dont shoot the same poi

[longwinters]

I have a ton of 308 cases and just got rid of that rifle and bought a 7m-08.
Figured I could resize the 308's to 7m-08. Seemed to work fine except the cases are about 2.015 instead of 2.025. Anyway loaded some up and the poi, using the same load etc... is about 1.5" higher and about 1" left. Grouping is a little bigger also.

I have done the same with 30-06 to 280 and it worked great, although I did not compare poi between the two.

Any thoughts or ideas? I guess I could just shoot all one or the other . . .but thats no fun.

Long

 

[Ol` Joe]

There were no other changes? Same lot of bullets, powder, ect? Distance to the lands the same? You`ve change the neck thickness for sure and I would bet the capasity of the cases differ also. Have you crono`ed the loads to see if the velocity is similar?
I wouldn`t worry too much about it, just verify your sights before hunting. On paper the differance is moot unless your in a match of some sort.

 

[R Flowers]

Well, it is hard to believe, but I had even more confusing results using necked down 308 brass in my 7-08.

I worked up loads in Remington and Winchester 7-08 brass and was quite pleased. I then got to thinking I could use some of the 308 brass I had lying around. I tried sizing some down and everything was fine except for them being shorter as you mentioned.

I thought I should check on grouping and point of impact so I loaded some up one morning. I loaded Remington and Winchester 7-08 brass. I loaded Winchester, Remington, and Federal 308 brass that I had necked down. All were sized in the same set of dies, all had the same lot of primers, same lot of powder, bullets from the same box, etc. All powder charges were weighed, all had the same OAL.

I went to the range and got surprised. The Rem and Win 7-08 brass shot the same just as before. The groups with the necked down 308 brass were ok but the darn point of impact was a mystery to me. The necked down Winchester 308 cases shot to the same point as the 7-08 cases. The necked down Federal and Remington cases both shot 2.5 inches higher!! What is with that?

I called the Sierra hot line since they are usually pretty helpfull. All I got was a smart-assed answer about "any time you change ANY component you will change the point of impact", and comments on how the short 308 cases could damage my chamber. Yeah right, I am not going to be shooting thousands and thousands of the darned things.

Anyway, I just gave up and ordered some more 7-08 brass.

 

[clearwater]

different brass has different case capacities, try weighing some different
brands. Federal 06 brass is heavy, winchester is light, Rem is in the middle. Don't know about 308 or 7-08 brass.

 

[longwinters]

When I resized and loaded these cartridges everything was the same from case namebrand to bullet to powder/load to primer. The only thing I was wondering, as has been mentioned, is about neck thickness with the resized 308. That extra brass has to go somewhere and if it isnt going to make the case longer it must be making something thicker ie the neck. After being fired the case length on the resized brass was the exact same as it was before being fired. I suppose if the neck thickness has increased it would not stretch as easily as with cases used in the caliber rifle that they were to be used in.

Long

 

[Rflshootr]

Check the OAL of the cases after you resize them. I can almot guarantee that they will be slightly longer than they started out. If you can get your hands on some Lake City brass, try some of them. BUT be careful with miltary brass as it is much thicker and loads will have to be worked back up from square one.

 

[Anonymous]

Neck thickness and increased neck tension was my first best guess. I'd compare the neck thickness of your sized .308 brass to the store bought 7-08 brass. Although it maybe a mute point now it could be some handy info for latter on. I hope that helps.