Looking for help:
I have several loads that seem great, then they get down to a one inch square and wont go any better. nice tight group of shots in each corner of the square, actually more like a diamond than a square. Nothing in the middle. I think the rifle shoots to four different POI. Its a double rifle, and both barrels do the same thing, but to different size squares, so it cant be the scope moving cause the scope wont know which barrel is shooting. Four sets of lands nad grooves. Looking for the way to end this groove-riding, or muzzle blast effect, or whatever.

So what can you suggest next:

I have tried 7 bullets, three weights, 4 powder type,several powder weight, checked scope mounts.
tuned seating depth,

Going to try:
concentricity, case weight,neck tension, deburred flash holes, luck,rifle action screws, who knoww what else/

[ 03-29-2003, 22:32: Message edited by: Jameister ]

Side by side barrels have much different shooting characteristics than a free floating single barreled hunting rifle. I believe the barrels are set so the bullets cross at 100 yards from a double or side by side barrels. Your shooting a scoped double rifle and thinking as if your shooting a free floating single barreled hunting rifle.
I would say MOA group at 100 yards from a side by side double is very good. I would think the side by side double rifle was designed to shoot with open sights at 100 yards and less. Two rifle barrels connected together side by side will have different barrel harmonic characteristics than a free floating barrel on a single barreled hunting rifle. You may be at the best accuracy potential that particular double rifle has to offer you. I would fire a few groups at 200 yards to see how the rifles POI is at that distance. I believe you will be surprised at the target when you see it.

Jameister.. If you really have af double that shoots that tight, then do not touch anything.

What caliber is it..?

Jameister, what calibre is your double, and what size are the groups from both bbls?

This is an overunder double. in stalking caliber of 8X57JR. shooting 170 grain bullets at 2500fps does best so far. Although 200 grain Sierra MK's did less than an inch per barrel, but I could not get convergence.

With the 170 grains, I can get about a 1.25 group of five from the bottom barrel, adn about double that with the top barrel, adn the center of the two groups are from an two to three inches apart. The barrel POI are two inches apart on a sideways plane, and no amount of powder and bullet combination will bring them together sideways. I suppose I could cant the barrels 35%, but they still dont come together vertically.

There is a regulation problem yet to be resolved, to get the two groups to superimpose, because they just do not want to with any of hte bullets or powder loads.

However, the amazing (to me) pattern of a simple diamond, or nearly square box, from each barrel, with the repeated shots hitting each of the corners, tricks me into thinking I just have to solve one more thing (runout?), bullet diameter? neck concentricity? and they will tighten up more...silk purse and sows ear come to mind, but this old merkel is the best looking rifle in my collection, and I just plain know it can do better than I have it at yet.

O----------0

===CT

0-----------0
------------0

------------------0-------00

============CB

-------------------0--------0
{_______ = one inch}
CT = center top barrel group
CB = center bottom barrel group

Dont know how this diagram will come out in your computer scree....

I am planning on having it re-regulated by gunsmith, but want to make sure I have a decent (best) load to send along with the rifle to get the best.

I just want to get less than two inches for both barrels at 100 yards, with 170 grains hunting bullet at 2500 to 2600 fps.

I agree there is no reason to expect or need this accuracy, but then again there is no reason to ever truly need more than two MOA for big game rifles either...

[ 03-30-2003, 10:38: Message edited by: Jameister ]

Jameister
You may have already tried this, but here is an idea, Try a slightly faster and a slightly slower powder. The difference in burn rate might make a difference.
I cam recommend J.J. Perodeau of www.champlinarms.com for your re-regulation and other work.
He IS NOT a Gunsmith....He is a GUNMAKER.

For such a rifle a 1" group is very good if it's at 100 yds. I suggest that you just be happy and go hunting.

I have a one inch group, and a 2 inch group, but they are still a few inches apart, which makes a 3-4 inch group.

There must be some body that has seen this square pattern group on a four lands rifling before?

okay..

it's a double.. sounds like it is shooting okay.

what does it do at 50 yards?

75?

which barrel is higher? if it's the top barrel, you need to go SLOWER, if it's the bottom, you need to go FASTER to get the seperation

jeffe

I have not shot at close range yet. My issue is what makes a square pattern of bullets from a rifle. the double barrel does not matter much (or does it?)it just confirms that both barrels do the same thing. A box pattern. Perhaps when my casemaster getshere I will find I have an offcenter reload product...

regarding the load development for convergence (since true rifle regulation is mechanical) I believe that for this rifle, it crosses with too fast a bullet, due to the regulation of barrels towards each other, and diverges (shoots apart) with too slow a bullet, due to muzzle jump.

This has been tested and confirmed with over a hundred chrony rounds, but certainly there could be several crossover points for reasons I will never understand, so I will try and go yet faster with lighter bullets, and can not go slower with hunting expectations.

Just complexed by the square patterns.

I have another bullet sizing die coming, and will experiment with intermediate bullet diameters.

[ 03-31-2003, 18:39: Message edited by: Jameister ]

The box group is due to the position of the barrels and how they are joined together. You may experiment until you shoot the throat out of both barrels with no improvement. Two center fire rifle barrels joined together will not have the barrel harmonic freedom to vibrate as they should to produce exceptionaly tight groups. Trying to produce handloads that will give the same results in two joined rifle barrels is probably not possible. Use a load that gives good accuracy from both barrels and live with that results.

The same thing happens in a over and under rifle with a rifle barrel on top and a shotgun barrel on the bottom. The rifle barrel will not produce the best groups because it is joined with the shotgun barrel and can not vibrate properly.

The double side by side rifle concept on the dark continent was a design that gave the shooter two fast powerfull bullets delivered at close to medium range. Dangerous game hunting in Africa's close cover situations demanded fast accurate shooting and the double rifle gave the professional hunter that advantage. They are still highly prized today and hold high resale value. I have not seen a double rifle that would group better than a good quality bolt action single barreled hunting rifle. If your determined to use a double rifle to hunt keep your shots at 100 yards and less.