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Milling a JP Longellow Rem700 Receiver Blank

winsorsaw

Plastic
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Feb 14, 2012
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I'm finally getting around to working on my JP Longfellow Remington 700 SA receiver blank. I have a CNC Sieg X2.

I'm working on a jig to hold the blank. My first task will be to drill the scope mounts and then the extractor opening.

My question is this: Is this mill going to be adequate? What methods, speeds, feed rates, end mills, etc. should I use for tackling this solid piece of 4140 still with my small mill?

I've milled some cold rolled steel in the past with mixed results. Most often burning up bits, I think because too slow of a feed rate.

any help would be greatly appreciated.

Thanks,

Rob
 
I made 4 receivers from Scott's blanks, I don't have any knowledge of your mill you want to use. If you drill and tap the stock screws first, you can make a simple holding fixture out of a rectangular piece of aluminum for most of the milling operations. All my milling was done with a 3/8" + 5/16" carbide 4 flute endmill, except for the bolt release slot. If you copied Scott's dimensions the locations for the scope bases was furnished by me, which are based in a Borden Alpine 1 piece scope base. Your better off holding the blank using the 2 1/4-28 action screws vs the 8-40 base screws. When you say extractor opening I am assuming you mean the loading port, and if I was you I would layout with dykum ink all areas you plan on milling. First thing I would check before any machining is the concentricity between the OD & raceway using Vee blocks on a layout table.
 
Thanks Para

Do you remember your feed rates, etc with the 3/8 bit? Can you describe how you check the OD/Raceways with the vblock setup or post a pic?

I've got a PTG bolt. It fits tight,but it does fit. I'll probably have to do some lapping to clean up the inside of the cylinder.

Thnks,Rob
 
Sorry I can't help you on feeds, I was a automotive chassis and body panel T & D maker all my working life before retiring years ago. We had 2 job clarifications, T & D machine, T & D floor (fitting, assembly, tryout). I put the majority of my time in the floor, but my receiver blanks were fed to where I get Amber to blue chips from the cutter using a 57 year old Bridgeport mill with no coolant. Speed was 1115 rpm. I will post a photo to simulate the checking of concentricity in Vee blocks.
 
Here are some photos, the one is a setup for checking concentricity of wire edm raceway to outside Dia. out of the 4 I got the worst one was .0025 out. You can also make snug fitting plugs for checking the bore. My partner & I are going to run off a 16 foot bar of preheat treated 4140 thru the EDM then cylindrical grind the OD down to 1.350 so there won't be any need for checking these.concentricity.jpgconcentricity1.jpgconcentricity2.jpg
 
I checked out-of-roundness on my mill bed with an indicator. The most it is out is .0005" at each end and across the length of the blank. IMG_0140.jpg
 
I recently finished making the 700 SA clone using JPL's blank. I used My J-head BP and carbide cutters. It was no problem as it machined easily. In fact, I gradually became suspicious of the blank's hardness. I had read on some forum that the blanks were approx. RC 30 and did not test my blank when I received it because I had no way to test it. So I found a good deal on a scleroscope on ebay and tested the hardness. It was about RC 15 or less . This is very soft compared to the typical Remington 700 which runs about RC 35 or so depending on where on the action you test it. I decided to consider the project an exercise and I am not going to put it in service. If I did make a rifle out of it, I'm confident it would be safe to shoot, but would wear and might gradually develop excess head space.

I acquired one of Gary Breiling's 17-4PH blanks to try again. He states that they are heat treated to condition H1025 which gives about RC 38 hardness. My tester verified the hardness so I am confident that the earlier test on JPL's blank is reasonably accurate. Anyway, I have finished the new action and it was easier to do than the first one. Practice makes perfect. I was surprised that it was not much more difficult to machine than the much softer JPL blank. I did not make any special fixtures to hold the blank. I scribed the vertical and horizontal centerlines on my surface plate with a height gauge. I did make a snug fitting rectangular steel bar to fit the bolt lugways as an angle reference. All machining except the receiver ring threads was done in a 6" Kurt vise using using a couple of precision ground V-blocks against the fixed jaw. I also used a piece of drill rod ground to a snug fit in the bolt bore as a reference. The hardest part for me was the extraction cam on the back edge of the receiver bridge. I could not figure out a way to machine it on my manual mill, so I hand filed and polished it. I'm using a PTG bolt modified to take a Savage bolt head. Next step is to find a barrel and stock.

RWO
 
RWO

Many thanks for the details for your project. Do you have a build thread with pics? Did you mill dry or use coolant?

I'm bummed to read RC15--suck! That makes this project, like you said, good practice but no real practical value. I've thought about Breilings blanks but last I checked he wanted $220. I might have to EDM a lot of my own and start over.

Thanks,

Robert
 
Robert,

Sorry, I have no documentation on my build. It never occurs to me to take pics. I always mill dry and mostly with carbide cutters. I do use compressed air to blow chips out on deep cuts. I do use cutting oil for drilling, tapping and reaming holes.. Coolant is just too much trouble for a hobby shop. The price for Breiling's blanks is still $220 AFAIK. As long as you have the JPL blank, I suggest you go ahead and practice on it. You can debug you work holding and work out the machining sequence. It will pay dividends when you start on the real thing. FWIW, this the sequence I used:

1. Bore out one end to form bolt locking locking abutments and cut barrel threads.
2. Cut rear angle from bridge to tang. I used a straight cut, but it's optional.
3. Cut bolt handle notch/rear of receiver bridge. The dimension from locking abutments to rear of bridge is critical so that you maintain max. extraction cam travel. Measure your bolt from rear of lugs to front of handle flange and make the cut about .010" shorter.
4. Machine and hand file the extraction cam as necessary. The stripped bolt will not close until you make the closing cam cuts on the leading edges of the receiver abutments. I used Gary's design of a file segment set into a bore fitting rod at 30 deg. and cut them by hand. It takes awhile to cut them, but you can control the process easily. Make both cuts identical within +/- .001". Measure the protrusion of the cam cutter body from the front of the receiver with a caliper or depth mic to get the distance for each cam. A stock 700 bolt has closing cam travel of 0.130". This is from the start of bolt lug engagement of the cams until the bolt is fully closed.
5. Mill the slot and drill the pivot pin hole for the bolt stop per the dwgs. Recommend you drill the hole first and then mill the slot. If you try to drill the pin hole across the open slot, stuff the slot with a piece of aluminum so that it makes a drill bushing to guide the drill point when it hits the other side of the slot.
6. Mill the ejection port. Mine is a single shot, so that was the only port I needed.
7. Drill and tap the holes.
8. Metal finish as desired. Bead blasting makes a nice finish after all the tool marks are polished off with 220 grit.

RWO
 
RWO

Many thanks for the details for your project. Do you have a build thread with pics? Did you mill dry or use coolant?

I'm bummed to read RC15--suck! That makes this project, like you said, good practice but no real practical value. I've thought about Breilings blanks but last I checked he wanted $220. I might have to EDM a lot of my own and start over.

Thanks,

Robert

Never assume anything based on hear say, I received 4 blanks over a 3 month period. All were completed and assembled into rifles (308, 260 Rem, 6.5x284, and a 6.5x47L.) the 260 was shot well over 2,000 times, and the 308 about 2,500 times. The 260 & 308 had about .0005 change in head space mostly due to lug abutment wear. All rifles were disassembled and the receivers were dropped off at one of the countries largest heat treaters for nitriding. Hardness was checked with modern equipment and the receivers read 29 Rc prior to nitriding. Scott had those blanks made from pre heat treated 4140 round bar, Material cost prior to any machining comes to $17 per blank. After Xmas I will post photos of the raceways being burnt out.
 
Hi Guys, I very much enjoy reading about your builds whether they are on my blanks or any of the others. You guys do exceptional work and I know from experience that pulling the trigger on a gun that you have made is very fulfilling.

I thought I would chime in on the whole blank situation since it always comes up that my blanks are more expensive than the JPL blanks.

There are some differences and reasons for that.

First I cut them one at a time to order instead of in a production setting. So you have options. Want a tighter bolt way or a .750 for a 338Lapua or a 3 lug. It's all the same price.

Second I furnish only certified material that I have the heat lot numbers for because I don't want you sitting behind an iffy piece of steel that I gave you. I get about a 1/3 of a blank for $17.00 instead of the whole thing.

Third there are no wire marks in my blanks. When you hold one up to the light and look down it you see only the light reflecting off the shiny surfaces. When I look down one and see wire makes that means I have a problem and that one would be a second.

Fourth I use 1.5" material again so you have options. I am also around to answer questions and help because I enjoy it.

So if I count my time worth anything much at all I am not getting rich but that's ok they are what they are.

I can also cut your material and I do that in a short blank for $160.00.

Anyway no matter how you get your blanks keep posting the pictures. I enjoy seeing our 2nd amendment rights played out in the most basic way. If you can build it. It can never be kept from you.

Gary
 
Some of these photos are 2.5 years old, the photo of 4 receivers sitting on BP table are being prepped for nitriding. The aluminum looking receivers are from completion of nitriding. The assembled rifle is a repeater chambered in 6.5x47 Lapua. The photo of the red dykum is laying some out.pratical3.jpgpratical4.jpgpratical2.jpgpratical1.jpg
 
How are you guys cutting (or getting around) the lockup cams for the bolt lugs in the end of the reciever? I've seen custom made tools and such but it always seems hodge podge to me. Course the only really good answer i can come up with is sinker edm...If I can find a good way to do that I may have to try and make a couple.
 
For just a couple filing them is about as easy as it gets. Maybe RWO will post a picture of His tool and I have some pictures of mine also that I will dig up.

I have a Cam Cutter that was designed and built by Tracey Milsaps that cuts both cams at the same time. It is great but would be a much bigger project in its self than the actions. I will get some pictures of it.

I also have some pictures of a cutter that a fellow who I sell blanks to in California uses and I will ask and see if it is okay if I post some pictures of it.

There are a lot of ways to do it but the file method is easy and simple for small numbers.

Gary
 
For just a couple filing them is about as easy as it gets. Maybe RWO will post a picture of His tool and I have some pictures of mine also that I will dig up.

I have a Cam Cutter that was designed and built by Tracey Milsaps that cuts both cams at the same time. It is great but would be a much bigger project in its self than the actions. I will get some pictures of it.

I also have some pictures of a cutter that a fellow who I sell blanks to in California uses and I will ask and see if it is okay if I post some pictures of it.

There are a lot of ways to do it but the file method is easy and simple for small numbers.

Gary

Cutter is radially ground a few thousandth under bolt lug raceway Dia. This is a T handle cutter. pratical5.jpg
 
I thought I would chime in on the whole blank situation since it always comes up that my blanks are more expensive than the JPL blanks.

Yours are also available. I have a few JPL blanks and they seem nice, but I wouldn't have any problem paying what you ask for one of yours if I needed another. SS, polished raceway, custom options? It's a deal at twice the price.
 








 
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