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I have a relatively new 270 win with a light weight stainless barrel. I don't reload but have found some factory rounds that group pretty well. The bore only has about 80 rounds through it. I can get 130gr SST's to group between 0.5 to 0.75 inches with three shots. However, after about a dozen rounds my groups start to widen out to 1.5 to 2.0 inches. Addtionally, the groups shift down a couple inches and to the left an inch or so. This has happened the last two ranges sessions and i started with a clean (or at least i think i had it cleaned properly) bore both times. I plan to go back again tomorrow without cleaning the bore to see where my groups start with a cold barrel. Any thoughts? "The best laid plans of mice and men often go awry" - Robert Burns | ||
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Self-lap it w/ JB bore compound. If that does not work, try different bullets. If that does not work, it may be one that you have to clean more often than others. | |||
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Heard of using JB but never done it. About how many laps we talking? "The best laid plans of mice and men often go awry" - Robert Burns | |||
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Depends on the length of time between shots as to groups opening up in regards to barrel heat . Fouling especially copper material left behind can also account for that . Clean the bore really good ; Fire # 5 rounds with 1-2 Minutes between each shot . See what the group looks like . Now go back repeat , using same time frame .If groups are opening up significantly then I would suspect Copper fouling is more to blame than barrel heat . JMO .  | |||
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I too woulud suspect copper fouling. Make sure the bore is absolutely clean - NO copper fouling. Use a good bore cleaner, then, if necessary, some Barnes -CR-10 or Sweets. Be sure to follow the instructions. It may well take some time for for the barrel to become conditioned and I would not use anything like JB except as a last resort. It may, in fact not be needed. Make certain your barrel is cool between shots. I always go by the feel of the barrel rather than the amount of time allowed between shots. Here in Fairbanks in the summer, it can be a very long time for the barrel to cool down between shots. Lottsa sun you know. Bear in Fairbanks Unless you're the lead dog, the scenery never changes. I never thought that I'd live to see a President worse than Jimmy Carter. Well, I have. Gun control means using two hands. | |||
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My first guess is that the constant sound of all that corn growing in Iowa is distracting your bullets and they aren't paying full attention to where they are going.  (Sorry for the corny joke.) After that, my suspicion would first turn to barrel heat. You might want to check to see that your barrel is really, truly, free-floated. A warm barrel can either warp or droop enough to touch one or more side (including maybe the bottom side) of the barrel channel, which WILL change point of impact. If the free floating is sufficient, I'd check the rest of the bedding to make sure the action screws aren't bottoming in their holes, and that the action is not bending slightly when they are tightened. If either of those is a problem, then something is going to chage, either for better or for worse, when the action is warmed by firing. Next, I'd check to see that the scope mounting is a good fit to the upper action surface, and tight to both the action and the scope tube. You can do the previously suggested J-B lapping either before or after any of my suggestions. The lapping won't harm the barrel using just J-B, and it may help tremendously. Even if it turns out it doesn't improve accuracy much in your instance, it will almost undoubtedly make the barrel a lot easier to keep clean. Good luck finding the answer(s) My country gal's just a moonshiner's daughter, but I love her still. | |||
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AC ; Not to argue only to inquire !. If a shot string rises or abruptly shifts left or right I would suspect the barrel touching or heat warp pressing on the channel .But doesn't shot string or group " Down " usually indicate fouling and therefore the loss of M V causing the shots too drop slightly ?. Is that incorrect ?. | |||
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I don't think there is any iron-clad answer to your question, Doc. His problem may very well indicate excess fouling, depending on how the particular powder burns, where in its "burn envelope" the pressures are at, what varnishes the burning deterrants lay down in the bore, and what the bullets may leave behind. (BUT, Is it not also possible that fouling or any other source of increased pressure may occasionally make for a better burn, and "increased" velocity?) It certainly is not always true that a barrel will shift postion enough due to heating to touch the barrel channel after just one, or just two, shots. Sometimes it takes three...sometimes a bunch more than that. Would you agree? Now, normally I would guess "most" gun writers say that barrels shoot away from wherever they touch the barrel channel...so, if they touch the bottom, they should shoot high. BUT, I don't think very many gun writers have a very good grip on the harmonics issues of barrels. Depending on he nodes, amplitudes, and frequencies created when the barrel touches the channel SOMEWHERE, it can end up moving the point of bullet impact darned near anywhere. Barrel harmonics are not simple phenomena, but very complex ones. I also think most gun writers have read somewhere years ago not to let a rifle barrel touch a tree or rest when firing because it will shoot away from said rest or tree. Then they leap to the conclusion that the exact same will always apply to touching the barrel channel too. Ain't necessarily so, as the old song goes. (The only reason it was true with the tree or other rest was because such a rest keeps the whole rifle from recoiling in the direction of the tree or rest. So it naturally does not veer as far in that direction as it normally would when fired, and the bullet lands farther in the opposite direction.) That's why I also suggested checking the scope mounting system, the stressing of the action when the screws are tightened, and whether the action might actually be a little loose in the stock because of the guard screws bottoming in their holes instead of drawing the barreled action truly snug into the stock. They all can contribute to the complex vectors which determine which way the bullet will ultimately fly. I only said I would start with those ideas I listed rather than with bore polishing because in my own personal experience they have been more productive in my "across the course" .30-bore, termite food stocked match rifles. But clearly, it COULD be any one or more of many things at work, including bore fouling. Best regards, AC My country gal's just a moonshiner's daughter, but I love her still. | |||
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AC ; Have you ever heard of using carbon paper and a thin paper ( I don't recall the type or name at the moment ) where one lays it down the barrel channel .Set in the action tightening the screw properly then off too the range . After firing a few sets disassemble and see where if any rub marks have transferred too the paper via carbon paper . I read something about that some years back and I'll be dammed if I can remember where now . Doc ... | |||
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Just a thought - I have more often than not (always actually) found that the grouping will shift down with increase in velocity. If this were so, then GrayDuck 'could' be experiencing heat and fouling build-up causing higher chamber pressure. Not sure that the groups would open up though, unless it's the fouling. But then surely GrayDuck would have noticed the fouling? Regards 303Guy | |||
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Boy, Doc, you have now put yourself square into a select group of us, known as "Really Old Pharts With Guns". Carbon Paper!!! Migawd!!! And, I presume you mean "Onion Skin Paper" too!! Here I thought I was maybe the only living human being who still has and uses a working old Remington manual typewriter! (Yeh, folks, made by the same GUN company.) I also have an old L.C. Smith "Tripewriter" (Smith-Corona, actually). Not to mention a much newer IBM Selectric 3 which I bought in 1981....Hell, it's still a mere baby, only 28 years old, barely broken in. Yes, I've heard of that method, and it works. I had just forgotten all about it. In my opinion though, it is mainly useful for rifles which intentionally have a pressure point out in the forend. Enables one to see how/where the pressure point is actually bearing. Of course, if a person has an "accidental" pressure point, it WILL pick that up too, but.... If a rifle is only clearing the stock by enough to let in a sheet of carbon paper on top of a sheet of onion skin paper, then it isn't actually free-floated at all to my way of thinking. Almost any barrel only floating with that tiny amount of clearance will frequently be subject to hitting the stock during the vibrations of actual firing. That is particularly so in termite-food stocks, which for the most part are living, moving things, always warping a minute amount in one direction (or several) as ambient humidity changes. Carbon Paper!...Onion Skin Paper!....Heavens to Murgatroid! Next thing you'll be telling me you still type stencils for that old mimeograph we used to make copies of our typed work before photostatic copiers were "invented" by Xerox..... I remember lots of nights as a very young sports reporter sitting up 'til 3 or 4 in the morning after games, fights, et. al., pounding those stencils out, correcting them, then inking them up and running copies for the editors and typesetters before the 5 a.m. press run in Honolulu....they were the only way to go, though. Ever try to correct the fifth carbon copy of anything well enough a cranky old typesetter could get it "set" right when reading at breakneck speed? .....and where do you think I got my first linotype bullet metal?....hadda keep those guys happy. Best wishes again, OLD PHART!! My country gal's just a moonshiner's daughter, but I love her still. | |||
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 Free float? Free float? I'll show you free float. Coming atcha. Sorry Doc don't have your E-Mail.  RogerOld age is a high price to pay for maturity!!! Some never pay and some pay and never reap the reward. Wisdom comes with age! Sometimes age comes alone.. | |||
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Boy, Doc, you have now put yourself square into a select group of us, known as "Really Old Pharts With Guns". AC ; I resemble that remark !.  I talked to an older friend whom I shoot with and it came up as sometimes useful in determining those " UNKNOWN " rubbing points . Obviously a free floating barrel IMO should be at least .020" clearance or #4 pieces of printing paper ( HP 24 lb. ream variety ). If one of my Rifles ever exceeds that warp factor ,it won't belong to me . My " OLDER " friend was born when Germany decided to Invade Poland , so he's got me by a few years !. Onion yep !! It wasn't rice or litmus I knew that much . Roger ; Shotguns don't count as free floating !.   | |||
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I'm certainly not the oldest guy participating here, but Heck, my dad and I listened to the "live" news reports of the German invasion of Poland on the short-wave 6 p.m. BBC news, as it happened. I've still got that large table-top multi-band Zenith radio, BTW. My country gal's just a moonshiner's daughter, but I love her still. | |||
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Oh, yes. Light "whippy barrels". I LOVE these guns!!! Just shoot, Clean, shoot and clean. Nothing magical. You can check your bedding, but from what you said in your first posting is natural. Heat and fouling will open your groups. Just use a GOOD copper solvent, as directed. Make sure the bore is free from fouling. Shoot and cool. Shoot and cool, then CLEAN!!! Time, and care will tell. My "whippy barreled" guns have many shots and PROPER cleanings eventually do things that make me feel very happy and satisfied. I had a Winchester FWT .25 WSSM that gave me FITS!!!! It would group sometimes, then crap on me after I thought things were good. Things started to improve, after many shots. One day. An old guy told me of my improper sand bag position when firing this rifle. I had my front bag too close to the stock end. Once I positioned the forward bag closer to the. magazine ,groups improved. This rifle is now amazing. I just worked a 80 gr. Barnes TTXB load that hauls ass at 3650fps, and groups .50" Just keep working with your fine rifle. These little rifles need lots of care, cleaning and time to really find the "jewel" in them. Good Luck. "The lady doth protest too much, methinks" Hamlet III/ii | |||
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Hi, 303Guy. - Sorry I didn't get to responding to this when you first posted it. Yes, sometimes bullets impact lower when velocity is higher. But not always. I have some rifles where they do, and others where they impact higher....mostly the latter. There are more than a couple of things involved. One is that increased velocity means decreased time in the barrel for the bullet. If the barrel is rising substantially, that may mean the bullet will strike lower because it left the barrel before the barrel raised as much as it did with low velocity loads. Another thing is the decreased time of flight with higher velocity. Faster bullets have less flight time to get to the target, so there is less time for gravity to pull the bullet downward...thus contributing to HIGHER impact on the target. This is particularly applicable in short range shooting where the flight becomes very short, time-wise. Another consideration is the amount of recoil generated by higher velocity loads. Usually, higher velocities (in the same cartridge case and with the same bullet) require more powder and create more powder gas ar higher pressure for a longer duration of time. That tends to increase recoil, which in turn raises the barrel higher, again RAISING bullet impact. Yet another consideration is how the rifle is fired. If the right handed shooter is using his left hand to pretty firmly hold the forend, muzzle rise will be reduced, and so will the resulting height of bullet impact, etc. If he holds the rifle differently between his "hot" high velocity loads and his "moderate" low velocity loads, more difference will appear. For instance, in my benchrest rifles, where I do not hold the gun with either hand when firing, faster loads always impact higher than low velocity ones. The guns are free to recoil upward any amount the charge will move them (which is why it is called shooting "free recoil" style). There are lots of other factors, such as whether the bullet just happens to leave on an upward oscillation of the muzzle, or a downward one...which is more complex, but does vary with velocity. Anyway, am sure you can think of more contributing elements. It is enough simply to know it can do either. Only experience with a particular rifle and manner of holding it will tell for sure in any particular circumstance. Best wishes, AC My country gal's just a moonshiner's daughter, but I love her still. | |||
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Thanks AC. You are right. It is only sometimes that it happens like when switching from a heavier, slower bullet to a lighter faster one, the lighter one often shoots lower. That would be due to longer time for the muzzle to lift during recoil as you mention. It does happen quite oftem with my Lee Enfields and I seem to think with my hornet too but there the changes are small. With a barrel heating and transfering heat to the cartridge in the chamber, it could concevably happen that the resultant pressure increase could lower the POI. If bore friction was simultaneously reduced by virtue of expansion, .... who knows what the effect might be? Anyway, it is thought provoking.  Regards 303Guy | |||
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