Just a little teaser

[bigngreen]

I'm kinda jacked to see someone else taking up the 270, I think the 175 Matrix VLD would shine in that case capacity but the 165 may be on the edge if you twist it up to fast, I think they have had jackets come apart in the 3250-3300 fps range. The 170 Matrix ULD looks good but I don't have anything that would hump them hard enough to test them fully since my WSM would probably only push it at 3050 fps or so.

I think the Berger 170 would be a stud, they've shot them and hunted with them a little so if it weren't for the insanity we'd be enjoying them!!

I can bring you a selection of boolits if you need them.

 

[MontanaRifleman]

I'm kinda jacked to see someone else taking up the 270, I think the 175 Matrix VLD would shine in that case capacity but the 165 may be on the edge if you twist it up to fast, I think they have had jackets come apart in the 3250-3300 fps range. The 170 Matrix ULD looks good but I don't have anything that would hump them hard enough to test them fully since my WSM would probably only push it at 3050 fps or so.

I think the Berger 170 would be a stud, they've shot them and hunted with them a little so if it weren't for the insanity we'd be enjoying them!!

I can bring you a selection of boolits if you need them.

I'll have to call CEB and find out the recommended twist. I'm guessing we're looking in the 7- 8 range. If a 7 is required I will probably go with a gain twist. In either case it will be 5R/5C rifling which should be a little easier on them than a standard 6 groove.

If you could bring maybe 3 of bullets of whatever that would be great. Also, my die is a FL bushing die and I have no bushing. These dies came about 3 months earlier than I expected so I'm a little unprepared. And it would be nice to know the seated OD before I order a titanium Nitride bushing so I get it right the first time. If you had a bushing I could borrow, that would be great. Heck, I could bring my Rock Chucker and size and seat them right there.

Now I gotta figure out a way to pay for this project after just finishing up 3 others

I am accepting donations for a good cause gun)

 

[Fiftydriver]

Kirby.

The 270 Montana is based of the 300 Dakota, similar to your AX, but I think a little less case capacity. I bumped the shoulder back abut .008 and decreased the diameter about .003 with close to the same taper. I'm going with a 40* shoulder and hoping to get a .330 long neck to ease the throat wear. The reason I decreased the case capacity was that the factory brass was a few thou smaller than the Dakota specs. I think this will help with case strength and life and it will need minimal fire forming after the initial sizing. I'm hoping that I can do load development and fire forming at the same time.

Matrix has a 170 gr bullet and CEB has a 165 gr bullet. Hopefully Berger will come online with a good heavy hybrid but I'm not holding my breath.

Yes, the berger will come but I to am not holding my breath!!!

Some lots of 300 Dakota brass were quite soft but others have been extremely strong. I think the current brass is pretty good so you should get good results with your wildcat. I have only shot the 165 and 175 gr Matrix and at velocities under 3200 fps they did very well. My 270 Allen Magnum chewed up the 175 gr version but some rifles shot the 165 gr very well, not sure the difference but figure its just a matter of length and RPMs.

Have fun!!!

 

[HARPERC]

Never even remotely considered a 270 anything-until now. Good Luck! Very cool!

 

[bigngreen]

I'll have to call CEB and find out the recommended twist. I'm guessing we're looking in the 7- 8 range. If a 7 is required I will probably go with a gain twist. In either case it will be 5R/5C rifling which should be a little easier on them than a standard 6 groove.

If you could bring maybe 3 of bullets of whatever that would be great. Also, my die is a FL bushing die and I have no bushing. These dies came about 3 months earlier than I expected so I'm a little unprepared. And it would be nice to know the seated OD before I order a titanium Nitride bushing so I get it right the first time. If you had a bushing I could borrow, that would be great. Heck, I could bring my Rock Chucker and size and seat them right there.

Now I gotta figure out a way to pay for this project after just finishing up 3 others

I am accepting donations for a good cause gun)

I'll grab my 270 cal bushing set, you could probably clamp a press to a table around there.

I know I have a good number of 165 VLD's and 170 ULD's but I don't know about the 175's, the 175's are just a stretched 165. The 170's are made with the stronger Corbin jacket, they look much like the old Wildcats.

 

[MontanaRifleman]

Yes, the berger will come but I to am not holding my breath!!!

Some lots of 300 Dakota brass were quite soft but others have been extremely strong. I think the current brass is pretty good so you should get good results with your wildcat. I have only shot the 165 and 175 gr Matrix and at velocities under 3200 fps they did very well. My 270 Allen Magnum chewed up the 175 gr version but some rifles shot the 165 gr very well, not sure the difference but figure its just a matter of length and RPMs.

Have fun!!!

Thanks Kirby, I'm sure this wil be a lot of fun!

I got this brass a couple years and am very impressed with the looks and feel. It is Hornady made, or so I was told and it looks like good strong tough brass. Time will tell

Never even remotely considered a 270 anything-until now. Good Luck! Very cool!

Thanks, glad you like it!

I'll grab my 270 cal bushing set, you could probably clamp a press to a table around there.

I know I have a good number of 165 VLD's and 170 ULD's but I don't know about the 175's, the 175's are just a stretched 165. The 170's are made with the stronger Corbin jacket, they look much like the old Wildcats.

Sweet, I will bring the press. Lets load up a couple of the 170's and we can pull them after I get the measurements. We can take some cool factor pics too

 

[royinidaho]

Hmmmmmm,While chew'in the fat with Grit, when he fitted a take off 270 AM bbl cause I shot out the original, we figgered a cartridge of your Montana design would be very close to ideal.


I didn't know about Kirby's 270 AX at the time. I'd best check the APS web page.


How do the AX and Montana cartridges compare to the AM?


I have a hunting life time supply of original Wildcats in 169.5 and 195 weights and am hankerin' to max out the new Nosler 150 ABLR. At AM velocities it hangs right with the heavier offerings.


270 Noslers of any type and weight at any velocity I pushed them to, in the original bbl, could not be made to come apart and were deadly accurate. The increase in from 0.496 to 0.625? Is a huge difference.


A 270 cartridge that would push the ABLR upwards of around 3500 and not be limited to WC-870 and US-869 would flat be a dream.


In the AM case I have been getting away with 7828ssc behind 140s and 150s but wouldn't even think (again) of using any stick powers with heavier offerings. [powder bridging, I think, may exceed proof loads!]

 

[MontanaRifleman]

Well Roy... as you know, Kirby used the 338 RUM as a parent for the AM and the 300 Dakota for the AX. And there is about 10 H20 gr or 10% diff between the 2. Kirby, I'm guessing, blew them out in AI style while I pushed the Montana in. so i'm guessing the AX has 3-4 grs mor capacity than the Montana and the AM about 10 gr more than the AX.

I wasn't too worried about loosing case capacity because I figured more capacity at that level looses a lot of efficiency, depending on what bullets and powders are available. RL33 is making this cartridge look very interesting. The AX too. And with the 150 bullets, Retumbo or H1000 might be good players. I thimk if you hit anything closer than a 100 yds with an ABLR with a MV of 3500, you would probably have a big explosion

 

[royinidaho]

I thimk if you hit anything closer than a 100 yds with an ABLR with a MV of 3500, you would probably have a big explosion

I don't much care. Just so its dead.

 

[Fiftydriver]

Well Roy... as you know, Kirby used the 338 RUM as a parent for the AM and the 300 Dakota for the AX. And there is about 10 H20 gr or 10% diff between the 2. Kirby, I'm guessing, blew them out in AI style while I pushed the Montana in. so i'm guessing the AX has 3-4 grs mor capacity than the Montana and the AM about 10 gr more than the AX.

I wasn't too worried about loosing case capacity because I figured more capacity at that level looses a lot of efficiency, depending on what bullets and powders are available. RL33 is making this cartridge look very interesting. The AX too. And with the 150 bullets, Retumbo or H1000 might be good players. I thimk if you hit anything closer than a 100 yds with an ABLR with a MV of 3500, you would probably have a big explosion

I in no way want to hijack this thread so this is only to clearify some information and that's all, want to keep this on the 270 Montana topic but just a quick clarification. The 257 AM and 6.5mm AM are based on the 338 RUM parent case, the 270 AM is based on the 7mm or 300 RUM so its roughly 0.100" longer in body length then its two smaller siblings. The larger 270 bore could handle the full length RUM case plus, its a since to form 270 AM brass from 7mm RUM brass.

Performance wise, in my testing, the 270 AM loaded with 140 gr Accubonds or 169.5 gr ULD RBBTs (old wildcats) will run 125 to 150 fps faster then the 270 AX loaded with the same bullet in same length barrels.

The 270 AM would easily break 3450 fps with a 169.5 gr ULD RBBT. The 270 AX would run right around 3300 fps with same bullet weight.

With the 140 gr Accubonds, the 270 AM will push 3650 to 3700 fps depending on barrel length. The 270 AX will be in that 3500-3550 fps range.

MontanaRiflemans predictions are exactly where I would expect them to be with a 140-150 gr bullet weight. I would like to mention that all my testing was done with powders we had 6 years ago. I have not tested the 270 AX with some of our new powders such as RL33 which I suspect will pick up a bit more velocity.

Again, no intent to hijack this thread, just posted to offer clarification and now we need to get back to the 270 Montana so please no questions about the 270 AM or 270 AX, if you want information on them contact me directly and lets keep this post on topic with the experiements at hand!!!

 

[royinidaho]

OK

 

[MontanaRifleman]

I in no way want to hijack this thread so this is only to clearify some information and that's all, want to keep this on the 270 Montana topic but just a quick clarification. The 257 AM and 6.5mm AM are based on the 338 RUM parent case, the 270 AM is based on the 7mm or 300 RUM so its roughly 0.100" longer in body length then its two smaller siblings. The larger 270 bore could handle the full length RUM case plus, its a since to form 270 AM brass from 7mm RUM brass.

Performance wise, in my testing, the 270 AM loaded with 140 gr Accubonds or 169.5 gr ULD RBBTs (old wildcats) will run 125 to 150 fps faster then the 270 AX loaded with the same bullet in same length barrels.

The 270 AM would easily break 3450 fps with a 169.5 gr ULD RBBT. The 270 AX would run right around 3300 fps with same bullet weight.

With the 140 gr Accubonds, the 270 AM will push 3650 to 3700 fps depending on barrel length. The 270 AX will be in that 3500-3550 fps range.

MontanaRiflemans predictions are exactly where I would expect them to be with a 140-150 gr bullet weight. I would like to mention that all my testing was done with powders we had 6 years ago. I have not tested the 270 AX with some of our new powders such as RL33 which I suspect will pick up a bit more velocity.

Again, no intent to hijack this thread, just posted to offer clarification and now we need to get back to the 270 Montana so please no questions about the 270 AM or 270 AX, if you want information on them contact me directly and lets keep this post on topic with the experiements at hand!!!

Sorry about that Kirby, I was thinking the 270 AM was the same parent as the 6.5. Thanks for the clarification.

And just to add to the clarification I'll link your pages on the AX and AM cartridges.

Allen Xpress Wildcats

Allen Magnum Wildcats

For others benefit, the 7 and 300 RUM are about 2-3 H2O gr more capacity and about .090 longer at the shoulder than the 338 RUM.

I do not at all mind talking about other chamberings in this thread. In fact I enjoy it. That's what we do in these forums. I think making comparisons help folks put things into perspective.

So by all means, feel free make all the comparisons you want.

 

[MontanaRifleman]

OK... so I went to the Townsend shoot today and took along my press, Dakota brass, Calipers, Imperial Sizing Wax, and bullet puller. Rhian did his part and brought some boolits and bushings. But..... wouldn't ya know.... I forgot the shell holder

Well, Rhian sent me home with the boolits and bushings and I did some sizing and seating and here is a pic.

From left to right,

6.5 WSM 140 Berger VLD
270 Montana 165 Matrix
270 Montana 170 Matrix
300 RUM 230 Berger Hybrid

 

[royinidaho]

I'm still thinkin' that the Montana cartridge is about optimum for the 150 and 165 grain offerings.

The pic reinforces my observation.