Necking down to 7mm-08

[1791PrecisionArmory]

I have 500 pieces of Lapua 308 brass. I cannot find any 7mm-08 brass currently (or anything else) So I decided I would buy some Forster 708 dies neck down and go. Sizing them down is easy, cases look fine, I'm not bumping the shoulder back at all.

Problem is, Seating bullets takes more than a normal amount of force to get them in. Is this common? I checked the expander ball and everything reads normal. Bullets I am seating are 162gr Hornady HPBT.

 

[280nosler]

Re: Necking down to 7mm-08

Technically the neck is now thicker than it should be as you have taken 308 brass and condensed the area of neck into a smaller diameter. You probably need to get a neck reamer to take the excess brass out, as not only will seating be difficult, but it will also increase the pressure behind the bullet upon firing.

 

[gvanhyning]

Re: Necking down to 7mm-08

You will probably have to do an inside neck ream. Inside reams aren't usually needed when necking up but almost always when necking down. I use necking dies with bushings to neck down. Using an oversized bushing can help prevent the need for reaming. Sometimes a "donut" may form at the bottom of the neck which requires reaming.

 

[Bill Larson]

Re: Necking down to 7mm-08

Hope you have`nt done all 500 pieces.........necking up is easier and creates less of a problem long run than necking down.Necking down invites "doughnuts"....
if you have`nt done them all......I would trade/sell off what you have and either get some 243 Lapua or 7-08 win. brass.
OMHO
bill larson

 

[1791PrecisionArmory]

Re: Necking down to 7mm-08

I only sized 3 cases. @ 68 cents a piece I didn't want to lose any cases. I'll just back order some 708.

 

[bohem]

Re: Necking down to 7mm-08

Neck ream and trim/chamfer the mouth will take care of that issue. You can use a bigger neck bushing if you got one of the bushing dies, this way you can avoid reaming, however I've noticed that much of the time when I neck down I need to touch-trim and chamfer for the issue to go away

 

[Fuzzball]

Re: Necking down to 7mm-08

Your 'new' 7-08 necks will be about 1 thou thicker than average, that's not enough to matter because average necks are quite a bit thinner than ideal for accuracy anyway.

Reaming is a poor way to thin necks. Outside turning actally uniforms the thickness while reaming does not.

Neck "donuts" come from necking up because part of the case shoulder becomes part of the new neck; sizing down reverses that and avoids the donut problem.

Chamfering case mouths is always a good thing to do but case trimming is only helpful if the cases exceed normal max length.

 

[427Cobra]

Re: Necking down to 7mm-08

I neck down Win 7-08 down to 260 in a Forster FL die, lube up your 308 brass and resize it to 284(7-08) in a non bushing FL die, necking down is no big deal, the problem you have is 308 brass is toooooo short, ask yourself if your comfortable with that.

 

[1791PrecisionArmory]

Winchester brass necks down easily with just the die. The Lapua brass and some of thicker necked Nosler and Remington brass has to be turned to fit in my chamber.

 

[msiebert]

I have necked down from 308 to 7mm-08 and on down to 260 and 243 with absolutely zero problems. In fact, I have never bought a 7mm-08 or 260 or 243 case in my life. The 243's have a little ring where the neck meets the shoulder that has to be fire formed out but it's gone after the first firing. They are not too tight and they are never too short. I always anneal the necks and I alway outside turn them. Maybe I am just lucky....but I seriously doubt it. I sure as hell aint lucky with anything else!!!! If yours are tight it is probably a matter of annealing and outside turning.

 

[JGorski]

I did 100pcs of LC brass into 708, had not one issue.

 

[Dkindels]

I have also gone down from 308 to 7mm-08. Noticed the length issue but after all case prep I didn't notice seating problems. And they shoot just fine.

 

[kutnicks]

I've also done this before. To get functional brass for my tight 7mm-08 chamber I needed to: FLS to 7-08, trim to length, and outside neck turn. Outside neck turning was required to get clearance for the bullet to leave the case. Be careful not to crush the cases during the first FLS