.243 Drifting Groups

[benjamin1031]

Hey guys, still pretty new to shooting and reloading so I wanted to tap into a little knowledge if I may. First of all I'm shooting a remington 700 SPS varmint LH in a .243 win. I've free floated the barrel and broke it in how it was recomended to me here( cleaning barrel between every round for 20rds then between groups ect.). My load is BR2 primers with 45grn of H4350 and a sierra 80grn SBT (will be switching to 95grn VLD soon). When I go to the range it is sighted in well until the barrel starts getting warm once the barrel is warm (15-20rds in 30min) all groups move about an inch and a half to the right. Elevation is fine but not sure why groups are drifting right. What the hell?!?! Any help would be appreciated. Ben

 

[Kenny474]

That is something that happens when a barrel starts getting hot, probably too hot. It is very common in rifles with sporter weight barrels, though thicker barrels are not immune either.

When barrels are made stress is put on the barrel in a number of ways, machining, rifling, fluting if the barrel is fluted, basically everything that is done to it puts some degree of stress on the barrel. Factory barrels are often straightened as well, where they are basically bent slightly in a press to make them perfectly straight if they were a little off. When you heat the barrel the stress retained in it can often make it shift a bit, causing the shift in group you are seeing. That is why most barrels are often "stress relieved", where they use different kinds of heat and cryogenic treatment to relieve that stress. I am not quite sure of exactly what they do, so someone else can probably explain that a bit better than I.

In my opinion, the action should have been bedded before the barrel was floated. For any rifle to be accurate the action needs a rock solid foundation. If it isn't fully supported, removing material under the barrel could hurt more than help. It may not be causing your issue, but it's something I would address.

Did you shoot the rifle prior to floating the barrel? If so did you have the same group shift?

When you are shooting, lay your hand on the barrel after a few rounds. If it's too hot to touch, let it cool down.

 

[Quackaddict]

That SPS stock is a joke, I bought in a 243 Win varmint with that stock and could see different points of impact depending on if you loaded the bipod or just held as light as possible. Even though you free floated the barrel, I would suspect that POS stock, find a used HS stock for 200 bucks, or something that is rigid and see what that gives you.

 

[Kenny474]

I had thought about the stock as well, but since it only happens when the barrel is warm brings my concern to the barrel. Though the added heat could be causing the stock to flex more, I would think the groups would be more erratic than a consistent 1.5" shift.

 

[tome]

Mine's a varmint contour & haven't had that problen..a 243 will heat up fast..espically in summer temps...don't shoot it till it's hot... it sounds like that's what your doing ..243's aren't known for long barrel life...and shooting it hot just shortens it..if you can't lay you hand on the barrel..it's to hot..also check scope bases..rings & stock bolts for tightness ...take another rifle w/ you..when the 243 starts to get warm..shoot the other rifle till the 243 cools down

 

[CanusLatransSnpr]

I'm with Quackaddict on this one, although I can appreciate where Kenny is coming from also. The stock on the SPS varmint leaves a whole lot to be desired. The stock alone was enough to scare me away from buying one. I could just see way too many potential problems with the way that gun was set up. Best of luck to you though!

Mike

 

[benjamin1031]

Rest assured I am aware of the SPS stock's shortcomings. The reason I bought one is because I believe that the 700 is a good starting point for me to get into long range shooting. I am going to try to not let the bbl get so warm when at the range but a far as the stock lets face it not everyone can just go drop 200 bones on a new one just because the one on it sucks. Is there anything that I can do for the stock that doesen't involve me spending 200 bucks?? Eventually I will buy a stock but right now I'm needing inexpensive solutions. And thanks for all the great info. Ben

 

[Kenny474]

I am unsure if it will work in your application, as I am a Savage guy, but Numrich has 40x centerfire stocks for $55. I have heard others say they are a good starting point, though I am unsure what would be needed for a repeater, as I know a lot were single shot. I am sure others will be able to let you know, or maybe have a cheaper solution.

Good luck

 

[SS427]

I agree the stock needs to go. I also think you are shooting too many rounds in the course of 30 min and your barrel is over heating.

I take 4 rifles to the range and over the course of 3 hours shoot 5 five shot groups in each. Even at that pace my barrels can still be a little warm when they come back up in the rotation. If I don't take 4 centerfire rifles, I toss in my 22 LR and plink with that while the barrels cool on my other guns. Shooting the bull is another good way to cool barrels.

Heating might not be your problem, but it could be.

 

[tome]

I dodnt know what you did to that stock to free float the barrel..the inside construction of that stock precludes bedding..i would try various soft shims between the barrel and the forend tip..keep adding or subtracting till you have steady tight groups..i had to do this w/ a ruger 1v..some rifle/stock combos work best w/ forend pressure on the barrel..all this costs is time & ammo..try some Varget & sierra 70 gr matchkings..shoot great in mine

 

[benjamin1031]

Means how I'm a total novice. I'll tell you how I floated the barrel. I used stainless shim stock between the action and the stock on the forward bolt that holds them together. Then based on some advice I heard here. I I tightened the two screws as tight as I was comfortable then backed them off a quarter turn at a time until the groups were as tight as I could make them.

 

[tome]

take the shim out...try some 165-170 gr loads..if no good..shim under the forend..if you look at the inside construction of that stock..the barrel was never ment to float..start over..dodn't over heat.

 

[Laurie]

Ben,

the odds are the drift is, as others have said, almost entirely due to heat - plus, what nobody has said, Remington using hammer forged barrels. They're made by boring a short, fat blank, inserting a mandrel which has a mirror image of the barrel interior including the chamber machined into it, and feeding it into a hammer forging machine that belts it along the length of the blank with a series of opposed hammers around the circumference. What was short fat blank is now a long thin barrel and the mandrel is pulled out leaving it rifled and chambered. Obviously, it's a bit more complicated than this crude description, as seen in the 2nd of the links below, but that's the general principle.

http://www.rifleshootermag.com/gunsmithing/RSgunsmith1/

http://technology.calumet.purdue.edu/met/higley/NotesOnHammerForgedBarrels.pdf


Most factory rifle barrels are hammer-forged. The equipment is expensive and the operators need a lot of skill and experience, but once up and running it turns out long runs of barrels very cheaply, hence nearly all large scale sporting rifle manufacturers using it, and all military weapons now have barrels made this way.

Apart from low cost, pros are a very smooth and hard finish, so life is good. Cons are it is a brutal way to treat a chunk of steel and inserts enormous stresses into the metallic grain structure. Even with post manufacture inspection, stress relieving and straightening, they tend to bend a little as they heat up, hence wandering groups. Not all hammer forged barrels do this, so it's a lottery as to what you get. To be fair, people like Remington have been using this process so long and are so good at the inspection / rectification, it's a rare example that does it really noticeably nowadays, but many will do it a little after half a dozen to ten shots.

The manufacturer can say reasonably enough for sporters that it's first / second shot accuracy in a cold barrel that count, and as long as they're consistent, the rifle doies what it's intended to do.

If this is the problem and from your description it sounds like it, restocking or playing with the bedding won't help. The cure is either keeping the heat down by shooting slowly and/or having regular breaks to let the barrel cool down, or rebarrel with a cut or button rifled custom production job from a barrel-making shop.

Nobody now makes target rifle or really top quality varmint rifle barrels this way. The nearest you get are heavy barrel sniper rifles from the likes of the Austrian Steyr company with its SSG series, FN-Herstal and so on. They have a huge amount of experience and do a lot of testing / rectification before fitting their barrels, so the results are pretty good, but rarely up to Krieger or Bartlein standards. You get what you pay for at the end of the day!

The long defunct English company Parker-Hale Ltd of Birmingham made all its barrels this way including for its various target rifles. They mostly worked OK by the standards of the day, a few worked brilliantly, and a few were absolute dogs and just wouldn't shoot or suffered severe impact changes. P-H was very good at taking any such rifle back and rebarrellong it free of charge to keep the customer happy. I had an ex-police P-H M87 sniper rifle in .243W (actually still have it but now with a 6.5mm Bartlein on) and it did just what you describe, but not nearly as much, maybe moving a half inch to one side at 100yds. You just compensate for it once you know its little tricks. In your case I'd see if Remy will put it right if you complain as you've got a major POI shift there..

Laurie,
York, England