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  1. #21
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    Default Re: Importance of a free floating barrel in a hunting rifle

    I completely agree with 414 here, in that free floated does not automatically mean better. my rifle went from an unbedded action (admittedly the BRNO stock has steel pillars built in) and a barrel that slightly touched at some places, to "free floated" when I sanded the barrel channel. prior to sanding the barrel channel I had sub-moa precision with various 150gr loads, as well as a 180gr load and a 220gr load. even better all the 150gr bullets shot to the same POI, while the 180gr grouped just a tad lower, and the 220gr quite a bit lower, but all in a vertical line.

    after sanding the barrel channel my groups with the same ammo mysteriously opened up. when I inspected it in detail (and this is strictly applicable to the BRNO "Standard" stocks with the very slender fore-end) I realised that the slender fore-end can still easily be bent to touch the barrel, even with a relatively generous relief below the barrel. this is mostly because the wood is so thin there. My theory (supported by a healthy understanding of structures and dynamics) is that before the mod, the contact with the stock served to create a dampening effect on the barrel, whereas after the mod the barrel was both less damped and got bumped by the fore-end when a shot was fired, each time slightly differently depending on where you rest the rifle, leading to bad consistency.

    To remedy this, I decided to bring a contact point back, which I did by putting a thin stack of paper between the barrel and the stock. this took away the (non-repeatable) physical impact of the fore-end on the barrel, replacing it with a repeatable contact point. the improvement was immediate, and I experimented with different positions for this support until I got the best results, which is almost-but-not-quite as good as it was before I decided to work on the stock in the first place)

    This is where I stopped and I've gone hunting in 2020 and 2021 with the strips of paper under my barrel! to fix this whole thing now (which was not an issue at all before I sanded the barrel channel) I WILL need to get a proper bedding job done, with a support under the barrel, just to get the gun as good as it was right from the start.

  2. #22
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    Default

    Quote Originally Posted by A-R View Post
    Those old ZKK600 series rifles' stocks were inletted by a drunk and blind Czech using a blunt axe. Well, that's what they look like to me, so any bedding job is likely a huge improvement.
    Some of them also had another screw attaching the barrel to the forend, right under the rear sight. On the ZKK602 (magnum calibers) there was a second recoil lug there too. This unconventional setup requires special attention.
    I have found that with a proper bedding job, these rifles would shoot well under 1 MOA with preferred loads.
    The question is what exactly constitutes a proper bedding job? There are more than one ways to do it properly, and many more to mess it up. Get someone experienced on those specific rifles to sort it out for you. Some experimentation may be required, if the first try does not deliver the desired results.

    I have seen that some rifles just flat refuse to shoot well with a free-floating barrel, so then a properly installed pressure point often does the trick.
    But free floating is always the first option.

    Keep in mind that a bedding job, no matter how well executed, can not fix a fouled barrel, throat erosion, damaged crown, wrong component choice, loose scope mount, crappy scope, flinching shooter or any of the 1000 other things that can affect accuracy on a rifle.




    Let's go Sarel !!!
    the roughness of the barrel channel and the two obvious and asymmetric contact points with the barrel are what prompted me to smooth out the barrel channel in the first place. I figure "if it shoots so well now already, think how much better it would be if we neaten this up and at the same time free-float the barrel..." Slim vang sy baas...

    the 3rd screw under the barrel also needs explaining, since it is very much a ZKK thing: the screw doesn't go into the thickened part of the barrel itself, but is far more cleverly designed. the underside of that thickened part has a lengthwise dovetail cutout into which a mating part fits, and the 3rd screw goes into that mating part. that mating part can slide axially along the dovetail cutout, which means the 3rd screw is not a full 3 degree of freedom constraint like a normal bolted connection would be, but only a 2 DOF constraint with the allowance of relative movement lengthwise between the stock and the barrel.

    I learnt early on that that screw should never be tightly tightened, then your groups go to shit. it only needed finger tightening for the best results. in retrospect that again makes sense, becuase it kept just the right amount of contact between the barrel and the fore-end. when I changed the barrel channel geometry, the boundary conditions and dynamics if the whole thing changed.

  3. #23
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    Default Re: Importance of a free floating barrel in a hunting rifle

    Bedding and free floating is exactly the same thing, all it does is eliminate variables.

    The problem with the process is that for many its aftermarket, when the rifle is built the manufacturer goes through a trial and error process to make the rifle shoot, they find a problem and work out a solution for it.
    Down the line the new owner tries to “fix” a perceived problem, and starts the process all over again.

    Personally, just out of pure curiosity, I would like to know what happens when those that ruined a rifle by removing a pressure point just add a tuner brake.

  4. #24

    Default Re: Importance of a free floating barrel in a hunting rifle

    Sometimes some shooters just shoot crappy. And try everything in the book to change rifle to improve it.

    But the problem is actually the shooter. Or the fact they are reloading crappy inconsistent ammunition.

    Because people believe shooting is just putting the crosshair on the target and pull trigger and bullet will go where crosshair was. Kinda forgetting there is alot happening between the shooter and the rifle when you start pulling that trigger till the bullet leaves the barrel that influences the accuracy and where the bullet is going.

    Most rifles are way more accurate then the shooter shooting them. Its just sometimes easier blaming the rifle.

  5. #25
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    Default Re: Importance of a free floating barrel in a hunting rifle

    Oom Drie, I did not have a working chrony - long story ja and batteries are cheap, I know I know.

    Can say its very mild. My go to load for a .270 Win 130 Gr bullet is 54 gr S365, I have never loaded 150 gr for self. I started a load at 49 gr batch 97 using a 150 gr Capstan bullet set far out at? 86 mm I think it was.
    Keeping in mind I was loading and testing old style, no chroni.
    49 gr shot like a .243 unsuppressed, very soft indeed.
    49.5 gr same
    50 gr started to kick back
    51 gr had a light 270 win kinda kick and primer indicated a slight flattening with well rounded edges.
    52 gr kicked like a .270 should with proper flattening of primer, but still with edges rounded. No warning signs present
    50 gr gave under a inch at 100m shooting over a bonnet in the bush.
    51 gr ???????????? I am confused. The group was 2 inch wide and 5 high, I can not work this out.
    52 gr same as 50 gr, but group is rotated 180 deg

    How 50 gr can be so far out i do not know, I am assuming I did something wrong.

    Also to mention, this is the last time I load like this, 3 + 3 + 3 looking for a group. I forgot a chat i had with Messor load 1 or 2 of each load and find your velocity wanted then adjust LCOL to tighten group.

    I will do velocity checks next range visit.

  6. #26
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    Default Re: Importance of a free floating barrel in a hunting rifle

    treeman, I'm sure you replied in the wrong thread...

  7. #27
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    Default Re: Importance of a free floating barrel in a hunting rifle

    Sorry folk - yes meant for Oom Drie se question on Batch 97 S365.
    https://www.gunsite.co.za/forums/sho...em-S365-Lot-97

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