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.

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

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 berg243

are they heavy for calibre projectiles and not the right twist or possibly not quite concentric when seated in the case.are the long seated ones accurate? the other thing to check that when chambering that the projectile is not having a bit shaved off or damaged.

They are a bit 30 but for a 10 twist things should work in my brno but they don't seem to

If it helps I'm happy to modify or change projectiles
if anyone's happy to share their tikka recipe I'm all ears

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

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

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....

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.

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

Originally Posted by Bill999

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 ?

I take it from what you say that they don't tumble when they are seated further out.

Seat one further out and use this until it feeds well:



You should still have some meplat left, the more the better of course.