Thread: What causes key holing in sub loads

I'm trying to work a load up for my 308 tikka barrel
If I seat them deep enough to feed they key hole, if I seat them out to engage lands they won't feed

I'm using lead cast flat nosed projectiles

What causes projectiles to key hole?
What things help to prevent it?

At what speed do lead projectiles grip and spin with modern rifle twists 1-10 to 1-11 ?

They should grip and spin as long as they exit the barrel, they may not be spinning fast enough to stabilse the lenght of bullet tho.

Is the trick to jam them into the lands or what?
I'd like a mag fed round if I could

How heavy are they? if you are trying to shoot 220gr subsonic out of a 11 twist you are always going to have problems.

And I'm using 8.5 gr of trailboss to push them
Accuracy is trash and they often go sideways thru targets

Originally Posted by Bill999

And I'm using 8.5 gr of trailboss to push them
Accuracy is trash and they often go sideways thru targets

get the accuracy sorted, but try to keep them hitting sideways. will probably be quite effective on pestilence....

@vietnamcam 200 gr flat nosed projectiles
Trademe cast ones 2 gas checks

Might be better to try some of @shooternz s 150gr ones.

How soft is the lead? Are they stripping through the rifling?

Two gas checks? Measure the length of one and whack it in this formula 150 x the bullets diameter in inches squared divided by the bullets length. The answer is the twist rate
eg bullets diameter is .308, length is 1.5 inch
150x.095/1.5 = 9.5 the twist needed is 1:9.5
My 185 grainers measure 1 inch, I run them at 1450 fps with no gas checks but a good lube.
Maca has raised a good point even with a gas check if you try and push them too fast they will strip, tumble and give you a big cleaning job. A lack of lubricant will also do you in.

Originally Posted by Marty Henry

Two gas checks? Measure the length of one and whack it in this formula 150 x the bullets diameter in inches squared divided by the bullets length. The answer is the twist rate
eg bullets diameter is .308, length is 1.5 inch
150x.095/1.5 = 9.5 the twist needed is 1:9.5
My 185 grainers measure 1 inch, I run them at 1450 fps with no gas checks but a good lube.
Maca has raised a good point even with a gas check if you try and push them too fast they will strip, tumble and give you a big cleaning job. A lack of lubricant will also do you in.

My sub guns action is Stained with the lube that comes with the projectiles so I think there is plenty of lube
The bullets measure 0.984inches
Am I right to think a gas check is a recessed ring at the base of the projectile filled with lube? As there's two of those and one more above that's not lubed

If I replace 1.5 inches with .984 it gives me 144 which I imagine is 14.4 inch twist
One gun is 1/10 and the other is 1/11 both seem to keyhole around a third of shots
I'm not having this issue with 165gr ballistic tips at around 1050fps
The only lead bullet Iv recovered so far was too damaged to tell if it's taking the rifling or pushing past it

Originally Posted by Bill999

Am I right to think a gas check is a recessed ring at the base of the projectile filled with lube? As there's two of those and one more above that's not lubedAttachment 97609

No a gas check goes on the bottom of the projectile to protect the lead base from the propellant gases, mainly used for supersonic

https://en.wikipedia.org/wiki/Gas_check

Geeze Marty lack of lube? Could be a age thing?beaver grease huh?

Dr Zogs sex wax, also good on surfboards

Hey Marty, does bearing surface length come into play with that formula?
Cheers