The "6mm Swiss Match Ackley" Cartridge

[SHootSTraight22]

I have hit my coldbore shots in the same kind of matches you shoot, 0 misses. I do not have a clue of what H4350 does in anything because I had never used it. Also have never compared my 6mm Competition Match against the .243AI .

I hope you have zero misses on big playing cards!! The ace center is what you need to hit, "the very center.." H4350 prevents my dope from varying throughout a days worth of shooting with some days starting at 28 degrees and increasing to 60 degrees by lunch time... You shoot in Florida, not much swing there!

 

[SHootSTraight22]

The 6.5 x 47 already has minimal body taper. There's but scant "improvement" available from Ackley-izing the 6.5 x 47 Lapua case. In another thread I pointed out the marked similarity between the 6.5 x 47 Lapua and the 250 Ackley Improved, the latter's body being about .010" longer but body taper and diameter at the base of the shoulder are essentially identical.

The only significant "improvement" might be in steepening the shoulder angle from 30-deg to, say, 40-deg, but I gather the perpetrator was aiming for more significant case capacity gains, not just any gains attributable to a steep shoulder (e.g. resistance to brass flow.)

Unless I'm missing something.

You can easily gain .110 in body by in corporating a 40 degree shoulder and blowing the case forward.. That would leave you with .200 neck for bullet grip.. Imagine a 6mm Dasher but longer, that's all it would be.. Add to that the bad *** 6.5x47 Lapua brass and you could easily run pressure up...The thing is everyone keeps saying 105gr Hybrids don't like greater than 3,150 and prefer 2,950-3,075fps... Well, we need to figure out why?? With other types of projectiles (arrows, missiles, spears, etc.) you can tweak the FOB... with other projectiles like arrows, flight is better with a farward FOB.. This maybe a subject for Litz??? I would be interested to here how bullets are effected by FOB... This maybe a good place to talk about the use of tungsten powder within the forward portion of a bullet or mixture of something?? Add to that "tweaking barrel twist" may throw another balancing act into the mix.. There has to be a way or a point precision starts back...

 

[SHootSTraight22]

I know personaly with a 6.5x47 their is a 2,900fps plus node with H4350 and 140gr hybrids.. The only problem I see with it is the powder compresses so much I feel it pushes the bullet out over time.. With that certain case the extra .110 in body length you wouldn't have this problem.. Think about it, one reason I would say the 6.5x47 cartridge is so accurate is because of it's certain fill percentage.. A case that has the ability to shoot under super pressures like it would most likely benefit more than those that will blow primer pockets?? Plus, it has a longer neck than most cases, which will allow you to incorporate more of that neck/shoulder into a new body???

 

[Brians356]

The only problem I see with it is the powder compresses so much I feel it pushes the bullet out over time..

Naw, just get the smallest hose clamp, band type with the worm gear, and clamp as tight as possible around the neck. Remove just before firing, but better chamber and fire it quickly - don't dawdle trying to dope the wind.

 

[Brians356]

You can easily gain .110 in body by in corporating a 40 degree shoulder and blowing the case forward..

Uh huh. Except that ain't an Ackley Improved. Not if you can't safely fire factory 6.5 x 47 ammo in it.

 

[SHootSTraight22]

You can easily gain .110 in body by in corporating a 40 degree shoulder and blowing the case forward..

Uh huh. Except that ain't an Ackley Improved. Not if you can't safely fire factory 6.5 x 47 ammo in it.

Why wouldn't you be able to blow your shoulders forward in it with factory spec cases?? Scott @ Vortex is on the other thread I created talking about doing that with his.. He had the reamer made for the 6-6.5x47 Ack. Imp. or Long Dasher, LOL... Go over to the "6.5mm and stuff thread..." Read his post...

 

[SHootSTraight22]

You can easily gain .110 in body by in corporating a 40 degree shoulder and blowing the case forward..

Uh huh. Except that ain't an Ackley Improved. Not if you can't safely fire factory 6.5 x 47 ammo in it.

What do you think an Ackley Improved case is? I call a short neck with a 40degree shoulder and blown forward body an AI.. What I call "Improved" is just sharpening the angle on the shoulder without the full blown forward body/shoulder.. Example,, a 6mm Dasher has an Ackley Improved shoulder/neck.. If at all different it aint nothing but a .00001...

 

[swd]

The beauty of Ackley's designs is they head spaced at the neck/shoulder junction for fire forming. Ackley designs never shortened the neck any more than it took to get a crush fit. Anything that requires false shoulders or hard jamming bullets to form like a Dasher or BRX that blow the shoulder forward aren't Ackley improved. They may be considered an "improved" case, but Parker Ackley isn't part of that equation.

 

[Brians356]

The beauty of Ackley's designs is they head spaced at the neck/shoulder junction for fire forming. Ackley designs never shortened the neck any more than it took to get a crush fit. Anything that requires false shoulders or hard jamming bullets to form like a Dasher or BRX that blow the shoulder forward aren't Ackley improved. They may be considered an "improved" case, but Parker Ackley isn't part of that equation.

I couldn't have said it better - but I tried.

If you steepen the 6.5 x 47 shoulder to 40 deg AND move the neck/shoulder junction forward 0.100" that's not an Ackley Improved strictly speaking, but it is an improved case. And it's then only ~.013" longer, body+shoulder, than the 250 Ackley. So you've essentially created (ignoring neck lengths) a 6.5-250 AI with a small rifle primer.

 

[Brians356]

Why wouldn't you be able to blow your shoulders forward in it with factory spec cases??

I never mentioned factory cases, I said ammo. Ackley spec means you can improve using factory spec loaded ammo. You couldn't safely fire 6.5 x 47 Lapua ammo in a chamber which has .100" excess headspace.