Keyhole
- Thread starter royboy
- Start date
If any rifled gun keyholes (bullets enter target sideways), it usually means either the the bullet is too small or otherwise not gripping the lands, or the muzzle of the gun is damaged and the bullet is exiting in an erratic manner. Rarely, it can be caused by a rifling twist totally unsuited to the bullet, but that is pretty uncommon with modern bullets, either in factory ammo or handloads.
Jim
Jim
g.willikers
New member
Tumbling before the bullet hits the target is different than tumbling after it hits the target.
The first is due to some kind of malfunction, but the second is by design.
The first is due to some kind of malfunction, but the second is by design.
bedbugbilly
New member
As James K says . . . it's a slug to bore fit problem - too small a projectile, it doesn't grip the rifling. Thik of it this way - it is bumping off the sides of the bore as it travels down it - no real grip to spin - when it leaves, it tumbles.
Many years ao, when I was shooting NSSA, I had this problem with a rifled musket - .58. Once I got the minie ball sized to the correct diameter - no more keyholes.
That's why when you use a lead bullet in reloads - take a 38 spl. for example, you use one larger than the bore - I usually size mine to .358 or even use them as dropped from the mold which may be a kosh larger than .358. It depends on which of my 38s I'm going to use them in.
If the bullet to bore fit is fine - then start looking at the barrel crown . . .
Many years ao, when I was shooting NSSA, I had this problem with a rifled musket - .58. Once I got the minie ball sized to the correct diameter - no more keyholes.
That's why when you use a lead bullet in reloads - take a 38 spl. for example, you use one larger than the bore - I usually size mine to .358 or even use them as dropped from the mold which may be a kosh larger than .358. It depends on which of my 38s I'm going to use them in.
If the bullet to bore fit is fine - then start looking at the barrel crown . . .
In my 460 BFR, if I load 45 Colts with 255 grain cast bullets and Unique powder(charge doesn't matter), they tumble like crazy. At 20 yds, they will impact anywhere within 5 feet of where you are aiming. Same bullet using any other powder, and they are fine. The same bullet loaded in 460 brass using 4227(1,500 fps) are quite accurate.
I haven't been able to figure this one out yet.
I haven't been able to figure this one out yet.
Glenn E. Meyer
New member
The NAA minis are known to key hole. Mine does with a 1 5/8 inch barrel.
Crazy88Fingers
New member
That sounds like a very... Unique problem.
I'll go back to bed now.
Bullets that tumble on impact are usually made with the rear heavier than the front. Some British .303 bullets had a composite core with aluminum at the front and lead at the back, but a hollow at the front will achieve the same thing.
Also, if a barrel has a rifling twist that just barely stabilizes a bullet, the bullet can tumble after it loses velocity or when it hits something that slows it down. That was the cause of the bullet "tumbling" in the early AR-15's, which was touted by Colt as a good thing because it supposedly caused more severe wounds. (As if the normal wound from a high velocity bullet would not be enough!)
Jim
Also, if a barrel has a rifling twist that just barely stabilizes a bullet, the bullet can tumble after it loses velocity or when it hits something that slows it down. That was the cause of the bullet "tumbling" in the early AR-15's, which was touted by Colt as a good thing because it supposedly caused more severe wounds. (As if the normal wound from a high velocity bullet would not be enough!)
Jim