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All Springer/NP/PCP Air Gun Discussion General => PCP/CO2/HPA Air Gun Gates "The Darkside" => Topic started by: UnderPressure on March 11, 2020, 07:49:15 PM

Title: What barrel twist rate and plenum size does your PCP airgun have?
Post by: UnderPressure on March 11, 2020, 07:49:15 PM
What barrel twist rate and plenum size does your PCP airgun have?

Also is the barrel choked or unchoked?



Some rifles I have some specs on:

1.) Umarex Gauntlet .22 (1 in 20" twist, 21 to 22cc plenum, choked barrel)

2.) JSAR Hawk .22 (1 in 20" twist, ?? plenum volume, unchoked barrel)

3.) ATI Nova Vista Liberty .22 (1 in 19" twist, ?? plenum volume, unchoked barrel)

4.) Gamo Urban .22 (1 in 21" twist, No plenum because it is unregulated, ?? choked or unchoked)



Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: scion19801 on March 12, 2020, 01:34:56 AM
Umarex Gauntlet .25 (1 in 20" twist, 24 cc plenum, non-choked barrel)
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: rkr on March 12, 2020, 05:44:50 AM
BSA barrels have 1:18" twist, what barrel does that Urban have if not BSA?
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: Bob Pratl on March 12, 2020, 06:22:28 AM
Great information...keep it coming. A spreadsheet with all of the popular AG's specs would be nice for future purchases.
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: Scotchmo on March 12, 2020, 09:09:30 AM
Quote from: UnderPressure on March 11, 2020, 07:49:15 PM
...No plenum because it is unregulated,...


When there is no regulator, the whole air cylinder is the plenum.
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: rgb1 on March 12, 2020, 01:36:26 PM

This is from an Urban purchased 6/17.......


  barrel OD                   .610
  twist                          21.0:1
  rifled length                14.2
  choke effective length   1.1
  breech land dia           .2149
  breech groove dia       .2207
  rifling depth               .0029
  choke land dia            .2133   
  choke groove dia        .2191
  choke constriction      .0016


                                     Ron
                               
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: rkr on March 12, 2020, 01:38:45 PM
Quote from: rgb1 on March 12, 2020, 01:36:26 PM

This is from an Urban purchased 6/17.......


  barrel OD                   .610
  twist                          21.0:1
  rifled length                14.2
  choke effective length   1.1
  breech land dia           .2149
  breech groove dia       .2207
  rifling depth               .0029
  choke land dia            .2133   
  choke groove dia        .2191
  choke constriction      .0016


                                     Ron
                               

That sounds very much like 15" BSA barrel. Unless they've changed the mandrels for hammer forging machines they are 18" twist.
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: EdinGa on March 12, 2020, 01:59:44 PM
The choke groove on my Urban is .217 based on measurements I've taken from fired 30gr BBTs.
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: Rohmpm on March 14, 2020, 01:58:10 PM
Quote from: scion19801 on March 12, 2020, 01:34:56 AM
Umarex Gauntlet .25 (1 in 20" twist, 24 cc plenum, non-choked barrel)

Dan, is that the factory barrel that is not choked.
How did you arrive at the plenum volume
Thanks
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: Bunyboyz on May 09, 2020, 11:22:45 AM
Do we have updates or confirmation on the gauntlet?

I have the urban that’s correct.

I could attempt numbers on flash but they are posted somewhere.

Boss gave me a unfired Gauntlet to try out this weekend

Really curious if the .25 is choked or not
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: UnderPressure on May 09, 2020, 12:27:58 PM
Quote from: Bunyboyz on May 09, 2020, 11:22:45 AM

Really curious if the .25 is choked or not

https://www.gatewaytoairguns.org/GTA/index.php?topic=171890.msg155947840#msg155947840 (https://www.gatewaytoairguns.org/GTA/index.php?topic=171890.msg155947840#msg155947840)
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: scion19801 on May 09, 2020, 12:36:18 PM
trust me folks. i have hand pushed enough slugs down my .25 gauntlet barrel to confirm it is NOT choked. barrel has a .2485" groove diameter. I've done enough cleanup and tweaking to know and have measurements for most of it.
Cant really recall where i got the plenum size. but read (in a post on there) that it was either 24 or 25 cc.

edit....Found the post
Quote
darkcharisma

Re: .222/223 is the best caliber for bullet shooters on a budget!
« Reply #67 on: February 16, 2020, 03:38:36 AM »
Quote

Dan. if I remember correctly. The gauntlet 25 cal can get up to 95fpe. I haven’t done it myself but SouthernGunner has. And it doesn’t look like he added plenums. So it’s actually 24cc for the gauntlet. I don’t know how many shots he can get off at 95fpe. Or what mods he has done to get there.
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: vatato on May 09, 2020, 01:02:15 PM
Hello everyone

I'm sorry for my question, I'm new in PCP airguns, what is a PLENUM?
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: dmeguy on May 09, 2020, 01:31:56 PM
Quote from: vatato on May 09, 2020, 01:02:15 PM
Hello everyone

I'm sorry for my question, I'm new in PCP airguns, what is a PLENUM?


The plenum is the portion of high pressure air available for each shot in a regulated gun. It sits between the regulator and the valve. Well, technically it includes the air in the valve, as well. Size of the plenum is generally measured in cubic centimeters. The size of the plenum directly affects the power level of the shot.
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: Ribbonstone on May 09, 2020, 02:06:27 PM
Bascially, the shot happens so fast, that all that can actually be used to move the pellet is the air between the regulator and the valve.  So plentium is the volume of air that between the regulator and the valve (include the internal volume of the valve itself).

In baseball terms.....it's the "on deck air"...they guys on the bench/in the locker room don't count.


As for twist rate....in most standard production airguns, it's not drastically different.....don't think the difference between 1:18 and 1:20 is really going to matter all that much.
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: K.O. on May 09, 2020, 05:20:37 PM
Quote from: rkr on March 12, 2020, 05:44:50 AM
BSA barrels have 1:18" twist, what barrel does that Urban have if not BSA?

In the old BSA Meteor Manual  I saw some years ago it said the barrels are  19 twist.. ;) So that is what I have always said...

Found a copy of one... look at page 4...

https://www.yumpu.com/en/document/read/28871556/bsa-guns-meteor-airguns-of-arizona (https://www.yumpu.com/en/document/read/28871556/bsa-guns-meteor-airguns-of-arizona)

Here is a BSA factory tour... listen starting about at 2:45 in...at about 3:00 you will hear 19 twist... so I am still going with 19 twist...

https://www.youtube.com/watch?v=jhm1HnJkDfQ (https://www.youtube.com/watch?v=jhm1HnJkDfQ)

both my .22 Buc and Urban are choked to .217... have not measured the choke of my .177 Buc yet...
Title: Re: What barrel twist rate and plenum size does your PCP airgun have?
Post by: ranchibi on May 09, 2020, 08:53:53 PM
JSAR Raptor .22 with 22” TJ non choked barrel 1:18 twist..plenum size?