Shortening a choked barrel (Artemis CR600W)

[nervoustrigger]

Right, nothing inherently wrong with the crown being recessed.  But it is suspicious to see it on a barrel that historically never has been.

[Ribbonstone]

Just a bit of minor “stuff”.  Deep recessed crown has save the look of several center-fire military rifles that I didn’t want to cut short.

Thinking the 2nd and 3rd line troops, when the officer saw them just goofing around, got them to polish and clean for inspection a whole lot.  WORSE with muzzle loaders.  Muzzles looked like blunderbusses. 

Back boring for 1” and re crowning in that recess preserved the (critical) visual for movie prop/ historic  re-enactors that wanted them to look “right” but still shoot well when not play-acting.(in Hollywood, many of them are back bored/tapped, blank firing restriction added down in the bore where you can't see it).

So far, airguns haven’t had that issue of visual authenticity   Cut it  slightly longer than desired and crown it, Work in “stages” if need be. If the first crown doesn’t look right...cut it ¼” and try again.  Takes me about 3 trys before I give up and buy a new barrel.

[elmury]

Ok, it looks deeper then it actually is but I'll loose at least ~3 mm to cut it straight.

Hmmm, I took a picture but the forum won't let me upload it as an attachment (to big??) and I'm not allowed to put a external link??

[elmury]

Ok, I ordered the aforementioned sander.

I have 2 remaining questions.

1. what diameter should the head of the famous slotted brass screw be for a .177 crown?

2. how to safely remove the plastic front sight on the GEN 2 barrels?
The 12mm hole in piece of wood trick?
Anybody knows if it's glued on or pressed on?

[elmury]

If the first crown doesn’t look right...cut it ¼” and try again.  Takes me about 3 trys before I give up and buy a new barrel.

I don't like that last sentence

[nervoustrigger]

A #6 round head screw is my preference for .177. 

[elmury]

A #6 round head screw is my preference for .177.

Thanks. Pardon my ignorance but what does #6 mean in metrics?

[nervoustrigger]

An example:
https://www.mcmaster.com/92453A151/

I don’t know of a metric equivalent but if you are shopping around, look for a true round head, not a pan head or truss head or some other semi-round head.  Here in the US they are almost always found with a slotted drive, sold in small quantities as a decorative screw for an antique sort of appearance when mounting brass hinges and such on vintage woodworking. 

[elmury]

I don’t know of a metric equivalent but if you are shopping around, look for a true round head, not a pan head or truss head or some other semi-round head.  Here in the US they are almost always found with a slotted drive, sold in small quantities as a decorative screw for an antique sort of appearance when mounting brass hinges and such on vintage woodworking.

Thanks a lot. Now I know what to look for.

[Reidy]

Hi all,

I wish to shorten the length of my Artemis CR600W .177 CO2 air rifle barrel.

After pushing pellets manually through the bore I notice;
- a narrow part in the beginning
- a wider part in the middle
- and a narrow part at the end of the bore.

So, in contradiction to many other CR600W owners/reports here on GTA, it seems my barrel is choked.
(perhaps European models come with choked barrels?)

Anyway, as I have understood, manufacturers choke their barrels to make them less pellet fuzzy.
Does all this mean that I can go on and cut my barrel, loosing the choke, re-crown it and end up having a nicely shooting un-choked barrel?

Lex.

Sorry about being late to this game.  Here's my experience with a barrel just like yours.

If it's tight some of the way down and then gets loose then hits the choke, if you remove that choke then you may as well junk the barrel. That choke is the only thing giving that barrel it's accuracy.

I have (had) a hatsan barrel like that and I wanted to remove the choke to shoot slugs. At first I bored out the end, like an old BSA springer, with no luck. I though it was because I hadn't crowned it correctly.  So I hacked off the end and turned an 11° target crown and polished it all up and it was still &^^&.

The pellet would lighty rattle in the last 1/3 of the barrel length when you pushed one down the bore to the loose area and shook it.

If you slug the barrel and it feels the same all the way down or has some little tight spots but could be polished up to feel smooth THEN gets tight at the choke, then you have a good chance of shortening it without any problems.

My now scrap barrel ended up becoming a breach donor to a slug liner conversion.

[elmury]

Sorry about being late to this game.  Here's my experience with a barrel just like yours.

If it's tight some of the way down and then gets loose then hits the choke, if you remove that choke then you may as well junk the barrel. That choke is the only thing giving that barrel it's accuracy.

I have (had) a hatsan barrel like that and I wanted to remove the choke to shoot slugs. At first I bored out the end, like an old BSA springer, with no luck. I though it was because I hadn't crowned it correctly.  So I hacked off the end and turned an 11° target crown and polished it all up and it was still &^^&.

The pellet would lighty rattle in the last 1/3 of the barrel length when you pushed one down the bore to the loose area and shook it.

If you slug the barrel and it feels the same all the way down or has some little tight spots but could be polished up to feel smooth THEN gets tight at the choke, then you have a good chance of shortening it without any problems.

My now scrap barrel ended up becoming a breach donor to a slug liner conversion.

Hi, thanks for your reaction.
Yes, that's exactly the horror scenario I was/am afraid of.
So I decided to try a re-crown first.

On the other hand, sometimes I think my barrel isn't intentionally choked at all but got "choked" by pressing on the front sight in the factory.
These are very soft and thin barrels.
Also, with these very cheap airguns, why go to the extra costs of adding a choke?

[Reidy]

[/quote]Hi, thanks for your reaction.
Yes, that's exactly the horror scenario I was/am afraid of.
So I decided to try a re-crown first.

On the other hand, sometimes I think my barrel isn't intentionally choked at all but got "choked" by pressing on the front sight in the factory.
These are very soft and thin barrels.
Also, with these very cheap airguns, why go to the extra costs of adding a choke?
[/quote]

I think sometimes they put the choke on to make up for a poorly made barrel. It brings the pellets back into good contact with the rifling for the last inch or so to get it true again. It saves having to make a perfect barrel. But there's also some great barrels out there with chokes on them too so 🤷‍♂️

[nced]

Hi, thanks for your reaction.
Yes, that's exactly the horror scenario I was/am afraid of.
So I decided to try a re-crown first.

On the other hand, sometimes I think my barrel isn't intentionally choked at all but got "choked" by pressing on the front sight in the factory.
These are very soft and thin barrels.
Also, with these very cheap airguns, why go to the extra costs of adding a choke?
[/quote]

I think sometimes they put the choke on to make up for a poorly made barrel. It brings the pellets back into good contact with the rifling for the last inch or so to get it true again. It saves having to make a perfect barrel. But there's also some great barrels out there with chokes on them too so 🤷‍♂️
[/quote]

"they put the choke on to make up for a poorly made barrel"
The HW barrels are pretty good factory barrels however the "barrel assembly" does have something to do with the consistency of the bore diameter. For example, the HW95 barrels were pressed into a barrel pivot block and pinned for decades. The action of pressing the barrel into the barrel pivot block gives a tight bore at the pivot block area, then the bore opens up to the nominal dimension. It's my opinion that the choke at the muzzle is to simply guarantee that the tightest part of the bore is the last 3/4" or so at the muzzle. Just for grinns I pushed a few new CPLs through the bore of my HW break barrel and made this "map"......................
 

I used to also think the choke was created by the pressing in of the front sight dovetails but changed my mind after buying a newer Beeman R9 years ago which came with no factory sights yet the barrel was still choked. Factory R9 barrel pivot block and muzzle break..........

[elmury]

I used to also think the choke was created by the pressing in of the front sight dovetails but changed my mind after buying a newer Beeman R9 years ago which came with no factory sights yet the barrel was still choked.

Yes, but that would merely indicate that in general Beeman R9 barrels are choked, with or without front sight.
It doesn't rule out unintentional choking by front sights on other brand barrels does it?

In my case with the SPA barrels, forum users here have reported unchoked barrels on them.
So I'm not convinced yet that I have a intentionally choked barrel.
(partially wishful thinking I admit)

[Ribbonstone]

Comment about cutting back ¼” and trying 3 times….figure if I got 3 good crowns and the barrel still won’t shoot, something besides the crown is wrong and I need to reevaluate.

Only problem with the slug by feel type of choke checking is that you can't feel the difference between a slight choke and a rough spot.

Can see that you want to save the threaded section; limits how much you’d want to trim off.  Doubt I could make a good deep recess crown without a lathe.

Just to be sure...this is a shallow recess crown (borrowed picture):

rs_kimber-model-8400_d by Robert Dean, on Flickr

If the recess was removed, but the flat crown protected by being inside a shroud or covered by an LDC, would still work.  The recess is a “bumper guard”.

Chokes work...likely for the reasons mentioned….what you find once you remove the chocked section might work great, might be pellet picky, or might not shoot well at all.

Mostly worked on cheap barrels (Crosmans/QB’s) and saved more of them that I lost….a few ended up as tomato stakes in the garden.

Common on Crosman were chatter marks in the bore, likely from the pilot on the cutter…the lands are kind of chewed up for the last 2/3”.  Hi-speed mass production probably is at fault (clamped in it’s high speed jig misaligned during it’s few seconds of cutting).

Old QB barrels seemed to have random tight and loose spots.  Have to say, the newer ones don’t suffer nearly so much from that.  Have saved one (that is an excellent shooter) by cutting 4 ½” off ; the tight spot became a choke.

Not dealing with heat expansion, air gun barrels can shoot great with slightly off center muzzles.

Long explanation….its how they USE to make nearly all barrels.  Bore a hole in a barrel blank and pass a rifling broach/button though.  May not end up with the muzzle dead center in the blank.  Blank lathed on hole center so  the holes come out looking even at the two ends. 

In between the breech and the muzzle, that hole can wander a bit.  Often find a cut off barrel with the hole off center.

f5a62be2-7e44-48ca-a8cd-b50770dc6721 by Robert Dean, on Flickr

This cut off one is visually off center….but it shoots so well, I’m still using it years later.



A mystery solved by re crowning:

Thought it real odd how this muzzle:

Image13_zps5879b8b9 by Robert Dean, on Flickr

Tossing out pellets shaped like this:

Image57 by Robert Dean, on Flickr


Recrowning...and it make sense (and shot better with out the round-disguise).

Image100-1_zpsa7607d53 by Robert Dean, on Flickr

[elmury]

Well I'll be darn.

1. Moved the barrel band to front (again) and tightened it normally.
10 shots first left target, .....mehhhhhh

2. Clamped the barrel down with the rear sight screw. (see pic)
5 shot second left target, .... almost hole in hole!

Hand drawn target dia ~8mm (~0.3")
Distance 12 meter (13 yards)

I dare not take the next 5 shots

[elmury]

Next 5 shots would also be hole in hole if I were a better shooter
I definitely rushed myself in the excitement.

[Ribbonstone]

At this point....are you going to wonder "why"...or are going to just accept "what is"?

[elmury]

At this point....are you going to wonder "why"...or are going to just accept "what is"?

Intelligent question! (don't get those too often these days)
The answer is both. I'm curious by nature so I will always want to know the why of most things.

To be clear. I enjoy trying to make this gun more accurate.
To me that's a big part of the hobby.
I enjoy the learning, reading posts from experienced people, like yourself, here on these forums.
The stories, the techniques, the tinkering and the science behind it etc. etc.

So yeah, I keep on wondering, tinkering, shooting and having fun!

[nervoustrigger]

That was the right answer.

You'll fit in just fine here!