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UpYoursPal

Could a new hammer/firing pin cause keyholing?

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Good afternoon revo heads.  A while back I pulled my S&W TRR8 out of storage and took it to the range for the first time in about 8 years.  The gun ran well and was plenty accurate.  I decided after some time that I wanted to try my hand at competing in the revolver division, so I bought a full moon clip setup and holster and everything.  I also purchased an Apex lightened hammer, and Wilson Combat springs.  That lightened the trigger pull considerably, but also gave me some light primer strikes, so I purchased an extended firing pin to deal with that.  I was now getting consistent ignition, but the accuracy of the gun began getting worse and worse. 

 

Eventually, I was getting rounds keyholing very often, and accuracy was just all over the place.  This was with both lead AND jacketed bullets.  The barrel looks fine and I've made sure to keep all of the firing surfaces clean, but my gun is just plain un-shootable now.  I'm talking like 8" groups at 7 yards.  It seems like the trouble started after installing the new hammer and firing pin, but it seems to me like that alone couldn't cause the sort of issues I'm having.  Am I wrong?

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No, the Apex Hammer and the new springs would not affect your groups like that.  The best thing to do is check out your loads more.  Also check to see if your bullets are jumping out of the cases when fired or are bullets coming loose after you fire previous shots.   Could be your crimp.  8 inches at 7 yards there is definitely something else happening.

 

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Have you checked to make sure your barrel isn't coming loose? That was a problem with some TRR8s. They are usually very accurate.

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No, a correctly installed firing pin/spring change wont effect any critical component of the "mechanical accuracy". It only effects the end users ability for better (or worse) ability to shoot the gun. Any keyholing and enormous group size like yours is either ammo or cylinder/bore related from wear/corrossion/alignment. I know you said you checked your bore and its fine. The TRR8 uses a barrel with a sleeved outer body. Check to see if the retainer nut shows signs of looseness. If it appears tight next check timing (now that your DA only slowly draw back the trigger watching that the cylinder stop drops  into each cylinder notch just before hammer releases). If even one doesnt you have a timing issue thats compromising alignment. After that only thing left is ammo. Incorrect bullet diameter, as Azshooter said bullets dropping out of cases, barrel has severe leading, or a too light of a powder charge. If you happen to be shooting lead bullets and a thorough cleaning hasnt been done lead buildup from cheap factory ammo will reak havoc on accuracy. (In a .357, after shooting a bunch of lead 38 ammo I run a cylinder of 158 gr .357's through the gun to flush the lead before I finish and go home to clean)

Edited by BallisticianX

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3 minutes ago, Dr. Phil said:

Have you checked to make sure your barrel isn't coming loose? That was a problem with some TRR8s. They are usually very accurate.

I will check this out!

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The barrel nut takes a special spanner wrench but you should feel movement if that is your issue. Good luck. Hope it works out quickly...

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When my barrel loosened up, I only had accuracy problems, no issues with tumbling. I've only experienced tumbling problems because of bad crimps, not to say that your barrel isn't the issue.

Sent from my XT1650 using Tapatalk

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Check that it is still timed correctly.  Changing the hammer could affect timing due to the hand positioning changing.  (Rare but can happen).

With an empty gun, slowly pull the trigger while applying slight pressure on the cylinder.

If timed correctly you should hear a click as the bolt locks into the cylinder notch.

Further once the hammer drops you should NOT be able to rotate the cylinder back cw.

 

If it doesn't lock up you may have to get an over sized hand or new ratchet. 

Or send it to a good gunsmith for timing.

 

Not being in time can well result in keyholing or horrible accuracy.

Edited by pskys2

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I had the barrel of my 327JM tighten up and bind the cylinder after two range sessions.

If the issue is a loose barrel, by the barrel/sleeve tool & feeler gauge set so you don't have to send it to S&W for repair.

SJC

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Checked again: Barrel is still nice and tight, but I took another look in the barrel and noticed this strange "ring" somewhere in the middle.  I'll try to take a picture when I get home, but it looks really strange.  The barrel also looks kind of dull, instead of bright and shiny.

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Clean it well with a stiff bore brush and see if the "ring" is a depression running around the barrel.  You possibly could have had a "squib" and fired another round after it.

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There usually is a slight ring where the barrel threads into the frame, more of a shadow than a ring.

If you shot plated bullets it is possible to over crimp them and have the plating peel off and stay in the barrel.

I'm convinced it happened to me at the 2007 Nationals.  I had loaded my ammo with a real deep roll crimp in an attempt to stop bullet jump.

On one stage (only one did it happen on) I had a shot that while it did more than "poof" felt strange, I hesitated expecting a tap on the shoulder (probably a .2 second hesitation though) then made the next shot which didn't feel any different.  But the target showed 2 bullet holes and a secondary odd shaped hole.  Cliff Walsh and I then checked the barrel and I saw the "shadow" I spoke of, but no obvious damage.  Had no other issues and the accuracy didn't change.  Still have the 625 and it shoots fine, with no key holing.

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Long and short, no. Hammer and pin can either set the round off or not, keyholing is a load problem. Your load is wrong in a very significant way vs. your bullet/barrel/velocity equation.

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Keyholing or tumbling is a bullet sized too small.

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23 hours ago, MattInTheHat said:

Long and short, no. Hammer and pin can either set the round off or not, keyholing is a load problem. Your load is wrong in a very significant way vs. your bullet/barrel/velocity equation.

This is weird because I don't reload .38 special, I only shoot factory.

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44 minutes ago, UpYoursPal said:

This is weird because I don't reload .38 special, I only shoot factory.

Interesting! Maybe just a barrel out of spec or a factory load that is slightly undersized. I just can't picture how the firing mechanism could be involved, but maybe there is some way. My only experience with keyholing was trying to use undersized Cowboy bullets at small velocities.

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Update: It turns out that my barrel was just very, very dirty.  Probably had some lead deposits in it.  Cleaned it out with some solvent and scrubbed for about an hour.  Groups are really tight now!

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4 hours ago, UpYoursPal said:

Update: It turns out that my barrel was just very, very dirty.  Probably had some lead deposits in it.  Cleaned it out with some solvent and scrubbed for about an hour.  Groups are really tight now!

Yea, Yea I was just going to say that, Yea that's the ticket.

 

Thanks for getting back and updating us, kind of forgot that option.  Though shouldn't have, I'd tired some early Moly Coated Bullets that the maker said you couldn't use "fast" powders with.  Big tell I should have paid attention to.  Bought 1k and the darn things turned my 1911 ans 625 into smooth bores within a hundred rounds even with their "prescribed" powders!  I was so upset I don't think I paid attention to the bullet holes.  But it does make sense.

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