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Thread: Recommend pressures

  1. #1
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    Default Recommend pressures

    Hi everyone

    I am new to the site and I have a few questions about air rifles and recommendations.
    At Huntex I bought a Kral arms NP-500 5.5mm (.22) its has a max fill and operating pressure of 250 bar.
    I got a free tin of pellets with it and noticed the pellets have better expansion at about 150 - 170 bar when shooting bottles filled with water at about 40m.
    Later on I read about regulated and unregulated airguns but could not find the answers I as looking for so here i am

    What is the recommended pressures to get the best results?
    Should I consider installing a regulator or is there no real difference?
    Would there be a difference when using slugs instead of pellets and what would I need to know?
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  2. #2
    Sharp Shooter
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    Hi PCPNewbie,
    Welcome to the world of PCP,s. The max fill pressure is 250 bar but as you noticed, between 150-170 you are getting more impact using water bottles. That is called the Sweet Spot. It is here that the air rifle is at it's most efficient. Regulating an air rifle has the advantage of every shot being pushed out of the rifle at the same pressure which increases accuracy and shot count. A fitted regulator would cost about R2000.

    Pellets/Slugs. I use pellets 18 grn in my Cricket which is +/- 30 FPE and very accurate. What is your intention with slugs? To me, the pellet manufacturers have put large amounts into R&D, so my call is Pellets.
    Last edited by MikeBrews; 06-05-19 at 11:21.
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  3. #3
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    Many barrels designed for use with diabolo type pellets are choked. The flexible skirt and narrow contact ring of the pellet head allows some small variance in pellet diameter to be accomodated. Slugs will be less forgiving and must be a very precise fit (yes some slug barrels are choked too). If you put a slug into a barrel choked for pellets there is no guarantee it will come out the other end with useable speed or accuracy. Slugs are usually much heavier and need much more power than pellets, so a rifle set up to shoot pellets probably won't shoot a slug very well. You can try them but I doubt your Kral is set up for slugs from the factory.

    Regarding the sweet spot for pressure: at high pressure an unregulated PCP experiences strong and fast pushback when the hammer strikes.....you'll get a short burst of higher pressure air. At low pressure the hammer experiences less pushback and will hold the valve open longer. This allows a longer puff of lower pressure air to be released. Somewhere in the middle is the sweet spot where you will get a group of shots with the highest air efficiency and power as you have discovered. Nothing wrong with filling to that lower pressure and topping up as needed.
    Last edited by JXV; 06-05-19 at 15:52.
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  4. #4
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    Quote Originally Posted by MikeBrews View Post
    Hi PCPNewbie,
    Welcome to the world of PCP,s. The max fill pressure is 250 bar but as you noticed, between 150-170 you are getting more impact using water bottles. That is called the Sweet Spot. It is here that the air rifle is at it's most efficient. Regulating an air rifle has the advantage of every shot being pushed out of the rifle at the same pressure which increases accuracy and shot count. A fitted regulator would cost about R2000.

    Pellets/Slugs. I use pellets 18 grn in my Cricket which is +/- 30 FPE and very accurate. What is your intention with slugs? To me, the pellet manufacturers have put large amounts into R&D, so my call is Pellets.
    I read that the slugs have better accuracy at longer distance e.g 100m the pellets i have lose a bit if track at 60m
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  5. #5
    Springer FT World Champion '09
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    With respect...

    I think you are a prime candidate to be sucked in to the whole 'Power' and 'hitting power' and knock down power' and 'stopping power' and 'pellet expansion' and 'pass-though' and '1000 fps' and '1200 fps' and... and... and...

    Seriously.... do some deep reading on this forum, and some deep searching - the forum AND your soul, before making any more purchases.

    You will find that the No. 1 priority with an air rifle MUST be accuracy. There beginneth the lesson on pellet vs slug!

    I can only assume by the mere mention of 'slug' and 'expansion' that you are thinking of killing stuff.

    Nobody 'plinks' with slugs. They are too expensive to punch paper with, and IMO, a total waste of time from a 'precision shooting' perspective (beyond personal experimentation to learn what others have already know/discovered on this forum).

    getting back to the shooting of animated critters... Rule no. 1 - Don't do it.

    Rule No. 2... If you MUST do it - ACCURACY over POWER every day!

    Rule no. 3 (up to at least 100) - Same as above!

    Slugs are designed (if you can use that term) for use in VERY high-powered airguns, and big-bore rifles. If you are shooting with a 5.5mm rifle, then any of the domed, skirted pellets will be a starting point for testing which one performs best in your rifle for PRECISE shot placement. I will challenge ANYONE on this forum to prove me wrong.

    There is nothing more soul-destroying when you severely wound a creature with a 'Super Predator Red Copper Tip hyper expansion depleted uranium monster stopper'... after taking its face off because the marketing bullshit fed by the salesman at Blades and Triggers (or any other real gunshop for that matter) got your ego pumped. No you CAN'T take down an elephant with it! NO... they are NOT for self-defense either! Remember... the sales person is on a comm-based salary!

    As Mike said.... pellets all the way! There is NO WAY a slug of ANY description will be better than a pellet for delivering ACCURACY - as well as energy, in perfect harmony.

    Read, research and read some more, before you spend money on anything other than a top-brand, standard domed pellet of whatever weight your gun likes, at a reasonable speed.

    IMO... lower speed as a rule of thumb delivers the best accuracy. Find the balance you need for your application.

    Welcome, by the way.

    Lots of love

    The Blud
    Last edited by Bludlust; 06-05-19 at 12:29.
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  6. #6
    Sharp Shooter
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    Good advice above.
    Be very careful should you decide to break the law and shoot at an animal.

    If i was in your situation i would look for an airgunner with a chrony.
    Shoot a full tank and make note every 5 shots or so of how many bar the tank is at.
    Go through the numbers and identify the sweet spot.
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  7. #7
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    Slugs usually have higher ballistic co-efficients than pellets (i.e. they theoretically hold their speed better). It is debatable if a rifle that is set up for pellets will shoot a (much heavier) slug fast enough to see this theoretical benefit. Normally you would need to customise your rifle heavily to increase power and change the barrel in order to use slugs effectively. Then it won't shoot pellets properly any more.
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  8. #8
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    Welcome to the world of the PCP

    I am also a newbie by definition but as noted before me, there is lots of valuable reading on pellets speeds and coefficients on this site.

    Luckily there are some brilliant YouTube videos on the questions you asked.

    Here is link to a video by one of the most respected airgunners worldwide, and he happens to hail from SA
    https://youtu.be/TLK5j2urOJ0
    https://youtu.be/TLK5j2urOJ0

    PS Don’t let the PCP bug bite, it will drive you insane
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