Anyone with experience on sizing one caliber into another?

[00Scot]

I recently built a 260ai with a CBI 28" 8twist barrel. First thing I did was order Redding 260ai dies and a Redding 260 Form die.

I also bought 100 7-08 cases and ran them through the form die,they go through it quite easy. Then lubed them up and ran them through my 260ai die. Since the AI chamber should be .004" shorter on headspace than a 260 remington you should have a slight crush fit,I also seated the bullets long to be into the rifling. I used a max load of powder listed for the standard 260rem. In my case I bought 100 cheap Prvi 120g hpbt and ran Alliant mr2000 powder. It will blow the shoulder out nice and sharp.

One thing I noticed is my loaded neck dia. was .288 with the necked down 7mm-08 brass. My chamber neck size measures .297" as close as i could measure. So I had a bunch of 308 brass I had necked down and loaded and it was measuring .294" a lot tighter but enough clearance I think to be good. I played with turning the necks on some of them as well to even them up.

I have used H4831,H4350,MR2000 and recently tried some Ramshot Magnum which I could not find data for. After working up a few loads for it to test velocity it got a 140hpbt over 3000fps. I'm gonna back off and try to run between 2900-2950 if it will shoot good there.

I would do like has been stated before and anneal your brass before necking down and sizing,I didn't have any split during forming but did split a few on firing and it was almost always the brass that gave me the largest neck to chamber clearance.

So far I like the 260ai,only shot it out to 630yards so far,next weekend going to shoot it at 1000 and see how it does. You'll definatley learn a few things and have some fun to boot. I would use some of the LC brass to get familiar with it then spring for some good stuff when you feel you can. Just make sure to measure neck clearance on the necked down 308 brass.

Thanks for all the info Shane, I have bookmarked this thread so I can return to it once I get going on the project. I plan to stick with my converted LC 308 brass if I can get it to shoot halfway decent. I don't want plan to buy other brass. Unless I just cant get the LC to shoot at all. Since this rifle is going to be strictly a hunter I'm not worried about absolute accuracy.

If I can get her to shoot a 5 shot group measuring somewhere in the .260 range at 500 yards then I'd be happy. So as you can see I'm not too worried about accuracy. ;D

I'm also hoping that the thickness of this brass will allow for more loading per case then some of the nicer brass that I could buy. But we shall see how that theory pans out.

 

[bozo699]

I recently built a 260ai with a CBI 28" 8twist barrel. First thing I did was order Redding 260ai dies and a Redding 260 Form die.

I also bought 100 7-08 cases and ran them through the form die,they go through it quite easy. Then lubed them up and ran them through my 260ai die. Since the AI chamber should be .004" shorter on headspace than a 260 remington you should have a slight crush fit,I also seated the bullets long to be into the rifling. I used a max load of powder listed for the standard 260rem. In my case I bought 100 cheap Prvi 120g hpbt and ran Alliant mr2000 powder. It will blow the shoulder out nice and sharp.

One thing I noticed is my loaded neck dia. was .288 with the necked down 7mm-08 brass. My chamber neck size measures .297" as close as i could measure. So I had a bunch of 308 brass I had necked down and loaded and it was measuring .294" a lot tighter but enough clearance I think to be good. I played with turning the necks on some of them as well to even them up.

I have used H4831,H4350,MR2000 and recently tried some Ramshot Magnum which I could not find data for. After working up a few loads for it to test velocity it got a 140hpbt over 3000fps. I'm gonna back off and try to run between 2900-2950 if it will shoot good there.

I would do like has been stated before and anneal your brass before necking down and sizing,I didn't have any split during forming but did split a few on firing and it was almost always the brass that gave me the largest neck to chamber clearance.

So far I like the 260ai,only shot it out to 630yards so far,next weekend going to shoot it at 1000 and see how it does. You'll definatley learn a few things and have some fun to boot. I would use some of the LC brass to get familiar with it then spring for some good stuff when you feel you can. Just make sure to measure neck clearance on the necked down 308 brass.

Thanks for all the info Shane, I have bookmarked this thread so I can return to it once I get going on the project. I plan to stick with my converted LC 308 brass if I can get it to shoot halfway decent. I don't want plan to buy other brass. Unless I just cant get the LC to shoot at all. Since this rifle is going to be strictly a hunter I'm not worried about absolute accuracy.

If I can get her to shoot a 5 shot group measuring somewhere in the .260 range at 500 yards then I'd be happy. So as you can see I'm not too worried about accuracy. ;D

I'm also hoping that the thickness of this brass will allow for more loading per case then some of the nicer brass that I could buy. But we shall see how that theory pans out.

Your joking I hope.

 

[00Scot]

I recently built a 260ai with a CBI 28" 8twist barrel. First thing I did was order Redding 260ai dies and a Redding 260 Form die.

I also bought 100 7-08 cases and ran them through the form die,they go through it quite easy. Then lubed them up and ran them through my 260ai die. Since the AI chamber should be .004" shorter on headspace than a 260 remington you should have a slight crush fit,I also seated the bullets long to be into the rifling. I used a max load of powder listed for the standard 260rem. In my case I bought 100 cheap Prvi 120g hpbt and ran Alliant mr2000 powder. It will blow the shoulder out nice and sharp.

One thing I noticed is my loaded neck dia. was .288 with the necked down 7mm-08 brass. My chamber neck size measures .297" as close as i could measure. So I had a bunch of 308 brass I had necked down and loaded and it was measuring .294" a lot tighter but enough clearance I think to be good. I played with turning the necks on some of them as well to even them up.

I have used H4831,H4350,MR2000 and recently tried some Ramshot Magnum which I could not find data for. After working up a few loads for it to test velocity it got a 140hpbt over 3000fps. I'm gonna back off and try to run between 2900-2950 if it will shoot good there.

I would do like has been stated before and anneal your brass before necking down and sizing,I didn't have any split during forming but did split a few on firing and it was almost always the brass that gave me the largest neck to chamber clearance.

So far I like the 260ai,only shot it out to 630yards so far,next weekend going to shoot it at 1000 and see how it does. You'll definatley learn a few things and have some fun to boot. I would use some of the LC brass to get familiar with it then spring for some good stuff when you feel you can. Just make sure to measure neck clearance on the necked down 308 brass.

Thanks for all the info Shane, I have bookmarked this thread so I can return to it once I get going on the project. I plan to stick with my converted LC 308 brass if I can get it to shoot halfway decent. I don't want plan to buy other brass. Unless I just cant get the LC to shoot at all. Since this rifle is going to be strictly a hunter I'm not worried about absolute accuracy.

If I can get her to shoot a 5 shot group measuring somewhere in the .260 range at 500 yards then I'd be happy. So as you can see I'm not too worried about accuracy. ;D

I'm also hoping that the thickness of this brass will allow for more loading per case then some of the nicer brass that I could buy. But we shall see how that theory pans out.

Your joking I hope.

What do you mean? Doesn't the AI in 260 AI stand for Accuracy in inches? Meaning that the 260 "AI" denotes that the cartridge is supposed to be able to shoot a .260 5 shot group at 500 yards?






ummmm.....yes I'm joking bozo699!

 

[00Scot]

I have a question about the 260AI. Will using a 20 inch brl cause me any major problems other then loosing a couple hundred fps? I havn't decided which rifle to chamber the 260AI in yet. So the answer to this question may possibly determine which rifle I "have" to use for the 260AI.

 

[ShaneG.]

Other than velocity being lower I wouldn't think it would hurt anything at all since it's going to be strictly a hunting rifle.

You might have to stick with the faster burning powders not sure how the short barrel would do with anything too slow.

I was getting from 1"-"1.25 groups today at 300yards with a little bit of wind and a 3.5lb trigger. I have been more than happy with my .260ai so far.

 

[00Scot]

Other than velocity being lower I wouldn't think it would hurt anything at all since it's going to be strictly a hunting rifle.

You might have to stick with the faster burning powders not sure how the short barrel would do with anything too slow.

I was getting from 1"-"1.25 groups today at 300yards with a little bit of wind and a 3.5lb trigger. I have been more than happy with my .260ai so far.

Great to hear! Keep us informed on how its shooting and your end results.

 

[2644ever]

I have a question about the 260AI. Will using a 20 inch brl cause me any major problems other then loosing a couple hundred fps?

I've gone thru that road too... Depending on the powder you use, you won't be losing that much speed, but the blast will be fierce not to say awesome and you won't obtain the best accuracy from that excellent cartridge. In my opinion avoid any barrel shorter than 24"in the .260

 

[2506]

Here is a little tip to keep in mind. When working with a great deal of military cases that need primer pocket crimps reamed and trimmed properly and inside the case primer flash hole burr removed. Get a RCBS Trim Mate Case Prep Center. You can get the little tool that screws into it to remove the crimp and a Lyman inside the case de-burr tool will screw right into it also. You can prep a case zip, zip, zip and you are done. It is WELL WORTH the cost of the prep center.

One other tip is when sizing down a case to another caliber raise the ram quickly in one fluid motion. Don't go slow and do not stop in the process. I have also found that Hornady One Shot spray lube really works good. Spray outside and inside the neck good and LET IT DRY. I don't get any dents that you can get with oil type lubes.

 

[00Scot]

Thanks 2506,

I have been eying that case prep center for awhile. I do believe that this project will be the perfect reason to go ahead and make the purchase. As for the One Shot Spray, I have been using that for years. And I love it.

 

[00Scot]

I have a question about the 260AI. Will using a 20 inch brl cause me any major problems other then loosing a couple hundred fps?

I've gone thru that road too... Depending on the powder you use, you won't be losing that much speed, but the blast will be fierce not to say awesome and you won't obtain the best accuracy from that excellent cartridge. In my opinion avoid any barrel shorter than 24"in the .260

That was what I was afraid of. Well it looks like the 260AI might just end up going on my T/C then.

 

[00Scot]

Anyone interested in trading 500-1000 pieces of Lake City brass?