Off-Center Primer Strikes

[Ben_hutcherson]

This isn't an S&W question, but I respect the knowledge here and hope that someone could give me some insight as to whether or not this is something that I should be concerned about.

I was sorting some brass from a recent range trip, and noticed some of the cartridges had a primer strike that was badly off center. I can track these rounds to one particular gun, as I know I only shot one particular brand of ammo(S&B Wadcutters) in that gun on that day, and that ammo made its way into no other gun.

I only shot one cylinder full through the gun, and didn't examine the brass before dumping it, so I can't report as to whether any particular round came out of any particular chamber. Every one of them went bang when I pulled the trigger, and I didn't notice any problems. I think that they were all shot double action, although I couldn't swear to it. Here is the brass. The one in the top row, in particular, concerns me

The gun is a Colt Police Positive Special. It has tight lock-up and the timing is perfect. I've not shot it a lot, but have put probably 100 rounds of standard pressure 38 special ammo through it(primarily Federal 158gr LRNs and Remington 130gr FMJs). I just checked it out when I noticed the brass, and everything still seems fine.

To try and repeat the problem, I dug out 6 rounds of spent brass that looked to have(relatively) light strikes on them, and loaded them up in the cylinder. Here they are before

And after dropping the hammer on each of them double action

Then again in single action

I can't seem to get the problem to repeat, but I'm still wondering if it's something I should be concerned about. Any thoughts on this?

 

[358156hp]

Take it out shooting again and take pics of the fired cases still in their original chambers if it happens again. We'll need to know what the exact case orientation is to help determine a possible cause. Colts "timing" is kind of funny compared to other brands. The cylinder doesn't lock up fully until the moment of firing.

 

[tomcatt51]

See if the S&B (aka JUNK) ammo creates drag on the cylinder rotating. Could (hopefully) be an ammo issue. If the off-center strikes only happen with the S&B ammo you just don't use S&B ammo. That's a good idea in any case.

 

[Ben_hutcherson]

I appreciate the responses. I'll follow up when I shoot it again.

I do know that Colt timing is a little bit funny, and when I've done my checks I do so with the trigger held all the way back. I have found, however, that the cylinder does lock up when the hammer drops about 3/4 of the way down.

As for the S&B, this is the only box I've bought of it, and I primarily bought it because it was the only brand of wadcutter I could find locally. Most of the time, I stick to Remington, Winchester, Federal, and CCI/Speer/Blazer. These were the only 6 rounds I've shot out of the box, and I haven't noticed the problem with anything else I've run through this gun.

 

[WR Moore]

Because the old design Colt lockwork doesn't lock the cylinder into final alignment with the barrel until the hammer is on the way down, cylinder alignment can be affected by how you hold the trigger. The trigger must be firmly held against the frame to maintain cylinder alignment. If your digit relaxes somewhat after the hammer releases, barrel/cylinder (actually chamber) alignment can change. You need to take care to hold the trigger completely back through the recoil of the shot, this is part of followthrough.

You might also have some issues on the ratchet that affects one particular chamber. As someone else noted, the ammo might cause some drag, but if so, it still points to a potential alignment problem, either mechanical or operator induced.

 

[all357mag]

It's most likely your ammo. S&B sucks!

 

[Ben_hutcherson]

I finally had a chance to shoot this gun again today.

Since some here had expressed concerns about S&B ammo, I tried it this time with some Federal 158gr LRNs. As can be seen, none are as badly off center as the ones shown above, but all are at least a little bit off center.

I shot 4 cylinders and photographed all of them, however all basically looked the same.

 

[dfariswheel]

That's not seriously off-center, but it is a sign that something is not exactly right, and the old Colt action has to be pretty "right".

This is usually a sign that timing is slightly off and may be getting to the point where it may be due for maintenance.
In the old Colt's the hand that advances the cylinder wears and causes the cylinder to not lock fully. Repair of the hand is considered normal maintenance, just like new spark plugs in a car.

Here's my instructions for checking timing in the old style Colt action.
Note the part about full cylinder lock up when slowly cocked. if it doesn't lock fully when slowly cocked, it's out of time. It's usually safe to shoot it because the trigger will force the cylinder the rest of the way, but you have to be sure it is locking fully or you get off-center strikes and possible firing in an unlocked condition.
This will be worse in double action.

BOLT RETRACTION AND "SNAP BACK".
Open the cylinder and look at the small "lug" in the bottom of the cylinder window. This is the cylinder locking bolt.
Cock the hammer, and watch as the bolt retracts into the frame and pops back out.
The bolt MUST begin to retract THE INSTANT the hammer begins to move.
There MUST be NO (ZERO) hammer movement possible before the bolt starts to retract.
The bolt should retract smoothly with no hesitation until it's fully retracted, then it must pop back out with a clean "snap".
There should be no hesitation, and no amount of "creeping" back out.

CYLINDER UNLOCKING.
Close the cylinder.
Use your left thumb or fore finger to again cock the hammer, closely watching the cylinder bolt as you SLOWLY cock the hammer.
As the hammer comes back, the bolt will retract away from the cylinder.
The bolt must retract far enough to unlock the cylinder BEFORE the cylinder begins to rotate.
If the bolt is still slightly engaged with the cylinder lock notch, the cylinder will be attempting to turn while still partially locked.
This produces a "catch" or "hard spot" in the trigger pull and will damage both the bolt and the cylinder lock notches.
This often appears as metal "pulled out" of the lock notches, with rounded off and burred notches.

BOLT DROP TIMING.
Continue to cock the hammer, LIGHTLY laying your right index finger on the cylinder just enough to prevent "free wheeling".
Watch for the bolt to drop back onto the cylinder. WHERE the bolt drops is CRITICAL.
The bolt MUST drop onto the leade or ramp in front of the actual cylinder notch.
If the bolt drops too soon, (in front of the notch ramp), it will mar the finish of the cylinder.
The bolt should drop into “about” the middle of the ramp.
If the bolt drops late, (farther toward the actual locking notch) the revolver may display "cylinder throw-by".
In this condition, during double action shooting the cylinder may rotate PAST the locking notch, and fire in an unlocked condition.
It's the nature of the Colt action, that a hesitant or jerky trigger pull by the user can induce throw-by in even a properly tuned Colt.
The Colt trigger should be pulled with a smooth, even pull, with no sudden jerks at the beginning.

CYLINDER LOCKUP.
Continue to pull the hammer back and both watch and listen for the bolt to drop into the cylinder lock notch.
The bolt must drop into the actual lock notch before or just as the hammer reaches full cock.
The most common Colt mis-time situation is the hammer cocks before the bolt drops into the lock notch. (Hammer is cocked, but cylinder isn't locked).
In this condition, with the hammer fully cocked, you can push the cylinder slightly, and you will hear the "CLICK" as the bolt drops into lock.
In my experience, most Colt's leave the factory with the bolt dropping a little late into the leade, but usually wear in to correct timing.
If the bolt drops onto the cylinder early, no real problem, but there will be extra finish wear.
If the bolt drops late (closer to the lock notch) the cylinder may "throw by" or rotate TOO far in double action and this can cause off-center primer hits and firing while unlocked.

Each of these checks should be done on EACH chamber. All of these checks are better done individually. In other words, do the bolt retraction check on all six chambers, then do the bolt drop test, and so on.

A properly tuned Colt will:
Have a smoothly functioning bolt with no sticky or hesitant movement.

Unlock before the cylinder begins to turn.

The bolt will drop onto the middle of the ramp.

The bolt will drop into the lock notch just before or as the hammer reaches full cock.

Have a smooth trigger pull, which does "stack" or get heavier as the trigger is pulled.

 

[Berserker]

I have noticed on a few of my guns, various brands, that it is slightly off. I was concerned the first time I noticed it, but then noticed more, so I kinda got complacent.

 

[Ben_hutcherson]

Dfariswheel,

Thank you for the detailed response.

I just finished going through all of your checks, and I can't detect any problems at all with it-i.e the bolt starts moving as soon as the hammer is pulled back a tiny amount, it "snaps" back up smartly, and on every cylinder drops into the middle of the ramp and then perfectly into the lock notch.

Any other thoughts as to where to check?

 

[dfariswheel]

Next check would be for a gummed up action or a weak bolt spring.
Read the part above about "throw by".

If the action is gummy or the spring is weak or fouled, the cylinder may be rotating TOO far in double action.

 

[GLV]

I had a 28 that was .010 off center--never found the problem, and the gun was a tackdriver, never a failure to fire. Who knows.

 

[What the]

Ben,

Just for grins check your hammer nose and make sure the rivet is in good shape and not broken, the nose should move in its groove front to back but should have very little side to side play.

 

[dfariswheel]

I got rid of the visiting company and gave this more thought.
Another check would be for chamber-bore alignment.
If alignment if off, you may get off-center primer strikes.

Alignment could be due to a bent cylinder yoke, or a problem with the cylinder stop.
In other words, the cylinder could be locking up slightly off center.

Then too, it could be that everything is okay, but for some wifferdill reason the gun is simply allowing slightly off-center primer strikes.

 

[Wizzerd Oz]

Wise Ones - This is also happening with my S&W 686 SSR gun. (This new gun has already been back to the factory once for the dreaded "Yoke Bypassing The Crappy New Retention Screw Assembly" problem, where they simply replaced the yoke.) Anyway, when I run the gun fast in matches (IDPA), I have had a total of three of these way off-center strikes and the gun goes <click>, which is not what we want to hear in the middle of a stage.

Bench testing slowly, it seems to lock up and time just fine. My gauges show that the barrel is in alignment with the bolt and each chamber, so carry up is good. However, sometimes when I dry fire the cylinder seems to bypass a chamber a wee bit and gets that previously mentioned "cylinder throw-by". The cylinder stop has free travel and it pushes down by hand and pops back up ok with bench checks.

So when I run the trigger really fast, is it inertia and momentum that seem to be taking over and the cylinder stop isn't catching the recess? These primer strikes on the edge of the primer also seem to happen on the second pull of the trigger when I know I have to hit a drop-turner or something fast on a double tap. If I can figure how to post a picture of the primer strikes I will, but it looks just like the worst one posted in Mr. Hutcherson's initial pic in this thread, above.

Thanx in advance for any clues!