Any up dates on the 260imp 30 degree??

[Raptor]

Just wondering if you guys who have them have done any more testing or how the load development is going?? Mine should be done in the next 10 days or so. The barrel got tied up getting melonited.

What are you using for fireforming loads?? I have some 123s loaded with 43.5grs of H4350 that shot really well in my old gun and was wondering if that load will work to fireform the brass with?? Thanks guy!!!

 

[daj]

Raptor,

I started fireforming with my old 260R load of 123 Scenars over 45.8gn AR2209 (H4350) and the cases were well formed.

I now fireform with 140VLDs over 44.9gn AR2209 for a MV of 2950fps in the 28" barrel.
The formed 260I30 cases run at the same velocity with 44.6gn AR2209.

It's worth mentioning that I am using up my old 243/260 Lapua brass that has 7x firings. Primer pockets on the formed brass are still tight after 3 more firings at the higher pressure.

In my rifle, your load of 123/43.5gn H4350 would generate pressure of over 50,000psi, more than enough to fireform I would think.

 

[Raptor]

Thanks daj, appreciate the info!! I hope mine will shoot well.

 

[BradY]

Daj- would like to know your thoughts on the amount of extra powder you need for fireforming. Im running 43.8gr 2209 in mine with 30 inch barrel but dont know velocity yet- will do soon hopefully. Guessing around the 2820fps mark. I have shot up to 45gr with 140's but this is the sweet area so far. I might try around the 44gr mark with 140VLD's to fireform as I have a heap of cases that need forming up.

 

[daj]

Daj- would like to know your thoughts on the amount of extra powder you need for fireforming.

BY1983, unlike most improved cartridges, the 260Imp30 does not increase case capacity from the parent case by much at all - at least not the way my chamber was cut. In fact my 260R cases increased in volume by only 0.3gr H2O when fire-formed into 260IMP30. With such a small volume change, I decided to fireform with my accuracy load plus about 0.3gr (2209). The little extra charge is required to compensate for the energy lost in fireforming. Both fireforming and formed loads run at 2950fps.

I would expect your velocities to be higher than 2820fps. According to QL, if my barrel was 30", 140 vlds (jammed 20T)/43.7gr 2209 would have me right on the node at 2930fps.

 

[Joe C]

O.k. so since I've been looking into the whole .260ai thing, can you please give me the long and short of why the 30degree instead of the normal AI?

Thanks!

 

[BradY]

Thanks daj. Im going to order a magnetospeed V2 to get velocity readings as the F1 chrony just doesnt work very well at all. Im running 140 hybrids with a small jump and have tested loads at 300, 700 and 900 meters for vertical spread. Anywhere from 43.5 to 43.8 has been very impressive across all these ranges but Ive shot up to 45gr with no pressure signs.

 

[flatlander]

Joe - maybe the 30* shoulder feeds smoother than the 40*? Dunno for sure, but I just received 6.5x08 Imp 30* finisher & RZ reamers, and will be doing a bbl for a SA M700 soon. I spec'd .459" dia at the shoulder, as opposed to the std 260's .4551", and moved the shoulder forward .0685", so there should be a slight increase in case capacity.

Did the same thing with a 7x08 Imp 30* last year, and have it running in a 25" bbl'd AR10. Wanting to do 26" sendro contour bbls in both 6.5 & 7mm for a bolt rifle. Can't see doing two complete rifles for cases so similar, so will probably set it up as a switch-bbl rig. Should be interesting to see how both stack up against 6.5x55AI & 284 Win. rifles I already have.

 

[Raptor]

daj,
I thought that the case was expanded like a .100 thousands or something like that?? I was thinking that would give it more case cap. I think the difference between the 6BR and the BRX is like .100 too.

Have any of you tried H4831 with the 140s yet? Thanks!!

 

[daj]

Raptor,

My 260 case shoulder advanced by approx. 0.06". My smith decided to head-space on new Lapua 260 brass rather than on the 308 Go-Gauge as requested. As a consequence, my chamber is a little shorter than it should be. However, the rifle flat out shoots factory 260 ammo, my old 260 handloads, and the new 260I30 handloads, so I am happy.

I have only tried Re17 and H4350 so far but H4831 looks good on paper (QL). The downside is that the load is more compressed at 105% fill compared with 101% for H4350 and 93% for Re17.

 

[Raptor]

I like your idea!! However mine is being done off the .308 gauge. My thinking is that 4831SC may be the ideal powder with the extra case cap. that you get. Of course I only have a lb of it!!

My 6SLR really liked H1000 and I wonder how that would work in the 260 imp. case or if you couldn't get enough in it?? Thanks for the updates. I am really getting anxious to get mine. Its been out getting melonited for the last 6wks. and I am still waiting......

 

[Triggerf16]

I'm shooting a 6.5SLR which should be pretty close to your 260 30 degree. I tested 42.5 up to 45.5 in .3 increments with Hornady 140AMax. I found nodes at 43.0 and 45.0 grains of H4350. The problem is the 45.0 grain load created loose primer pockets in the Winchester 243 brass.

I settled on the 43.0 grain load. I estimate velocities between 2820 and 2850. I'll shoot it over a chrono and at range to verify velocity. The barrel is new, so I expect velocities will change after 250 rounds.

I like the longer neck on the SLR compared to the Ackley. I'll trade a bit of velocity for the longer barrel life of the long necked case.

 

[Raptor]

Whats your accuracy like with the 6.5SLR??I really looked at going with the SLR but I had picked up 500rds of Lapua 308 brass and had sized it down to 260. I know Robert said to stay away from the Lapua in the 6SLRs so that is why I decieded on the 30 Degree improved.

It appears that 4350 is the way to go just like in the stock 260s. I am going to try the 123s because I really liked them in my last 260. I don't care which bullet it shoots as long as it likes at least one!! Ha