This question is directed at anyone who actually partisapates in competitive benchrest shooting, or is extreamly compitent at shooting hunting rifles from the bench.

I have been experiencing some odd unexplainable sessions while shooting from the bench while at the range. My situation is this.

I have been shooting and evaluating 12 gauge 2.75" magnum sabot slugs out of my two bolt action, fully rifles slug guns.

Slug gun #1 is a 12 guage 3" maguum Browning A-Bolt Slug Hunter. I bought it new and it is in perfect working condition. The scope on it is a Leupold VariX-II in 3-9x40mm.

Slug gun #2 is a 12 gauge 3" magnum Marlin 512 Slugmaster. I also bought it new and is in perfect working order. The scope on it is a Leupold Shotgun scope in 2.5-8x33mm.

As a written in stone rule of mine I always inspect each rifle before and after every range session for any loose scope rings or mounts as well as for any loose action and stock screws. I also use extreamly small amounts of white-out applied on certain spots of the scope rings slot screws, and ringe screws to alert me to any tell tale movement or loosining of my scope mounts.

The scope rings I use on all my rifles and muzzleloaders are Burris Weaver style "Z" rings. I have been using these rings on my rifles for over 10 years now and never once have thay ever come loose. So I strongly doubt the root of my problem is being caused by eithor my rifles or my scopes

Now for my question. I went to the range back in January of this year on what was a near perfect range day. Winds were less than 10mph with it being calm most of the day, temp was cool in the mid to high 50s and himidity was also low. It was partly sunny. Not at all a typical January day in NW Indiana to say the least.

I was shooting slug ammunition from three different makers, each of which were all of the same lot#s and was always stored in air-tight ammo cans untill shot.

I shot so well that I simply could not beleive it, I mean had anyone told me thay were shooting the three shot 100yrds groups I was getting I would have SERIOUSLY doubted it even possible. The Remington Core-Lokt Ultra sabot slugs were averaging WELL under 1.5" for a three shot 100yrd group with three, three shot 100yrd groups actually under one inch no less!!! The Core-Lokt shoots a 385grn, .50 caliber bonded core projectile. Advertized velocity is 1900fps. This is factory loaded 12ga sabot ammunition after all, not my hanloads, and here I was getting handloaded rifle ammo performance out of factory loaded sabot ammunition. And excellent performance at that. You should have seen the crowd that was gathering as thay looked in utter amaizment at the groups I was getting. All of the other shooters at the range that day that saw my groups all said that unless thay would have seen it with their own two eyes thay would have never beleived it. Bottom line is in the real world with sabot slug ammunition if you can get three shot 100yrd groups at or below 3.5" you usually do back flips.

The second sabot ammunition I was shooting was Winchesters Partition Gold Sabot slug. It also shoots a 385grn .50 caliber projectile. The accuracy I experienced was EVER so SLIGHTLY less spectacular with the 100yrd three shot average being at 1.75" with several 100yrd three shot groups right at 1.1", but still out of this world for 12ga shotgun sabot performance none the less.

The last sobot ammo I was shooting was Lightfield IDS Commander sabot slugs. This is a 12ga 3" magnum sabot load that shoots a .62 caliber, 465grn projectile at an advertized velocity of 1800fps. My three shot 100yrd average with the Lightfields was 1.53", always with two of the three slugs touching on paper.

Now for my problem that I for the life of me can not explain, although I do suspect some possable causes. Durring my next range session I was not able to come even close to the first range sessions level of accuracy with any of my slug rifles shooting any of the sabot slug ammunition, which buy the way was all of the exact same lot# as the ammunition I shot durring the first reange session I described above. My three shot 100yrd average had doubled and in some cases increased 350%!, but as far as I could tell after closely inspecting every single aspect of my shooting, from my scope mounts, my scopes themselves, to my rifles, to my ammunition, and to my shooting form, nothing had changed what so ever. The range condidtions were actually better than I had durring the first range session, and in the case of my last session, the range conditions were the best I have ever experienced, with almost no perceivable wind at all.

Now for what I think may have happened. It might just be as simple as I had a bad range session. But what struck me as particularly strange is my point of impact changed rather drasticly with all three types of slug ammunition. The change was always 2"-3" higher and 1.5"-2.5" to the left. If only my groups opened up and I had not experienced the POI change, I would have just written it all off to a bad day at the range. But what could possibly cause such a large change in POI, if my scopes are still both good, and i beleive this to be so, because the odds of having two scopes fail durring the same range session are bordering on the impossable I would think. I was also able to sit at the same bench, and both my slug rifles were at the same level of the bore being clean as in the first range session.

It could quite possibly be caused by my shooting rest or a combination of my shooting form and my rest. The rest I use is a combination of a "Protector" rear bunny ear bag filled with heavy sand and a "Benchmark Shooting Rest" with the rear screw removed so it rests in the "Protector" rear bunny ear bag. The front of the Benchmark rest sits on two rubber tiped screws that adjust for elivation. I also place a 25lb bag of lead shot on the front portion of the Benchmark rest infront of the fine elivation adjustment knob. I have tried to make a sort of free recoiling rest that also absorbes as much of the utterly punnishing recoil of the 12ga 2.75'& 3" magnum sabot loads I shoot as is possable.

So I guess that the rest could some how be affecting my over all accruracy, but I have no evidence to support this as the cause. I guess what I am asking from those far more knowledgeable than myself is this:
Is it possable that one of or a combination of the fallowing things that I did could have caused such a dramatic change in my accuracy and a change in my POI? Things like my shooting form and consintration while shooting as well as my shooting rest. And lastly, could a POI change like I described be caused simply by a bad shooting session at the range? I am 1000% sure that neithor my rifles or the optics are at fault here.

Your thoughts and ideas please.