Thread: Another 260 Improved

Well after reading all the 260AI stuff of late, I decided to crank my project into G
I've gone down a different path to all you 40 degree Ackley disciples and made up a 260WI (Whitley 30 Degree Improved) My train of thought was based on the fact that a lot of your current modern rounds like 6.5 Creed, 6.5 x 47L, 6mmBR and the likes are all made with a 30 degree shoulder, this must be for good reason. So I discovered the Whitley range of improvements and got a reamer cut over a year ago in the States. Also bought a Shilen match barrel to go with it.
It's now all screwed together on a T3 action and tonight I ran some fire forming rounds through it to check the chamber before the rifle gets its final finish.

I started with 43gr 2209 behind a 129gr Hornady, @R93 for the info here thanks and also made some 44gr & 45gr to see if I needed more grunt to form the shoulder, 43gr was enough by the looks as the other two didn't show any better form nor pressure signs either. I'll save myself some powder.

Standard Lapua 260 case with the newly formed 260WI



3 different loads, same result



This 30 degree is a lot easier to form than my last Ackley I had.

Looking forward to how it shoots. Nice sharp shoulders there.

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How much increase in capacity?

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Don't quote me but H2O capacity of a standard 260 Lapua case I think is 53.8gr vs 55.9gr for that same case FF in Ackley 40 degree, so I should be somewhere in the middle.
There are a few other good reasons to go this way though, like reducing case trimming etc....

Just to be different is reason enough

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I haven't had to trim a case after initial forming in my Ackley yet.

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@R93 no I never did on my 257AI either, only had 60 cases with that and they lasted 20 years of normal hunting. Lost a few with split necks but that was me being lazy and not annealing.

I hope mine last 20 yrs. I always lose the odd one in the bush after a shot.

I tipped over a deer with a mate a while back and he was miffed and got pretty angry with how long I spent looking for the case.😆


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I had my first split neck a while ago, I loose so many cases I have never had to trim any.

@Mathias is this reamer still in your hands? I might be keen on borrowing/hiring it if possible.

Originally Posted by R93

I hope mine last 20 yrs. I always lose the odd one in the bush after a shot.

I tipped over a deer with a mate a while back and he was miffed and got pretty angry with how long I spent looking for the case.


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Ha ha in the early days of my 308 using reloads I had shot deer, got up to them, gutted etc and then sometime later found the spent brass in my top pocket. Cannot ever remember extracting it and putting it there. I too hated loosing brass.

@Mathias nice looking brass. I have never yet had to trim my AI as well. Wee problem though was once formed my brass was shorter than AI specs so no need to trim. Plus I checked them and all lengths uniform so never trimmed. Have never grown. Your cases look to have formed to much the same length as the parent brass.

Originally Posted by zimmer

Ha ha in the early days of my 308 using reloads I had shot deer, got up to them, gutted etc and then sometime later found the spent brass in my top pocket. Cannot ever remember extracting it and putting it there. I too hated loosing brass.

@Mathias nice looking brass. I have never yet had to trim my AI as well. Wee problem though was once formed my brass was shorter than AI specs so no need to trim. Plus I checked them and all lengths uniform so never trimmed. Have never grown. Your cases look to have formed to much the same length as the parent brass.

Yeah side by side they look even, though I must run the vernier over them to see exactly. One interesting note is that this design of improved actually slightly increases the neck length when formed as the datum point at the top of the shoulder is moved back and a larger radius is used to prevent possible donuts.

Well a few months have passed and I've fire formed all my cases and got around to loading up some sample full power rounds with 3 different projectiles. I do like the 129gr LRAB's so I poked a few of these down the tube along with 123gr Amax & some 140gr Amax just to see what speed I could attain.
All loads were with RL17 & CCI 200 primers.
Our local range is still out of action, so I had to visit a different location and had to put up with shooting over the bonnet of the truck at a range of 122m, less than ideal for accuracy. I also had the Magnetospeed hanging off the end for all shots.

All bullets shot pretty well and I'm sure I will do better when I get on the bench.
I got very light ejector marks on my max loads with each projectile listed below.

123gr Amax 45.5g = 3097 fps average for 3 shots
129gr LRAB 45.5g = 3099 fps average with an ES 7 (woohoo)
140gr Amax 44.5g= 2961 fps average. 44g was a nice load @ 2938 av and an ES 6, but I wrecked the group with a pulled shot.
So I'm fortunate that this barrel seems to like all and the speeds are good. Next plan is to lengthen the throat on this chambering by about 4mm to make use of the long action and get those projectiles out of the powder space.

Couple of pix of the targets


And yes another bloody Tikka T3

@Uplandstalker any progress with your loads?

@Mathias very kindly lent me his reamer so I could do much the same on Rem Model 7, 260.

Keeping the original lightweight factory barrel, now at 18.5 inches, factory stock, Hardy suppressor and shooting off a bipod on the ground at 100yds. 140gn Berger VLD Hunting. All RP cases, prepped the same, necked sized with a Lee Collet die. with CCI Large Mag primers.

Limited to mag length in the M7, but with this reamer, this is around 0.05" off the lands, and can only go forward another 0.01" before I start having issues with the length in the mag box. 5 shot strings. I don't have a heap of photos, but heres the numbers:

N160 powder:
44.5 - 2661fps 8ES - shoots the best groups I've had in any rifle. 0.3" (every group I've shoot with this load give the same group size and similar ES)
45.0 - 2697fps 11ES - tight groups 0.5"
45.5C - 2718fps 28ES - tight groups, but the cases are getting slammed! I didn't fire the need loads of N160. 0.5". Raised Ejector marks.

2209 powder:
43.5 - 2693fps 65ES - 1.2"
44.0 - 2722fps 27ES - 1.0"
44.5 - 2755fps 80ES - 1.1"
45.0 - 2770fps 29ES - 1.2"
45.5 - 2831fps 72ES - 1.2" Some pressure in the base from the ejector.

The big question now is do I continue to play around with the 2209 loads, or take the slower load with the N160 and shoot the deer in the eye ball? I'm thinking accuracy over speed!

I have a new stock in transit at the moment. This will be action bedded and truly floated (unlike the factory stock),