What do I try now?

[Bug]

Recently aquired a Spanish Mauser in 7X57. Tried a few loads with the two molds I have - Lee 130R and the GB 7mm soupcan. They didn't do too well (gross understatement).
Decided to lop about 3/4" off the end of the barrel, as boolets would slip right in. After shortening & recrowning, I do have pretty fair rifling to the end. The bore is dark, but the lands are strong. I've been afraid to shoot this thing at more than 50 yds, as the boolets are sometimes beginning to turn around (keyhole). I don't want them comming back at me!
At this point, I don't think juggling powders is going to do much good (guess I could be wrong?). But if you have suggestions, I'll try them. All slugs so far have been of air-cooled WW, and gas checked. Velocities from 1200-1500fps. Also tried a vew jacketed, but of course they were worse - considerably smaller, too.
The Lee nose works out to be a reasonably tight bore rider as cast. The soupcan might as well not have a nose. I thought about a Lyman 160 Silhouette mold, or the RCBS 168gr semi-point, but both these molds, from Midway, will cost more than I have in the rifle! Okay, it's a junky rifle, and the mold would be a good investment anyway, but can you think of anything else to try first?
All suggestions appreciated, Thanks.

[Blackthorne45]

Have you tried slugging the barrel to get an approximate bore diamater?

[fourarmed]

A lot of military 7mms are throated for a long, roundnosed bullet. A friend of mine has an LBT mold cut to a throat slug from his Venezuelan Mauser. Bullets weigh 180 grains, he sizes them .288, and they shoot beautifully. I'm guessing you need to look at the biggest bullets you can find.

[Bug]

Oops, forgot to mention that.
Near as I can get, the bore is a nominal .285". I've gone as large as .286 by hand lubing, and sizing just enough of the lower end to get the gas check crimped. Doesn't seem to be making any difference from .284 to .286".
One thing I haven't tried yet, is to soften the boolet up, by using a half-and-half WW & Pb alloy. It should obturate easier, anyway. I've just been using already-cast stuff I have on hand.

[Linstrum]

Hey, there, Bug, sorry to hear you got a key-holer. But don't give up on it yet.

The first thing you have got to do at this point is slug the bore to find out exactly what diameters the grooves and lands are. To get good results you can't keep on guessing. Key-holing can be due to the projectiles not spinning fast enough to stabilize them, and not spinning fast enough is caused by the boolit "jumping" the rifling from being too small or the rifling being too weak from wear to grab the boolit and it strips the surface of the boolit, causing leading. What happens next snowballs into a leaded bore that is very hard to get clean. Slugging the bore will show you what is going on inside the bore. Get a 36" long 1/4" diameter brass brazing rod from your local welding supply store and some PURE LEAD 45-grain 0.312 caliber round buck balls. Unload your rifle, remove the bolt, and clean your bore as best as you can. Oil up the bore real good with a few drops of regular engine oil, drop a ball down the chamber, then take the brass brazing rod and using a hammer drive a ball down through the bore with the rod. The brass rod won't scratch or scrape up the inside. Take the ball after you get it out the muzzle and measure the diameters across the raised ridges and grooves to get two sets of measurements. The smaller measurement will be the land diameter of the bore and the larger will be the groove diameter of the bore. When you get those let us know what they are. The 7mm Mauser bore measurements varied quite a bit in new rifles and with wear they can be all over the place. Once you know what the diameters are then you can figure out what to do next, but until then you are pretty much flying in the dark.

Another cause of key-holing can be the crown not being square. I have re-crowned a few barrels without precision tooling with just a file, machinist’s square, tight fitting ramrod, and a countersink, but it was pretty much luck that I got it right. Special tooling is best when re-crowning a barrel, either a lathe or a spot-facing tool with a long bore guide to align it and get it perfectly square.

Good luck!

[Bug]

Okay,
Maybe I ought to start from square one. I don't think I'm being clear.

1. The first thing I did was to clean the bore. Several days with Wipe-out, Butch's, J-B paste, etc, and I finally had a clean bore. Dark, but not pitted badly - and the lands are strong.

2. the next thing I did was slug the bore. The tightest spot left the slug at .2845-.2850" - measuring with a caliper. I don't have a ball end mike, and that's about as close as my meager talents will let me get.

3. First outing, I tried some loads with the Lee and the soupcan GC bullets out of WW, air cooled, sized and checked at .285. Incidentally some were with red dot, and some with 4895?, or something similar. Velocities ran from about 1100 fps up to 1670-ish.

4. I got some keyholes with the first batch. Maybe 3-4 out of 20. Most all shots printed on a Redfield target at 50yd. I also tried a few jacketed 140s, and have no idea where they went, as none hit paper. That's when I discovered the very worn bore at the muzzle (as in almost no lands). I chopped off about 3/4" and recrowned. Now I have a nice tight square crown, with lands all the way to the end! And the Lee 130s nose is a nice, tight, finger-press fit at the muzzle.

5. Next, I tried some as-cast bullets I hadn't got around to sizing & lubing yet... I hand lubed them, and only ran them down in the Lubamatic far enough to crimp on the gas check. They ran right at .286". the results were about the same, including a similar number of keyholes. No leading issues with any loads.

6. I'm way off the leade with these bullets, as I'm sure it's throated for 175gr-ish round nose bullets.

7. Three things I haven't tried yet, are seating the bullets out where there's only enough in the case neck to hold 'em; a really soft alloy, and a bullet up around 170gr. Oh, and maybe .287-8" bullets! I do intend to try seating out, and the softer alloy before buying another, heavier, longer mold. I just thought I'd ask here, before going further. I know there's someone that's "Been there, Done That".

[StarMetal]

To measure the slug for groove to groove diameter you use a regular mike with flat anvils. It's very hard to measure the bore off a slug. Best measure the bore with precision rod gauges.

From reading what's you've done and got so far I'd say you didn't get an accurate groove to groove measurement with the calibper and I'll bet your real groove is alot bigger.

Let me tell you about a brand new FN 7x57 barrel I got. I was shocked to find out the groove on it was .288 to .2885. This openned up a whole can of worms like the standard for 7x57 back in the days of the 93 and 95 Mausers sure didn't look like it was .284. Okay with that said I have a 150 gr Lyman Loverin that casts at .285 out of the mould. It sure doesn't shoot good out of my new barrel, but it sure doesn't keyhole either.

One time I bought a 95 Chilean on a trial basis. That is if I wasn't satisfied with it I could send it back. Well with that same Lyman Loverin it keyholed every shot at 50 yards. Slugged the bore and it was in the high .290's. It went back, it was shot out. It took that drastic of an oversize bore to key my bullet.

My experience is if you have a rifle that shoots a bullet good, one where the bullet is touching the leade in or even getting engraved by the rifling and you move the bullet back alot so it doesn't.....you still should get ok groups. I've never had one that moving the bullet way back made them keyhole. I would think too that a shorter bullet would take more to make it keyhole then a longer one.

Your 1600 fps load is enough to stabilize those 130 lees too. 7x57's have a fast twist also.

I'm thinking it's shot out. If it's not shot out too bad, that is real fat groove, you may get a fatter bullet to work in it or a by using a bullet alloy that will let the gas pressure obturate the bullet the bore and groove dimensions.

Joe

[Paul B]

Bug. This be Paul B. from DQ's ex site. I'm thinking a big part of your problem is the very long throat most 7x57 rifles have. I happen to have a bit of a weird 7mm mold by RCBS, #7mm-168-SP is the marking on the box and on the mold, but the mold does not look like what the number says it should be. It's a gas check bullet weighing about 175 gr. in WW and should work well in a long throat. Iyou have, or have access to a set of RCBS handles, you're welcome to try it. I an pick it back up when I go to Spring come the Christmas holidays. All I need is a snail mail addy.
Paul B.

[StarMetal]

Paul...save you and Bug the money of shipping and possibly losing your mould and just send him some bullets to try. I'm pretty sure that isn't going to cure his problem.

Joe

[RayinNH]

Bug, I have some boolits cast from the RCBS 168-SP. They are water dropped , unsized ,unlubed and no checks on them. I you want to finish them up send me a PM...Ray

[Buckshot]

..................Keyholing is a stability problem. Maybe the crown, but you say after your work it's in good shape so we can forget that. Next up with a cast boolit would be undersize for the groove. You said you slugged the barrel and the groove is .285" or so, but .286" slugs are still keyholing.

That leaves 2 things. The boolit is being damaged somehow, someway in the trip from the case to the muzzle. Or the throat and leade combination is so large and/or long that the short(er) boolits don't enter it concentricly.

What did jacketed bullets do after the crowning job?

You could have a chamber that is not on the same axis as the bore. If so the throat and the leade can be worn out of round. It is also possible that the chamber in the neck area may be extra generous and the cartridge may lay oriented to one side.

If the bore has strong lands, and a consistant groove and you have a fresh correctly done crown, then it SHOULD shoot with correctly sized boolits.

I have a M95 Chilean Infantry rifle whose bore is so worn the lands just look like a shiney spiral. I can see no 'edges' on the lands atall. Add to that that the grooves are dark. I think the leade ends somewhere up under the rear sight :-) Yet it will shoot the Lyman 150gr Lovering pretty consistantly up to about 1600 fps. rying to drive it faster just makes the groups bigger and bigger.

You can forget any bore rider designs, ha! They just tumble and spray all over as there is no bore for them to ride on.

....................Buckshot

[Bass Ackward]

After reading what Jack posted about having no rifling at all in a section of a barrel and what PSB did for his groups, I would fill the case up to the shoulder with a slow enough powder and add at least a Lee dipper of .5cc to .7cc of PSB and see what happens.

[Wayne Smith]

One thing you haven't done is a chamber cast. This will nail down your chamber/bore relationship and the length and condition of the throat. It's relatively easy to do. Get some Cerrosafe from Brownells and put your plug up where you will get some of the rifling. This will also give you a good negative of the rifling, and you can see how much is left