[Peter M. Eick]

I have a heavily shot old colt nickeled diamondback 4" 38 special revolver. I have shot it over 46,000 times that I have documented. It is my oldest centerfire and I have had it over 30 years now. I used to shoot it a lot because it was my only gun but now it is occasionally used.

I was out last weekend with it and concluded that it is not that accurate of a gun. At 15 yrds I was printing 4" groups with it. All reasonably scattered but still 4" 50 shot groups is pretty bad. With my 2" detective special I was doing more like 3" for 50 and that is a hard one to aim well.

I know I am not the best shot, but this is worse then I would have expected. The ammo was 148 hbwc's with 2.7 grns of bullseye which should have been accurate.

So, where should I start looking to figure out why this revolver is not more accurate?

I was thinking I should get it recrowned, but because it is nickeled I think that is out. I have cleaned it a lot and the barrel looks good (no leading) but who knows. It locks up tight in single action and colt put a new bolt spring in recently and tightened it up.

Suggestions, thoughts comments?????

Thanks

[Cosmoline]

How's the timing?

[kanook]

How about a 158 gr bullet.

[Oyeboten]

What ammunition?


Measure the Bore, and, if need be, elect fatter Bullets...

[Lee Roder]

are you shooting from a machine rest or by hand? don't know about you, but after 50 rounds, my eyes and arm get tired so concentration becomes just so much wishful thinking.

maybe your accuracy differences are due to differences in your grip? the barrel is moving as the bullet exits its bore.

[Oyeboten]

Timing and Lock-up still 'good'?


What ammunition?


Measure the Bore, and, if need be, elect fatter Bullets..!

[Peter M. Eick]

Timing was just reset by colt when they replaced the bolt spring. Less then 2000 rnds down it since Colt, so I expect it is pretty close.

Ammunition is my own reloads. With other guns like my 38/44 outdoorsman I can put 50 shots into under 2" at 15 yrds with it.

Looking through my old picture collection, I found this group I shot with it in 2006. This was before the bolt spring broke.

http://pages.sbcglobal.net/eickpm/diamond_030506.jpg

I do all my shooting offhand, no machine rests and use the 50 shots as a measure of my and the guns skill. I guess I could try it off a rest, but I have little skill at that.

I can measure the bore today with a set of plug gauges I bought. I will report that back later.

It had not occured to me that maybe Colt buggered up the timing when they fixed the bolt spring. I had not really considered that. I assume the next step is a range rod to check the alignment of the cylinder to the barrel and to do a manual check of the timing right?

Anyone want to talk me though a Colt timing check? (if not, I know I can find it via search).

[Oyeboten]

Ooops...no idea how I posted twice with the same message...sorry.


You could try a VERY light load...shooting straight down into a 5 ( or 30) Gal Bucket of Water...and examine the Bullet...

[Peter M. Eick]

More information.

A .358+ plug will enter each cylinder chamber with equal ease. The .359+ plug will just barely start and will not enter. It goes in all of the chambers the same distance.

My normal HBWC bullet can be introduced the "WRONG" way (from the front) to the cylinder with ease. You can drop it in the normal way and it will usually fall all the way through the cylinder and out the front.

A 158 lasercast SWC will easily fall through the cylinders.

I examined the crown under a magnifying glass. Yuck. The nickel is starting to fleck off at the front of the termination point of the rifling. There is a lot of roughness right here at the very termination point of the rifling. The rest of the crown looks good.

Lockup is consistent and correct as best I can tell. I could not find a range rod yet, but it locks up tightly and the bolt drops where I expected on every cylinder.

Comments?

I assume if I get it crowned, I will have problems with the nickeling? The crown if interesting. It is a flat face then the rifling had been cut back say .125 and the crown hole is slightly bigger then the barrel.

[dfariswheel]

A properly done re-crown won't remove all that much nickel.
If you look at the Colt's with the heavy Diamondback and Python barrels, the crowning is actually on the sharp side.
All that's needed is to cut a slight bevel, just barely enough to remove any roughness and give a sharp end to the rifling.
You don't re-cut the entire flat face of the muzzle.

Next, check the front edges of the chambers. These need to be sharp with no bevels or rounded mouths.

Check the forcing cone.
This can only be checked by using a plug gage from Brownell's. This gage gages the outer mouth of the cone. That diameter is what's critical, not the degrees of taper of the cone.

[Oyeboten]

Sounds like the Cylinder Bores check out alright...


Barrel Bore?


Forcing Cone...as dfariswheel has just elaborated...


Not much left after these...


Other than, the Bullet's diameter and composition, vis-a-vie the Barrel's Bore diameter, and, the FPS/Charging.

If the Bullet is not squishing or upsetting enough to fully occupy the Bore, there will be some inaccuracy issues.

[Peter M. Eick]

I will get a forceing cone plug gauge ordered.

I presume that recutting the crown is somewhat beyond the average worker? (I say this since I am ordering from Brownells, should I also order a cutter while I am there?)

There will be a lag in this thread I think while I order up the plug gauge and have to go away on work for a bit.

[Jim Watson]

Look closely at the forcing cone clean, brightly lighted, and magnified. It might be cracked. It might be eroded oversize in which case the barrel would have to be set back a turn.

[Jim K]

Please forgive the suggestion, but lacking a machine rest, have you tried having someone else shoot it, preferably an experienced pistol shooter. As one who is of mature years, I do sometimes notice that my eyesight is not all it was when I was a mere boy of sixty. The sights radius of a 2" barrel require less focus shift than the sights of even a 4", and that can result in problems for some eyes.

46,000 round is a lot of shooting, but lead WC loads like you describe are easy on a gun, and it should be good for twice that, easily.

As one of the few folks who still know the old Colt lockwork, I can't imagine how replacing the cylinder bolt spring could affect accuracy, but will note that if the bolt or the bolt window is worn, the Colt hand can actually force the cylinder past the correct alignment point. If you use a range rod, make sure you pull the trigger and hold it back while making the alignment test.

Jim

[chevyforlife21]

get a rifle:rolleyes:

[Peter M. Eick]

Thanks for the suggestion of getting someone else I trust to try it out. I did that already and my range buddy agreed that the revolver just was not that accurate. We both shot it a fair amount and got the same basic results.

I have my order ready with brownells so I should get the gauges in a week or so. Unfortunately work takes me away from town so I won't be able to mess with this project for a month or so.

Thanks for the tips.

[10X]

Mr Eick, I have seen some of your targets on this forum before. So it is not the shooter.

With 46,000 lead rounds down the barrel, any possibility there is some lead buildup, even if it is hard to see? I have seen auto barrels that shot as if worn out after 10,000 plus lead rounds. They required a major brushing and cleaning and all of a sudden shot well again.

Have you tried any jacketed ammo to see how that shoots? There may be barrel wear that jackets would compensate for.

[4sooth]

Guys--if nothing else a Colt Diamondback or a Python is arguably one of the most accurate revolvers made. My Diamondback or Python would shoot into 1.5 inches at 25 yds. from right hand barricade with monotony.

From 15 yards standing without support the groups displayed are typical for 50 rounds of deliberate shooting with any good quality handgun. From a barricade or rest that gun will do slightly over a 1 inch group at that distance--assuming no time constraints and an experienced shooter.

[CCW1911]

Give the barrel, forcing cone and every cyl hole a very good cleaning. Make sure every trace of lead or copper is gone and try it again. One other thought is the ammo, I had some 148 wadcutters that just wouldn't shoot a couple of times. One batch of bullets the skirt was coming off the bullet, the other was undersize. Try some different ammo even if this stuff shoots good in another gun, Colts can be picky.