K31 bedding and vertical dispersion

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  • Last Post 08 November 2018
ten-mile posted this 25 October 2018

My K31 has been giving me problems with vertical stringing.  It was in unissued condition when I bought it 3-4 years ago.  Using the NOE K31 bullet and 15 grains 4756 it would shoot 10-shot one inch groups pretty much on demand.  I set it aside for a while concentrating on my 223 and 308 in Production class.  Since my nephew and I decided to make our first trip to KC this year, I got out the K31 for the military regional.  I had sold my hoard of 4756 to friends so loaded 21 grains 4759 with the NOE bullet.  I coudn't get any kind of grouping at 100 yards due to severe vertical stringing.  I thought perhaps the barrel is warping from the heat so tried loosening the front band screw (it had to be very tight in the past).  That helped so I made a different screw that would let me adjust the tension and hold it there.  That worked, or so I thought.  I then tried four powders in differing amounts and settled on 21 grains Accurate #9.  The target shows my 100 yard sight in target, the right hand 3 shots were first then I adjusted to get the left 3 shots.  At 200 yards all my shots were 10s and Xs.  I felt pretty good about that and packed up my stuff for KC.

Imagine my chagrin at the match when the vertical dispersion had come back with a vengeance!  I tried everything during the match and nothing worked.  I did find that AA#9 does burn very hot and intend to use something else in the future.  However, I could use some advice on what others may have found regarding proper bedding for their K31s.  I would like to finish above last place next year.

 

 

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Ken Campbell Iowa posted this 25 October 2018

following this thread ...

i might mention that i like to watch the "" gunny "" shooting show on tv ...  they use a high speed camera to show the bullet leaving the barrel, the target blowing up, and the auto-action working, the brass flying .... neat !! ..  i swear you can see the bullet wobbling as it exits ... 

but it also shows the barrel ... i think ...  coiling and winding up and bending .... i think ...  

i wish we had one of those cameras ...  that guy on you-tube that shoots flashlight batteries in his 12 gauge has one ...  

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when standing and looking at a 1-inch bull at 100 yards with plain eyes, i am amazed that we can strive to hit that almost invisible dot at that far distance !! .... 

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i also have long told everybody that they are just wasting ammo by shooting a rifle that isn't " glass " bedded and screw-pillared.   i get more gentle with that utterance over the years, but i mean it in a helpful way ...  when putting your elbow in different places on a concrete bench can screw up a group, shouldn't the rifle act as one piece, not a bag of parts that shakes apart and re-assembles randomly at every shot ?? 

i love those k31 ...  had one for awhile, so hope you get yours tamed . 

ok, it is interesting to shoot them  " as issued " .... to see how good they were in the field for the soldiers ....  and i bet some occasionally shot as well as perfect " glass " bedding ....    but why not optimize yours to be as good as that rare lucky example .. ?  i am not sure about the cba rules i confess.

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as you ask, experience with your model rifle is best, ....  but in general, you can get great results with about 1 oz. of ( devcon/jb .. ) ...  don't need globs of material ... just the recoil features, and the pads under the stock screw areas and the receiver ring.  relieve everything else, including barrel   i like to bed just one recoil feature, usually the recoil lug ...   relieve everything else, such as magazine box, rear tang, etc.    if the recoil feature is wimpy, i like to bed a larger metal insert into the stock behind the recoil feature ( lug ) " glass "   ... to spread the shock a bit.  military stocks especially are sometimes oil-softened.

keep us informed .

ken

 

 

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RicinYakima posted this 25 October 2018

Issue means as Issued! You want to play with the rifle and glass bed it then it is Modified Class. That is the whole purpose of Issue Class is to see what an "as issued to a average soldier" rifle will do.

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RicinYakima posted this 25 October 2018

Ten-Mile, I'm sorry, but I have never shot a K-31 let alone taken one apart. If it was a turn-bolt I would bet on a bedding problem, but with straight-pull could it be not locking evenly? Ric

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ten-mile posted this 26 October 2018

I  forgot to mention that I am shooting in Mod-Scope with the siderail clamp mount and a Leupold FX-3 6x42 scope.  I am not against removing a little wood but want to avoid doing so.  It has been stored at pretty much constant temp and humidity since I got it.

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Wineman posted this 26 October 2018

For a steel and wood issued military rifle, they can be scary accurate. The bedding is at the front action screw and there usually a metal shim there. Most internet advice is to have the front band screw "just tight" so the barrel gets out of the trap of the forend. My biggest complaint is that they have very short throats and most cast need to be deep seated to even chamber. I have no issues with jacketed full power loads (except the loose barrel made the stock chip). I have never found a load that shot consistently well with cast. I have had a similar experience, get a good load at home and then go to a match and a train wreck (with a M1903a3) happens. Some here would recommend some kind of filler (dacron, polyfill) but at your own risk especially with the faster powders. If it shot well once, it will again but cast loads can be so finicky a small change can make a big difference. Honestly, I have never shot a group that was much better with cast in any of my military rifles, and I'm not sure if that target has vertical stringing. It is a "clean" target with 2 x so where to complain except group size? Someday I will shoot 1" groups on a regular basis (probably in heaven)  but for now I have to be happy with 2" groups all in the black. Even the CBA Military championships don't have many 1" groups at 100, more like 2" (2 MOA) although this year someone shot a 1.1" 10 shot group at Puyallup so it is possible but the average for nine shooters 10 shot agg was 1.935".

Cheers,

Dave

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2kbill posted this 27 October 2018

I got a nice K31 at the Nationals this year from a good friend from PA, and put the aperture sight set from Swiss Products on it, to shoot in Mod Iron class.  Shot the Sept. & October matches with NOE K31 bullet and 17 gr. 2400.  99-5x, 95-2x, 99-5x, 95-4x @ 100 yds.  200 yds dropped off considerably, 92, 94, 92, 92. Vertical stringing!  I got an adjustable front iris and my testing with this is promising - but still not quite where I want to be.  Will be trying some different charges w/2400, and maybe different powders.  I think I will be sticking with the NOE bullet, it fits pretty well. 

You asked about bedding!  I have no idea, sorry!

 

Region 3

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fa38 posted this 04 November 2018

 

Have you tried relaxing the bedding from the action screws when you are not shooting the rifle and using a torque wrench  to set the action screws prior to shooting the rifle.  The constant pressure when the action screws are tight may alter the tension on the barrel bearing on the stock. 

This seems to happen on my Rem 03-A3 with stock up pressure on the barrel at the fore end of the rifle. 

 

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Wineman posted this 04 November 2018

To me it is all part of the fun. I know that none of the military rifles I own, can match a free float hand guard AR. I rescued a M1903a3 that had been made into a deer rifle. The barrel was slightly cut down, but since it is a four groove and shot well, I kept it. Looks a little funny but not much more than the original funky no front sight look of the M1903a4. Off a Caldwell rest at 100 I could get two shots in one hole and then, wham one out an inch away (jacketed as a trial). So it's either a POS or not a bad group (no fault of mine of course...).

Dave

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onondaga posted this 04 November 2018

There is good logical fixes for vertical dispersion, I've used them. That doesn't help on a bad when I get horizontal dispersion. My best rifles get circular dispersion in small groups and I have always blamed that on rifling because my best archery accuracy was always with zero degree straight fletched arrows and a well tuned bow.wink

Gary

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JeffinNZ posted this 08 November 2018

Have you tried giving the barrel immediately in front of the chamber a good clean to remove any carbon build up? 

Cheers from New Zealand

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Ken Campbell Iowa posted this 08 November 2018

just for general interest ...  22 rimfire match shooters live and die with their barrel "" tuners "" ... ( since they can't load their own ammo  ) ...

adjusting the tuner/weights by 1 or 3  thousandths can make the group shapes change ... not just vertically but also

horizontal, right hand oval, left oval, and most importantly ... bigger and smaller ....  generally the big to small ratio is about 3 to 1 .  lengthening the barrel 1 to 3 thousandths !! .... 

oh, and this with very stiff, 1 inch dia., stubby 20 inch long barrels on stiff actions.

kinda spooky.

possibly might help explain good and bad days for you competition types at the big match ...

ken 

tuners make your match 22rf go from 0.1 to 0.3 inch at 50 yds.   would it make your deer rifle go from 2 inches to 6 inches at 100 yards ??  ...   or just from 2 inches to 2.6 inches ?? ..  or no effect ?? ... easier to twist the tuner than pull and reload all new ammo ...

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