Part 1 of ??:
I'm working up/building my "Ultimate Long Range AR" over the next few days and am going to document some of the work I'm doing to it. I'll soon post in the "SH Semi-Auto Rifles" section the specs (and goals) of the gun and some completed pics.
I've messed with AR's for over 30 years, I was an USAR Ordnance officer for 8 years (1981-1988) (schooled heavily in the system, and got to work on a few over the years) and have been an avid hobbyist gunsmith and competitor since the early 80's. Also had a gun shop for several years and have worked on hundreds of these rifles. I have a pretty complete shop with about any machine tool I need, but most of these mods can be done with hand tools, a hand drill and a Dremel.
Some of these mods may be controversial and many will say they are not necessary, and that may be true, but they really make a nice gun that will work and feel so slick you won't believe it. I also believe anything you do to make the rifle return to battery more consistently can only help the accuracy and reliability. Anyway..........
Bolt Slick up......
These mods will reduce or eliminate the "brass shaving" problem many rifles exhibit, it will also increase reliability in several ways and make the return to battery very consistent. These pics are of a DPMS LR bolt, but all these things will be the same for AR-15's also.
Remember, on all these mods, you are only polishing and slightly (a couple of thousandths) rounding the corners off, you ARE NOT removing a lot of metal.
Get the following tools:
A pack of black emory paper in mixed grits of 220-400
Dremel tool with some buffing pads and polishing compound
Hand drill or drill press or lathe
Can of brake cleaner
600 grit lapping compound, here's what I use....
http://www.brownells.com/.aspx/sid=4058/pid=1137/sku/_600_Lapping_Compound
A fine sharpening stone.
COMPLETELY disassemble the bolt and clean all the oil off everything with brake cleaner
Start with the extractor, look at the pic below and polish the area where the extractor slides over the rim of the case, start with the 320 grit paper wrapped around a round rod and finish up with the Dremel, it should look like a mirror after you're done. Don't mess with the actual "hook" that grabs the case rim. I also smooth up the sharp edges on each side of the extractor groove, as these can scrape off brass as the case rim turns during bolt rotation.
Check the ejector spring in the hole and make sure it slides freely with nothing grabbing in the hole, stone the sharp edges of the spring where it can rub/scrape on the sides of the hole.
Check the ejector in the hole and make sure nothing rubs, polish the face (that touches the shell head) of the ejector, use the stone and the Dremel to a mirror finish.
Now the bolt body.....
The flat, sharp edge on the bolt face (where the extractor sits) needs a small chamfer put on it, also the edges of the ejector hole needs smoothed up. Think of the case head turning and sliding against these sharp edges with several thousand pounds of pressure on it......and you wonder why there are brass shavings there???
Chuck the tail of the bolt body (the small end) in a drill or lathe, and while spinning it, wrap some 320 emory cloth around a small, flat tool and polish the bolt face.
Here's what it should look like when you are finished:
Now to the bottom of the bolt; put the bolt in the carrier and find the lugs that grab the shells from the magazine, here's a pic:
Slightly round and polish the rear sharp corners (bolt carrier side only) of these lugs, as they can scrape the shoulders of the cases in the mag as the bolt cycles to the rear. (Not all calibers/mags will hit here, but I do it on everything anyway)
Now we can lap the bolt lugs to the barrel extension......
Take an empty case and cut it in two, then find a spring that will fit inside the case like this:
Clean the locking lugs on the bolt and inside the barrel extension with the brake cleaner.
Assemble the bolt and carrier group all back together, WITHOUT the ejector and extractor in the bolt.
Put a little of the 600 grit lapping compound on the rear (bolt carrier side) of each of the bolt locking lugs.
Put your spring loaded cartridge in the chamber, slide in the BCG, and assemble the rifle.
Pull back slightly on the charging handle (1/2" or so), just enough to work the locking lugs and slightly retract the bolt. The spring inside the case needs cut so that the rifle recoil spring will close the bolt.
Work the bolt 100 times or so, put new lapping compound on the lugs every 25 strokes or so. I watch the wear pattern on the bluing on the back of the lugs and quit when I get to about 70% contact on all the lugs, many rifles only hit 3 or 4 lugs when new.
You will NOT create excessive headspace by doing this if you use the 600 grit, it is very fine, and will only knock off the high, rough spots on the lugs, it is basically doing what 500-1000 fired rounds would do to a stock bolt.
That should finish the bolt, I'll do another writeup when I get time on the carrier and some other stuff.
I'm working up/building my "Ultimate Long Range AR" over the next few days and am going to document some of the work I'm doing to it. I'll soon post in the "SH Semi-Auto Rifles" section the specs (and goals) of the gun and some completed pics.
I've messed with AR's for over 30 years, I was an USAR Ordnance officer for 8 years (1981-1988) (schooled heavily in the system, and got to work on a few over the years) and have been an avid hobbyist gunsmith and competitor since the early 80's. Also had a gun shop for several years and have worked on hundreds of these rifles. I have a pretty complete shop with about any machine tool I need, but most of these mods can be done with hand tools, a hand drill and a Dremel.
Some of these mods may be controversial and many will say they are not necessary, and that may be true, but they really make a nice gun that will work and feel so slick you won't believe it. I also believe anything you do to make the rifle return to battery more consistently can only help the accuracy and reliability. Anyway..........
Bolt Slick up......
These mods will reduce or eliminate the "brass shaving" problem many rifles exhibit, it will also increase reliability in several ways and make the return to battery very consistent. These pics are of a DPMS LR bolt, but all these things will be the same for AR-15's also.
Remember, on all these mods, you are only polishing and slightly (a couple of thousandths) rounding the corners off, you ARE NOT removing a lot of metal.
Get the following tools:
A pack of black emory paper in mixed grits of 220-400
Dremel tool with some buffing pads and polishing compound
Hand drill or drill press or lathe
Can of brake cleaner
600 grit lapping compound, here's what I use....
http://www.brownells.com/.aspx/sid=4058/pid=1137/sku/_600_Lapping_Compound
A fine sharpening stone.
COMPLETELY disassemble the bolt and clean all the oil off everything with brake cleaner
Start with the extractor, look at the pic below and polish the area where the extractor slides over the rim of the case, start with the 320 grit paper wrapped around a round rod and finish up with the Dremel, it should look like a mirror after you're done. Don't mess with the actual "hook" that grabs the case rim. I also smooth up the sharp edges on each side of the extractor groove, as these can scrape off brass as the case rim turns during bolt rotation.
Check the ejector spring in the hole and make sure it slides freely with nothing grabbing in the hole, stone the sharp edges of the spring where it can rub/scrape on the sides of the hole.
Check the ejector in the hole and make sure nothing rubs, polish the face (that touches the shell head) of the ejector, use the stone and the Dremel to a mirror finish.
Now the bolt body.....
The flat, sharp edge on the bolt face (where the extractor sits) needs a small chamfer put on it, also the edges of the ejector hole needs smoothed up. Think of the case head turning and sliding against these sharp edges with several thousand pounds of pressure on it......and you wonder why there are brass shavings there???
Chuck the tail of the bolt body (the small end) in a drill or lathe, and while spinning it, wrap some 320 emory cloth around a small, flat tool and polish the bolt face.
Here's what it should look like when you are finished:
Now to the bottom of the bolt; put the bolt in the carrier and find the lugs that grab the shells from the magazine, here's a pic:
Slightly round and polish the rear sharp corners (bolt carrier side only) of these lugs, as they can scrape the shoulders of the cases in the mag as the bolt cycles to the rear. (Not all calibers/mags will hit here, but I do it on everything anyway)
Now we can lap the bolt lugs to the barrel extension......
Take an empty case and cut it in two, then find a spring that will fit inside the case like this:
Clean the locking lugs on the bolt and inside the barrel extension with the brake cleaner.
Assemble the bolt and carrier group all back together, WITHOUT the ejector and extractor in the bolt.
Put a little of the 600 grit lapping compound on the rear (bolt carrier side) of each of the bolt locking lugs.
Put your spring loaded cartridge in the chamber, slide in the BCG, and assemble the rifle.
Pull back slightly on the charging handle (1/2" or so), just enough to work the locking lugs and slightly retract the bolt. The spring inside the case needs cut so that the rifle recoil spring will close the bolt.
Work the bolt 100 times or so, put new lapping compound on the lugs every 25 strokes or so. I watch the wear pattern on the bluing on the back of the lugs and quit when I get to about 70% contact on all the lugs, many rifles only hit 3 or 4 lugs when new.
You will NOT create excessive headspace by doing this if you use the 600 grit, it is very fine, and will only knock off the high, rough spots on the lugs, it is basically doing what 500-1000 fired rounds would do to a stock bolt.
That should finish the bolt, I'll do another writeup when I get time on the carrier and some other stuff.
