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Old 260 Remington barrel

7K views 15 replies 9 participants last post by  mrdux 
#1 ·
About a year ago I bought a used Remingtom model seven in 260 remington caliber with a 20" brl.. Based on the info I dug up I decided to try some 120 grain factory loads for the upcoming deer season. After several boxes of Remington and Federal loads I could not get the gun to shoot very good groups. Most were around 2-1/2 MOA.

I sent an email to Remington along with the serial number of the rifle and they told me that my rifle had a 1 in 10 rate of twist and that it would not stabilize the shorter bullets well. They suggested I try the 140 grain Corelock bullets and WALA, 1 MOA groups. This is new ammo, not 10 year old stuff.

I'm zeroed about 1" high at 100 yds. and they are hitting almost 8" low @ 200 yds. Based on the data in the Nosler book I have they should only be about 2" low @ 200 with a +1" @ 100yds. Unfortunately my Chrony does not seem to work all the time so I didn't get any true velocity readings. I'm going to try again the next trip to the range and see if I have any better luck. Also, from the Nosler book, if my MV is about 2200 FPS I would expect to see -8" @ 200yds.

Something doesn't seem right..... Does anyone have any thoughts??

Also, If I were to handload some 129 grain Hornadys would the 1 in 10 twist stabilize these bullets or would they be too short as well?
 
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#2 ·
it sounds like the ammo isn't delivering the advertised speed. to be honest with you 2 1/2" is fine for most deer hunting ranges, basically your shots are hiting within 1.25" of your point of aim. how were they grouping at 200?
i find it hard to believe that the 120's wouldn't work in your rifle but anything is possible...
 
#3 ·
The first thing that I do is clean the snot out of the bore to make sure there is no Copper fouling . I find it hard to believe that 1/10" twist won't stabilize 120 Gr. bullets in the .260 Rem . I shoot 120s in my 7mm-08 with MOA accuracy and it is also 1/10" twist . Make sure that bore is clean and keep tinkering with different loads , bullets and powders , it will shoot if it's right !
 
#4 · (Edited)
The bore is clean and in good shape. Like I said I get right on 1 MOA with the 140 grain bullets. I was thinking maybe the oglive is too far from the lands when using the 120's. Seating them out a little further might give better results. Remington's recomendation to move up to the 140 grain bullets was spot on. I'll chrono them and find out for sure what the velocity is. If the factory stuff really is only going 2200 FPS this becomes a malign load and I'm changing to something else.

I'm curious to know if anyone else had similar expierences with this combination. Do you think the 129 hornady's will shoot well out of a 1 in 10 barrell? The 200yd groups were just over 2-3/4".
I only shot 2, 3 shot groups @ 200yds. That range would be verrry long in the deer woods of PA where I hunt. I do shoot groundhogs whenever I get the chance though and that's why I really want 1MOA out of this gun.
 
#5 ·
DC,

There is definitely something wrong, there. It sounds like you're not getting anywhere near the velocity you should from that 140gr Remington load. I don't blame you for not being happy with 2-1/2" groups at 100 yards but I can't figure out why that gun wouldn't stabilize the 120gr bullets. It's not like those are light-for-caliber and 1:10 should not over-stabilize the 120s, nor should they come apart.

You're not shooting open sights, are you? If you're getting a 1" group at 100 yards, I'm presuming you have a scope on the gun, but if you have open sights, that might help explain being low at 200. I would for sure run those factory loads over a chronograph and then sight in about 3" high, unless you're really anticipating shots of 100 yards or less.

More than anything, I would do like Oneoldsap said: Clean the gun really well and then maybe check the stock/action to make sure everything is tight and bedded properly.
 
#6 · (Edited)
Bullets too short will be overstabilized, not understabilized. It is bullets that are too long that become unstable. The result of overstabilizing may be a little bit of extra wobble that opens groups up a bit, but not usually hugely. Admittedly a 140 grain Core-Lokt is about ideal for the 10" twist in that caliber, but the 120's aren't overstabilized nearly as much as a 150 grain bullet is in a .30-06 with a 10" twist barrel is, and they can still shoot quite well. I think the main problem you are having is just that the loads weren't optimized for a 20" barrel. If the freebore is on the long side, that may work better with a 140, too. If you start hand loading though, I'm sure you'll be able to make 120's and 129's shoot. Read Dan Newberry's site for what I think is the best way to go about it, especially for loads that need to be within SAAMI length for magazine feeding in a hunting rifle.

24" barrels with a tight SAAMI minimum chamber is what the published muzzle velocity will be figured with. Remington claims 2750 fps MV for their 140 grain Core-Lokt load. Allowing that your gun will likely have a roomier chamber than the test gun and that it has the shorter barrel, I think 2600 fps is a more realistic expectation.

If I use a sight 1.5" above the bore line, my computer generated tables show only 2.7" drop at 200. If I go to iron sights .75" above the bore line, then 200 yards becomes 3.6" low. Either way, 8" isn't likely. Iron sights have POI affected by lighting conditions (light's up sights up) if they are what you are using? Also, is the 200 yard target accurately surveyed? If it were 250 yards, you'd be getting closer to that 8" drop point.

I suggest you try zeroing at 200 yards, then firing at 100. I show you should then be about 2.4" high at 100 and well within the 8" deer kill zone. If it is a lot higher, when you move back, we're missing something.
 
#9 · (Edited)
Unclenik has a good point on the "200yd" target. Maybe it is closer to 250. I'll verify that. I'm using a Leupold 3-9 vari X II compact scope. I don't believe the problem is in the cleaning or bedding or anything like that because the 140's do so well.

I would have thought that I had a bad box of factory bullets but I shot 3 boxes of Federal 120's and 3 boxes of Remington 120's and got the same results pretty consistently. Based on Remington's recomendation and the good results I got from switching to the 140's I just gave up on the 120's.

First I think I'm going to chronograph the 140's and verify range of 200 yds and verify the 8" drop.
Then I think I'll try working up some 120 or 129 gr. loads and see what kind of results I get.

I never heard of overstabilizing a bullet before. Basically it roataes too fast and comes off of it's axis??

I use a +1" @ 100 yd zero because I like to shoot groundhogs over the summer and most shots are inside of 250yds. So out to about 150 I can pretty much hold on the hog, or GROUND GRIZZLY as I like to call them, and I compensate for drop beyond that. 200 yards would be a mighty long shot on a deer for me. Of all the deer I've ever shot I can only think of 2 that were over 100 yards and one of them I shot with my Freedom Arms 454 Casul.

I figured the lighter bullets were a lost cause. I'll keep at it a little longer. Thanks for all the advise!
 
#10 · (Edited)
I have a older Model 7 with the 18.5" barrel, and it shoots 120s and 129 Hornadys very well. The 129s are my prefered bullet weight in the 260. Quite honestly, Remington has proven once again that they have their heads you know where. The 1-10" twist is marginal for a 140 grain bullet and useless for 160 grain bullets unless you push them faster than the 260 is capable of.

Load some 129s or 130 Noslers over H4831, Rel-19, or Rel-22 and you should see 1-1.5" groups if you do your part. I use winchester's discontinued WXR powder and get groups under 1" and almost 2700FPS out of the stubby model 7 barrel. Rel-22 and WXR are the same powder but different lots, so that may be where I'd start if I were you. Somewhere around 45-46grs.
 
#11 ·
About a year ago I bought a used Remingtom model seven in 260 remington caliber with a 20" brl.. Based on the info I dug up I decided to try some 120 grain factory loads for the upcoming deer season. After several boxes of Remington and Federal loads I could not get the gun to shoot very good groups. Most were around 2-1/2 MOA.

I sent an email to Remington along with the serial number of the rifle and they told me that my rifle had a 1 in 10 rate of twist and that it would not stabilize the shorter bullets well. They suggested I try the 140 grain Corelock bullets and WALA, 1 MOA groups. This is new ammo, not 10 year old stuff.


Something doesn't seem right..... Does anyone have any thoughts??

Also, If I were to handload some 129 grain Hornadys would the 1 in 10 twist stabilize these bullets or would they be too short as well?
Your 20" barrel, with it's 1-in-10" twist, should stabolize 120 grain bullets. I could see that it would NOT stabolize anything 140 and over due to the barrel length and rate-of-twist. Normally a 6.5 caliber has a 1-in-8" twist for 20 inch barrels. If your barrel was 22"-26" then the 1-in-10" twist would work with 140 grainers. In this case someone at Remington was incorrect saying that a 140 gr. would stabolize better than a 120 grain bullet. I once owned a custom rifle in 6.5 Roberts and it had a 1-in-8" twist and it shot bullets of 120 grs. to 160 grains very accurately.
 
#12 · (Edited)
Dcsnyder,

Overstabilized just means spinning faster than is optimal. That exaggerates any small imperfections in mass symmetry in the bullet, such as might be caused by slight unevenness in jacket thickness or from a core void. That increases the wobble. It also increases bullet yaw which increases drag a bit.

It is also possible to understabilize a bullet short of going completely unstable. This allows perturbations in the bullet nose that occur at muzzle exit to go underdamped. The bullet path is then actually helical as the nose spirals around the average trajectory position, and may never settle before reaching the target.

There is quite a range of twists over which high quality modern bullets with its nearly perfect mass asymmetry will fly function reasonably well. A gyroscopic stability calculator, like the one on the JBM ballistics site, will return a number called the gyroscopic stability factor, s, such that a bullet with a gyroscopic stability factor of 1.0 will be on the edge of instability. Below 1.0 it will be unstable and the nose will describe ever widening circles until the air finally pushes the nose hard enough to cause it to tumble. Above 1.0, the bullet is more and more stable for the reason that the faster you spin a gyroscope, the harder it is to turn it to a different direction.

Sierra suggests s should must fall between 1 and 3 for rifles, but that is just to function. 1.3 to 2.0 is recommended for best flight by Don Miller and Harold Vaughn feels 1.4 is an ideal compromise between spinning too little and spinning too much, while Miller and a couple of others like 1.5. I've seen a number as high as 1.7 suggested as optimal, which is what the military's preferred 11" twist M14 match barrels get with the old 173 grain match bullet.

Military guns are often set up for more like 2.0 to 3.0 with ball ammo (though they sometimes have had to change when they got it too low, as with the original M16 twist). This is because of the need for light-for-length ammunition, like AP to be stabilized and for ammunition to remain stable in extreme cold anywhere in the world. For example, a Springfield or Garand with 10" twist fires a 152 grain bullet at 2800 fps, giving it an s=2.9, just a shade under Sierra's recommended upper limit. It still shoots OK.

In the case of your bullets, I found the 120 grain bullets would see about s=1.9. Not right on the optimal number, but just fine by Miller's 1.3-2.0 critera. A 140 grain CoreLokt seemed to be right at about 1.50 at your likely velocity of 2600 fps or so. Very nice.

Why should that CoreLokt be so ideal when others are saying 140 grain bullets won't stabilize in this barrel? It's because weight and velocity are lesser consideration in stability than length. Length is by far what matters most because length is what provides the lever arm by which air pressure overturns a bullet in flight, making it tumble. Shorter is therefore easier to stabilize and longer is harder.

From the same barrel, a flat base, round nose bullet and a long boattail the same weight, fired at the same velocity, will have dramatically different stability numbers just because of their difference in length. Thus, a .308 150 grain Sierra round nose at 2800 fps only needs an 19 inch twist to fly optimally, while a 150 grain Sierra MatchKing bullet at the same velocity wants a 12" twist for similarly optimal stability.

So, when people say a twist won't stabilize a certain weight, it usually means some bullet or bullets of that weight have not been stabilized by it. When gun writers make the statement, assuming they are cognizant of the fundamentals, then it is a generalization that bullets of this weight typically have lengths great enough that this twist won't stabilize them. Not that there are necessarily no bullets of that weight that the gun can stabilize.

In case of your 140 grain CoreLokt, it is simply short enough that it does well with the twist you have. It's about 0.1 inch shorter than a Sierra MatchKing of the same weight. Where your 10" twist is about perfect for the CoreLokt, the MatchKing wants a 9" twist to get the same s value. With the 10" twist I get s=1.2, so it should not be unstable, but won't be inside Don Millers optimal range. A Berger 140 grain VLD will be 0.2" longer and will be unstable in the 10" twist barrel (s=0.97) and would require an 8" twist to be optimally stable.

Some will suggest just increasing velocity to increase stability, but the effect is much less than length or twist change produces. This is because even though the greater velocity makes the bullet spin faster, it also pushes the bullet nose into the air faster, so that it needs that extra spin to be stable against the additional air resistance. The latter doesn't fully cancel out the former, but the net stability increase produced is modest. For the Berger bullet to achieve s=1.50 in a 10" barrel like the CoreLokt has at 2600 fps, the calculator says it would have to be driven at close to 10,000 fps; not something it would survive even if it could be done.
 
#13 ·
So Remington was correct in telling me to switch to the 140's due to the longer bearing surface ( on the lands) of the flat base corelock bullet? But, as you suggest, a boat tail bullet of the same weight, in a boat tail design may lack adequate bearing surface.

So, the 120's are shorter, assuming the same flat base design the it makes sense that they would not stabilize as well as the longer 140's in a 1/10 twist but they may stabilize better in a 1/9 or 1/8 twist. That make sense to me.

By the way I fugured out what's up with the 8" drop @ 200yds. The target I ws looking at was one I used just to "get it on the paper" it was not the one I used once the gun was zeroed +1" @ 100 yds.

I'm 4.5" low @ 200yds. Your estimate of 2600 fps sounds about right to me now.

Turns out, I'm and idiot!

I think I'm still going to tinker with the 120's. Everyone else seems to be able to shoot them with satisfactory results. I'll play with the OAL a little and see what happens.

Thanks!
 
#15 ·
So Remington was correct in telling me to switch to the 140's due to the longer bearing surface ( on the lands) of the flat base corelock bullet? But, as you suggest, a boat tail bullet of the same weight, in a boat tail design may lack adequate bearing surface.
Longer bearing surface will help the bullet line up and not tip in the bore. Than can help with accuracy. The issue with the boattail for stability has to do with its total length and not its bearing surface length.

So, the 120's are shorter, assuming the same flat base design the it makes sense that they would not stabilize as well as the longer 140's in a 1/10 twist but they may stabilize better in a 1/9 or 1/8 twist. That make sense to me.
Backwards. The 140 grain CoreLokt, which at 1.22" is short for its weight, likes the 10" twist at 2600 fps. The shorter 120 grain CoreLockt, at 1.075" length, only needs an 11.25" twist to get to the ideal s=1.5 at about 2750 fps (what I think it might get to from your barrel). The shorter bullet has a shorter lever arm from its center of gravity for the air resistance to try to push it off course with, so it needs less spin to be stable. The 10" twist will slightly overstablize it, but not enough to be a problem.

Seating depth may provide a solution. A bullet runout gauge may help? In some instances it does little, but with some bullet and barrel combinations it can cause an inch or more of group enlarging.

Glad you figured out the drop problem. We all confuse ourselves at one time or another.

 
#14 ·
Remember that Remington brought out their .244 Rem. with a 1-in-12" twist which would only stabolize bullets under 100 grains. Remington viewed the .244 as a Varmint load which 80 grain would be more accurate at long range shots. While Winchester developed their .243 with a 1-in-10" rate of twist for bullet weights 100 to 105 grains, vewing the their .243 as suitable for Deer with 100 grain bullets. Eventually Remington changed the rate of twist in their 6 mm Cartridge to 1-in-9" to stabolize 100 grain bullets for Deer sized game. The simply renamed the .244 to the 6 mm Remington and dropped the .244 head stamp. Too late as the .243 over took both .244 & 6 mm in sales thus the .244 became obsolete leaving only the 6 mm with it's faster twist.
 
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