Re: Strange Groupings

29 November 2004, 14:49

Ku-dude

Jim,

There are a couple of things to consider. First, from what you say, you were working up this load and got to a particular velocity and this started. If this is so, you may want to add another .5gr of powder if the load was safe, and continue to work up the ladder. One would expect to find harmonics that do what you are describing (two bullets right on the peak and the next a little before or after).

Second, once you arrive at the velocity you desire, if you have not previously experimented with seating depth, you should. I'd start by slicing a case neck on an old case, insert a bullet far enough out to engage the rifling, and chamber it. Remove it carefully and measure the overall length. Do this 10 times and take an average. Then back off this length by 10/1000 as point of beginning.

Third, you don't say if you are letting the barrel cool or not. If so, with a light barrel, it may be barrel heat. Let it cool and try three shots from a cold/cool barrel.

It would be helpful to know which of the three shots is drifting out. If it is the third, I'd opt for heat.

Practically, very few animals are going to let you take three shots at them. If you missed with the first two, you ain't gonna get a third shot. Ku-dude

29 November 2004, 12:01

djpaintles

Denton, Maybe I was just too lazy. I hated manual figuring standard deviation when a spreadsheet would do it for me.
I know that there are some types of statistics that are very useful for shooting, in Long Range Black Powder Shooting we load for low velocity variation because thats what will make your shots string vertically. I just get a little frustrated separating the wheat from the chaff as far as useful statistics go.
I have no idea why it is so Statistically, but in my hunting rifles I feel a lot more secure about a hunting load that shoots 10 3shot groups well on 10 different days than one that shoots 3 10shots groups well on the same day. I want a gun that shoots a load the same in varying conditions not necessarily one that shoots a statistically more valid # of shots etc. Oh and thanks for having a sense of humor I wasn't trying to be too mean to anyone.........DJ

30 November 2004, 13:00

Hot Core

Quote:

Sunday, I went out and shot some 5 shot groups. It's funny. I used to always shoot 5 shot groups, until some folks on this board convinced me that I should be doing 3 shots. The "flyer" tends to be the 2nd shot. As a generalization for 5 shots, I get the 1st and 3rd touching, the 2nd at the greatest distance (1.5 or 2 in.) and the 4th and 5th somewhere in between. I have tried varying COL. I am now on to trying different powders.

Hey Jim, Due to the thin barrels I typically use, once I finally get a Load Developed, I'll normally go to "Combined 1-shot Groups". I do shoot 3-shot groups during the early Load Development. But, everyone should use what gives them the most confidence.

It appears from the above that the shots which open your groups are "not necessarily" related to the barrel getting hot from repeated shots and changing position due to internal barrel stresses. That looks like GOOD NEWS to me.

The BIG problem is it could be due to a whole list of things including "cleaning" if you are not doing so at the Range. Could be the old loose scope base or rings, an internal scope problem, movement of the action in the bedding, inconsistent lock time(clean the bolt).

Quote:

I am using IMR 4350 with 140 gr. Nosler AccuBonds.

It still might be as simple as not having tried the correct Powder for your specific rifle. One other thing which is very aggravating is that occasionally, for some unknown reason, a particular rifle just doesn't shoot a specific bullet or a specific bullet weight as well as it does others. Just because "you"(or I) like a specific Bullet or Powder doesn't necessarily mean every rifle will.

It may be as simple as shifting to H4350 or H4831. Or perhaps a 130gr or 150gr bullet is what your rifle will just shoot the best. If you have a few on the shelf, try them. Or perhaps you can swap for a few with a buddy.

Perhaps try a box of 130gr Fed, Rem, Win Factory Ammo and see what it does. You at least end up with some more cases this way.

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Meanwhile, don't let it put you in a negative mood when you are shooting, or you may have to re-shoot those particular Loads. Keep good "Records" so you can sit back in the old easy chair and study the Targets and Loads in your 3-ring Load Development Binder.

Enjoy getting the Trigger Time, because you have a fine barrel and there will be a point where it all comes together.

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Make sure your rifle is empty and go in a very quiet, slightly dark room with it. Sit down and Dry Fire it a couple of times with your eyes closed and concentrate ALL YOUR ATTENTION on the Sear Releasing. Use the very "tip" of your trigger finger on the trigger and see if you can detect ""ANY"" creep or drag at all. If you can, the problem might be as simple as "Polishing" the Sear Surface on that "easy to get to" M70 Trigger Assembly.

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Best of luck to you.

P.S. You are NO WHERE NEAR needing a bunch of statistics to confuse this issue further.

29 November 2004, 14:18

zoomzoom

I've always tested my loads with 4 shot groups.......if I had any flyers I would work on it until the flyers were no more...pretty simple I guess.

Didn't need to use any science type data.......they never get over arguing about science anyway.........evalution versus creation is a good example...........I go for the creation theory myself.

Oh, back to the bullet group thing.....the shelf of Trophies from my HUNTING rifle says my theory works pretty good....even up against a few varmit shoots in the past.

29 November 2004, 12:28

denton

Quote:

I hated manual figuring standard deviation when a spreadsheet would do it for me.

Everybody ought to do that once, but more than once is very disrespectful of students' time and energy.

30 November 2004, 05:56

Jim in Texas

Quote:

Hey "Jim in TX", Just curious if the shot going wide is "always" the 3rd shot, or can shots 1 & 3 or 2 & 3 be making the smaller group?

Sunday, I went out and shot some 5 shot groups. It's funny. I used to always shoot 5 shot groups, until some folks on this board convinced me that I should be doing 3 shots. The "flyer" tends to be the 2nd shot. As a generalization for 5 shots, I get the 1st and 3rd touching, the 2nd at the greatest distance (1.5 or 2 in.) and the 4th and 5th somewhere in between. I have tried varying COL. I am now on to trying different powders.

27 November 2004, 20:22

djpaintles

Quote:

And 3 shots is not a good number to base any decision on...

This isn't necessarily true. In a hunting rifle if a given load puts 3 shots into less than 1" at 200yds every time from a cold barrel you have a heck of a load and a great hunting rifle. If you have to take more than 3 shots at a big game animal you probably need more practice from field positions than from the bench. Target rifles and varmint rifles of course are a different story.

I've had a couple Winchesters that had the same problem. I Cryo'd a 375 H&H that would put 2 in the same hole and then the 3rd was always off somewhere else in no particular order of the shots. After Cryo'ing the rifle didn't put 2 into the same hole like it did but it would put 3 into 1" or so - which was OK for the 375. I don't think it was just flinching on the 3rd shot because on the same day my 416 Rem M-70 was shooting 3/4" groups regularly and it definitely kicks a good bit more than the 375. The reason I cryo'd the 375 was I had a theory that maybe the Hammer-Forging process winchester uses to make it's barrels might sometimes leave some built up stresses in the barrel. With only 1 barrel froze it's too soon to tell if my there is anything to my theory or not but it did help the one I cryo'd.

Another factor (probably less likely than the others mentioned) that might be worth checking is the concentricity of your Ammo. I've been starting to check more and more of my reloads and it is surprising how much it can vary. I checked some 270 reloads that I had made and the same lot of 50 loads the Concentricity varied from .0012 runout to .006 runout (the tool I'm using is accurate to .0004). This probably isn't enough to make a 1.5" difference at 100yds but runout can vary even more than that. Most of my really good groups shot lately are with ammo that has been straightened to less than .002 runout with a Bersin tool.

Where I working with your gun the first thing that I would do would be to try 2 other powders. The Classic standard for 270 Win's is of course H-4831. I have been getting superb results with RL-22 with both 130 TSX's and 140 Accubonds. I think either powder is likely to give better results in a 270 than IMR-4350. If none of the powders work you might consider cryo'ing your M-70. If you do please let me know I'd be interested in how yours responded..........DJ