Author Topic: Rifle shooting two groups?  (Read 1415 times)

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Offline Scott Fisher

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Rifle shooting two groups?
« on: November 27, 2003, 08:16:13 pm »
I have a Tikka .270 that is shooting two groups in a five shot string.  I fired 10 groups with different handloads and I would get 3 rounds touching or near touching and two rounds which would be either low high or right between 3 to five inches away and would also be touching or near touching.  There is a distinct pattern each and every time.  I took the action out of the stock and every thing seems to be okay.  The barrel is free floated and does not touch.  I fired very slowly and did not let the barrel get hot.  The screws in the action are tight and so are the scope mounts.  Has anyone encountered such a problem with a rifle shooting two groups.


Offline Rogue Ram

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Rifle shooting two groups?
« Reply #1 on: November 27, 2003, 09:59:20 pm »
I have a similar issue, but believe its my scope.

Problems like this should only a couple things. The action may be moving around and may require bedding. The barrel may walk when warm, but what happens when you go beyond 5 shots? Do shots 6 through 10 go back and do the exact same pattern?

The other likely suspect often is a scope.  I've been down this road recently with the gun I mentioned. While I haven't solved the problem yet, I do know the scope is a problem. My scope is made by a very well known American company.........as I have come to find out, these scopes are getting a reputation for getting damaged by recoil from much more than a .30-06......in addition the adjustments on these scopes are worthless because on many they are not repeatable; say one click left, shoot, no movement, next shot, it moves because the recoil jarred the scope's internals into position. A person I would easily qualify as an "expert" in the field (no pun intended) verified what I suspected about this. So, sorry for ranting, but if you rule everything else out, switch scopes/guns and don't be afraid to return scope to the maker or get a quality one if it proves less than desireable.

RR

Offline gunnut69

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Rifle shooting two groups?
« Reply #2 on: November 28, 2003, 08:22:41 am »
In my experience a scope gone south will generally spray bullets is no discernable pattern.  The situation you're having is usually a bedding problem but can be several situations..  Is the action bedded stressfree?  You say the barrel is freefloated, so if the front action screw is gradually loosened does the front receiver ring rise up or move at all?  Your hand on the wood metal juncture as the action screw is loosened slowly will tell.  Also use the same test to be certain the rear action screw is not bending the action as it's tightened.  Not having worked on a Tikka I don't know it's idiosyncrasis but the action screws must NOT bottom in their holes and the front screw should not pass thru into the locking recesses.  Be certain the bottom metal is stopped by the inleting and does not pinch the magazine assembly between the bottom metal and the action...  Normally I'd advise checking the barrel bedding for a high spot.  This can cause the barrel to pop from one side of the high spot to the other.  I've seen this produce exactly the pattern you're discribing.  Check the bedding and let us know what you find...
gunnut69--
The 2nd amendment to the constitution of the United States of America-
"A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed."

Offline Scott Fisher

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Rifle shooting two groups?
« Reply #3 on: November 28, 2003, 09:36:08 am »
Thanks for the advice gunnue 69.  I can tell you are very knowledgeable about rifles.  The first scope I put on sprayed bullets all over the place, any where from 5 to 8 inches apart.  I took the gun apart and checked the bedding and nothing seemed awry, infact the stock is laminated and the inletting was perfect. I than replaced the scope with a Weaver Grand Slam and the first three shots just about touch with factory ammo. This action has only two screws to hold the action in place. I know from experience that an action with a middle screw must never be tighened more that just slightly snug, or it will bind the action.  I fist thought that the barrel was getting hot and touching the sides, but I shot very slowly and every two shots I would slide a .005 piece of paper between the barrel and stock to see if it was touching and it was not.  I tried your suggestion of loosening the front and rear screws very slowly and seeing if the action moved and it did not.  The recoil lug is a seperate piece and fits inside a milled out slot in the stock.  The only thing that seemed strange is that the lug does not fit snugly into the slot, but has about a 1/16 of an inch gap. When I put the action back into the stock I made sure the lug was up against the back of the slot before I tightened the screws.  In another post under bolt action rifles someone suggested that the action screws should not be over tightened, and that was not the case with my situation. Again I want to thank you for your response, but I am still scratching my head!  I shot my sons .270 yesterday and shot a 1/2 inch 5 shot group, so I know I have not lost the ability to shoot.

Offline gunnut69

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Rifle shooting two groups?
« Reply #4 on: November 28, 2003, 08:45:08 pm »
Perhaps you found the problem and didn't even realise it!  You said the recoil lag wasn't tight against the stock..  Check the screw holes in the stock for areas where the wood is burnished or bruised.  I'm guessing the recoil lug isn't absorning the recoil, it is transfering to the stock thru the screws.  This will create a real problem as the action is pushed from side to side pivoting on the sction screw that's hit the stock in it's clearance hole.  The recoil lug can have clearance at the front and sides, and MUST have clearance beneath it.  It should fit tightly against the rear of the mortice.  Enlarge the clearance holes in the stock and also be absolutely certain the magazine is not touching the stock either.  It too can cause the recoil to be spread to the stock other than at the recoil lug.  Keep us informed..
gunnut69--
The 2nd amendment to the constitution of the United States of America-
"A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed."

Offline Howler

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Rifle shooting two groups?
« Reply #5 on: December 10, 2003, 01:47:38 pm »
If every thing seems ok with the rifle you should check your bullet run out!
lots of rifles are very picky about cartridge R.O. I myself would think that a bullet hitting the the throat with alot of R.O would create a different vibration pattern,not to mention deform the bullet.

Offline gunnut69

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Rifle shooting two groups?
« Reply #6 on: December 10, 2003, 11:27:40 pm »
Runout can indeed open groups but it usually causes a random dispersal ad there is no set pattern for where the bullet is pointed when it is fired.  In this instances the rifle is shooting quite well, just to seperate groups.  I would bet money the recoil lug is causing the problem.  It should fit tightly against the stock(at the rear) and in this case it should also fit the slot in the action tightly.  I would set the lug in it's slot in the metal and peen the trailing edge of the slot over to tighten it's fit, also install a witness mark on both lug and slot so it's always returned to the same spot in it's slot..  I'd then glass the the action, with recoil lug in place, into the stock.  With 0 clearance all around, at least in this case because of the seperate lug.  If care is taken to not disturb the rest of the inlet and the barrel channel, your problem will most likely go away.
gunnut69--
The 2nd amendment to the constitution of the United States of America-
"A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed."

Offline Howler

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Rifle shooting two groups?
« Reply #7 on: December 11, 2003, 05:23:50 am »
Your right!  R.O usually just causes groups to simply open but there is more to R.O than just the cartridge R.O!  In checking R.O you should always check the fired brass to see what you have to work with. Could be a chamber slightly out of rnd.

Offline gunnut69

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Rifle shooting two groups?
« Reply #8 on: December 11, 2003, 10:08:56 am »
Misaligned chambers will surely damage a rifles grouping ability but I still believe the '2 groups' thing is being caused by something which changes from one position to another, i.e. a crooked inlet or an inlet which flexes the action or prehaps a sloppy fit with the recoil lug/abuttment, which allows the recoil to be handled at least in part, by one of the action screws.  I'd even go further and guess the rear screw is the one that is hitting it's clearance hole.   A simple test to check if this is the problem would be a credit card shim behind the recoil lug.  If the 2 grouping problem stops, the problem is found.
gunnut69--
The 2nd amendment to the constitution of the United States of America-
"A well regulated militia, being necessary to the security of a free state, the right of the people to keep and bear arms, shall not be infringed."