Barrel Choking

[rsterne]

Definitely NOT Silicone based (eg SuperLube).... I would use a Moly grease, for sure....

Bob

[Taso1000]

Bob,

I think you got what I meant but just to be clear. I'm talking about lubricating the pins the rollers rotate on.

Also should I use a lubricant between the rollers and the barrel? Or will I then have trouble turning the barrel because it's too slick?

Bob, you had mentioned  pin gauges. Can you explain and guide me what size to order?

I am afraid I may over choke. Lol I over do almost everything. 

Taso

[MichaelM]

I agree with Bob....  Moly based lube for sure....

[rsterne]

I was referring to the pins that the roller rotates on as well, I don't think you need to (or want to) lube the barrel, the roller might skid on it.... Pin gauges are generally a "go / no-go" style of two different diameters, and you probably don't need to choke more than 0.001"-0.002", and ideally you should be able to measure to 0.0002", so you may have fun getting the gauges you need without spending quite a bit of money.... I don't have any, I just know that is the proper way to do it.... I have never choked a barrel....

Bob

[nced]

Bevel grinding was a success with the bench grinder and a drill going the opposite direction.  I'll post some pictures when I get the pipe cutter back together.

Now my question what should I lubricate the rollers with?  I have Super Lube, Ultimox and Loctite moly paste.  I think I read moly is for high pressure applications.

Thanks,

Taso

When I modified my pipe cutter for swaging my muzzle I used molly paste to lube the axle. Even with the molly lube the pressure on the axle when rolling was great enough that I could feel the heat generated by friction when touching the roller after the swage. To determine the amount of choke I would frequently use a coated cleaning rod to push through new CPLs to detect when there was a "felt constriction" at the muzzle before the pellet exited which is the same "gage" used with the "clamp blocks". Once the tightest constriction through the bore was at the rolled choke the swaging was stopped. IMHO, the only purpose of a choke is to guarantee that the tightest portion of the bore is the last 1/2" before the pellet exits. My chokes weren't as tight as a factory HW choke but certainly worked well as this 50 yard target shot years ago will show...........
Uploaded at Snapagogo.com
While the choke for this target was done with my "clamp blocks" and vice, I see no reason why a rolled choke wouldn't be at least as good.
That's two 50 yard "bucket and sticks" groups a bit under 1/2" ctc. I was so pleased with the first group using holdover that I zero'd the R9 at 50 yards and shot group #2 so it seems that my choke at least didn't hurt my accuracy.

[darren]

Number drill bits
15=.180
16=.177
17=.173
Best I can suggest without buying pin gauges

[Taso1000]

Thank you all,

What is the standard .177 air rifle bore dimensions?  Lothar Walther lists on their site .176 for the lands and .182 for the grooves.

I was curious should I "standardize" the barrel to some dimension?

Ed,

I was going to try your pellet test fit method till I read where you found some pellets were oval.  Then I thought about resizing the pellets like you mentioned.

But I guess the choke will ultimately resize the pellet on exit.

Obviously choking down the barrel till the pellet heads touch the grooves would be a bad thing because of drag.

I know some pellets will either be skinnier or fatter than spec or somewhere in between.

Taso

[nced]

Number drill bits
15=.180
16=.177
17=.173
Best I can suggest without buying pin gauges

IMHO....pin gages only indicate the diameter at the choke, not the choke diameter relative to the tightest constriction in the rest of the bore. A lot of the old style R9 barrels I've had were constricted at the breech end where the barrel was pressed and pinned into the barrel pivot block. IMHO (again) there is a possibility of choking the bore more than necessary (not necessarily a good thing) without testing the progress of the choke by pushing new pellets.

Granted.....if you make the choke tight enough it will be smaller than the tightest constriction, however that is an unknown without pushing through a new pellet.

[rsterne]

Ed, your comment about some R9 barrels being tightest at the breech inrigues me.... I wonder if the concept of choking pellet barrels is merely a fix for the fact that many Springer barrels may be choked at the wrong end when pressed into the breech.... ie the choking was to fix a problem, and once discovered (or advertised) became the "thing to do" with all airgun barrels.... even ones that weren't pressed into a breech block....

Bob

[Taso1000]

Intriguing! 

[nced]

Ed, your comment about some R9 barrels being tightest at the breech inrigues me.... I wonder if the concept of choking pellet barrels is merely a fix for the fact that many Springer barrels may be choked at the wrong end when pressed into the breech.... ie the choking was to fix a problem, and once discovered (or advertised) became the "thing to do" with all airgun barrels.... even ones that weren't pressed into a breech block....

Bob

Don't know for sure but I suspect the choke is simply to guarantee that the muzzle stabilizes the pellet if it was swaged down previously in the bore. As you know, airgun rifling is very fine and bores are very precise so it takes very little variation in the barrel boring and rifling to create a tight spot "early on" which causes the pellet to rattle down the rest of the bore and exit at various amounts of alignment. Just a personal opinion that makes sense to me because there is some reason some airgun manufacturers add the barrel choking step. I've often wondered if HW chokes their muzzles by pressing in the front sight dovetails, however my fixed barrel HW77k had a choked barrel and the front sight dovetail was on the cocking lever retaining bracket rather than dovetails pressed onto the barrel itself (hummm, I don't think that there were dovetails pressed in the muzzle under the retaining bracket but I could be wrong!   

[rsterne]

Yeah, I've seen muzzles with dovetails pressed in, and figured that was adding a choke as well, all in one step....

Bob

[K.O.]

The black ox replacement pins are $2.50 each. do not know about shipping...

http://www.meyergage.com/products/individual-gage-pins/


 I bet about a .002 choke is enough on a .177

[moorepower]

Crosman barrels are .1755.

[Sfttailrdr46]

Bob,

Thank you for your input, I appreciate it.    

I was trying to figure out how to apply the force on the hydraulic ram consistently and repeatedly.  I haven't yet.  Maybe a hydraulic fluid pressure gauge could be installed somehow depending on the unit. 

I was thinking rotating the barrel 120 degrees, or less, each time and compressing to make it even all the way around but that is still not as even as the rollers on the pipe cutter.

I was hesitant on a pipe cutter because in reply #33 Whitefang said the rollers were digging into the barrel versus rolling and I would still need to buy a heavy duty pipe cutter and figure out how to replace the cutter.

I have a light duty pipe cutter but I don't think it would be strong enough to choke the barrel even if I could figure out how to replace the cutter with a roller or ball bearing.

I don't have a problem farming out the choke labor but I figured if I was going to choke 6 or more 1/2" barrels shipping will start to add up. 

I enjoy learning how to do stuff by myself.  Most of my posts are about me tinkering with new things lol  If I can't do it, then I can't do it.   

Taso

The key to the pipe cutter is go slow with the tightening process the ham handed approach will dig the rollers into the barrel in and not allow the rollers to move freely to much pressure will cause binding so small incremental  tightening of the handle is necessary

[nced]

The black ox replacement pins are $2.50 each. do not know about shipping...

http://www.meyergage.com/products/individual-gage-pins/


 I bet about a .002 choke is enough on a .177

"I bet about a .002 choke is enough on a .177"
As long as the choke is the smallest fart of the bore I'm thinking that less than .001 is more than enough. When I was choking my own cut off HW barrels I would choke just enough that a pushed pellet would have a bit of added resistance at the muzzle. The pressure needed to push a new pellet through the bore from breech through the choke was about 1/2 of a standard HW factory choke at that time (over a decade ago). I did notice that the pellet fit to leade of my newer .177 HW95 was considerably tighter than the older .177 R9. I just finished working up a newer HW95 for a fellow that was having accuracy issues and noticed that the choke was considerably tighter than any other HW piston gun I've messed with so perhaps HW has tightened up their .177 bores.

Anywhoo........here are two 50 yard 5 shot groups shot from my .177 R9 fitted with a .177 R1 barrel that was home "chopped and choked" when living in West Virginia.........

Both groups were shot "bucket and sticks" and the 1st group was shot aiming at the bull where the secong group was shot after re-zeroing the R9 for 50 yards and aiming "dead on".
LOL.....this is the only R9 that ever shot the Beeman FTS pellets well and choking the muzzle till there was just a tad of extra "squish" at the muzzle worked real well.
 

[Taso1000]

Thank you Don.  Yeah I had imagined if I tightened too much too fast I'd create like a speed bump that I'd never get straightened out aside from cutting off more of the barrel and starting over.

But it seems that very little choking is necessary.  I haven't choked any barrels since I don't have a range close by do see the results of my experimentation.   

Taso

[Taso1000]

Hi All,

I recently realized I never posted pictures of the finished "choker".  So I just took some pictures to post.  So all totaled it cost me $75 for a used pipe cutter off ebay, a pair of replacement rollers from amazon and shipping on both items.

Unfortunately I have not been able to test the effects of choking because I don't have a long range to do testing on.

Thanks,

Taso