airgun repair question

[MLee388407]

Does anyone on the NG know how they attach those plastic front sight hoods and
ramps onto the barrels of air rifles such as Beeman's FX-1 or an Anschutz 35?
Im guessing its gotta be some kind of glue or expoxy. Also has anyone tried to
cut and recrown an air rifle barrel with hand tools? Thanks in advance

Mike
rec.guns.

[Mitch Haley]

MLee388407 wrote:
>
> Does anyone on the NG know how they attach those plastic front sight hoods and
> ramps onto the barrels of air rifles such as Beeman's FX-1 or an Anschutz 35?
> Im guessing its gotta be some kind of glue or expoxy. Also has anyone tried
> to cut and recrown an air rifle barrel with hand tools?

How bad is the crown now? Do you need to cut the barrel back a bit, or can you just lap
the existing crown?
You may be able to recrown without pulling the sight, get some fine lapping compound such
as JB Bore Paste, and a brass round-head screw with a head a
bit bigger than the bore. Chuck the screw in a hand held drill, goop it up
with Bore Paste, and rock the drill back and forth as it turns, frequently
stopping to turn the barrel a bit. When you've polished an even margin all
around, clean the barrel and test-fire. Most of the plastic sights are pressed
on, you can usually heat them and tap them off. The trick with cutting back the barrel is
to get the face square to the bore, not an easy task with hand tools.
A good machinist can probably file it square after cutting, but I can't.
Mitch.

[MLee388407]

Mitch wrote

>How bad is the crown now? Do you need to cut the barrel back a bit, or can
>you just lap
>the existing crown?
>You may be able to recrown without pulling the sight, get some fine lapping
>compound such
>as JB Bore Paste, and a brass round-head screw with a head a
>bit bigger than the bore. Chuck the screw in a hand held drill, goop it up
>with Bore Paste, and rock the drill back and forth as it turns, frequently
>stopping to turn the barrel a bit. When you've polished an even margin all
>around, clean the barrel and test-fire. Most of the plastic sights are
>pressed
>on, you can usually heat them and tap them off. The trick with cutting back
>the barrel is
>to get the face square to the bore, not an easy task with hand tools.
>A good machinist can probably file it square after cutting, but I can't.

Mitch

I thought of that last nite....the crown maynot be that bad. The last owner
didnt clean from breech to muzzle and the cleaning rod abraded and flared the
crown. Looks like about a mm or two worth of abrasion. I found several web
pages on a do it yourself crown job. The method was pretty much what you
described. Im going with a Brownells lapping tool Powers Customs makes just
for the purpose though. One thing Im not sure about, one method I read about
doesnt talk about rocking the drill, it advocates drilling straight down onto a
vise held leveled off barrel. Does anyone else have an opinion? Heres the
url for the websites if anyone is interested.

http://members.global2000.net/~remling/airguns/DIYBarrelRecrowning.htm

http://myhome.zaobao.com/home/a/airgun/airgun_gb/diy_crown_gb.html

Mike
rec.guns.

[Mitch Haley]

MLee388407 wrote:
> One thing Im not sure about, one method I read about doesnt
> talk about rocking the drill, it advocates drilling straight down onto a
> vise held leveled off barrel. Does anyone else have an opinion?
> Heres the url for the websites if anyone is interested.
>
> http://members.global2000.net/~remling/airguns/DIYBarrelRecrowning.htm
>
> http://myhome.zaobao.com/home/a/airgun/airgun_gb/diy_crown_gb.html

The 2nd link is a more detailed description of what I suggested,
I was merely paraphrasing Larry from memory. Larry Durham (AKA "LD")
is probably our top home tinkerer here in the states, and has had
several successful designs for tunes and has designed/built a couple
of guns from scratch which have real advantages over any of the production
guns out there. He's a fully qualified machinist, but prefers to crown
barrels by hand with the brass screw to setting them up in a lathe.
Like you, I questioned the brass screw method when he first posted it.
He convinced me that the brass would hold the abrasive better than steel,
and that rocking a round-headed lap would prevent cutting a groove in the
lap which might mess up the crown.

I have several problems with the 1st link. The valve grinding compound is
more abrasive than the bore paste. Trying to hand-hold a twist drill steady
enough to avoid grabbing is impossible, that would require a lathe or
stiff drill press. I'd rather cut it off flush and start over than ream
with a hand drill. Making a tapered lap is more work than buying a 10 cent
screw, and you can't rock it, so it will get a notch worn in it where the
crown hits it. The grinding advice seems pretty far out, I can' imagine
hand holding a dremel tool any more than I can a twist drill when trying to
do ultra-precision work. All that said, the advice there will probably
result in a vast improvement over the factory crown on the Chinese rifle
pictured there.

LD has his own folder on the Delphi Anything Goes Airgun Forum,
where you can see pics of his latest airgun project, a scratch-built
FT rifle that shot 7/16" groups at 50 yards right from the start:
http://login.prospero.com/dir-login/index.asp?webtag=maccari

[Mitch Haley]

Mitch wrote

> LD has his own folder on the Delphi Anything Goes Airgun Forum,
> where you can see pics of his latest airgun project, a scratch-built
> FT rifle that shot 7/16" groups at 50 yards right from the start:
> http://login.prospero.com/dir-login/index.asp?webtag=maccari

Sorry, bad link, try this one:
http://forums.delphi.com/maccari/start/

[MLee388407]

Mitch

I just did the job rocking the drill with the brass round headed screw. It
worked out pretty good. The rifle just went from 1.25@10m to .5@10m. I know
the gun will do better with a scope since the front sight has a big bead that
obliterates the dot targets I use. Thanks for the advice.

Mike
rec.guns.