A Team PCP Tuning Procedures
4
Tuni ng your Benjamin PC P with the use of the Hammer Spring Tensi on Adjuster and Hammer Stroke Adjuster by Ray and Hans Apell es ~ The “A” Team Caution: All testing should be done with muzzle pointed in a safe direction and into a safe backstop!!! ! Principles Preparation: There are many different ways a PCP may be tuned/adjusted. With the adjustable Hammer Spring T ension and Adjustable S troke you have virtually all you need to tune a PCP to your liking. This Document will give you a brief introduction into adjusting and from there you will need to experiment to get the performance you desire. A ce rtain amount of for ce is required by the hammer to open a valve to achieve a p articular velocity with a given pellet. This can be applied in a variety of ways. At one extreme the hammer can be moved a long distance (stroke) w ith a low spring tension. At the other extreme the hammer can be moved a very short dista nce (stroke) with a very high spring tension. And there is everything in between. Each method yields a different firing characteristic. It is up t o the end user to decide how he would like the gun adjusted to suit his needs and firing characteristic desires. A long stroke, low spring pressure setting will give a very light cocking ef fort and long spring life. As the hammer opens the valve, the pressure from the reservoir combined with the valve return spring pressure w ill close the valve. With a light spring pressure the hammer is likely to be thrown back far enough (and off of the valve stem) that the hammer spring then gets re-tensioned and the hammer gets throw n forward to hit the valve stem again and expel more air. This can be heard and sounds as though the gun is burping out air for as many as 3 or 4 burps per shot. A sh ort stroke, high spring pressur e setting will yield a heavy cocking ef fort and possibly shorter hammer spring life. As the hammer opens the valve, the pressure from the reservoir combined with the valve return spring pressure will close the valve. With a heavy hammer spring tension the hammer can't get thrown back so far (or possibly not even off t he valve stem) as to tighten up the hammer spring and throw the hammer back onto the valve to burp out more air . There is the small possibility that the valve may also close slower, allowing more air to escape, because of the added hammer spring tension keeping the hammer against the valve. This method of tuning usually yields a shor ter sharper crack at discharge. This method yields little to no Hammer Bounce. The best balance between the long stroke low spring tension and the short stroke high spring tension is what is desired. The following guide will help you achieve a setting that will give you the desired velocity. It will be up to the user to achieve the balance they desire for an optimal setting. An optimal setting will give the highest efficiency yielding little to no hammer bounce, reasonable cocking effort and good shot consistency . It would be a good learning experience to try each method so as to learn the characteristics of each in your particular gun. St art with the long stroke low hammer tension (which is very similar to the factory setting) and then try the short stroke high hammer tension method. After learning each you can then find a balance between t he two. When finding the balance, if you can hear any air burp then you should adjust more to a shorter stroke higher hammer tension. Y ou are looking for that fine balance which can only come from experience. At the end of this document you will find a method for determining charge pressure and shot count. It is advisable to do each for the 2 different methods so you can see the difference in shot count and velocity curve which will give you an idea of the efficiency you have achieved in each. After finding your s etting for each method, y ou can determine that sett ing by inserting the adjustment wr enches and counting how many turns to get back to the end stops. An example would be 7 turns in hammer spring, 5 turns in stroke yields 850 fps with x yz pellet with a 2000 psi charge for 25 shots. Using this method you can always get back to a particular setting while you are trying different settings. A) Hammer S troke Adjustment (HSA ): With the gun assembled, adjust the hammer stroke to the longest stroke position. This is done by inserting the Hammer Stroke Adjustment (HSA) allen wrench through the Hammer Spring T ension Adjuster (HST A), through the spring, into the hammer and catc hing the Hammer S triker. Then turn counter clockwise until the Striker is to the fully retr acted position. This is the start position for your adjustments. B) Hammer Spring T ension Adjustment (HST A): With the gun assembled, adjust the Hammer Spring T ension to the least tension position. This is done by inserting the Hammer Spring T ension Adjustment (HT A) allen wrench into the end plug and catching the HST A and turning counter clockwise until the Hammer Spring T ensioner is to the fully retracted position. This is the start position for your adjustments. Revised 6/1/2009
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Transcript of A Team PCP Tuning Procedures
5/16/2018 A Team PCP Tuning Procedures - slidepdf.com
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TuningyourBenjaminPCP withtheuseoftheHammerSpringTension AdjusterandHammerStroke Adjuste
byRayandHans Apelles ~ The“A”Team
Caution: Alltestingshouldbedonewithmuzzlepointedinasafedirectionandintoasafebackstop!!!!
Principles
Preparation:
TherearemanydifferentwaysaPCP maybetuned/adjusted.WiththeadjustableHammerSpring Tensionand AdjustableStrokeyouhavevirtuallyallyouneedtotuneaPCP toyourliking.
ThisDocumentwillgiveyouabriefintroductionintoadjustingandfromthereyouwillneedtoexperimenttogettheperformanceyoudesire.
A certainamountofforceisrequiredbythehammertoopenavalvetoachieveaparticularvelocitywithagivenpellet.Thiscanbeappliedinavarietyofways. Atoneextremethehammercanbemovedalongdistance(stroke)withalowspringtension. Attheotherextremethehammercanbemovedaveryshortdistance(stroke)withaveryhighspringtension. Andthereiseverythinginbetween.Eachmethodyieldsadifferentfiringcharacteristic.Itisuptotheendusetodecidehowhewouldlikethegunadjustedtosuithisneedsandfiringcharacteristicdesires.
A longstroke,lowspringpressuresettingwillgiveaverylightcockingeffortandlongspringlife. Asthehammeropensthevalve,thepressurefromthereservoircombinedwiththevalvereturnspringpressurewillclosethevalve.Withalispringpressurethehammerislikelytobethrownbackfarenough(andoffofthevalvestem)thatthehammerspringt
getsre-tensionedandthehammergetsthrownforwardtohitthevalvestemagainandexpelmoreair. Thiscanbeheaandsoundsasthoughthegunisburpingoutairforasmanyas3or4burpspershot.
A shortstroke,highspringpressuresettingwillyieldaheavycockingeffortandpossiblyshorterhammerspringlife. Asthehammeropensthevalve,thepressurefromthereservoircombinedwiththevalvereturnspringpressurewillclosevalve.Withaheavyhammerspringtensionthehammercan'tgetthrownbacksofar(orpossiblynotevenoffthevalvestem)astotightenupthehammerspringandthrowthehammerbackontothevalvetoburpoutmoreair. Thereisthesmallpossibilitythatthevalvemayalsocloseslower,allowingmoreairtoescape,becauseoftheaddedhammersprintensionkeepingthehammeragainstthevalve. ThismethodoftuningusuallyyieldsashortersharpercrackatdischarThismethodyieldslittletonoHammerBounce.
ThebestbalancebetweenthelongstrokelowspringtensionandtheshortstrokehighspringtensioniswhatisdesiredThefollowingguidewillhelpyouachieveasettingthatwillgiveyouthedesiredvelocity.Itwillbeuptotheusertoachievethebalancetheydesireforanoptimalsetting. Anoptimalsettingwillgivethehighestefficiencyyieldinglittletonohammerbounce,reasonablecockingeffortandgoodshotconsistency.
ItwouldbeagoodlearningexperiencetotryeachmethodsoastolearnthecharacteristicsofeachinyourparticulargStartwiththelongstrokelowhammertension(whichisverysimilartothefactorysetting)andthentrytheshortstrokehighhammertensionmethod. Afterlearningeachyoucanthenfindabalancebetweenthetwo.Whenfindingthebalance,ifyoucanhearanyairburpthenyoushouldadjustmoretoashorterstrokehigherhammertension. Youarelookingforthatfinebalancewhichcanonlycomefromexperience. Attheendofthisdocumentyouwillfindamethoddeterminingchargepressureandshotcount.Itisadvisabletodoeachforthe2differentmethodssoyoucanseethedifferenceinshotcountandvelocitycurvewhichwillgiveyouanideaoftheefficiencyyouhaveachievedineach.
Afterfindingyoursettingforeachmethod,youcandeterminethatsettingbyinsertingtheadjustmentwrenchesandcountinghowmanyturnstogetbacktotheendstops. Anexamplewouldbe7turnsinhammerspring,5turnsinstrokyields850fpswithxyzpelletwitha2000psichargefor25shots.Usingthismethodyoucanalwaysgetbacktoa
particularsettingwhileyouaretryingdifferentsettings.
A)HammerStroke Adjustment(HSA):Withthegunassembled,adjustthehammerstroketothelongeststrokepositionThisisdonebyinsertingtheHammerStroke Adjustment(HSA)allenwrenchthroughtheHammerSpring Tension
Adjuster(HSTA),throughthespring,intothehammerandcatchingtheHammerStriker. ThenturncounterclockwiseutheStrikeristothefullyretractedposition. Thisisthestartpositionforyouradjustments.
B)HammerSpring Tension Adjustment(HSTA):Withthegunassembled,adjusttheHammerSpring Tensiontotheleatensionposition. ThisisdonebyinsertingtheHammerSpring Tension Adjustment(HTA)allenwrenchintotheendpluandcatchingtheHSTA andturningcounterclockwiseuntiltheHammerSpring TensioneristothefullyretractedpositioThisisthestartpositionforyouradjustments.
Revised6/1/20
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C)Ifitispossible,makeanidenticalreplacementofthetransferportbutchangetheIDto.110"orsmaller.ItisrarethaPCP needsatransferportlargerthan.110toachieve20ftlbs.Ifyouaretryingtosignificantlyreducethepowerof(asexample)theDiscoverythenyoumaygosmalleryet. Asanexample,onethatwetuneduseda.105"transferporttog
justbelow20ftlbs. ThetransferportintheDiscoveryislargebecauseitisdesignedtoworkwithCO2aswellandneethelargersizeforthelowerpressureCO2gas. A TransferPortthatislargeenoughtogiveyouthevelocityyoudesirebutnomorewillgiveyouaflattervelocitycurve.ItisnotmandatorythatyoureplacethetransferportbutitisbeneficiaInthecaseoftheMarauder,turnthetransferportadjustmentallthewayin(clockwise)andthenturnitout4revolution(counterclockwise). Thisisthestartingpointfortheadjustabletransferportwhichisnowallthewayopen.
1)Setupachronographstationwiththeassembledgunonsandbagsinfrontofthechronographsoyourreadingswilconsistent. TheMuzzleshouldbeatleast18inchesfromthefirstsensortopreventincorrectreadings.
2)HaveinitialadjustmentsofthePCP setto A,BandCabove.
Note:youwillinitiallybetuningforaparticularchargerangesoyouwillneedtochargetheguntothesamepressureeachtimeandevery5shotsorsotomaintainpressureduringsetting.Changesinchargepressurewillgiveyouchanginreadingsthatwillconfusetheissue.Oncethesettingsarecompletethenyouwilldeterminecorrectchargepressureandnumberofshotsforthatpressure.
3)Chargeguntoapressurethatwillbealittleabovethemiddleofyourdesiredchargerange.Example:Ifyouarelookingtochargeto2000psiandshootto1000psithenchargeto1600psifortesting.
4) Turnin(clockwise)thehammertensionuntilyoufeeltensiononthehammerspringandthenturn1morerevolution
5)Chronographashottoseewhereyourvelocityis.
6)Increasehammertension1turn.
7)Repeat5and6untilyourdesiredvelocityisreached.
8)Shortenyourhammerstroke1/2turn.
9)Chronographashottoseewhereyourvelocityis.
10)Ifyourvelocitystayedthesamegoto8.Ifyourvelocitydecreasedgoto6.
11)Keepmakingadjustments(remembertochargeevery5shots)andchronographinguntilyouaresatisfiedwiththefoftheshotcycle. Thisislearnedthroughexperienceandcannotbeadequatelyexplained.
4)CockHammer.
5) Turnin(clockwise)thehammertensionuntilyoureachfullcoilbindandcannotturnthehammertensioninanyfurth(gunmayfireduringthisadjustment).Firegun.Cockthehammeragain.Ifitwillnotcockthenturnhammertensiono1/2turn.Cockgunagain.Repeatuntilgunwillcockreliably.
6) Turnhammertensionout2to3turns.
7)Chronographashottoseewhereyourvelocityis.
8)Shortenyourhammerstroke1/2turn.
9)Repeat7and8untilyourdesiredvelocityisreached.
Youmayseethatasthestrokeisdecreasedthevelocitywillactuallyincrease. Thisisacommonphenomenonasamefficientsettingisreached.
Adjustments:
Method1
Method2
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10)Keepmakingadjustments(remembertochargeevery5shots)andchronographinguntilyouaresatisfiedwiththeoftheshotcycleandvelocity. Thisislearnedthroughexperienceandcannotbeadequatelyexplained.
IfyourPCP hasan Adjustable TransferPort(asdoestheMarauder)thenyoucanfinetunethevelocity.
1) Turntheadjustmentscrewin¼turnatatimeandchronographashot.
2)Makeanother¼turnadjustmentandchronographanothershot.
Repeattheprocessuntilyoureachyourdesiredvelocity.
DuringthisprocessyoumaynoticethatthePCP getsquieterandblowslessairbutthevelocitydoesn’tchangemuch.
Thisiscommonasyouareachievingamoreefficientsetting. Yourshotcountwillincreaseaswell.
AnotherbenefitofaPCP withanadjustabletransferportisthatyoucandramaticallyflattenavelocitycurvebyrestrictthetransferportandincreasingtheenergyusedtoopenthevalvestem.
Youwillincreasetheusablechargepressurebandandincreaseshotcountintheprocess.
Youwillhavetoexperimentwiththesettingstoachievethistypeofbalance.
Itwillnotbeexplainedindetailhere.Itismentionedheresoyoucanstrivetoachievesuchabalanceasyouaregainexperiencewiththeotheradjustments.
FineTuningVelocitywithan AdjustableTransferPort
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Testingforchargepressureandshotcount
RayandHans Apelles~
1)Chargegun100psioverthetestchargepressureandfireashotthroughthechronograph.Recordthechargepressureandthevelocity.
2)Repeat1untilyounoticeavelocitydropofapproximately100fpscomparedtoyoursetvelocitywithyourtestchargpressure.
3)Chargetothehighestpressurerecordedin2.
4)Shootanentirechargethroughthechronographrecordingeachshot. Thevelocitieswillslowlyclimb,reachapointwheretheylevelofforpeakandthendecrease.Continueuntilthevelocitydecreasestomatchthevelocityfromshot#
5)Decidewhatisanacceptablevelocityspreadfromyourshotstring.IfshootingField Targeta20or25fpsspreadshouldbeyourmaximumandsomeevengoto35.Ifhuntingorplinkinga50orevena100spreadmaysuityourneeEachindividualmustmakethatdeterminationfortheirneeds.
6)Examineyourrecordedshotstring.Findthepeakorleveledoffvelocityandsubtractyouracceptablevelocityspreafromthatpeakedorleveledoffvelocity. Thisisthestartandendvelocity.
Asanexample: Thevelocityfromshot#1mayhavebeen800fps. Thevelocitypeakwas900fps. Theacceptablespreadis25fps. Thestartandendvelocityofthestringshouldthenbe900-25=875fps.
7)Lookdowntherecordedshotstringtillthefirstinstanceof875fps(fromourexample)isrecorded.Seewhatshotnumberthat875shotis.
Fromourexample:shot#1was800fpsandshot#10was875fps.
8)Chargeguntothepressureofshot#1inthestringandfire(fromourexample)10-1=9shotsoverthechronograph.Shot#10wouldnowbethecorrectvelocity,andthechargepressurethatisinthereservoiristhecorrectchargepresstoachieveit.
9)Determinethechargepressureinthereservoir:Usingafillerorpumpwithagauge,chargegunslowlyuntiltheneeonthegaugestopsorjumps. Thatstoppingorjumpingisalsowhenyoumayhearthecheckvalveopen(alittleclicksound). ThatpointonthegaugeisthepressurethatisleftinthegunandshouldbeyourdeterminedchargepressureThegunshouldnotbechargedabovethatpressureforthewaythehammertensionandhammerstrokeisbalanced.Thegaugeonthegunitselfcanalsobeusedtodeterminechargepressure. Alwayschargetheguntothepointonthe
gaugewhenyouwereabouttotakeshot#10fromtheexampleabove. TheGun'sgaugeisnotalwaysaccuratebutitshouldbefairlyconsistent.Beingasmallgaugeitcanbedifficulttoalwayshitthesamespot. A magicmarkermarkowaxpencilmarkonthegaugemayhelp. A pieceofclearpackingtapecanbeputoverthegaugefaceandthencuttoedgeofthegauge. Thenmarkthetapewithamagicmarkerandapplyanotherpieceoftapeoverthefirsttopreventtmarkfromwearingoff. Thestartandendpressurescanbemarkedinthiswaysoyoucantellataglanceifyouarewiyourpreferredpressureband.
10)Shoot5or10shotsoverthechronographtoremovesomeofthechargefromthereservoir.
11)Chargeguntothedeterminedpressureandshootoverthechronographrecordingeachshot.Whenthevelocityfrshot#1isreachedafterthevelocitypeaksthatisthelastusableshotfromthecharge. Theremaybeafewshotsafterthatvelocityisreachedthatmatchitsoshootandrecordafewmoreshotstoseeifthevelocitydrops.Crossoffanyshthatarebelowyourstartingvelocityonceyourendingvelocityhasreachedyourstartingvelocity.Countthenumberofshotsandthatisyourshotcountforthechargeforthewaythehammertensionandstrokearebalanced.
ThesearejuststartingpointsfortuningyourPCP.Ifthechargepressure,velocityspreadandshotcountarenotwhatyouwouldlikethenstartoverfromthebeginningatadifferentinitialchargepressure. Themoreexperienceyougetfollowingthesebasicproceduresthemoreyouwillbeabletowringoutofyourequipment.
Enjoyandshootsafe.
The"A"Team
Revised11/24/2
