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Chassis vs Stock Accuracy

generalzip

Old Salt
Full Member
Minuteman
  • Jun 30, 2010
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    Houston, tx
    I've got some evidence that would suggest certain types of combinations of stocks/chassis and actions are more accurate with one another. Has another else experienced this? Some friends have found that some of the popular chassis out there (MPA/MDT) are less accurate/consistent than some of the stock options such as foundation and manners. Has anyone else found this to be case? I know some propose bedding any stock or chassis but some of the appeal to the chassis is the money you save in not having to bed it. Curious to hear some opinions from folks with first hand experience testing this.
     
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    First, are you talking in terms of absolute or relative? Tactical rifles will never keep up with benchrest rifles, chassis or stock. No way in hell.

    I can say my AI AX AICS chassis shoots just as well as the last McMillan I had. There shouldn’t be much difference, if any, between a properly bedded stock and a properly machined chassis.

    None of them will touch a properly built, glued in BR rifle.

    There’s a lot that goes into a rifle shooting well. If it needs bedded and isn’t, you’re not getting the most from it. The action also plays a role. A lot of actions that are heat treated after machining warp. That causes problems.

    Tooling wears out, and both chassis and stocks can suffer from poor inlets due to worn tooling that causes enough misalignment to have the lug contacting at less than 100% contact.

    If it’s a traditional stock, it is my firm opinion that it should be bedded. If it’s a chassis and the recoil lug isn’t making 100% contact with the lug inlet, it should either be replaced, or bedded. There is no reason you should pay the prices we pay for parts, if they’re out of spec. I don’t give a shit who’s name is on it, right is right and wrong is wrong. With a traditional stock, a rough inlet is the way things work, and we bed them. On a chassis, if it’s not right, make them fix it or get a different one.
     
    Let me clarify with an example. Same
    Barreled action in a MDT/MPA properly torqued etc shoots half inch groups with maybe 1 flier. Take that same BA and throw it in a foundation and it shoots .3s. Same ammo scope everything only a stock change. Curious if other people have experimented with this.
     
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    Stick some Dykem or Prussian blue or something similar on the contact surface of the recoil lug and place it in the chassis, torque it down, shoot a group, and see what you get. It should either show full contact, in which case your problem lies elsewhere.

    Process of elimination, if the lug is not square, it’ll give you headaches. If you pull the action out and don’t see a perfect blue recoil lug print on the chassis recoil lug inlet’s contact area, it’s not square and is likely the culprit. If it’s square, then it’s something else.

    Also, some people don’t shoot chassis as well as stocks. Could be something as simple as that.
     
    Stick some Dykem or Prussian blue or something similar on the contact surface of the recoil lug and place it in the chassis, torque it down, shoot a group, and see what you get. It should either show full contact, in which case your problem lies elsewhere.

    Process of elimination, if the lug is not square, it’ll give you headaches. If you pull the action out and don’t see a perfect blue recoil lug print on the chassis recoil lug inlet’s contact area, it’s not square and is likely the culprit. If it’s square, then it’s something else.

    Also, some people don’t shoot chassis as well as stocks. Could be something as simple as that.
    +1
     
    So this is something that we get from time to time too and it usually presents itself as "Hey I had my gun in (insert stock here) and moved it to your (insert MDT chassis here) and it doesn't shoot the same/as well. Is this normal and how do I fix it?"

    Now granted, I do not have the same experience as a lot of you guys/gals out there and have never ventured too far down the glued BR guns rabbit hole, but there is no way that a barreled action in a stock should shoot the same as in a chassis, in my opinion. When you inlet and bed a good stock, you are basically guaranteeing contact between a good portion of the bottom of the action and the rear face of the recoil lug, maximizing your contact. Furthermore, if you have any variation in the action or stock, that will be taken up by the flex in the stock as it is cinched down with the action screws.

    Now to compare this to an aluminum chassis, you don't have the same forgiveness that you'd get with a fiberglass or wood stock. If there is any variation in your action, the aluminum doesn't deform and wrap itself around your action like the bedding compound in a stock will, however, it generally provides a much more rigid and robust surface to mount against. Now granted, we take some extra measures when inletting and designing our chassis to account for action variation/concentricity, potential metal deformation and correct chassis contact points, but as @bourbonbent said, tooling wears out and no two chassis are perfectly identical.

    What my point is, is that when switching the same barreled action and load between a stock and chassis (or vice versa) you will have to make some adjustments due to the interface between the action and stock/chassis, as well as the induced harmonics. I don't think it's fair to say that a chassis or a stock will shoot better simply due to the fact that there are too many variables!

    Just some thoughts on the topic, but I suppose I am biased too :)
     
    Let me clarify with an example. Same
    Barreled action in a MDT/MPA properly torqued etc shoots half inch groups with maybe 1 flier. Take that same BA and throw it in a foundation and it shoots .3s. Same ammo scope everything only a stock change. Curious if other people have experimented with this.

    I had an experience with my Vector. Would shoot in the ~ .3’s consistently in my KMW with a mini chassis, no bedding. Would do the same in a Manners with mini chassis. Dropped it in an ACC and it’s ~.7” spoke with mdt and they are getting me an ultimatum version ACC to try instead. Love the ACC, I think it’s far and away the best chassis/stock from a pure PRS standpoint.
    Just sometimes tolerances don’t line up.
     
    Why can't the action be an integral part of the chassis to avoid all such problems?
    It works great. I've tested it extensively in the German MG34 and MG42 machineguns.
    The closest solution today is the Eliseo tubegun chassis with a glued in Pierce action.
     
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    I've got some evidence that would suggest certain types of combinations of stocks/chassis and actions are more accurate with one another. Has another else experienced this? Some friends have found that some of the popular chassis out there (MPA/MDT) are less accurate/consistent than some of the stock options such as foundation and manners. Has anyone else found this to be case? I know some propose bedding any stock or chassis but some of the appeal to the chassis is the money you save in not having to bed it. Curious to hear some opinions from folks with first hand experience testing this.


    Something as simple as switching my apa fat bastard and area 419 hellfire with each other had the same effect switched them back and gun shoots as it did before probably because I developed the load in that configuration my point is if something like a few grams difference in weight on the barrel or the different design of the brakes could cause that variation I can easily see how a different stock or chassis can change the way a gun reacts to a load I would think it would be a matter of changing seating depth or powder charge to optimize everything in the new configuration I think as long as everything is in order with any of the chassis you mention they should all support that degree of accuracy

    That said with my defiance action I do feel a difference in the way the bolt runs in my mpa chassis with a v-block style inlet compared to the krg bravo it was in before that has an inlet that supports the entire action so there is clearly something changing there that could be improved with some bedding
     
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    Let me clarify with an example. Same
    Barreled action in a MDT/MPA properly torqued etc shoots half inch groups with maybe 1 flier. Take that same BA and throw it in a foundation and it shoots .3s. Same ammo scope everything only a stock change. Curious if other people have experimented with this.

    You could also be experiencing subtleties with just how "shootable" and forgiving one stock is versus the other. The Foundation stock has a low center of gravity forend and other lines in its design that is are proven performers in a lot of other conventional stock designs (MCS, McM and KMW Sentinel) as well as a wider forend for more surface contact with bags, etc. Almost no chassis' currently exhibit these traits.

    I have come to have a lot of faith in a few "chassis" designs as far as their ability to be consistent.

    Since using the IMB and refining it over the years, I have stopped pillar bedding complete rifles. The IMB is just as expensive and time consuming to implement as a pillar bedding job but I have a bullet proof interface between the stock and barreled action. All complete rifles are test fired and have to have 3 consecutive groups under 1/2 moa fired on one sheet of paper to get shipped. A by product of this is that I end up with a lot of groups to document across a large range of calibers, etc. I don't think the IMB is out shooting the bedded guns but I believe it is not giving anything up either. I think there are a handful of other good "bolt in and go" systems out there as well.

    ./
     
    I am currently shooting a Curtis Axiom, bartlein barrel chambered in 6.5 Creedmoor. Gun came with a bedded McMillan Game Warden, and shot a little under 1/2 mos at 100 yards off the bench. Than tried it in a Manners mini chassis, seemed to open the group up a bit. Same with an MPA chassis. Now in MDT I shot for the first time today, .35 group. Then just shooting small targets at 125 off bipod it was lights out. So this chassis it seems like it is super consistent. I believe recoil lug is sitting square against chassis. For me MDT seems to shoot as well as my McMillan, but fits me much better.
     
    Last edited:
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    There are 3 locations on most any rifle that need proper rigid support. The recoil lug, and the areas around the 2 action screws.

    If those 3 spots don't make square/proper contact BEFORE you start torquing action screws, you're inviting problems. Twisting, bending, etc... Especially during firing.

    Everything else, like doing a complete bed job or gluing the two together is getting into the noise zone where it gets harder and harder to prove you made an improvement.
     
    I’ve shot just as good with a properly fitted chassis (properly fitted to me and the gun) as I have with a properly fitted stock.

    For me it’s just a preference on which one I use. I’m a bigger guy 6’3” with longer arms so a stock (such as my manners or HS) that is not adjustable for LOP etc is always less comfortable to shoot then say my MDT ESS chassis that is adjusted to fit me.

    My LOP is about max where even most chassis can go so I usually set it at 15.5”. My HS/manners have a fixed position of 13.5”. I shoot good with them but there not as natural for me as shooting with a longer/proper LOP
     
    I was in an LE SWAT Sniper course two years ago. First thing we did every morning was shoot a group of five rounds, at 100 yards, being mindful to observe that first round (cold bore round). One of the local agency guys was running a stock Rem 700 in a McRee's chassis. His cold bore shots were not consistent day-to-day. One of the instructors, a well known dude, whom many of you may know, indicated that the ambient temperatures can fuck with the zeros in some of these rifles that are in chassis.

    He stated that the cold air can cause some molecular-level retraction of the aluminum. That would then cause a variance in the action-to-chassis interface, which would obviously mess with his ability to maintain his zero. We were shooting in April, which here in Idaho can still have some relatively cooler mornings.

    One of my rifles is in an MPA chassis. I bedded it and it absolutely improved the accuracy of the rifle. It is an absolute laser.
     
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    See Tubb ATR....


    Why can't the action be an integral part of the chassis to avoid all such problems?
    It works great. I've tested it extensively in the German MG34 and MG42 machineguns.
    The closest solution today is the Eliseo tubegun chassis with a glued in Pierce action.
     
    Why can't the action be an integral part of the chassis to avoid all such problems?
    It works great. I've tested it extensively in the German MG34 and MG42 machineguns.
    The closest solution today is the Eliseo tubegun chassis with a glued in Pierce action.

    ^^^^^I've been saying this for 10 years now!!!!

    If this was done on a mechanically assisted opening/closing Fortner straight pull type action it would rule the world of precision repeaters. There, I just made someone else a multi millionaire. And if someone comes out with one you better send me a free rifle!!!


    You guys are forgetting 4 major things with comparing benchrest rifles and precision rifles.

    #1 - 1-2 oz triggers on the BR rifles.
    #2 - rifle tracking straight back in expensive benchrest bags and fancy front rest vs tac bag and bipod.
    #3 - BR rifle means less human contact, precision rifle means more human contact.
    #4 - Never seen a tactical rifle repeater in 6mmPPC???!!! There's a reason why in short range benchrest this cartridge dominates.

    But yes, glued in has it's merits.
     
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