PGS today

Today’s work was a repair grade.  This one has been waiting since Semester 1.  My Dad has a .22 Magnum Marlin 782 that I reblued.  However, there was a problem was with the scope mounting dovetail. 

The problem was that the dovetail was too shallow.  When the rings were tightened, the claws had nothing to grab on to because the groove was so small.  So, no matter how much you played with it, the rings wouldn’t stay put, and a scope wouldn’t go on.

So what I did was machine the groove deeper.  I measured the angle on the dovetail, and found a dovetail cutter with the same angle from Brownells.

Once I had my cutter, I made a few passes to widen everything out, leaving a crisp groove that was deep enough for a scope ring to grip.

Now that there was some purchase there, I was able to to fit rings to the top of the gun.  Now, once I blue over the cuts in the top of the receiver, I’ll be able to mount a scope.

PGS today

Once I got the barrel for Red’s Marlin chambered and test-fired, I needed to slim the barrel down a little bit.  The inch and a quarter tube just wasn’t working.  Today’s (and yesterday’s) work was contouring the barrel.  There are three different rates of taper on the factory barrel, and to make sure that the tubular magazine fit, I had to match all three, and in the right spots.  But I got it done well enough that the new barrel will fit in the old stock without any gaps in the inletting.

In addition to being more graceful an dworking with the magazine (a minor consideration) it also trimmed a lot of weight from the gun.  The blank weighed in at 8.5 pounds.  Now, the barrel weighs two.  That’s right, six and a half pounds of barrel got turned into chips.  So, depending on how you look at it, those chips were worth almost $11 a pound, or the remaining barrel is $46 a pound.

PGS today

Today’s work was putting everything on the Marlin together to make sure it functioned.  I made a chamber cast and it came back within spec, so I put all the guts back in the rifle and it was off to the range.

Not very impressive, but it works.  Not that I was trusting the thing, exactly.  See the lanyard coming back off the trigger?  Yeah.  There was a good yank on that, preceded by the unspoken prayer of everyone who’s ever had an unfamiliar or untested firearm in front of them: ”I sure hope this thing doesn’t blow up on me.”  But it went well.  Now that everything works right mechanically, I can make it right cosmetically.

PGS today

Today’s work was to get the chamber cut in Red’s Marlin.  Once I got that done, I was able to cut out the rest of the shank.

As you can see, it’s not a simple shape to machine.  First I short-chambered the barrel.  That means that I didn’t get the chamber cut completely out.  I stopped ten thousandths out.  Once that was done, I went ahead and cut the angle for the feed ramp at the top of the hood.  As the cartridges feed up from the magazine, that ramp guides them into the chamber.  After that, I used the mill to cut out the hood.  Finally, I headspaced the rifle (completed the chamber) and made sure everything worked smoothly.  Tomorrow I’ll double check that everything fires correctly, but for now, everything is where it needs to be, with the exception of an extractor cut in the shank.  I’ll make that after I contour the barrel.

PGS today

I got the shank cut for Red’s Marlin today.  It’s kind of funny looking right now, but it threads on smoothly.

The factory barrel is below it for scale.

This is kind of a funny rifle to work on because it’s so small.  To explain, I’ll use a picture of the front of the receiver.

See the big ears on either side of the receiver?  They restrict how thick I can make the barrel.  In addition, see how the scuff marks from the old barrel overlap the hole for the magazine tube?  There’s a groove milled in the old barrel for the magazine to nestle in, but that’s also kind of restricting as far as how thick I can make the barrel.

So, the shank on the barrel looks like this right now.

The thick part of the barrel is 1.250″ inches, which is close to standard diameter for centerfire bolt rifles (at least over the chamber).  The first step is the absolute largest diameter I can make the barrel for the Marlin.  Most of the bolt rifles I chambered previously used about that size as the bottom of the barrel threads.  The threaded portion here is the actual shank for the rifle.  It’s pretty small.  To get to the bottom of the threads on this barrel, I had to turn almost three-quarters of an inch of barrel off.  But that part’s done, and I can start chambering on Monday.

PGS today

Today’s work was getting Red’s Marlin ready to chamber.  Things aren’t really linear at all when working at the school.  No lathe to chamber a Krag with?  Then pull out the other barrel and lead lap it.  All you need there is a vise and a cleaning rod.

So that’s Red’s barrel, ready to go.  It’s a Shilen chrome-moly 6-groove tube as well.  The bore diameter is .358 for the .35 Remington cartridge, and the twist is one in 14 inches. 

I spent most of the morning lapping the bore, then faced and sixtied (yes, I’m turning a noun into a verb.  Standard USMC procedure.) the ends.  I’ll put it on the lathe tomorrow and see how close I can get to a working gun.

PGS today

The next repair I had in the pattern was my .22 rifle.

My .22 is a Remington 511.  That’s the box magazine fed variant of the Remington 51- family of rifles.  Red has the 510, which is a single-shot.  There’s also a tubular magazine variant known as the 512, and the 513 target model. 

While it’s a nice little rifle, especially for under $2oo, I decided I’d like to put a scope on it.  The only problem is that the receiver isn’t built for it.

Now, I could go a couple different ways with this.  The first is I could groove the receiver for what’s known as “tip-off” rings.  But what I wanted to do was treat this rifle as a scaled-down centerfire, not a loud BB gun.  For that I needed bases and rings (I went with the Weaver style), not necessarily to deal with recoil, but because I think they look better. 

The problem was trying to get a base with a small enough radius on the underside.  See, most Weaver bases are contoured to fit around the top of the receiver on a centerfire rifle.  However, those are a lot bigger in diameter.  If I were to use one of those, it would hang off the sides of the receiver.  Not really what I was going for.  So, I got a chunk of 1.25″ square stock and started in.  I bored out the correct diameter with the lathe, then contoured the top with the mill.  When I was done, I had two Weaver bases, but contoured on the bottom to fit the small rifle.

It really felt like building a model airplane or something.  Those screw holes are only a half-inch center to center.

Once I had the bases built, I went ahead and drilled the receiver, then tapped for standard 6-48 sight mounting screws.

I ground the four screws flush with the inside of the receiver, then I was able to mount my bases, just like a centerfire.

PGS today

While I’ve been working on the Krag a lot recently, it’s hardly the only thing I’ve been doing.  There are repairs to be done and two other custom guns to work on.  Sometimes the two dovetail (no pun intended) nicely.  In this case, I’m working on Red’s Marlin 336 in .35 Remington.

At this point I was kind of obligated to customize it for her.  After all, I did make her a shotgun, so it naturally follows that I would have to make her a rifle to match, right?  Anyway, that’s what she says.

This morning I lapped and stoned the action until it worked nice and smooth (as the saying goes, “slicker’n hog snot on greased glass”.).  While I was disassembling the rifle, I noticed a dent in the magazine tube.

This is at the very end of the magazine tube where the plug on the end is held in with a screw.  The screw was too long for the tube, and when it had been tightened down with perhaps more torque than was needed, it raised a blister on the other side.  It’s not immediately noticeable because this side of the magazine tube is against the barrel.  However, it is there and it’s prominent enough to actually drag against the barrel when the magazine is removed.  Well, it had to go.  The way to fix this is to literally beat the dent back in.  However, we need to support the thin-walled tube, otherwise the force of the hammering will just cave in the end.  NOT what we’re looking for.  So, I had to make a forming mandrel first.

The mandrel is about 10 inches long so I can get to a dent at any point in the magazine, depending on which in I go in from (the magazine is about 20 inches long).  The large end is a couple thousandths smaller than the nominal inside diameter of the magazine tube, so I can create the correct shape.  Once I had the mandrel made, I was able to use it to pound the dent back into shape.  When I was done, it’s as if the dent never existed.

 

PGS today

The latest thing in line for the Krag project has been getting the barrel ready to chamber.

This is the barrel as I got it.  This is an unturned blank.  You can buy them pre-contoured, but I’ll turn it down to shape later.  The black stuff all over the outside is the scale left from the stress-relieving process.  It doesn’t look like much, but the magic is all on the inside.

The stamping here denotes the barrel’s DNA.  The manufacturer is Shilen, and the caliber is .308″ diameter.  The “C” next to the caliber means it’s a Chrome-Molybednum alloy steel (also known as Chro-Moly, or barrel steel).  The “6″ on the bottom left denotes it’s a 6 groove barrel.  Finally, the “10″ way down at the bottom means the twist rate is one complete turn of rifling in 10 inches. 

I spent a few hours lead lapping the bore once I got the barrel.  It’s kind of irritating, but it’s worth it.  The process there is that we cast a lead slug around the end of a cleaning rod.  Once the lead cools, it has an exact cast of the inside of the bore.  Then, we coat the lead with lapping compound, and, using the lead to hold the abrasive, run it up and down the bore.  We progress to finer grits as the barrel burnishes.  When it’s done, the barrel is much smoother.  This helps to improve accuracy while reducing barrel fouling.

Finally, I went ahead and faced off the barrel so it will be ready to chamber here soon.  Now everything’s just waiting over the weekend.  I’ll hit it again come Monday.

PGS today

The next step in working on the Krag was to face everything off to the centerline of the bolt.  So, using the mandrel I made, I lined everything up between centers and, turning the whole mess very slowly, faced everything off true.

Now where the barrel is going to mate up with the receiver is dead flat.  I realize that there are some pits and a witness mark left.  However, this is one of those things that, while necessary to make everything go together right, can easily be taken too far.  I took maybe five thousandths off the front of the receiver.  I don’t really want to take any more because what that does is starts cutting away the threads I need to put the barrel on.  So, a little is good, but that doesn’t mean that a lot is better.