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Offline bugdust

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pistol scope problem
« on: August 16, 2011, 10:52:02 AM »
I have a Burris 3x-9x pistol scope. It is mounted on a 10 inch contender with 223 barrel. The contender is held in a Ransom Rest. the scope is sighted in on the center of a cross on the target. After firing a shot the scope cross hairs are off center both elevation and horizontal as much as two or three inches. I found by playing around that if I open and close the contender hard the scope cross hairs come back to the center of the target. Is this caused by a defect in the scope or the way it is mounted. the base is a contender base and the scope is held in place with quick release thumb screws . It was installed by a gunsmith and appears tight.The Ransom Rest holds a tight group and the scope centers the group only when I slam the contender shut ( most of the times).
 
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Offline SHOOTALL

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Re: pistol scope problem
« Reply #1 on: August 16, 2011, 11:32:32 AM »
Contenders can be difficult sometimes . The first idea is the scope has problems , if possible check on another gun . With a Contender it might be a lock up problem . The gun shouldn't be so hard to close if bolts are correct and springs are good. Reloads need to chamber correctly also. Mark the bolts with a magic marker or felt tip pen and close normal open and see if the marks on the bolt go at least half way up the incline. And both should show same. Its been some time since I shot Contenders but those two ideas came to mind. Others may have a better idea.
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Offline MePlat

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Re: pistol scope problem
« Reply #2 on: August 16, 2011, 12:31:21 PM »
BUGDUST:
If you will just stop and think you will realize that the barrel is not locking up at the same place all the time.  It is not a barrel that is screwed into a solid action.  It can move.  All you are interested in is if the BARREL and LOAD shoots well and that can be told by benching the gun.  Not a Ransom Rest deal.
If you use a Ranson Rest you will need an adjustable base for windage to get the crosshairs on windage wise and the elevation adjustment on the Ransom Rest to bring it into correct elevation.  Then fire it.  If you can get it to repeat after each shot all the much better but if it doesn't you will have to adjust the rest each time it doesn't repeat.
Better still and alot easier if you just bench the thing.
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Offline bugdust

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Re: pistol scope problem
« Reply #3 on: August 16, 2011, 03:02:51 PM »
You know Meplat I think you have the answer. I never considered the barrel not returning to the same spot after every shot. I have both elevation and windage on the rest. The only thing not locked down is the barrel before loading and before the shot. Slamming it close hard after loading the cartridge must seat the barrel in the same spot.  The recoil from the shot must do the same. This is why the groups are much smaller than the variaton seen through the scope if I do not slam. I am going to follow up on this idea. thanks.
 
Bugdust
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Offline charles p

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Re: pistol scope problem
« Reply #4 on: August 16, 2011, 03:34:00 PM »
Not an expert, but it seems to me that the barrel and scope are like one unit - they are bolted together.  Wherever one is pointed, so it the other.  What am I missing?
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Offline bugdust

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Re: pistol scope problem
« Reply #5 on: August 17, 2011, 10:09:29 AM »
charles p:
You are not missing anything. However if the barrel points in a different direction after every shot because it is loose the scope will point in the same direction.  If the gun is fixed in a Ransom Rest the cross hairs will be off the point of aim after the shot. This is the problem. Then again it may be the scope. I am going to run some tests to get to the bottom of this and report back. Right now I am betting on a loose barrel.
 
bugdust
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Offline bobthenailer

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Re: pistol scope problem
« Reply #6 on: August 20, 2011, 12:27:05 PM »
Even though they make grip inserts for the contender ! you will not get satisfactory results useing a RR with a contender or any other like SS pistol with interchangeable barrels .
 I had a RR years ago when most handguns had iron sights and no reliable means of mounting  scopes or red dots them .  i now do all of my testing from a rest with a red dot or a scope!  with contenders , rpm xls , xp 100 and  a aray of handguns with excellent results
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Offline bugdust

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Re: pistol scope problem
« Reply #7 on: August 22, 2011, 02:18:27 PM »
I conducted a test consisting  of 30 rounds fired in the ransom rest without adjustment and 30 rounds where I adjusted the rest to put the scope hairs exactly on the center of the target after every shot. The test without adjustment produced three inch average 5 shot groups and with the scope adjusted for every shot 5 shot groups averaged two inches. I have always gotten 1 inch groups with the ransom rest with this load. Two inch groups are not acceptable and there is some thing wrong with the gun not just the barrel. Also it was not breaking some primers and there was a problem closing the action. I have not ruled out the barrel causing the scope to shift. If that is the case then a ransom rest test may not result in the true accuracy of a contender since one normally realigns the sights before each shot which would make the groups larger than when using the ransom.I took the gun to a gunsmith and when it is repaired I will do the same test again. My experience with using the ransom rest is that groups will be twice as accurate using the rest as benching with a scope. Even more so when testing heavy recoiling loads.My grip will never be as consistant as the grip of the rest. I will report back after the next test.
 
bugdust
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Offline Singleshotsam

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Re: pistol scope problem
« Reply #8 on: August 30, 2011, 04:39:09 AM »
My first move would be to ditch the quick release rings...  I've never seen anyone have luck consistantly with those things unless they are the high end tactical style made by badger ordnance or warne (and those aren't cheap.).  Put on a set of bolt on rings and make sure the base, and ring screws are all torqued to the proper specs. 
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Offline Singleshotsam

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Re: pistol scope problem
« Reply #9 on: August 30, 2011, 04:42:24 AM »
Do you have a hammer extention on?  I've never had luck w/ hammer extensions consistantly hitting primers on a factory gun when the extension was on.  When I take them off the guns fire fine.  It sounds like several small problems to me rather than one big problem...
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Offline bugdust

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Re: pistol scope problem
« Reply #10 on: February 22, 2012, 12:30:52 PM »
I sent the gun to a gunsmith. The gunsmith could not solve the problem so he sent it  to the factory. The factory kept the gun for over four months. They did a great job.  The gun feels and shoots likes new. the gun is over 30 years old but they fixed it free.Then I had a problem getting to the range.
 
I did another test . 30 shots without adjusting the Ransom Rest and 30 shots adjusting the rest to put the scope on the poa. Same results. the groups were about 15 percent smaller when I adjusted the rest. To be sure I was right I purchased another hand gun scope. A cheap BSA for 79 bucks. This scope is great. Better than the 350 dollar scope I was using except that scope has more power . 3-9 instead of 2-7. the BSA has a longer eye relief which is great for a six five long arm guy like me.
 
I put this scope on my 357 Max because it has the right base. Shot 30 rounds 200 grainers. The scope came back on the button every time. Which means the gun was ok but the other scope was bad-wrong. To check this out I put the new scope on the 223 barrel after putting on a new base This was the barrel that was causing all the problems. Same problem -scope not coming back to poa.Lesson learned. Some contender barrels do not lock up right  and some do. This should not effect accuracy but it can screw up tests when using a Ransom Rest. When testing Contenders on a Ransom Rest better use a scope too. On the other hand this is a good way to check scopes. I am going to put my rifle scopes on the contender barrels and use the Ransom to check them out.
 
Glenwood
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