Wandering Group Centers

[Picher]

I went to the shooting range a few days ago and fired several batches of handloaded .223 Rem ammo through two rifles. The groups had about the same POI when shot through my Stainless-Fluted, heavy-barreled Rem 700, but the POI wandered considerably more when shot through my plastic-stocked, bedded/floated, 700 ADL.

The handloads were various ages, bullet weights, powder types/charges, yet the Varmint rifle shot the groups much closer to the original POI than the "budget" model.

I was "cleaning out" batches of ammo, for the most part, but also had one recently-loaded batch that seemed more uniformly placed in both rifles. Anyone notice similar variations among rifles.

Note that this wasn't intended to be a serious test, but just a recreation outing. At least it's a good reason to be more uniform in bullet selection and powder selection/charge weights.

 

[d2wing]

This is a frustrating. Sometimes you can track down an issue to a particular mechanical problem. Sometimes a rifle will only shoot with a particular load. And some rifles just don't shoot.
A gunsmith friend of mine said when he wants an accurate rifle he will buy a batch and test them all. He will keep the best one and sell the rest. Then he will work on the accurate one.

 

[Dr T]

I have seen wandering groups from a couple of Rugers (an American and a M77 with a laminate stock). I think that the American was due to the flimsy plastic stock. The laminate still perplexes me.

 

[jmr40]

*While a lighter weight barrel CAN be consistently accurate, it is more likely to happen with barrels with a little more meat in them.

* Factory barrels CAN be consistently accurate, but you're more likely to find an accurate aftermarket target barrel.

* Most of the time there is no rhyme or reason to it with factory barrels. Sometimes you get lucky, sometimes you don't, but you increase the odds with the above.

I think that the American was due to the flimsy plastic stock.

The bedding system used on the Ruger Americans completely eliminates the stock from the equation. Other more conventional rifles depend on a recoil lug and the action to be a perfect fit with a stiff stock for best accuracy. The American doesn't even have a recoil lug and no part of the action even touches the stock. It rides above the stock sitting in the metal "V" blocks. To be fair Savage deserves credit for developing the concept used on their Accustock. As long as there is enough room between the stock and barrel to avoid them touching when fired the stock can be flimsy and not effect accuracy.

The Ruger 77 uses an odd angled action screw. They have always hurt Rugers accuracy potential. It is possible to get one bedded to shoot right, but far more difficult and most people can't do it.

 

[taliv]

read up on all the barrel harmonics theories. as you vary the exit time at the muzzle (based on different powder charges etc), I'd expect POI to shift. wandering through "nodes".
heavier barrels probably have less deflection and thus groups wander less.

 

[Varminterror]

The Ruger 77 uses an odd angled action screw. They have always hurt Rugers accuracy potential. It is possible to get one bedded to shoot right, but far more difficult and most people can't do it.

There’s a lot about the Ruger M77 MkII and Hawkeye design which hurts them as a precision rifle, but the action screw isn’t part of it. Bedding the action does take an extra step compared to a standard round tube action with 90deg screws, but it’s really not a challenge (I actually use the same number of steps, and same process for the Ruger action as 700 type actions now, takes longer, but yields more consistent results.

I’d easily agree most people DON’T KNOW HOW to do it properly, but if I can do it, anybody can. I’d challenge that most folks don’t really know how to bed any rifle, and further, even fewer know how to check their bedding job - or even that they SHOULD check it.

The biggest culprit I typically see in M77’s is action pressure by the magazine box. Simple to relieve, and pays back in spades.

 

[Picher]

I think the problem may be the factory plastic stock, which doesn't sit on the bags well and is difficult to hold consistently. The rifle also may react differently to various loads at a greater rate than the stiffer-barreled, better-stocked varmint rifle.

 

[Nature Boy]

Can you post a picture of the targets?

 

[Skylerbone]

I see POI shifts more often with rimfires when testing different brands. You expect some vertical with velocity change but looking at group centers of sporter .22s show noticeable windage.

 

[Chuck R.]

I went to the shooting range a few days ago and fired several batches of handloaded .223 Rem ammo through two rifles. The groups had about the same POI when shot through my Stainless-Fluted, heavy-barreled Rem 700, but the POI wandered considerably more when shot through my plastic-stocked, bedded/floated, 700 ADL.

The handloads were various ages, bullet weights, powder types/charges, yet the Varmint rifle shot the groups much closer to the original POI than the "budget" model.

I was "cleaning out" batches of ammo, for the most part, but also had one recently-loaded batch that seemed more uniformly placed in both rifles. Anyone notice similar variations among rifles.

Note that this wasn't intended to be a serious test, but just a recreation outing. At least it's a good reason to be more uniform in bullet selection and powder selection/charge weights.

Honestly I wouldn't be shocked by this at all.

I've done OCW tests, with as little as a .2-.3 difference in powder charge and seen a POI change, never mind the delta's you've described.

Now IF I had a wandering POI with the exact same load, or an issue with group size, I'd look hard at it.