Bad 7mm Mauser

[mooman76]

I bought an old 7mm Mauser. The bore isn't perfect but for the age doesn't look bad either. I finally was able to take it out and try some reloads and @ 50 Yards it wasn't even on paper. The rounds were all over the place.
I started with 10g. of unique and 130g Lee 7mm lead bullet,
tried 10g. Unique w/ 145g RCBS 7mm lead bullet and when those were way off I shot 36.0g Varget w/ 140g jacketed bullet.
All were bad. When I got home I discovered lead on my muzzel so I slugged the barrel and it came out .287 at the widest point and .277 at the narrowest point. I'm looking for options on what to do to correct this. I really don't want to have a custom mould made for this old of a weapon!

[Bret4207]

First thing to do is get the bore really, really clean. Use steel wool, chemicals, electrolosis- whatever it takes. Then check your mounting screws and make sure they're tight and the bedding is acceptable. Same with sights. Then try the jacketed stuff. 5 rounds will tell you if it will shoot. If it's still all over then check and maybe recrown the muzzle. If it shoots jacketed, get it clean and try slugging the bore and throat. Go for a boolit 1-2 thousandths over bore and try more like 8 gr Unique. Start with that and see what happens.

[StarMetal]

First you need to clear up something. You said you slugged it and it came out .287 at the widest point and .277 at the tightest point. Can't be. If those are groove diameters the .287 is correct, but not the .277. Most all the old 7x57 mausers had an on average of .287-.288 groove diameter. This is why Oldfeller is running a mould sale for a fat short 7mm bullet. In fact I had recently bought a brand new 7x57 short barrel for my Brazilian carbine project and it measured .288 groove diameter. So I made me a swage up die on my lathe to swage my .285 Lyman 150 grains up to .290.

It'll be hard to get that thing to shoot really good unless you find a mould that will throw a fat enough bullet or have 45 2.1 talk you through the basics of how to get it to shoot.

Joe

[Junior1942]

Look at the rifling an inch or two below the crown and see if there's any rifling there at all due to cleaning rod wear. If there isn't, it won't shoot accurately, especially with cast bullets.

[azcoyhunter]

mooman76

I have had the worst luck, with the Lee Mold you tried.

I can get 5 to 8 holes in a snuff can at 100 yards with J word bullets, but with my cast I could not even get it on the paper.

On my rifle, the boolits were not long enough to engage the lands of the rifling, and it was disapointing, to say the least.

Let me know what you find out.

Clint

[HORNET]

mooman,
I believe that you and azcoyhunter have the same problem. The specs for 7mm barrels are different now than they were a hundred years ago. Many old 7mm's run .287-.288 for groove diameter while current specs are more like .284. The old Lyman and Ideal molds were cut to fit these and my 287308's fit my '93 Mauser almost perfectly but the nose has heavy interference with the lands in a modern 7 Mag barrel. The RCBS 7-168-FN fits the 7 Mag perfectly but only runs .285 dia. (as the LEE probably does) and won't group in a bushel basket at 50 yds from the old Mauser. This a not uncommon in many of the old milsurps as well as some other calibers ( standard .22 cf groove was .227 a century ago, for example).
You have to slug at least the throat and match the boolit to the throat. This may require finding an old mold or lapping or BEAGLING a new one. Changing to a high antimony alloy like straight lino can boost as cast dia a little if that helps. It can be done. Good luck, [smilie=s:

[mooman76]

Thanks for all the replys, they have been very helpful!
Just thought I would let everyone know what I desided. I gave up on the gun being a real shooter after the first time I shot it but would like to at least get my bullets on paper so I don't feel I totally waisted my money.
Any way I don't want to put alot of money into this gun beings I have many others that already shoot much better than this one so I am going to slightly inlarge the Lee mould I have so I can try cast bullets and maybe even get some bullets different from ebay to try. Sometimes I see a mixed lot of bullets in small quantities so I can try different ones.

[StarMetal]

This is the problem I've worked with. Remember I said I made a swage up die to bring my loverin up to .290. Well depending on what bullet you use and how long it is, and you fatten it up to fill the throat, two things are going to happen. If it's not a bore rider and/or it's long it will hit the leade in too soon resulting in having to seat the bullet extremely deep in the case. Second depending how tight your neck portion of the chamber is and you have a fat bullet, that neck area in the chamber might not let the brass expand enough to release the bullet. I have both these problems but only the neck tightness problem when usind 30-06 brass sized down and trimmed. After I swage my loverin up to .290 then I have size a good portion of the nose back down to .284. I then end up with a two step diameter bullet. There's not a real easy way out of this situation. A fat bullet alone isn't it.

Joe

[mooman76]

StarMetal,
I remember what you told me and I appreciate the help and advice but I don't have the means or the knowledge you have to make a swage up die and I refuse to spend allot of money on a gun that cost me less than $100. I can however take a few thousands off a $10 mould to help fill the rifleing. If it doesn't work I'll put the gun up in my collection and probubly never shoot it again. If it does work then maybe I got a nice plinker! The bullet mould is a short bullet, it's the only one Lee makes for 7mm.

Once again thanks for your help and to all that contributed!

Mooman

[azcoyhunter]

Shooters

What I was thinking is I need a longer boolit, not necessarly a fatter bullet???

Clint