Thread: .260 Improved.

I am severley bored at work due too massive flooding in the area and being trapped onsite. So I have decided to do a report on a new barrel tuiman2 and I have been tinkering with, for the last few trips made home. No photos yet as I am a forgetful prick and left my camera in NZ. I will endevour too post some when I get home in a couple weeks.

Around six months ago, after the thar ballot and a bit of research I decided to get Abe to make up a .260 AI barrel for my Blaser. Never having owned an Ackley improved cartridge I thought the .260 improved would work out easy and make decent use of the 40 degree shoulder in terms of ballistics. Its also good fun screwing around with new shit.
I wanted a 6.5 in a short action, not that it mattered in an R93 as it can run long or short depending on magazine. But I planned on this being a bit of an allrounder cal that can stretch its legs if needed.

We had some dramas for a while but ended up learning a lot about the AI, especially when chambering it for an R93 action. Never the less, we got it sorted. Heaps of thanks, has to go to old sneeze who brains I picked relentlessly over the last few weeks.( surprisingly, he had a few seeing he is from the Nelson area) He managed to slowly fault find and come up with suggestions via text messages and pm's.
Thats whats great about this place, its bound to have people with experience to help when ya need it.
And Abe who's was as eager to figure things out as I was, so I would stop bothering him. He put in a few late nights of his own time, with me peering over his shoulder.

Anyway. I started out with a Trueflite #3 contour 24" UM barrel and it didnt shoot. Back to the drawing board! Abe suggested a Vulcan of the same specs. After nutting out some issues that were the same with the Vulcan I reckon I now have a spare barrel in the trueflite which I am sure when needed, will shoot fine

I had to chuck a heap of Lapua brass and started fresh. I fire formed with ASN-30 and a M16 patch to get a nice sharp AI shoulder.
Loaded up some formed cases.
I started out with RL-17 for powder, as it seemed the best before we sorted the issues. I wanted to use 130 scirocco's or 140 Amax which the barrel was throated for.

I do all my development at 200yrds. She proved too be accurate but slow from the first 3 rounds down range.
Firing all shots thru my chrony it was good to see as the loads sped up, the groups shrank.

The scirocco shot reasonably but the Amax was wicked accurate. I didnt muck around with the scirocco much more but I reckon I could get more accuracy as it speeds up as I was using the same charge and seating depth as I was for the Amax.

Over 15 rounds the Amax had an ES of 13fps and was doing 2965fps. No pressure signs at all. I should mention I have a laser thermometer and tried to fire a group in a consistent tempreture range, taking temps from the same spot on the chamber/barrel. So it took a while.
I loaded up a wee batch and took my time confirming the load. It averaged .7" 3 shot groups with some that were way under that.
Speed was excellent and I am on the 9-10th turn on the brass. Stoked!

I didnt anneal one case and ran a pretty tight neck, from .297 reamer down too .293 loaded with a .291 bushing. I reckon I could muck around a bit with neck tension, annealing and shoulder bump and It could easily be bench rest accurate. But thats boring for a hunting rig

So for the .308 being the parent case and no where close, ballistically, using the same weight projectiles, I reckon Improving the .260 is well worth it.
High BC 130-140 grn projectiles going close or more than 3000fps+ with great case life and 100fps faster than the standard, is a good thing in my book.
FFing the cases while being a slight pain, without projectiles is piss easy and a bit of a laugh if ya do it the smiddy way
Lots of tinkering to do yet but so far, I am very pleased.