Grouping - semi vs bolt.

This is a discussion on Grouping - semi vs bolt. within the Defensive Rifles & Shotgun Discussion forums, part of the Related Topics category; I came to a conclusion which I think has some logic. This is merely a recounting of an observation/deduction. I do not expect micro groups ...

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Thread: Grouping - semi vs bolt.

  1. #1
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    Grouping - semi vs bolt.

    I came to a conclusion which I think has some logic. This is merely a recounting of an observation/deduction.

    I do not expect micro groups from my semis compared with same cal in bolt - and one reason I think is the possibility - probability even, of bullet tip distortion, even if very slight.

    What really brought this to mind was re a problem I used to have with my L1A1 - a Century ''less than perfect'' rifle! I did some work on the feed chamfer (I set up gas valve too BTW) and smoothed things up and now functionally it runs well but - think of the round stripping off mag - first from left - then from right and so on - it feeds by bullet sliding past chamber chamfer on one or other side.

    This will apply to most semi's with double stacking. My FAL, Mini-14, AK, SKS etc ... I assume same too with AR family.

    I noticed with L1 that even when a round had fed to full chambering, if I removed it and inspected the bullet, there was a visible slight marring of the nose - not much but IMO enough to affect absolute axial symmetry - and so flight stability potential.

    Furthermore, inspection of the chamber mouth chamfer often shows a slight copper color as feed rubs bullet nose against this area - both left and right.

    Most bolt feeds strip off a single stack mag but also - feed round in a more linear fashion and probably less aggressively too.

    So - IMO comparison might be with, say, .308 - a 1/2 MOA performance from a good bolt, as against MOA plus from the semi.

    Obviously barrel lengths and action effects also come into play but it strikes me this bullet distortion potential is a significant reason for many semi's never being able to outclass a bolt action.

    There ya go - just P95 musings - again
    Chris - P95
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    VIP Member Array Euclidean's Avatar
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    With a few weird exceptions, the bolt action will always be more prone to greater accuracy. Fewer moving parts and all that.

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    VIP Member Array Bud White's Avatar
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    Most semis bounce the bullet into the chamber ala 1911 Theres few rifles that can be as accurate at super long ranges as a bolt but semis werent designed for that either

    The few exceptiong being the Soviet Drungoff(SP)_
    and the Walther semi auto and of course the German HK PSG1 there will be almostas good as a bolt gun if not running with it neck and neck

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    VIP Member Array ExSoldier's Avatar
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    Cool Bolt Mystique

    Quote Originally Posted by Euclidean
    With a few weird exceptions, the bolt action will always be more prone to greater accuracy. Fewer moving parts and all that.
    I think that a lot of the Bolt Mystique is due to the free floating of barrel and proper stock bedding. An awful lot of 1000 meter shots were made overseas using the M21 Sniper System which is merely a gussied up M1A. Also the use of 168gr BTHP Match Ammo is critical for optimum flight stability, when using the .308 loads.

    In any case this kind of accuracy is really only useful in precision shots like a police officer might need. For example a military sniper need only be assured of hitting the cranial vault which is about 3x5 or even 4x6 on the forehead. But a SWAT sniper, faced with rescuing a hostage being used as a human shield has to strike EXACTLY one centimeter below the earlobe to cut the medulla and stop all reactionary muscle movement. See? For military purposes a semi is quite sufficient. Note that both the PSG-1 and the venerable Soviet Dragunov are military weapons. So was the M21. Although it is a fact that many more modern day sniper rifles are in fact bolts, the Barrett M82 cal 50 is a semi. According to the Geneva Convention, the cal 50 is never to be used against personnel only. Snipers get around this by saying: Well see....I was aiming for the HELMET or the WEB GEAR which is in fact....military equipment!
    Former Army Infantry Captain; 25 yrs as an NRA Certified Instructor; Avid practitioner of the martial art: KLIK-PAO.

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    If semis are less accurate why have the Camp Perry hi power service rifle seen the semi as the favorite for a long time? M1 Grands, M1A's and now AR-15's. Partly , because of the semi auto stages, I'm sure, but the semi auto guns seem plenty accurate at 600 yrds.

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    VIP Member Array Euclidean's Avatar
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    You guys realize though when you're talking about some incredibly accurate semis, you are almost always talking about:

    #1. A platform that lends itself to great accuracy. I'd go so far as to say that most semiautomatic platforms on the planet do not lend themselves to this. For example, try making an SKS shoot sub 1 MOA.

    #2. A semi platform that's been tweaked to death. Sure AR15s can be very, very accurate, so can 10/22s and so are Baretts. Then again I know lots of people who can put a cartridge in your brainpan 500 yards away with a box stock Remington 700. Let's compare the cost of a Remington 700 to a tweaked out semi for a second... Or on a micro scale, compare a bolt action .22 to a semiauto .22. Without any tweaking, the bolt action is 99% of the time more accurate and it probably costs about the same.

    I'm just saying that a bolt action is a cheaper way of getting that mind numbing accuracy for most people most of the time and probably always will be.

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    Very good point Rocky - which I should have remembered. I would need to inspect close up the chamber and throating on a Garand and see if the feed chamfers are better than average. Ahh but hang on - the 8 round cllp, does that feed a double stack mag or single stack? It is this feed left/feed right aspect which seems in many cases to enable some bullet effects. I have no M1 to check on.

    With 5.56 (AR category) and so a much smaller round, possibly the effect is limited too - the .308 seemingly is more prone to the problem.

    My main observation was with bullet tip distortion possibilities on the L1A1, which I am sure did not help accuracy tho as many say and is generally acceptable, many a semi will not stay up there with the bolts.

    There again - even at 600 yards, MOA is still very adeqate against 1/2 MOA! Maybe I am just being pedantic (again!).
    Chris - P95
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    "To own a gun and assume that you are armed
    is like owning a piano and assuming that you are a musician!."


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    VIP Member Array Bud White's Avatar
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    Euc your also talking about a semi that was made to be super accurate just high rate f fire and have a anemic round in the sks again here $$$ matter

    Ill stack my box stock 742 woodsmaster remington 30-06 with a 3x9 scope against a Remington Bolt 700 30-06 3x9 any day

    infact i have and its just as accurate as dads bolt gun i bought him with the free floated barrel and all that ..

    No all semis are inaccurate and not all need to be tinkered with my AR is plenty accurate so is my Cetme though not as much as said above 30-06 but better than SKS by far maybe slightly less than the AR

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    VIP Member Array Rob72's Avatar
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    Quote Originally Posted by Euclidean
    I know lots of people who can put a cartridge in your brainpan 500 yards away with a box stock Remington 700.

    I'm just saying that a bolt action is a cheaper way of getting that mind numbing accuracy for most people most of the time and probably always will be.
    Mmmmm. "Stock" 700 series , or the PSS? Stock anything (unless you get a bad specimen from the factory) from Bushmaster, RRA, Springfield, Remington, etc., should pull 1.0-1.5moa, semi- or bolt. The PSS (Police Sniper Special), M1A Supermatch, etc., should be 0.5 moa out of the box. "Mindnumbing" accuracy (0.5 moa or less )won't be "cheaper" with either mechanism- a Robar bolt will run in the same range as a tuned MSG-90, or SA Match.

  11. #10
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    M1 Garand feed double stack. Also the cartridge overall length has to be shorter for semis to fit in any mag. Bolt guns can fit longer OAL cartridges sometimes. (less bulllet jump from the case to the rifling. ) AR's are suppose to be more accurate than gas piston operated guns. I don't know if this is true or not. SKS and AK's are made to much looser tolerances than many other gun. Thus operate better in dirt, mud ect, but less accurate.

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    Administrative Ban Array Bruces45's Avatar
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    I have had both semi's and bolts that would just not shoot straight, I had a Rem 7400 308 that on a bench rest would hit 3"-4" apart every shot, and when it was Hot, forget it I would be lucky to hit a 6" paper plate at 75 yrds. I also had a Win 70 pre 64 30-06 that was about the same, I traded those lemons off after realizing why I got such a "good" deal on them.
    My hunting rifle is a Win 70 reatherweight 308 with a fixed 4 power scope and I can bench rest it and take out dimes at 100 yrds everytime, even when hot. Where I live you really don't need a super accutate 1/2" gun cause most shots are only 30-75yrds out, and mainly on running deer (I like to HUNT, not sit).
    The most accurate semi i have ever owned was a Win model 100 308, man that thing was a blast to shoot.

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