Choke removal and accuracy.

[robs5230]

You mention about shortening Diana barrels as well, I was very tempted to shorten the barrel on my Diana 34 but after pushing a pellet through the bore I found the tightest choke on any of my rifles, you really do have to give the pellet a really good shove to get it out the end, I'm now reluctant to do so.

Pete

I've never checked mine but I do have 2 280k's here that I will check. I reckon these are just shortened and threaded 34 barrels. I'll report back.
My son has my pro compact with him soI'll check that over xmas when he's back

[jon_h]

I have a rapid (FAC running at 35ish ft/lb pellet dependant) that has an anschutz barrel. On the rapid forum I was told it would have a tight choke and only like bis mags and harder pellets because of this.
With bis mags, doing my bit rested, I can get a finger size hole at 50 yards on a good day rested. I tried jsb’s of varying weights and couldn’t get any kind of group together at all.
I was told the tight choke is fine with harder pellets but deforms the skirt of softer pellets and hence sends them a bit wayward. Everything I’ve checked thoroughly backs this up.

I’ve pushed pellets through it and an inch off the end would take the choke off, but I’ve just stuck with bis mags.

Removing the choke would arguably (supposedly) improve my accuracy with softer pellets.

[bozzer]

I guess it could be down to the barrel as well.

I find LW tight all the way down to the choke where they get tighter. But I've been loaned one barrel (can't remember make) which was seemingly choked both ends, because the middle was so baggy that once past the lead in I could blow it down the barrel with my mouth.

I'll guess BSA ... They fitted them as standard on the Supertens in 0.177.

[RobF]

Funny you should say that about HW barrels not being choked. I've always believed that and stuck by my opinion that the only "choking" on HW springer barrels is imparted from the crimping of foresight grooves.
However, I was royally shot down either on here or the "other" forum less than 2 months ago by those who stated without doubt, and seemed to have some proof, that they were.
I suppose with this being in doubt, after all that, all I can say categorically is that I've shortened HW and Diana springer barrels with no loss of accuracy.

I've got access to LW, HW, BSA and Aeron CZ barrels, all off the shelf. They're all blank so I'll do a quick test. AFAICR they're all choked.

[Hsing-ee]

Back in the mists of time an airgun with a choke on the barrel was supposed to be less pellet-fussy.

So if you found the right pellet for your chopped barrel then everything will be OK. Just don't expect it to group with Milbro Caledonian, the lopsided arse of a pellet that most of us grew up on.

[piggy589]

Weihrauch and Diana barrels. The last time the subject of choked barrels came up regarding HW, I was informed all HW barrels are choked.
I've shortened HW80 barrels to 10" without losing accuracy.

Likewise with a couple of BSA's,accuracy actually seemed to improve .

[jon_h]

Certainly with LW barrels you can order choked or un choked from factory.

[look no hands]

Well I did a bit of pellet pushing tonight on my BSA barrels and was surprised at the results, I've always been lead to believe that BSA barrels where choked, the three .22 full length barrels I have (2x Mercury S thicker type and a Supersport) have no noticeable chokes and the pellets almost fell out the end, the one .177 Lightning barrel (10") has no choke but the two .25 Lightning barrels both have chokes, the older .243 size is tight as a nuns chuff at the breech end but not so tight at the muzzle and the newer proper .25 barrel is really tight at the muzzle (but isn't tight at the breech end), I even noticed that the BSA pylarm .25 pellets are different sizes, I have two older tins that are looser in the barrels but the newer ones (the yellow BSA logo on the lid seems a slightly darker yellow than the earlier ones) are tighter.

I've not tried the barrel on my Airsporter so can't comment on that.

Pete

[TonyL]

A few more little factors to consider if we are talking shortening the barrel and (maybe) losing the choke, leading me to think that even when we're talking of a single specific barrel, we'll not be actually talking "like for like"

Shortening the barrel is going to reduce the "barrel time". A microscopically small amount, maybe, but it will be there. So pellet exit will occur at a very slightly different interval in the cycle. Depending on the set-up (obviously talking boingers here), that pellet is going to exit at a different point in the surge cycle. So, unless you are lucky enough to have perfect straight line recoil and surge (dependant on weight distribution, stock set-up etc), this will vary. Along these lines also, if we are talking very short barrels and if the user wants to restore velocity to previous values, we're generally going to need more spring force, increasing recoil and surge slightly (although, maybe, speeding the cycle up).

Also, and maybe more importantly, consider the excellent work that Jim Tyler did a while ago on barrel vibrations and where in the cycle of these vibrations (nodes, anti-nodes, speed of acceleration of barrel deflection) the pellet exits.

So, it all starts to get a little "interwoven". Take one barrel, conduct a scientific test to measure the effect of losing the choke (if present) and you're looking to alter lots of other facets, so you can't actually measure the effect of losing the choke on one single barrel independently from other factors.

Where does that leave me? Well, as said previously, I've never personally shortened a barrel. Unlikely to give it a go, too. But two of my 80s - a standard one with Venom tune and the Lazaglided Predator have both had their barrels shortened by Venom and are superbly accurate.

P.S. Both of these 80s also have the Venom Slimtech silencers.

[Shed tuner]

You mention about shortening Diana barrels as well, I was very tempted to shorten the barrel on my Diana 34 but after pushing a pellet through the bore I found the tightest choke on any of my rifles, you really do have to give the pellet a really good shove to get it out the end, I'm now reluctant to do so.

Pete

if the choke is that tight, it's too tight. personally that'd tempt me to chop it.. certainly if it's uniformly tight all the way. You could always chop it leaving just a smite of choke in place - should gain a good 40 fps, allowing less spring.

[look no hands]

if the choke is that tight, it's too tight. personally that'd tempt me to chop it.. certainly if it's uniformly tight all the way. You could always chop it leaving just a smite of choke in place - should gain a good 40 fps, allowing less spring.

The only reason I wanted to chop it was because I found a Diana 34 SM online and I always loved the look of that rifle, the shorter barrel and Manders silencer really suited it, in the past I've been told by Tony at SFS that Diana barrels were choked and if you removed them you'd lose all accuracy, now I'm not sure if to shorten the barrel on my Diana 34 and add a silencer to make a SM copy or sell mine and by the proper SM I've found.

Pete

[RobF]

Well a little update.

Got around to testing a LW unchoked barrel on a Steyr today running at 780 fps with JSB Exacts and the groupings were as good as I've had with a choked barrel in the same gun and at the same range. They were pretty much on par with my benchmark so I'll eat humble pie on this one and say yep they can be as good.

There's a couple of pics of the groups at 30 & 50m over on STB (just cos I can attach pictures easier there)

[Shed tuner]

Well a little update.

Got around to testing a LW unchoked barrel on a Steyr today running at 780 fps with JSB Exacts and the groupings were as good as I've had with a choked barrel in the same gun and at the same range. They were pretty much on par with my benchmark so I'll eat humble pie on this one and say yep they can be as good.

There's a couple of pics of the groups at 30 & 50m over on STB (just cos I can attach pictures easier there)

Good to hear Rob

That's certainly been my experience, i.e. they can be as good, but with a less than optimal barrel unchoked can get bad very quickly...

[look no hands]

Well a little update.

Got around to testing a LW unchoked barrel on a Steyr today running at 780 fps with JSB Exacts and the groupings were as good as I've had with a choked barrel in the same gun and at the same range. They were pretty much on par with my benchmark so I'll eat humble pie on this one and say yep they can be as good.

There's a couple of pics of the groups at 30 & 50m over on STB (just cos I can attach pictures easier there)

Good to hear Rob

That's certainly been my experience, i.e. they can be as good, but with a less than optimal barrel unchoked can get bad very quickly...

I was going to say, if you compared a top quality barrel made without a choke and a choked barrel that has had it's choke removed, would they perform the same?

In other words do barrel makers rely on a choke to cover up imperfect bores?

Pete

[RobF]

I was going to say, if you compared a top quality barrel made without a choke and a choked barrel that has had it's choke removed, would they perform the same?

In other words do barrel makers rely on a choke to cover up imperfect bores?

Pete

Hi Pete,

We can do that. I say can, dunno if we will or not. I've got the LW I had access to today, and a choked version of it, and I guess we could lop that off and recrown it to simulate that... gulp. Might stick that one further down the list of things to do