Vibration nodes and cross sticks

[45bpcr]

Hello all,

Long time lurker here. Thanks to Texas Mac and his book I'm once again going to start enjoying my Sharps and my Browning.

I've always shot these rifles either off hand or off a bench. I want to start using cross sticks and seem to remember an artical along time ago from the old Shooters.com site about determining the "sweet spot" on a barrel.

IF memory serves me right it involved holding the rifle by the muzzle hanging and slowly hitting the barell along it's lenght while feeling for the least amount of vibration.

That wolud be the point to rest it on the cross sticks. Does this sound right?

45Bpcr

[felix]

That would be correct as far as the barrel alone is concerned. ... felix

[Hip's Ax]

Thats what I've been told and I was shown to hold the rifle in your left hand by the forward wood and "knock" on the barrel with your right hand. The right spot can be felt easily (no vibrations) and I put a white target paster there and make sure the barrel is on the sticks in that place before each shot. You have to do it pretty often as the paster does not stay on the barrel too long due to cleaning and oiling.

[NickSS]

I have found that on my sharps the barrel needs to be rested either just in front of the hand guard or about three inches behind the muzzle. Seams to work with all of my rifles.

[Don McDowell]

What Nick said.

[montana_charlie]

IF memory serves me right it involved holding the rifle by the muzzle hanging and slowly hitting the barell along it's lenght while feeling for the least amount of vibration.
Hold the rifle by the receiver, with the muzzle hanging down.
You can feel the vibration in your receiver hand, and you can hear it.

It goes like thummm, thumm, thum, thup thup ... and them thum again when you move past the spot.

It helps to remove the staff of a tang site, as it can add it's own vibration to the mix.

You don't have to hit the barrel hard. A small plastic hammer works great, but you can do it with your knuckle.

CM

[Doc Highwall]

Another way that will get you close is say you have a 30" barrel.

Divide 30"/ 2 =15" node

15"/2 = 7-1/2" node

7-1/2"/ 2 = 3-1/4" node

These should be close to nodes on the barrel and my first choice would be the 3-1/4" , place a piece of tape there and try on that and also just in front and just in back of the tape.
My second choice would be the 15" just in front of the forend doing the same thing with tape.
Actually firing the gun at the longest distance you can will show which spot has the least vertical.

[montana_charlie]

Another way that will get you close is say you have a 30" barrel.

Divide 30"/ 2 =15" node

15"/2 = 7-1/2" node

7-1/2"/ 2 = 3-1/4" node

These should be close to nodes on the barrel and my first choice would be the 3-1/4" , place a piece of tape there and try on that and also just in front and just in back of the tape.
My second choice would be the 15" just in front of the forend doing the same thing with tape.
Actually firing the gun at the longest distance you can will show which spot has the least vertical.
That math doesn't work out right if the barrel is tapered, and most of them are.
CM

[oldracer]

I have made a set of long and also short cross sticks and plan to try them next week when I do my weekly load testing. As part of getting ready I asked about a dozen present and past BPCR competitors in the San Diego area and all but two said they rested the barrel on the sticks immediately forward of the forend. The reasoning in all cases was the same: the possible harmonics issue was not as important as getting the exact (or close) same hold for every shot. I also read all my back issues of Black Powder Magazine and there are several articles where the authors said the same thing. So that is what I plan to try, for starters anyways as I have found so far that every gun has to be tested to see what works best.

As a side note, in an earlier post I noted the sine wave pattern on my barrel when I left it coated with oil and I did measure the distance between the "peaks" of the pattern and I noted that one did start right where the wood ended in front.

[Don McDowell]

Probably of equal importance of where the sticks are placed, is keeping the same grip on the guns wrist,and consistant trigger pull and follow thru, for each shot.

[wills]

I have read put talcum powder on the barrel, fire the rifle, and you can tell by the powder where the node(s) is(are).

[semtav]

Hold the rifle by the receiver, with the muzzle hanging down.
You can feel the vibration in your receiver hand, and you can hear it.

It goes like thummm, thumm, thum, thup thup ... and them thum again when you move past the spot.

.

CM

Just tried that with my 34" barrelled 1885 Win . I could definitely hear the dead spot. Seemed to be about 4" long, is this normal or ar most of them an exact spot?

[montana_charlie]

Just tried that with my 34" barrelled 1885 Win . I could definitely hear the dead spot. Seemed to be about 4" long, is this normal or ar most of them an exact spot?
I've only done this with one barrel, so I can't say how others will come out. But, my 'sweet spot' is about eight inches ahead of the forearm tip and seems no more than an inch or two long.

Listening with a stethescope may provide more exact results, but I just put some masking tape in the center of what I think is 'dead'.

My spot is lightly forward of 'halfway' on my barrel, and that appears right for a tapered piece of metal. I expect the next null is slightly forward of 'centered' between my current spot and the end of the muzzle. But, the vibration changes created up there are too faint for my ear to pick up.

One final note, then you'll know all that I have to offer.
The forearm wood should be relieved so that it doesn't touch the receiver on a Sharps rifle (maybe opthers, too). That is true, even if you don't care where the sweet spot is.

But, if you are hunting your sweet spot, and the wood is touching barrel steel and receiver steel, I suspect it might put you in the wrong place.

CM

[bigted]

just to clarify here...this is going to be the sweet spot to rest the barrel on that will lessen the verticle string correct?

this seems to be my worse problem in my groups so far...maybe you have helped me with keeping my groups small enough that my confidence will return...lol

[montana_charlie]

just to clarify here...this is going to be the sweet spot to rest the barrel on that will lessen the verticle string correct?
Actually, a barrel moves in a circular motion, and it's more pronounced the further it is from one of the null points.

A slow-motion video of a guitar string will give you the idea.

So, the muzzle of your gun may be pointing up, down, left, or right when the bullet exits. As long as your sights are adjusted to compensate, and your velocity stays the same, you will always have the bullet going the same direction as it leaves.

But, if you are resting the gun on a segment of barrel that moves a lot when the barrel vibrates, that will add to the (already compensated for) muzzle whip ... and will further randomize the bullet direction.

Because the vibration meets resistance from the x-stix in the 'down' and 'sideways' directions, the final result of the 'bounce' will be primarily an 'upward' vertical dispersion added to whatever the muzzle is doing.

Sound reasonable?

CM

[bigted]

yes thanks

[TCLouis]

and posted here . . .

akgrouch,,,i also have the very same rifle you describe and my loads also go verticle with little horozontal for the string. i recently 'learned' about the vibration affect with these long heavy barrels and i for one am looking forward to trying it out with this rifle and my browning hiwall as well. it goes something like this;

hold the rifle by the action with one hand and tap with the other hand [or a small plastic hammer like i have...an inertia style bullet puller would work as well] along the barrel length to find where the vibration is the least.[ my rifles have a dead spot that has no vibration at all]. this is the spot where the barrel should be rested for the best accuracy out of a rifle/barrel.

makes sense as mine all seem to climb or drop in the verticle string that blows my great groups with all 6 of my 45-70's. some are scoped and some have the tang sites and the browning and uberti have the longrange 'soul' type sights. i use the post front sight insert in both mine but have that teardrop looking front peep insert for them as well.

thought id pass along what im learning to all.

[waksupi]

Years ago while shooting with Ted Thompkins, I saw he had some adhesive tape on his barrels, to mark the sweet spot. We of course harassed him unmercifully, asking if his barrel had an "owie", amoung other things. Most can't be posted here.
Considering Ted generally out shoots most of us, I do pay attention to what he does, and try it out. It does make a difference. Every thing except the bowler hat, that is.

[KCSO]

Years ago we tested our m/l cross stick guns by shooting groups at 2" intervals from muzzle to just past the entry pipes and found that each gun has a sweet spot. I was just talking last nioght to a sharps shooter about this and he switched from muzzle rest to just in front of the fore end and cut 1/12" from his group. It does make a difference so try several points till you find the best one for you.

[stubshaft]

What you are describing is called the "parallel node". Here is an article describing how a barrel actually vibrates:

http://www.ozfclass.com/articles/1/psm_2005_03.html

[montana_charlie]

What you are describing is called the "parallel node".
Oh, uhhh ...yeah! Parallel node ... that's Latin for 'sweet spot'.
CM

[Ramslammer]

G'Day
We were discussing this a few days ago. I reckon if you made a sling type rest for the sticks the barrel may not bounce as much.
Juddy

[myfriendis410]

So, from this thread I can assume that my resting the forearm on bags is not going to give me the best out of my Sharps? Or is this just in relation to using crossed sticks?

[Doc Highwall]

It will relate to anything that contacts the forend or barrel and you will have to experiment with your gun to find the best place to rest it. I would decide as to how you want to shoot the gun either off a bench-rest or with crossed sticks or even one of the hand rests and be methodical with testing. You could put tape every two inches starting at the muzzle and shoot a series of five shot groups at each taped spot and narrow it down. Then make sure you keep the targets as part of your load development. This I could easily see taking several range trips but you could also practice your wind reading skills at the same time.
Don't forget to write down all the weather conditions, what front and rear aperture you used along with size of target.
I would use a target that is at least six minutes of angle doing this as it is a test of the gun and load, not the shooters sight.

[myfriendis410]

I have been using a 3" target orange "dot" pasted on the back of a replacement center, with a fine post and peep. It's really one of those deals where you want a sunny day with no wind to really work the rifle. That's a tough call out here where our range is 800 yards from the Pacific ocean and the marine layer (read that: FOG) is usually present.

I do have a card of different front sights on order to see if there is anything there that will allow for more precision than what I have already.

I shot a range session today, resting the bag on the barrel just forward of the forearm. Shot a couple of decent groups, but only lots of rounds downrange will tell the whole story.

Thanks for the help!

[montana_charlie]

How do you align your peep and post with the bullseye?

That's really a rhetorical question, with no need to answer unless you want to.
I am using the question as a segue into something I learned a couple of months ago.

I was reading (online) a very old book about rifle shooting. It was really aimed at setting up a marksmanship program for the U.S. Army ... which didn't have one at the time ... but it covered a lot about actual shooting.

Near the end, there was a discussion about globe sights, and how they were being used by target shooters of the period. Most of the inserts available then are the same as we have now ... except for one or two.

But, when reading about the use of the post insert, I learned something completely new to me.

Those shooters (mostly shooting long range matches) would not place the bull 'on top of the post', nor would they try to set the top of the post in the center of the bullseye.

Instead, they would align (say) the left side of the post with the right side of the bull, and raise the muzzle until the post was level with the top of the bull.
With this sight picture, windage and elevation settings were adjusted for a center hit in the bull.

Using this alignment, they could 'hold off' by an easily visible amount to allow for changing wind. (The left of the post and right of the bull were aligned on days when the wind was from the right. In a left wind, the post would be aligned on the other side of the bull.)

Equally visible was the actual top of the bull and the top of the post ... with neither 'hiding' part of the other.

My first experience with 'peep sights' was in the military, shooting the M1 Carbine. We were taught to hold at six o'clock on a bullseye, and 'center mass' on a silhouette target. Of course, nobody expected to shoot very far with that 'rifle'.

CM

[Doc Highwall]

Thing have changed some montana_charlie, I have never heard of holding a front post sight like that.
Today I would recommend using a front post that appears as wide as or slightly wider then the aiming black with a 6 o'clock hold. I know that it has worked for me with the M-14 replacing the national match front sight with a regular M-14 sight when shooting the national match course.
A lot of people think using the national match allows them to shoot better at first but when your eye gets tired or the light conditions are less then favorable you can see the larger post better especially with older eyes.

[Kenny Wasserburger]

Doc,

That is pretty much what I have found also with the good ole M-14 when I shot one at that little match they call Camp Perry. And my Navy armor also cut mine down quit a bit.

KW
The Lunger

PS
BTW what Charlie Posted I also have read off in a older Book. Must of figured on steady conditions from the Same Direction all day.

Wonder what they did in reversals? not shoot?

[RMulhern]

MC

"Those shooters (mostly shooting long range matches) would not place the bull 'on top of the post', nor would they try to set the top of the post in the center of the bullseye.

Instead, they would align (say) the left side of the post with the right side of the bull, and raise the muzzle until the post was level with the top of the bull.
With this sight picture, windage and elevation settings were adjusted for a center hit in the bull.

Using this alignment, they could 'hold off' by an easily visible amount to allow for changing wind. (The left of the post and right of the bull were aligned on days when the wind was from the right. In a left wind, the post would be aligned on the other side of the bull.)

Equally visible was the actual top of the bull and the top of the post ... with neither 'hiding' part of the other."

No reflection on you MC but what you read was formulated by an IDIOT!!

[45bpcr]

Thanks all for the ideas,
I've been banging on the barels of my Browning, My Sharps and my Pedersoli Gibs. There's tape in a couple of places on each rifle.
I'll grab some Magnaflux powder from the shop when I head to the range next. It'll be interesting to see where the agreements lie.

here's me

http://www.youtube.com/watch?v=TtchCnMtk_w

45bpcr

[45bpcr]

I got a chance to shoot today. It was a multi-purpose range session.
Shooting at 500 yds I shot a ten shot group that measured 19" horizontal and 14" vertical. This was with the forearm resting on the bag just short of the schanable tip and the rear bag snuggled into the pistol grip.
The 2nd ten shot group I shot with the barrell resting in the "dead zone", about 10 " in front of the forearm. With just the barrel on the rest I can't use a rear bag due to lack of elevation in my front rest. The group shot this way measured 13" horizontal and 12" vertical.

A very noticable difference.

I was also working with a new bullet. I treated my self to a couple of Paul Jones moulds. A #45001 for my Sharps and my Browning and another for the Pedersoli Gibbs I've been working with.
Mr. Jones certianly makes nice stuff. The bullets I cast weighed 337 / 338 grains with only a few that were light using 20-1 alloy from Roto Metals. They also are perfectly round and measure 359.
So some load developement is in order. Todays load was that bullet, CCI LR BR primer, 90 grains Swiss1 1/2 drop tubed through a 37 in tube and compressed .10 with a .060 veggi wad. This leaves 2 grease grooves exposed. They were sized with a .459 die and lubed with SPG.
All my bullets to date have been cast with lyman molds and I've always had the best luck with the Postell. The bullets that drop from Mr. Jone's mold look almost to pretty to shoot. :-)

45bpcr

[Lead pot]

I had two bench rifles a .22 hornet and a .222 both rifles had a 2" round barrel. Now you would think that they would not move but they do.
I maybe a donut with a thumb screw and slid it over the barrel till I saw the group tighten. They work.
But I also found that if you rest the rifle the same way on the bags or sticks that we use and the load is uniform chances are that the rifle will react the same.
When when the impact changes chances are that you changed something like the load or hold.