I posted on GTA but for those of you who only do AGN here's my Texan mod.
The chamber of AirForce Texan rifles is too short.
For other DIYers here’s some detailed explanations how I fixed that.
Most bullets barely enter the barrel by finger force and since there is no bolt handle and/or probe to act as a force multiplier to help engrave the bullet into the rifling like on other styles of airgun you push in till it hurts your finger tips... and that’s just not good enough.
And so a great deal of the bullet usually hangs out into the ‘loading tray’ of the barrel. Hard to get consistency that way and consistency is the biggest key to accuracy.
This adversely effects accuracy because the bullet frequently ends up slightly cocked (usually the tail of the bullet is raised slightly in my experience) and when launched/fired it is swagged down into the rifling lopsided. Who cares if your only shooting 50 yards but if your shooting for precision or long range it MAKES A DIFFERENCE.
On both rifles I used a variety of bullets (I most commonly shoot) to test the depth they could be inserted with finger pressure and determined that the .257 needed 0.175 deeper and the .457 needed 0.200 deeper (see Pics of bullets in the chamber, before and after on the .257).
Note: I started out with the criteria of at least one caliber of bore contact as a minimum length to ensure a ‘squarely aligned’ bullet in the bore. Since most of the slugs I fire are fairly heavy/long the actual depth I would be cutting would be more than that which was even better. I wanted most of the bullet(s) to be in the bore for my rifles.
So I decided to make the chamber longer on both my .257 and .457 Texans.
I used throating reamers from:
https://www.reamerrentals.com/SearchResults.asp?Cat=25
I ordered them online and USPS delivered them in a Flat Rate box in two days. You get them for three business days but you can pay extra and get them for 14 days if you need. I also got the ‘insurance’ in case I accidentally chipped or broke one although with my experience it was unlikely. I expected the job to be done in one day and only take an hour total for both guns… and that included pulling the barrels out of the guns so did not need more days. It took 10 times longer to write this up than to do the job on both rifles combined.
Technically a cautious person could manually hand ream their chamber with a tap wrench T-handle, the reamer ends are 3/8” square ended. I would NOT use a crescent wrench for this as it would put side force on the reamer and cut the barrel wrong or even break the reamer!!! Use of a T wrench keeps the side forces minimized. You just have to take TINY bites as you feed forward and watch how deep you go… stopping a couple of times to extract the reamer, clean out the chips in the bore and test fit your bullet till it goes as deep as you want. Of course you would want to keep it VERY straight with no side force but the reamers are live piloted and do a pretty good job all by themselves. You would find that it cuts the rifling out so easy it only needs thumb n fingers on the T-wrench and a light to medium forward pressure, not a gorilla grip pushing and turning the reamer.
LOTS of lubricant in the barrel and on the tap is NECESSARY! I use TapMagic myself.
I however, have a small lathe, so used that to center everything (like a jig) instead of doing it manually. BUT, I NEVER TURNED IT ON!
First I GENTLY test fit by hand the reamer into the barrel, rotating with my fingers as I slid it in deeper to see when the reamer would touch the existing rifling lead in the barrel. I then measured with a caliper (from the end of the barrel to the ends of the flutes on the reamer) that to establish a datum point. Yes I might be off .002 or even as much as .005 but in this case the exact depth of the chamber extended is not THAT critical like headspacing a powder burner chamber. The depth I’m extending the throat is not based on only one bullets exact chambering need but is an average of different bullets length/profile for ‘best fit for all’… so I figure there is a +- of 0.010 anyway for ‘good enough’. Its why it could be done by hand too, not that much depth precision needed.
With the gears set to neutral on the headstock - I put the barrel into the 3jaw chuck and instead of using a live center in the tailstock, just used a drill chuck. The intent was to hold the reamer non-rotating and I would turn the chuck holding the barrel by hand, SLOWLY feeding the tailstock forward a few thousands at a time.
NOTE: In this procedure DO NOT feed the reamer forward with the tailstock screw unless the chuck holding the barrel is turning or you will break the reamer! (Also, don't turn a reamer backwards without pulling it back out of contact as it dulls the cutting edges, or could chip them)
I ran the reamer in till the datum distance I’d measured earlier was close, then with my left hand started turning the chuck about one revolution every 15 seconds and while SIMULTANEOUSLY, SLOWLY feeding the tailstock forward at about a .01 at a time with my right hand. If you can't use both hands at the same time then have some one else do it for you!
In a minute I could feel the reamer was taking a bite with just a bit of drag turning the lathe chuck with my hand. You are not boring the whole barrel, just taking out some of the raised rifling so it does not take much to do that.
I fed the tailstock forward about 90% of the depth I’d determined and pulled the reamer back, blew out the chips in the barrel and test fit a bullet in till it touched the new lead distance. I saw that I was very close to the desired seating depth so used a cleaning rod to bump the bullet back out and reinserted the reamer forward… BEING VERY CAREFUL to approach the cutting depth slowly again so I did not take a huge bite and ruin the barrel or chip the reamer cutting edges. It only took me one test fit on the .257 barrel but it took two test fits on the .457 to get the ‘perfect’ depth I wanted.
Doing this the maxims of “Haste makes waste” or “Measure twice, cut once” are good to follow for a successful/satisfactory job.
I am NOT a photographer, just using my cell phone camera and resizing to fit the forum so I did the best I could with these photos.
First, here's the .457 reamer
.457 Lead before throating
.457 Lead after throating 0.200 deeper (the photo is foreshortened so it does not look that much deeper)
Note also that there is not a ridge, the taper just is shadowed in the pic.
Before and after of my 327gr BTHP
Before and after of the NSA 154gr
Before and after of the NSA 290gr FBHP
Before and after of the NSA 372gr cast Spitzer
Before and after of the NSA 350gr BTHP
Note that the pictures are in order of accuracy in my .457 Texan which has a Doug Noble valve, his hammer spring and I use a TalonTunes carbon fiber tank and fill to 3400.
The chamber of AirForce Texan rifles is too short.
For other DIYers here’s some detailed explanations how I fixed that.
Most bullets barely enter the barrel by finger force and since there is no bolt handle and/or probe to act as a force multiplier to help engrave the bullet into the rifling like on other styles of airgun you push in till it hurts your finger tips... and that’s just not good enough.
And so a great deal of the bullet usually hangs out into the ‘loading tray’ of the barrel. Hard to get consistency that way and consistency is the biggest key to accuracy.
This adversely effects accuracy because the bullet frequently ends up slightly cocked (usually the tail of the bullet is raised slightly in my experience) and when launched/fired it is swagged down into the rifling lopsided. Who cares if your only shooting 50 yards but if your shooting for precision or long range it MAKES A DIFFERENCE.
On both rifles I used a variety of bullets (I most commonly shoot) to test the depth they could be inserted with finger pressure and determined that the .257 needed 0.175 deeper and the .457 needed 0.200 deeper (see Pics of bullets in the chamber, before and after on the .257).
Note: I started out with the criteria of at least one caliber of bore contact as a minimum length to ensure a ‘squarely aligned’ bullet in the bore. Since most of the slugs I fire are fairly heavy/long the actual depth I would be cutting would be more than that which was even better. I wanted most of the bullet(s) to be in the bore for my rifles.
So I decided to make the chamber longer on both my .257 and .457 Texans.
I used throating reamers from:
https://www.reamerrentals.com/SearchResults.asp?Cat=25
I ordered them online and USPS delivered them in a Flat Rate box in two days. You get them for three business days but you can pay extra and get them for 14 days if you need. I also got the ‘insurance’ in case I accidentally chipped or broke one although with my experience it was unlikely. I expected the job to be done in one day and only take an hour total for both guns… and that included pulling the barrels out of the guns so did not need more days. It took 10 times longer to write this up than to do the job on both rifles combined.
Technically a cautious person could manually hand ream their chamber with a tap wrench T-handle, the reamer ends are 3/8” square ended. I would NOT use a crescent wrench for this as it would put side force on the reamer and cut the barrel wrong or even break the reamer!!! Use of a T wrench keeps the side forces minimized. You just have to take TINY bites as you feed forward and watch how deep you go… stopping a couple of times to extract the reamer, clean out the chips in the bore and test fit your bullet till it goes as deep as you want. Of course you would want to keep it VERY straight with no side force but the reamers are live piloted and do a pretty good job all by themselves. You would find that it cuts the rifling out so easy it only needs thumb n fingers on the T-wrench and a light to medium forward pressure, not a gorilla grip pushing and turning the reamer.
LOTS of lubricant in the barrel and on the tap is NECESSARY! I use TapMagic myself.
I however, have a small lathe, so used that to center everything (like a jig) instead of doing it manually. BUT, I NEVER TURNED IT ON!
First I GENTLY test fit by hand the reamer into the barrel, rotating with my fingers as I slid it in deeper to see when the reamer would touch the existing rifling lead in the barrel. I then measured with a caliper (from the end of the barrel to the ends of the flutes on the reamer) that to establish a datum point. Yes I might be off .002 or even as much as .005 but in this case the exact depth of the chamber extended is not THAT critical like headspacing a powder burner chamber. The depth I’m extending the throat is not based on only one bullets exact chambering need but is an average of different bullets length/profile for ‘best fit for all’… so I figure there is a +- of 0.010 anyway for ‘good enough’. Its why it could be done by hand too, not that much depth precision needed.
With the gears set to neutral on the headstock - I put the barrel into the 3jaw chuck and instead of using a live center in the tailstock, just used a drill chuck. The intent was to hold the reamer non-rotating and I would turn the chuck holding the barrel by hand, SLOWLY feeding the tailstock forward a few thousands at a time.
NOTE: In this procedure DO NOT feed the reamer forward with the tailstock screw unless the chuck holding the barrel is turning or you will break the reamer! (Also, don't turn a reamer backwards without pulling it back out of contact as it dulls the cutting edges, or could chip them)
I ran the reamer in till the datum distance I’d measured earlier was close, then with my left hand started turning the chuck about one revolution every 15 seconds and while SIMULTANEOUSLY, SLOWLY feeding the tailstock forward at about a .01 at a time with my right hand. If you can't use both hands at the same time then have some one else do it for you!
In a minute I could feel the reamer was taking a bite with just a bit of drag turning the lathe chuck with my hand. You are not boring the whole barrel, just taking out some of the raised rifling so it does not take much to do that.
I fed the tailstock forward about 90% of the depth I’d determined and pulled the reamer back, blew out the chips in the barrel and test fit a bullet in till it touched the new lead distance. I saw that I was very close to the desired seating depth so used a cleaning rod to bump the bullet back out and reinserted the reamer forward… BEING VERY CAREFUL to approach the cutting depth slowly again so I did not take a huge bite and ruin the barrel or chip the reamer cutting edges. It only took me one test fit on the .257 barrel but it took two test fits on the .457 to get the ‘perfect’ depth I wanted.
Doing this the maxims of “Haste makes waste” or “Measure twice, cut once” are good to follow for a successful/satisfactory job.
I am NOT a photographer, just using my cell phone camera and resizing to fit the forum so I did the best I could with these photos.
First, here's the .457 reamer
.457 Lead before throating
.457 Lead after throating 0.200 deeper (the photo is foreshortened so it does not look that much deeper)
Note also that there is not a ridge, the taper just is shadowed in the pic.
Before and after of my 327gr BTHP
Before and after of the NSA 154gr
Before and after of the NSA 290gr FBHP
Before and after of the NSA 372gr cast Spitzer
Before and after of the NSA 350gr BTHP
Note that the pictures are in order of accuracy in my .457 Texan which has a Doug Noble valve, his hammer spring and I use a TalonTunes carbon fiber tank and fill to 3400.
