Need help solving keyhole issue.
Out of 120 rounds I had four keyholes at 25 yards. I need help to solve this problem.
Load: .38 Special Starline case, 2.7 gr. Bullseye, Federal #100 primer, Precision Delta 148 gr. HBWC match lube, light roll crimp.
Handgun: 6" Smith & Wesson 686-6 .357 magnum,Alching Smith & Wesson Mini STS Scope Mount , Venom Vortex red dot sight.
Any help solving this issue welcome.

Verify your bullet size versus your bore size. Have you slugged the barrel? I would also up your powder charge to3.0 to insure your HBWC is obturating properly.

Your load and components look good, although I don't shoot under 2.9 BE. So that's probably not it. How does the 686 do with other loads? Was general accuracy good otherwise? And, I hate to ask, but was the paper flat against a backing to prevent tearing of the hole giving the appearance of a keyhole?

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Some collect art; I shoot it!

I have slugged the barrel but I do not have a three point micrometer to check diameter at this time.

Targets are flat.

Any leading in the barrel. I have not had good experiences with lead bullets in ECM rifling and I believe that your 686-6 may have an ECM rifled barrel. BTW, run wet patch down the barrel on a brass jag, if it starts to shred after just two stroke you have the same degree of leading I experienced with my 620.

Personally, I think you add a pinch of powder to get just a touch more stability, and thoroughly clean ALL the lead and copper out of your barrel. Then fire a few shots for fouling and test again.

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Science plus Art

As stated try 2.9grs of powder and see if it helps.

Also try 2.7grs with a heavier crimp with a flush bullet.

My 686 6" did better with cci primers vs f100.
You might try 2.8grs of red dot or 3.2grs of w231 if you have any, also.

Really and in short, you need a faster twist rate in your barrel rifling to truly stabilize hollow base wadcutters in flight. Tweaking loads is just masking the true problem. I've studied this in depth.

I know you said the paper is flat, but make sure it is tight against cardboard backer.

That's a very light load to begin with so depending on what type of powder thrower you are using what you may be seeing is the throwers inconsistency with dropping the charge. I run 2.9gr of green dot under a 148 hbwc for an M52. And while I don't see it in the targets, if there is a metering issue I notice right away based on how she cycles.

Otherwise, as sated above, the charge might not be enough to get the velocity to a point of stability out of that barrel. Depending who you ask 148 stabilize in a very fast twist rate such as 1:10, 1:12, 1:14. Youre working with a gun if I recall correctly as 1:18.75

^^^^ What he said! ^^^^ If you get accuracy with a M52 load, you know what it takes for consistency. I shoot solid cast wadcutters in my M586 / M686 revolvers with successful results; round holes, good groups, and minimal leading.

148 grain HBWC are very accurate bullets out to 50 yards when everything is correct. Determining the causes of the problem(s) can be frustrating.

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S&WHF 366

What kind of expander are you using??? I like to use the lyman m-die when I load any hb bullet for several different calibers. Traditional expander dies are made for short .357" jacketed bullets. The m-die has a llloooonnngggger body to expand the case where it counts, at the base of the bullet. It also has a step in it that makes a shelf in the top of the case mouth that aids in starting the bullet straight. A picture of a lyman m-die.


Picture of a m-die next to a factory expander. If you look at the factory expander you can see where the brass has left a ring where it stops being expanded. Huge difference in the depth that it goes into the case compared to the m-die. That is what protects the base of the soft lead bullets.


If the bullets are seated crooked or being swaged down at the base too much. Bullet skidding will occur which in turn affects accuracy & stability. When I see #'s like 3% or 4% of my loads tumble, things like this come to mind. If incorrectly loaded the bullet will tumble as soon as it leaves the reloading press and long before it ever is in the revolver.

HBWC's are a long bullet and care should be taken when seating them in a properly expanded case. A picture of the 3 main wc/hbwc bullets I use/shoot in the 38spl's & 357's.
left: h&g #50 148gr button nosed wc
center: flat nosed 148gr hbwc from a custom mold
bottom: lyman 358395 148gr button nosed hbwc


Just something to think about

You never listed your oal for the load you are using. What you need to do is:
Measure the oal
write it down
study it real hard
Then wad the piece of paper up and throw it out

Some people don't like to use/shoot 38spl's in their 357's. Myself I love using 38spl's in the 357's. There's more length to work with in the cylinders of the 357 mag revolvers. Length ='s opportunity

A couple of 38spl loads I use for plinking in the 357's. The 640 bullet (left) is crimped in the lower crimp groove & the 148gr wc is crimped in the middle lube groove.

Those loads might look funny but they do manage to put bugholes in paper.


A 175gr wc for the 44cal's cast from a custom mold. They are desgned to be crimped in the bottom/top lube/crimp grooves. The thinking was when you find a good load for your 44mag with the bullet loaded so that the small end of the bullet stuck out of the case. You would be able to have the same load using 44spl cases by simply turning the bullet around and seating the bullet so the large end of the bullet stuck out of the 44spl case.


Well thought out but I look at that bullet and see 4 different seating depths to test.
Seat flush
Seat in any of the 3 lube/crimp groves

More testing of hbwc bullets:
This time I was testing 220gr hbwc's for a s&w 624 44spl. I tested loads with the bullets flush, seated in the top lube groove, middle lube groove. And yes, had to turn them around and make huge hp's to test.


I've thinned the herd over the last decade, old eyes, old hands. Don't shoot to much bullseye anymore. I still use/shoot hbwc's, these are the main hbwc's I use.

top left 32cal
top right 35cal
bottom left 44cal
bottom right 45cal

And yes I do also load the 148gr/38spl hbwc's flush for specific revolvers.


A little off topic:
I also use/shoot swc and fn hb bullets for the 35cals/44cals/45cals. The only way I get any of the 14+ hb bullets I use to shoot/work is by using the long bodied lyman m-die to expand the cases for all of the different calibers.

The fbi used a 158gr hollow based hollow point bullet for their fbi/38spl load.


Buffalo bore has 1 of the best 38spl sd loads/ammo out their for snub nosed 38spl's. Their 20a 158gr lead hp doing 1000fps from snub nosed revolvers.

Being of semi-sound mind and having a love for hb bullets, had to do the 1 up/mines bigger & better thing. The end result is a 210gr swc hb hp bullet doing 1000fps+ out of a snub nosed 44spl.


Better than the fbi bullet
better than the buffalo bore load

Do a little thinking outside the box, your targets will reward your efforts.

Alright 1 more hb bullet description:
2 of my favorite bullets for a nm 1911 chambered in 9mm.


The green bullet/plinking load


Standard 9mm bullet, good results.

The red bullet is actually a lyman 35870 150gr hb bullet that lyman started listing/selling in 1900 for the 38lc. I re-designed/made a new hb pin and the bullet is now 130gr with a stronger/thicker hollow base that expands up to the middle drive band. A 10-shot group @ 50yds with that red hb bullet in the 9mm


I size all my cast/lead 9mm to .358" and use a custom expander I made to expand the 9mm case to protect the longer/larger in diamerter lead bullets. A picture of a standard 9mm expander next to my custom expander.

More important maybe, verify each cyl throat size. One or more may be undersized. Regardless of the bore, if the cyl throats are small the bullet is going to skid in early in the rifling & not stabilize properly.

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NRA Cert. Inst. IDPA CSO

My past with keyholing causes me to suggest pin gauging the cylinder bores, and adjusting the bullet size to at, or just above that measurement. Also-does it keyhole with 357 ammo?

Well if the bore is 0.357" & the throats 0.356", you will need to open the throats for best results. If the throats are larger, yes sizing to that may help accuracy but keyholing is often an undersized bullet.

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NRA Cert. Inst. IDPA CSO

I agree with this. ^^^

Size your billets to your cylinder throats, not the bore. Undersized bullets can tilt when fired in the cylinder throat. If your bore is larger than your cylinder throats, you have a problem.

The virtue of HBWC's are that the base will expand to meet the barrel dimensions. I use plated 148 gn HBWC projectiles in my S&W Victory model with a .360 barrel. I too had key holing with the original load of just over 2 gn Mulwex AP50N. By raising the land to 2.4 gr the key holing issue resolved itself.

Try taking your powder load up slightly.

In my 6" 686 AFS I load 4.2 gn Tightgroup under the same 148 gn HBWC. I put four rounds into the 9 ring of an International Rapid Fire target at 50 meters, single action unsupported while sitting at a bench recently. Velocity is around 875 fps for a 129.5 power factor (120 minimum required for the event I shoot).

Also: powder drop consistency is important. With my old Lee Auto Disc measures consistency was all over the place. 10 drops of powder could have a low to high variation of .7 of a grain. I have gone to the new Lee Auto Drum and while consistency is much better (no more than .1 of a grain up and down over 10 drops), I do not rely on the drum resetting itself. The spring is not powerful enough for the drum to return fully to index each time and while you can set the measure so that it drops the required powder without returning fully to index I prefer to manually turn it back after each drop. That resulted in 9 drops right on the money and 1 drop .1 gn light.

Lots of good information here. I had a similar problem with some roll crimped 158 gr. plated bullets. I found I must not have had the seat/crimp die tightly screwed into the press. I increased the roll crimp a bit, re-crimped that batch of ammo, and the problem is gone.

All these opinions about throat size and load adjustments do nothing about the underlying main problem and that is the factory twist rate of 1:18.75 is not fast enough to stabilize well, a hollow base wadcutter bullet.

Then likely every round would keyhole, not just a few. If the shooter is loading random cyl with 5rds for his group, then there will be a random keyhole if one cyl throat is smaller, even 0.001" smaller. Why the old timers used to test shoot groups from one cyl then repeat for all 6 & mark any offending cyl. The only way to get it right is make them all uniform in dia, ideally the same as the the bore + 0.001".

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NRA Cert. Inst. IDPA CSO

It seems we have focused on the load as being the culprit
in the keyhole issue - which it could be. But - - - -have we considered shooter technique?

Many years back while shooting BE, one of the military shooters did a demonstration on keyholing by using heel pressure on the grip at the time of trigger let off. Could make the bullet keyhole right or left and call the direction of the keyhole depending on heel pressure.

Just a thought

Sorry, calling BS on that. Your grip doesn't affect the rotation of the bullet. IT does affect POI, but not bullet stability.

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NRA Cert. Inst. IDPA CSO

Point is, you wouldn't have a keyholing issue at all if the hbwc's were shot out of a 10 to a 14 twist barrel, regardless of load or if a chamber was a thousandth off. The factory twist rate of 1:18.75 is right at the cusp of the long hbwc bullet losing its stability. The barrel was designed for 158gr bullet.

Did the twist rate change in the 686 at some point? The reason I ask is I had a 6" gun back when they were first available and it would literally cut the X ring out of a B27 at 20 yards, and all would land in the 10 ring at 50 if I didn't yank on the trigger. This was with HBWC's supplied by the department I was shooting with. Not doubting the twist rate issue as I'm still and always learning.

I recently worked with a M-15 that was keyholing at times and it turned out to be a pretty good amount of thread choke. It was with 140gr. RNFP's. Lapped out the thread choke and all is well now.

Dan

I have one for a five groove barrel. If you'd like to mail me a few slugs for measurement, PM me.
Do you have access to a chronograph? That might be some good info as well.

I have a Mod 25 that has thread choke. How did you lap it out? I'd love to know, because pistol smiths are scarce around here.
I don't want to hijack the thread, so PM me if that's a concern.

I purchase one target at the range and then tape my Dirty Bird targets onto that. They are flat. I am anal about my shooting and I even make sure my targets are straight and level and centered on the target used as a backer.

Measured today at work.
Cylinder throat size:
.3576
.3576
.3576
.3576
.3574
.3576

Slug looked odd on the three point mic so I looked at it using an optical comparator with Quadra-chek 3000 system. I seen how the rifling is not straight cut and is not polygonal. I digitized slug and the measurement was .3548 using largest size of "lobes".

Your throats are close enough. So I would check dia of say 12 bullets. Are you using the infamous LFCD to crimp? Is all your brass the same manuf? Bullets do not randomly keyhole w/o a reason.

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NRA Cert. Inst. IDPA CSO

I use an RCBS uniflow. I have done gage R&R on it and it will repeat nicely within about half a tenth of grain. I have tested by weighing each charge on a beam scale and also throwing ten charges in pan and weighing sum of all charges and all is well. I measured strings of ten and many singles, not just one and done.

I also use Lyman M die

PM sent

Dan

No keyholes with .357 ammo. Only the Precision Delta 148 HBWC keyhole and that was only about four out of 120 rounds. Hornady 148 HBWC do not keyhole. Just trying to find a solution as I purchased 1000 Precision Delta's and I am going to shoot em'.

Bingo Give the man 2 cigars
Without a chrony and Greenhill
A man becomes lost very quickly

Barrel Twist Calculator

Me thinks you are low on the powder end of the equation
I fire my loads in the shop thru a chrony as I add or subtract powder
I don't need to fiddle with targets till I get the basics right
Least with Greenhill
Your will know if the combo is worthy of even loading or a waste of your time

OK - call it what you may, wouldn't have believed it if I hadn't seen it.

I don't know what you claim to have seen or if you understand the term "keyhole", but think about how that is even possible? It's not a Hollywood movie where you can bend the bullet flight path by flicking your wrist. As long as the crown of the barrel is in good shape, the rifling supports the bullets weight for the intended vel & the bullet fits right, it is not going to keyhole, no matter how you shoot it. Diff POI, certainly, but you can not make the bullet turn in flight & keyhole. I've shot handguns from just about every conceivable shooting position, including holding a gun upside down. I have never seen such a thing.

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NRA Cert. Inst. IDPA CSO

This was always my understanding of a keyhole

Attached Images

Keyhole.jpg (31.6 KB, 4 views)

Fortunately, I have never exp such a thing.

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NRA Cert. Inst. IDPA CSO