keyholing

[sixxgunnernick]

What is it? How does it occur?

[rjrivero]

When a bullet strikes the target in profile.

It occurs if the bullet is not sufficiently stabilized by the rifling for whatever reason. These reasons can include bullet too long for the rifling rate, wrong velocity for the rifling rate, worn rifling, wrong bullet size.

Why do you ask?

[Brian Pfleuger]

It can also occur when a bullet loses speed down range, particularly if it crosses the sound barrier.

12ga slugs can keyhole at 100 yards or less under some conditions, even when properly stabilized early in flight.

Improperly loaded ammunition, for the reasons stated by rjrivero above, can keyhole almost as soon as the bullet exits the barrel.

[ScottRiqui]

I've had keyholing at 25 yards with .223 ammo when the primer pocket was too loose and the primer popped out during combustion. In this case, the velocity (and therefore the spin rate) was likely way too low to stabilize the bullet.

[kraigwy]

Many reasons, some down right confusing.

Too Small of bullet for the bore, wrong twist, lead too hard (cast bullets), too slow of velocity, and here is one thats confusing, TOO FAST of a bullet.

I found that out two weeks ago shooting a BP Creedmoor match (800 - 1000 yards). I was pushing a 500 grn 45-70 cast lead bullet too fast, I was trying to keep my BC up by pushing the bullet past 1300 FPS. Strange Thinks Happen out West. I was told I was pushing my bullets too fast, and you could hear them flying through the air, sounded like a buzz saw.

I backed off the powder to 1150 fps and it ended the problem.

So you just got to play around to find out what's causing Keyholing. Dont rule out nothing.

[chris in va]

I had really bad keyholing with my CZ 75 and cast 'boolits' I made. They were .356 in diameter, the barrel slugged at .355. Essentially they skidded down the barrel without engaging the rifling properly and became severely unstable when reaching the target, going in sideways.

I had to fatten them up to .358 before they would fly straight.

[sixxgunnernick]

Thats what I thought it was. Funny lookin holes in my target..I thought it was to much crimp. Kimber sis ultra..berrys 230 grain roundnose.. .452 diameter..620 fps..4.4 grains of titegroup. What do you guys think?

[CowTowner]

I think you need to add a little more powder and get the speed up.
Try moving up to 4.5 and 4.6 grains of Titegroup and see if the bullet stabilizes. Max is 4.8 grains according to Hodgdon for a 230 gr LRN or FMJ.

[Rifleman1776]

Stop using Marlins.

[Unclenick]

Sixxgunnernick,

There's a barrel defect you should look for if the load change doesn't help? I've run into it twice in other people's guns. One a S&W Model 41 .22 LR target pistol that keyholed, and the other in a Dan Wesson revolver barrel that keyholed. In both instances, examination of the muzzle (gun unloaded) and a recovered fired bullet for the DW, clearly showed the depth of the rifling was shallower on one side of the barrel than on the other. This unbalances the symmetry of the bullet mass, causing it to wobble in flight, helping air pressure turn it sideways.

[sixxgunnernick]

I tried 4.6 Gs of titegroup and my shots went higher on me but then again I put my front sight on target. So maybe 4.6 Gs of TG and put my sight just below the bullseye like I'm suppose to..right. I know my speeds are slow but at 4.4 I like the recoil getting back on target faster. I should bump it to 4.6 and loosen my crimp a tad.

[CowTowner]

But did going to 4.6 grains resolve the keyholing issue?

[Don P]

With regards to keyholing my 9mm were keyholing bad and the reason I found was my over all length was too short. I maxed the length out so they still chambered and functioned in the magazines and that cured MY keyholing issues.
What is your OAL?

[Unclenick]

Don,

That's the first I've seen that diagnosis, but it makes sense. If the chamber is generous enough, the bullet is turning a little and entering the bore at a slight tilt. Since soft bullets are easily swaged by the bore, that reshapes the bullet to be a little asymmetrical which makes it wobble as I described for the defective bores.

I always try to seat cast and plated bullets out to headspace on the bullet rather than the case mouth, which prevents that (see attached image).

[sixxgunnernick]

is 1.26 When I started these batch I did twenty one rounds of 4.2 grains 4.4 grains 4.5 and 4.6 I liked the accuracy and low recoil of the 4.4 and the 4.6 rose up high. I shot a couple hundred more last night and they looked o.k. normal. ? Am I going nuts? When I shot the 4.6 I can't recall what they looked like.

[Unclenick]

Ahh, the record keeping curse. Do and you feel like you're accumulating a lot of worthless paper; don't do it and something critical comes a long to make you sure wish you did.

Try the bullet headspacing trick if your magazine will tolerate the extra length? It may not with the round nose shape, which is long compared to SWC's, but usually they do. The maximum COL numbers are just about guaranteeing industry-wide magazine fit and feed, and are not about ballistics. Going longer is fine as long as it doesn't interfere with magazine fit or feeding.