If your bore is .354, then 9mm heavyweiths (147 grain Lyman) would work better to match up to the barrel.  Of course, you could be loading too fast and hot for the type of alloy that is in those bullets too.  Try to find a load that is slower and possibly some softer alloy projectiles. 

     I don't think it shot a lot of jacketed at all, the bore must look brand new to be that tight.  I don't think I'd get too bummed, some of my revolvers take more attention than I think they should, they're just special.  I may shoot a firearm for an entire spring and summer season before I have usable loads, no hurry on load testing for the powder range.  Patience is absolutely manditory there. 

    Ron

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[email protected] posted this 22 October 2010

Hey inthebeech, I just read your post on the .354 bore of your Officers Model. I have several Colts, An Officers Model built in 1925, an OP built 1932, an OP built 1956, and a Police Positive 38SW built 1919, all have the .354 bore. They all shoot great. I cast 148 gr. Wadcutters,125gr. round flat,and a 180gr. round flat all of straight or water quenched W.W. I had a I frame Trooper .357 that also shot great but I never slugged the bore on it. I've slugged the throats and if i recall they where all around .357-.358

I never saw any advantage to the hard alloy bullets. They actually lead more than the softer alloys do: leading the throats where the softer alloys don't. I get a litte easily removed leading in the barrel but it doesn't seem to affect acuracy. The old Officers Model will shoot about 1 to 1 1/2"  groups from a rest at 25 yards. The OP from 56 will do the same.I hope you didn't already give up on that Colt.

From what I read .354 Groove diameter was Colts standard size for the 38. Some where along the line they made it bigger but I don't know when.

Don't worry, that Colt will shoot unless something is really out of wack.

   

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Dale53 posted this 22 October 2010

I was never a Colt fan but I had friends and fellow shooters that were. I NEVER doubted the Colts' accuracy and their performance showed that.

I suspect your problem is bullets that are too hard. Size to suit the throat and cast of air cooled WW's+2% tin and I'll bet it'll shoot fine.

It might be time for you to start casting your own bullets. Come right on in, the water is fine.

FWIW Dale53

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cityboy posted this 22 October 2010

I have never owned a colt, but my memory tells me I read someplace colts have a tight bore.

 

Jim

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gregg posted this 23 October 2010

I have A Dan Wesson like your Colt. Not like I spent alot of time trying but. Shoots jacketed bullets well . Lead a pain. Never tried slow WCs or GC bullets. Kep us posted

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[email protected] posted this 24 October 2010

Seeing that the throats are .3594 try a .359 to .360 cast bullet of wheelwieghts and I'll bet it shoots. Even a harder cast bullet would probably work as long as it filled the throats. They will sqeeze down to fit the barrel not causing any problems.

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chboats posted this 24 October 2010

I have a Ruger security six 357 that I couldn't keep on the paper at 25yds. Slugged the throats and the barrel. the throats were from .356 to .358. Had all the throats opened to .358. The grove is .352. Fire lapped it with 40 rounds of 320 grid. I size to .359. Now it will hold under 2 inches at 25 yds in the right hands. sorry to say not in my hands. Before I found out the bore was so under sized I shot a lot of full power jacked loads with no preasure problems. As Flashman says size to the throats and I bet it will shoot great.

Carl

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gregg posted this 25 October 2010

chboats wrote: I have a Ruger security six 357 that I couldn't keep on the paper at 25yds. Slugged the throats and the barrel. the throats were from .356 to .358. Had all the throats opened to .358. The grove is .352. Fire lapped it with 40 rounds of 320 grid. I size to .359. Now it will hold under 2 inches at 25 yds in the right hands. sorry to say not in my hands. Before I found out the bore was so under sized I shot a lot of full power jacked loads with no preasure problems. As Flashman says size to the throats and I bet it will shoot great.

Carl I don't think I could do this to an old Colt????? Then again????I could do it to a Dan Wesson.B) Fire lapped it with 40 rounds of 320 grid

I have to ask and the bore grew to what size???

.352 to what??

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Ed Harris posted this 25 October 2010

IGNORE the groove diameter of your barrel.

Measure the CYLINDER BALL SEATS~!

Bullets should be dimensioned to fit that.

Bullet hardness should not exceed 12 BHN.

Then you get groups like this.

73 de KE4SKY In Home Mix We Trust From the Home of Ed's Red in "Almost Heaven" West Virginia

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chboats posted this 26 October 2010

gregg - After I fire lapped the security six I slugged the barrel again. The grove was still .352. It opened up no more than .0001. what did change was the forcing cone. It was smoother and a litle more taper. I think that the biggest thing was that now all the throats were the same and I was sizing to the throat, as Ed said. I guess the point of my first post was that a tight bore didn't make that much difference it's how everything else fits. Carl

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TonyT posted this 29 October 2010

As Ed Harris stated, I would not be too concerned with your measured grove diameter. Those Cot OM's shoot tight groups provided the bullet bis not too hard.

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Dale53 posted this 16 February 2011

inthebeech; Try Remington Hollow Base Wadcutters ahead of 3.0 grs of new Alliant Bullseye:

http://www.midwayusa.com/viewproduct/?productnumber=1601192625

That revolver should shoot well under an inch at 25 yards off a rest (and I bet it will with that load).

Dale53

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billwnr posted this 16 February 2011

I'd slug the barrel from both ends and not push the slug all the way thru to the other end.

You may have a tight spot somewhere (probably at one of the ends).

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Little Debbie posted this 24 February 2011

Modern (1950s to 1980s) Colt double action revolvers gave always had. 354/355 bores. As someone else mentioned that is nothing to even think about. The best ones (Python/OM Match) have always had minimum dimention chambers too. This is perfect because .358 lead bullets always shoot well. They are great paper guns, but have no durability shooting +P or. 357s. In the old days they were competative PPC guns out of the box. Enjoy your OM, they are works of art.

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Vassal posted this 24 February 2011

My Officers Model 38 (CA 1929) has a bore of about .355 - .356 ( I can't quite remember) The cylinders are .357 .  as my first hand gun I have essentially been spoiled for all others. It stays loaded with cast HPs next to the bed;)

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Chargar posted this 25 August 2011

Older Colt barrels have always measured .354-.355. The largest one I had was a 1963 vintage New Frontier (.357 Mag), that ran .356.

The cylinder throats on these sixguns tend to run larger than Smith and Wesson at .359.

In spite of these numbers the Colt Officers Model and Officers Model Match shot head to head with Smith and Wesson K-38s for many years in Bullseye competition. Some shooters preferred Smith and others Colt.

I have shot thousands and thousands of 38 Special cast bullet loads through these tight Colts with bullets sized .358 and .359. I have never had a problem and have had great accuracy.

You are worrying about something that is not a problem.

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