AusVarmint

The 243 was a T3 whatever the factory twist is. The 6/250 was built specifically for the 70 nbt. I think it is 1 in12 . The 87 vm stabilises in it

Vermingone for me a 1-10 and use the 75 Gr V-Max flat out

Righto food for thought. Thanks for the input fellas.

Vermingone,

Sorry to jump on here late!

A similar thing started to happen to my CZ, so it gave me the excuse to get the setup below.

My setup uses a 1:10 twist Shilen in Sendero profile finished at 25 inches. I exclusively use the 87 Vmax, which is outstanding at all ranges and on all cuddlies including a few deer that have got in its way.

Could throat erosion be an issue on the old barrel?

Good luck!

Regards,

CZ

CZ yes that may be. Is that sorted out by a touch up with a reamer ? Would excess carbon around the neck of the case indicate this ?

Sorry for the slow reply Vermingone.

I'm no expert, but think that throat erosion would be picked by measuring an increased distance to "bullet jam" in the rifling. If you are not using handloaded ammo, not sure how you could determine this. A bore scope may also help in terms of what is going on. I just remember that the same thing happened to my factory .243 barrel and the smith said it was due to throat erosion. He said adjusting the seating depth could help, but I chose the new barrel option instead

You could either seat the bullets further out (i.e. increase in OAL) to see if that helped, or a touch up with a reamer (and other necessary work) by a smith could also help.

Hope this helps a bit,

Regards,

CZ

Righto that might be a plan while I find the necessary cash to re barrel then. Thanks for that.

I bet that barrel is full of carbon. Clean it back to steel then get it checked with someone with a bore scope. That will tell you if theres a problem. Your crown could also be stuffed and it might be a cheaper fix than a new barrel.

The other thing to price up is a new quality barrel and fitting is going to be around $1000. For an old gun it might be a better option to upgrade to a new Howa or tikka or something else.

Brad we scrubbed the carbon outta it with some Sweets 7.62 then conducted the targets above.
Do crowns just bugger up or do they require contact with something ?
I hear ya about the cost thing.

Sweets wont remove caked on carbon. Get some JB paste or iosso paste on a nylon brush and give it 10-20 strokes in the throat and a couple more all the way up and back, with a couple of patches of sweets on there first. You will be amazed at the black crud with the first wet patch after. The feel of the barrel will be smooth to patch out. It might need more than one application of this. For the sake of $15 a tube of iosso might get it shooting again.

Crowns will also wear with round count, but can be ruined by dragging a cleaning rod with a half unwound jag back across it, or accidentally while carrying it around or on the back of a ute. Easy way to tell is it should have even flash marks on the crown after a shooting session. If one is more or less or producing a different shape soot mark, I would bet a recrown would help out.

A simple recrown with a counter sink tool will fix that though Brad? Yeah?

DSD wrote:A simple recrown with a counter sink tool will fix that though Brad? Yeah?

don't laugh i had a mate do this and it worked a treat but fcuk it's rough as guts .

so when i shortened a BSA sportsman 10 for my son out came the drill and presto

.75 to 1" at 50y which was better than it ever did .

Theres actual crown tools that you can use by hand. PT&G sell them. Ive seen someone use a drop saw. Sure the bullet exited the barrel but that was about it. My gunsmith does the crowns on my barrels just the way I like them. Dialled in on a lathe and cut very sharp and square.

same here but he retired