What 6.5 wildcat is this?

[Jimbag]

Did a chamber cast of an unknown 6.5. Need to know what if a common wildcat or a one off.
Cast Neck .300 dia, length .342
Cast base is .479dia
Cast shoulder is .465 dia
Base to shoulder length 1.740 +/-
Case OAL 2.170
Shoulder is 40degrees
I am not a riflesmith, so length is the cast plus recess depth in bolt.
Barrel has no extractor cut

Looked around a lot and found no drawings that suit this

 

[okie]

I could make a WAG from looking at a pic---lol

 

[Jimbag]

WAG away

 

[JLT]

.260 AI would be my guess.

 

[Jimbag]

260 AI would definitely fit in the hole… hmm Like I said the length I have is an assumption..good guess

 

[JLT]

260 AI would definitely fit in the hole… hmm Like I said the length I have is an assumption..good guess

Chamber neck length and case neck length are often quite a bit different. My .260 AI reamer cuts a generous neck length relative to 'consensus' case neck length/OAL case length.

 

[okie]

View attachment 1474812View attachment 1474812
WAG away

you called my bluff.

 

[okie]

6.5x .308? looks improved

 

[Jimbag]

6.5x .308? looks improved

It is improved, 40 degree shoulder.

 

[okie]

Looks like JLT nailed it

 

[Jimbag]

Chamber neck length and case neck length are often quite a bit different. My .260 AI reamer cuts a generous neck length relative to 'consensus' case neck length/OAL case length.

The cast represents only the portion of supported brass in chamber. The rifle is an RSA Musgrave which has a recessed bolt face of .105, barrel has no extractor cut.
I am adding the recess to the chamber cast lengths to get an assumed OAL to base. This methodology is weak, but I don’t have gauges.

 

[JLT]

If you have any .260 Rem brass, take an empty and chamber it. If it is a properly cut Ackley Improved chamber, you should feel slight resistance in closing the bolt - headspace on the AI is .003" - .004" shorter than the parent case. If that's what you experience, then the odds are greatly in favor of a .260 AI chamber. Your diameter at the shoulder is very close to my fired .260 AI brass - I just checked three cases.

 

[Jimbag]

Appreciate your input, 100%

 

[NZ_Fclass]

Looks a little long for a 260 @2.17, which is 55mm ish. Is this a wildcat on the 257 Roberts/7x57/6mm Remington? Either way, It's worth pursuing.

 

[Jimbag]

More digging has a turned up reamer print for the 6.5x55 AI which really fits well the casting dimensions

 

[nksmfamjp]

That seems a lot like 6.5x55 ai.

 

[Laurie]

I'd say 6.5X55AI. This was a modestly popular improved match cartridge maybe 20 or so years ago, although it goes back a lot further. It was an alternative to 6.5-284 when that was still a wildcat. I can remember a few being used in the early days of F-Class. Dies were always problematic, and often had to be special order jobs. Some people had the view that the 6.5X55AI whose capacity falls in between the standard version and the 6.5-284 was the best of the three. It was certainly an excellent performer and had good Lapua basic brass available. As many people throttled the 6.5-284 back a bit to get better barrel life, a similar-performance improved 6.5X55 running with 100% fill-ratios makes sense.

Since that time, 6.5X55 Imps haven't gone away, but the 40-deg shoulder Ackley version has maybe gone a bit out of favour with 30 and 35-deg shoulder models now 'in'. If you do a search on this forum, there are several threads on 6.5X55 Improveds of which the GWI seems the most often mentioned.

 

[ebb]

The .480 base dimension is the give away

 

[paperpuncher]

6.5 Vais is real close

 

[Jimbag]

The piece is from a fullbore shooters estate. It fits well with the early days of F class.
In the estate there are a few rebarreled pieces that needed casts made to identify chambering. This was one which left me at odds.
I very much appreciate the input.