I would bet the “ crack” is a gouge left from reaming the bore of the bbl. A chip got in between a flute n the bbl n left it’s mark. If u are really into learning gunsmithing, slug that bbl and mark the tight n loose spots. Bbls. Such as this where not “ match” grade. This might be an excellent opportunity to cast a lead lap n smooth out some imperfections. Slugging, Check to see if the crown is tight or loose, is the area in front of the chamber tight or loose. Lead is a “dead” metal so any imperfections will have a direct effect on accuracy. Look up some of the old Bill Calfee articles from Precision Shooting. He detailed a lot of info on slugging n evaluating bbls.
Marlin/Glenfield 780 22lr bolt project complete
- Thread starter Shooting in the wind...
- Start date
I agree, I went to a machining technology school for a few years and was in an industrial machine shop for another 6 years running a variety of Cnc and manual equipment. I rebuilt a Delta Rockwell 11x36 metal lathe and also have a decent size mill at home so I know alittle about machining. I also graduated Gunsmithing school last November. Guns are my thing lol.
I tried this with a Savage Bsev 22lr I had years ago to diagnose a bad barrel. Sent it to savage and sure enough it was. Accuracy really sucked before I sent it back, after it was returned it would shoot 3/4 “ at 100yrs with Federal Gold Metal match ammo.
Here are a few pic of the inletting of the forearm and action. I used my mill and a ball end mill. Turned out pretty good I think. I would have like to have seen more squeeze out but I think it will be sufficient. I’ll post a pic late tomorrow after I get it out of the stock.
redrockranger
Silver $$ Contributor
You got it .
Well I been pretty busy, got the rifle bedded and while I was at it I also recessed and inletted the “bottom metal” plus bedded it aswell. I also machined down a mandrel and sleeve to press out the barrel. Re-crowned the muzzle to 11 degrees. I also polished and rebuled the bolt, no pic of that yet but it turned out pretty good. Plus I machined a new part for the bolt. Just got done buffing the action and barrel to enhance its appearance. Will post more pics when it’s completely put back together.
Well it’s complete and was a success, this rifle before wouldn’t hold but a 2” group at 50yards before even with premium ammunition. The one pic depicts the polished bolt head and blued bolt. The next depicts how nice the barrel look after a light polishing job. The last show a 9 shot group of Federal Gold Metal Match. 8 of the shots landed into right at 1” and the 9th which was a flier landed 1/4 inch away. So I think 8 shots in an inch compared to what it was before with the same ammunition is a 100% improvement. I can’t wait till I can get my hands on some better ammunition as I think it can do better than 1” but I’m happy with the results.
Your skills are coming along nicely. That's pretty cool to take an old classic like that and bring it back better than it was out of the factory. Excellent practice IMHO.
shortgrass
Silver $$ Contributor
I'd be interested to know what school you graduated from..
SGW Gunsmith
"Accipere non casus-Virga Bis"
Over the years, and for the most part, I've found that the 80 series of Marlin bolt action .22 rifles have held some very descent accuracy from the barrels provided from the factory. It may have something to do with the "Micro-groove rifling", but I can't prove that to be a positive FACT, but those I've tested do shoot very well for the cost involved. I've bought several of these Marlins at gunshows where the seller has broken off the cartridge guide in the rear end of the chamber and afterward has had "moocho grandee" trouble with live round feeding.
I have a Marlin Model 81 with the factory barrel set up in what I call my "contraption" to test all brands of .22 rimfire ammunition that I can get my hands on:
This rig clamps around the front receiver ring and I start testing with the barrel completely floated. Then, using the tiny adjustable aluminum "V" block, I'll try those same rounds to see if maybe an "upward pressure point" will either improve or desecrate previous accuracy and group size.
I've also cut muzzle face to an included angles of 11° degrees, 9°, 10°, 12°, and 13° with the barrel in a 4-jaw chuck dialed in to zero with a 0.2170 gage pin in the barrel to as close to 0 as I can get it with a 0.0001 indicator. I haven't found that the muzzle face angle of one or the other to provide a change for the better in accuracy. But, what I do after the face angle change is to "lap" the 60° actual crown with #800 valve grinding compound to make sure there is no slight burr left behind from the face angle changes. That does a lot to promote a good flight for the .22 lead bullet once it leaves the barrel.
Projects like these are what piques my life-long shooting of these fine .22 rimfire rifles.
All of my machining ability was learned as an apprentice tool maker and then a journeyman for 16½ years in a prototype toolroom environment. I know have a full fledged machine shop to do all the things I want to do.
I have a Marlin Model 81 with the factory barrel set up in what I call my "contraption" to test all brands of .22 rimfire ammunition that I can get my hands on:
This rig clamps around the front receiver ring and I start testing with the barrel completely floated. Then, using the tiny adjustable aluminum "V" block, I'll try those same rounds to see if maybe an "upward pressure point" will either improve or desecrate previous accuracy and group size.
I've also cut muzzle face to an included angles of 11° degrees, 9°, 10°, 12°, and 13° with the barrel in a 4-jaw chuck dialed in to zero with a 0.2170 gage pin in the barrel to as close to 0 as I can get it with a 0.0001 indicator. I haven't found that the muzzle face angle of one or the other to provide a change for the better in accuracy. But, what I do after the face angle change is to "lap" the 60° actual crown with #800 valve grinding compound to make sure there is no slight burr left behind from the face angle changes. That does a lot to promote a good flight for the .22 lead bullet once it leaves the barrel.
Projects like these are what piques my life-long shooting of these fine .22 rimfire rifles.
All of my machining ability was learned as an apprentice tool maker and then a journeyman for 16½ years in a prototype toolroom environment. I know have a full fledged machine shop to do all the things I want to do.
I also have a machining background which does help a lot. Theres no better way to learn than 1st hand experience. You can read as many books and watch as many videos as you want but hands on is where it’s at. Knowledge is king in this profession.
I graduated from SDI last November, it’s a good school and I learned alot, read many books and watched many videos. We also had projects which they send you in the mail to complete and we’re graded on. It was a fun experience. I would have rather went to a formal school but with a fiancé and 3 kids at home made that impossible. Being I have a back round in machining and woodworking has made this adventure alot easier. I have a total of almost 12 years machining experience and 2 years of a machining technology school. I also have a few years making custom doors and columns. There lots of little tricks I learned from my woodworking job that transfer directly into gunsmithing same goes for machining. I have been a gun fanatic my entire life and also been reloading for 20 years aswell. Now if I was just starting from scratch I would highly advise a newbie to take a machining technology school and wood working classes. Possibly an apprenticeship, which is a no go in my area. However, there are many things that can only be learned from experience.
SGW Gunsmith
"Accipere non casus-Virga Bis"
I also built a "barrel removal press" to safely press the barrel from out of the receiver. The front plate goes up against the front face of the receiver, the rear plate against the back face of the receiver, after all the parts on the barrel and the receiver have been removed and the retaining cross pin has been driven out. Only way that I've found, and use, to replace the broken cartridge guide safely:
The threaded rod, with the brass working end, pushes the barrel forward and then off. Once the *new* cartridge guide is inserted the barrel is pushed back into the receiver with a lead dead-blow hammer or with using a hardwood block and ball-peen hammer, but I prefer the lead hammer most often.
The threaded rod, with the brass working end, pushes the barrel forward and then off. Once the *new* cartridge guide is inserted the barrel is pushed back into the receiver with a lead dead-blow hammer or with using a hardwood block and ball-peen hammer, but I prefer the lead hammer most often.
I made a custom mandrel and bushing to remove mine. The bushing slides over the barrel with about 0.005 clearance while the mandrel went through the reciever and I used my shop press to push it out. I read all over the internet about removing the barrel on these and seems like everyone avoids them like the plague, quite frankly I don’t see what the big deal is. Wasn’t hard just needed some careful thought on how to do it properly without reverting back to our Neanderthal ways lol.
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