Cold Bore POI Shift After Magpul Stock Install

[Bidwell]

I recently changed my Ruger American Standard 308 (gen 1) stock to a Magpul Hunter. Generally it seems to be helping accuracy and is nicer to shoot, but I've noticed my cold bore poi shift is more significant. The first cold barrel shot is dead on my zero that I had with the original stock, but then all subsequent shots are about 2 inches high. Two range sessions, same behavior. All non cold bore 3-5 shot groups have been 1.2 moa with frequent sub moa groups.

With my old stock, I was about 1 to 2 moa consistently, with the occasional sub moa group. But I never noticed this big cold bore poi shift. Is it possible the stock is somehow influencing this? Obviously, good way to find out is by switching back to the original stock to test, but wanted to get some opinions. It's starting to get cold, I'm wondering if that's causing some issues as well. I'm turning this ruger into my bench rifle and will get a really light hunting rifle soon. So I'dike to just do whatever I can to, regardless of weight to get the best accuracy I can. I'd like to get consistent 1 moa or lower groups. Just ordered a timney trigger and also thinking about cutting the barrel down to 18 inches and getting it threaded. I'm curious to get thoughts on the barrel shortening too, and trigger. Worth it or not from an accuracy standpoint? Thinking a stiffer barrel could help things. I'm at 60 in lbs for receiver screws, wondering if playing around with that number might change anything. Also thought about cryotreating the barrel to relieve stress, but I may just be going overboard now!

Thanks!

 

[jackieschmidt]

Action to Stock Bedding might be a little off in the new stock.

As for the shorter barrel, about all that will do is cost you velocity.

 

[Bill Norris]

I recently changed my Ruger American Standard 308 (gen 1) stock to a Magpul Hunter. Generally it seems to be helping accuracy and is nicer to shoot, but I've noticed my cold bore poi shift is more significant. The first cold barrel shot is dead on my zero that I had with the original stock, but then all subsequent shots are about 2 inches high. Two range sessions, same behavior. All non cold bore 3-5 shot groups have been 1.2 moa with frequent sub moa groups.

With my old stock, I was about 1 to 2 moa consistently, with the occasional sub moa group. But I never noticed this big cold bore poi shift. Is it possible the stock is somehow influencing this? Obviously, good way to find out is by switching back to the original stock to test, but wanted to get some opinions. It's starting to get cold, I'm wondering if that's causing some issues as well. I'm turning this ruger into my bench rifle and will get a really light hunting rifle soon. So I'dike to just do whatever I can to, regardless of weight to get the best accuracy I can. I'd like to get consistent 1 moa or lower groups. Just ordered a timney trigger and also thinking about cutting the barrel down to 18 inches and getting it threaded. I'm curious to get thoughts on the barrel shortening too, and trigger. Worth it or not from an accuracy standpoint? Thinking a stiffer barrel could help things. I'm at 60 in lbs for receiver screws, wondering if playing around with that number might change anything. Also thought about cryotreating the barrel to relieve stress, but I may just be going overboard now!

Thanks!

Swapping stocks can definitely affect the way a rifle will act. Seen it happen several times.

 

[Bidwell]

Thanks for the replies so far. I'll try remounting the stock. Since it will be a range gun, sacrificing one round isn't a huge deal, but not ideal either. I'm trying to get this cheap hunting rifle to do things it wasn't designed to do so there will be compromises. It's sort of fun trying to troubleshoot. Any experiences with cryofreezing barrels? It's pretty cheap and sounds like it couldn't hurt.

Action to Stock Bedding might be a little off in the new stock.

As for the shorter barrel, about all that will do is cost you velocity.

 

[K22]

If it's strictly a range rifle, then the cold bore shot is not a big deal. With that said, bedding is critical to precision shooting in my experience. As others have said, changing a stock can have a significant impact.

For me, the cold bore shot is critically important - it is the "money shot" since while I spend a lot of time at the range in practical practice session, I am a hunter. Therefore, all my rifles must produce a clean / cold bore shot within my needed POI within the needed MOA.

Aside for bedding issues, the main culprit in clean and cold bore shots in my experience came from bores where aggressive copper solvents were used. It would take some rounds, the amount depending on the individual rifle, to re-established desire POI. Once I was cured of "internet cleaning expert disease", all my rifles settled down and met my performance objectives. This appears not to be case with your rifle since the old stock didn't exhibit this problem, but I couldn't resist sharing my rather dubious experience when I went into the cleaning weeds.

 

[Bidwell]

If it's strictly a range rifle, then the cold bore shot is not a big deal. With that said, bedding is critical to precision shooting in my experience. As others have said, changing a stock can have a significant impact.

For me, the cold bore shot is critically important - it is the "money shot" since while I spend a lot of time at the range in practical practice session, I am a hunter. Therefore, all my rifles must produce a clean / cold bore shot within my needed POI within the needed MOA.

Aside for bedding issues, the main culprit in clean and cold bore shots in my experience came from bores where aggressive copper solvents were used. It would take some rounds, the amount depending on the individual rifle, to re-established desire POI. Once I was cured of "internet cleaning expert disease", all my rifles settled down and met my performance objectives. This appears not to be case with your rifle since the old stock didn't exhibit this problem, but I couldn't resist sharing my rather dubious experience when I went into the cleaning weeds.

That's an interesting insight! I've used Boretech Eliminator twice now, not sure if that qualifies as an aggressive copper solvent, but I know the formula is targeted for it. I'm in CA and I like to practice shoot in national forest land, so I'm basically using copper rounds all the time. Barnes ttsx, 130 grain. I hand load so slightly mote economical to do so. I'm going to switch to my old stock just to verify this cold bore shot shift is due to the stock. Thanks for the note, something to think about. I should mention that I've probably only put 15 rounds or so through the rifle since the, maybe it needs more time to settle.

 

[K22]

That's an interesting insight! I've used Boretech Eliminator twice now, not sure if that qualifies as an aggressive copper solvent, but I know the formula is targeted for it. I'm in CA and I like to practice shoot in national forest land, so I'm basically using copper rounds all the time. Barnes ttsx, 130 grain. I hand load so slightly mote economical to do so. I'm going to switch to my old stock just to verify this cold bore shot shift is due to the stock. Thanks for the note, something to think about. I should mention that I've probably only put 15 rounds or so through the rifle since the, maybe it needs more time to settle.

With only 15 rounds down the bore, I do not think you could draw any conclusions at this point especially if you went through that so called "barrel break in" process, stripping the cooper out after each shot which would never allow the bore to establish any equilibrium. I could go on about this, but it will only produce a heated debate which I want to avoid since I am not a Hall of Fame shooter or competitive benchrest shooter, I just have a lot of experience shooting at the practical level, i.e., varmint precision level.

Bore Tech Eliminator, as far as I understand it, it not an aggressive copper solvent like Sweets and Cu+2. Many shooters I know use it with excellent performance results. I would just be sure you get it all out of the bore after cleaning and mostly importantly prevent it from entering the trigger assembly which a quality bore guide should accomplish.

 

[BoydAllen]

There are no guarantees with factory barrels. Having said that until you have proper bedding, your cart will be before your horse. There is a way to check your bedding. I can point you at how to do that. When I was working with factory rifles, I thought that it was smart to copy what competition shooters do. None of them would simply bolt and action into a stock and expect to do well at any benchrest match, long or short range. Accuracy is a weakest link thing. Simply choosing to ignore an important factor does not make it go away.

 

[Bidwell]

With only 15 rounds down the bore, I do not think you could draw any conclusions at this point especially if you went through that so called "barrel break in" process, stripping the cooper out after each shot which would never allow the bore to establish any equilibrium. I could go on about this, but it will only produce a heated debate which I want to avoid since I am not a Hall of Fame shooter or competitive benchrest shooter, I just have a lot of experience shooting at the practical level, i.e., varmint precision level.

Bore Tech Eliminator, as far as I understand it, it not an aggressive copper solvent like Sweets and Cu+2. Many shooters I know use it with excellent performance results. I would just be sure you get it all out of the bore after cleaning and mostly importantly prevent it from entering the trigger assembly which a quality bore guide should accomplish.

Sounds good, thanks! Understandable. I should further clarify that it's only been 15 rounds since the last cleaning. I have probably close to 800 rounds in total. Apologies for any confusion on that.

 

[Bidwell]

There are no guarantees with factory barrels. Having said that until you have proper bedding, your cart will be before your horse. There is a way to check your bedding. I can point you at how to do that. When I was working with factory rifles, I thought that it was smart to copy what competition shooters do. None of them would simply bolt and action into a stock and expect to do well at any benchrest match, long or short range. Accuracy is a weakest link thing. Simply choosing to ignore an important factor does not make it go away.

Any notes or resources you have on bedding would be much appreciated. I've thought about doing that myself but also have a gunsmith close by that will do a better job at a reasonable cost. I may have him remount my scope with some new rings and install an aftermarket trigger. It's tempting to chop the barrel to 18 inches since I keep hearing shorter and stiffer is better. Others disagree. It's not like its shooting bad either, seems like a gamble that might not be worth taking.

 

[Coyotefurharvester]

If the action is being flexed you will see cold bore poi shits.

 

[Bidwell]

If the action is being flexed you will see cold bore poi shits.

Interesting. I did see a tutorial on how to measure for that in a Gordy Gritter video. Maybe I'll pick up a dial indicator and try to measure flex while tightening the screws. My action screws are torqued to the minimum 60 in lbs, so if it is the action flex sounds like I'll need bedding. The magpul stock comes with nice steel mounting blocks but maybe that's not enough.

 

[LCazador]

Sounds good, thanks! Understandable. I should further clarify that it's only been 15 rounds since the last cleaning. I have probably close to 800 rounds in total. Apologies for any confusion on that.

At 800 rounds you probably have a rifle that has started to change it's shooting qualities. With that said a new stock can change many things. You can start with the way it rides the bags and where the best contact points are on the bags. I saw a friend recently change stocks and he found the new stock shot better with the front end 4-5 inches past the front bag. Have any of your bench habits changed since you got the new stock?
Does the new stock have the same slope at the butt and does new stock have a bag hook? Shortening the barrel will open a whole new set of issues and threading the barrel will also add new variations in groups. Installing a brake or silencer will change things even more.

 

[6.5 forever]

Action screw tension might have a effect

 

[Bidwell]

At 800 rounds you probably have a rifle that has started to change it's shooting qualities. With that said a new stock can change many things. You can start with the way it rides the bags and where the best contact points are on the bags. I saw a friend recently change stocks and he found the new stock shot better with the front end 4-5 inches past the front bag. Have any of your bench habits changed since you got the new stock?
Does the new stock have the same slope at the butt and does new stock have a bag hook? Shortening the barrel will open a whole new set of issues and threading the barrel will also add new variations in groups. Installing a brake or silencer will change things even more.

I didn't think about how the rifle itself may changing after X many rounds. In terms of bag and shooting technique, I haven't really changed anything. I usually try to keep the bag as close as possible to the trigger. I did that in the past since it seemed like it would reduce any potential bending of the stock forearm with the cheap ruger stock. I can try different positions, that would be a great test. The stock bending is no longer an issue. No bag hook on the stock.

I'm going to hold of chopping. As you said, it just introduces more potential issues and variables . I really don't want to complicate things right now.

 

[AlNyhus]

Interesting. I did see a tutorial on how to measure for that in a Gordy Gritter video. Maybe I'll pick up a dial indicator and try to measure flex while tightening the screws. My action screws are torqued to the minimum 60 in lbs, so if it is the action flex sounds like I'll need bedding. The magpul stock comes with nice steel mounting blocks but maybe that's not enough.

Pick up one of these, add a dial indicator and know for sure.

Rifle Action Bedding Checker | eBay

This version works on most barrels including 1.25" F-Class barrels. This is a new version that I think is easier to attach by reducing the number of screws and the ability to. The indicator is not included.

www.ebay.com

 

[Bidwell]

Pick up one of these, add a dial indicator and know for sure.

https://www.ebay.com/itm/325485181171[ [/UR

Didn't know those existed, thanks!

 

[BoydAllen]

Any notes or resources you have on bedding would be much appreciated. I've thought about doing that myself but also have a gunsmith close by that will do a better job at a reasonable cost. I may have him remount my scope with some new rings and install an aftermarket trigger. It's tempting to chop the barrel to 18 inches since I keep hearing shorter and stiffer is better. Others disagree. It's not like its shooting bad either, seems like a gamble that might not be worth taking.

I would not do anything to the barrel until you have done a post bedding load workup. Also, I have known a lot of so called gunsmiths that do not do match level work. The important thing is not convenience, but rather performance. When he installed the scope, if the rings were not the Burris ones with the inserts, did he bed the base to the receiver and lap the rings. or did he just screw things together?

 

[Bidwell]

I would not do anything to the barrel until you have done a post bedding load workup. Also, I have known a lot of so called gunsmiths that do not do match level work. The important thing is not convenience, but rather performance. When he installed the scope, if the rings were not the Burris ones with the inserts, did he bed the base to the receiver and lap the rings. or did he just screw things together?

I ended up calling Magpul today. The tech there was really helpful. Gave me a few pointers like torqueing the front action screw down first then the second. Then try incrementing the torque by 1 inch lbs if I'm still getting a poi shift on the cold bore shot. He didn't recommend bedding since it shouldn't be necessary with the aluminum frame of the stock. But, didn't say I couldn't do it either. Basically, he said he's heard of people having these issues and likely it's due to uneven torque on the action screws. I did use a torque screwdriver though. But maybe the action isn't quite perfectly set in the stock. I'm starting to lean towards an improper install since my cold bore poi shift is almost 3 inches, that seems way excessive for a shift caused by the warming of one bullet.

I actually installed the scope myself with the Burris zee rings. I'll be the first to admit that this could be at the minimum compounding any shifts in poi.

 

[Bama73]

My pillar and glass bedded savage Axis did this last year unbeknownst to me. First cold bore shot was 7" high. Each successive shot was in the normal spot. Cost me a nice buck. Turns out my front action screw had backed off some. Re torqued them and back to normal.