Will a 280 Rem reamer completely clean up a 7X57 chamber. It looks to be really close in some spots. Anybody here have some experience with this rechambering?

In most cases no. You will end up with a step in the neck area .Better to set the barrel back a thread or 2.

Since they share the same base diameter and the .280 case is larger in length by .3" and shoulder diameter by .02", where is the step coming from?

I haven't done this conversion yet, but was planning to and assumed (yeah, I know about assumptions) it worked ok.

I did it, yes it needed the cleanup but it's a fine idea: do it, but get a skilled worker to do it.

Oh yes: get the 11-degree target crown while you're doing it....

I thought about this at one time.
One possible problem I encountered is in the neck area.

From the Speer #12 book
280 Rem neck dia .3150
7 X 57 Mauser dia .3207
The 280 body is not long enough to clean upthe 7X57 neck.

Would make an interesting looking cartridge.

May or maynot be a problem based on the original chamber size.

Might want to make a chamber cast and measure before you try it.

Setting the barrel back is the safe way.

[This message has been edited by trigger (edited 05-21-2002).]

[This message has been edited by trigger (edited 05-21-2002).]

Ahh, ok, now I see what you mean. Depending upon the original chamber, you may have a .005 step at the base of the neck. Interesting! I wonder if you'd notice it?

SamB,
the length of the step would only be .035 inches so one turn on the barrel or a relief cut on the barrel shoulder equal to one turn would elminate it when you rechamber.

Chic

A picture is worth 1000 words. Thanks

One alternative would be to rechamber to 7 x 57 Ackley. Case capacity would put it right in the middle between the standard 7 x 57 and the 280. You probably could ALMOST reach the same velocity as the 280 but a little fiddling with the 280 could put you 100 - 150 fps over the AI. I've had both but not at the same time and I don't have any data from that period to give you any real number comparison. They both did the job well on deer, antelope, pigs and just about any varmint I pointed at. Didn't take on anything larger.

What velocity differences will one realize? With a strong modern action, one can get over 2800 FPS with 160-grain bullets in the 7X57, and 3000 with the 140 grain... A 7X57 AI will do a little better.

Just a question regarding the conversion. Didn't the military or european 7x57 have a slightly different land and groove diameter than US produced bbls? I noticed that in the GS solid or hvhp listing he was specific as to where and who the 7mm bbl was manufactured by. I guess the only way it would matter is if it was an old military bbl or would it?

The barrel in question is a new manufacture Kreiger that was chambered in 7X57 and never used. I can get a deal on it, but I don't need another 7X57 (yet). Everything about it is perfect for my 280 project except the original chambering.

ForrestB--

First off make sure the magazine is long enough for the 280. (Amazing how many times that's forgotten.)

Pour a chamber cast first and measure the neck. Then measure the 280 reamer. It's easy to see if it'll clean that way.

Different Bore Diameters??

That's on the 8mm. They were .318 and later changed to .323

I knew about the 8mm but here is the info that I was referring to.

http://gunlinks.zibycom.com/members/002245268/Site2/284285.html

I was wondering if this was specifically for GS bullets or would the difference affect the standard 7mm bullets.

Carnivore---

I haven't seen a .285 bore in a post-war rifle and have never seen a .285 barrel that didn't shoot .284 bullets very well.

I think it's a distinction without a meaningful difference.

I didn't know if there was a meaningful difference, still a huge rookie in the grand scheme. I have both bbls, and was pissed when I saw rheyy werre nit inteerchabgable/ keybvtoard going to hell//virrrss maybbee...................................................trry again later

I saw a .286 barrel on a Browning A-Bolt. Didn't shoot very well. Browning claimed it was within specifications.
The problem mentioned with the neck is common in other cases too. Frequently a factory chamber is a little biiger than expected. I run into this occasionally when rechambering to the AI cartridges. It is necessary to set back a thread then sometimes a ridge is left 1/16" back from the case mouth. So either the neck has to be made bigger or the barrel set back the length of the neck. Regards, Bill

European barrels are often tighter than am. but with larger groves, that makes whem accepting more bullet variations. But maybe not so accurate with a particular bullet as a am.

I have that slight bulge at base of the neck but have found it bothers me not at all. I neck size to the bulge till full length resize is required, then the bulge disapears for 1 firing. I gained about 200fps & as a bonus gained 1 of the most accurate guns I have. I found it very hard to get the 7X57 to shoot under 2" yet immediatly went to 3/4" groups. I believe the oversize neck & deep throat in the 7X57 neck makes it hard to get proper bullet alignment & accuracy!

Europeans often cut deeper grooves than is the practice here (.01 vs .008, for example). This made some 7mm bores .285" to .287", rather than .284". In Europe, they often also shot undersize bullets (compared to groove dia.). If I remember correctly, an example of this is the M88 8x57J bore, which was .320" to .322" groove diameter, even though they were firing .318" bullets in it.......

This is all good news. A new keyboard was in order too. A five year old can wreck anything.!!! This isn't my thread but the info has been very good. I have a 7x57 and a 280AI done by Mr.Ricks. I have not loaded for the mauser yet because of the bullet thing. Common thought here seems to be just do it, and I am going to. Thanks guys.