Yesterday's range results............

[Richard]

Not a whole lot of good stuff to report this week but here goes anyway.
Let me mention that the weather was near perfect ranging from 61 to maybe 75*; wind for the most part was not a factor and the sky was sort of hazy/sunny. I consider all shots being held "dead nuts" on the dot in the center of the orange spot........in other words, no shooter error. What you see is how the gun spit it out. The difference in group size is more a product of the bullet/sabot/load combination. This is not bragging, but I was that confident these groups should have all been bug holes. Be that as it may.......................
First of all I wanted to duplicate the loads Dennis shot.
Targets 1 & 2 are single powder loads of SR4759......I think Dennis shot 47 gr. with a 200 XTP and B/H sabot? I shot 48 gr.
What is amazing about this powder is the EXTREMELY low ES's. 11 fps for the first target with the XTP and 12 for the second target with the SST. Here the SST grouped a little better than the XTP.
The next two targets...3 & 4 were with Dennis's duplex of: 11 gr. 4759 under 54 gr. of H-322. The ES's were "fairly" low but in this case, the XTP shot smaller than the SST.
On target #5 I switched one powder to get a different combination.... that was N-130 was substituted for H-322. Definitely not great but the ES on the first four shots was only 12 fps with the final shot making it 28 fps. Still not bad for a ML? So why the bad group?
On group #6 I went back to a standby triplex 10/23/34---N-110/N-120/H-322. While it did group four of the five shots in just over a 1/2", it did throw one out?
#7 was the same load using the 200 SST and it grouped worse
The last group was duplex I had not shot before in the amounts I used. This also was poor.
While the single powder loads of 4759 gave low ES's they did not produce the groups I would like ...............and I'll be back at it next week
Richard

[dennis31]

Richard, Is load #6 a new one N110,N120,H322. H322 instead of N130. Looks like good velocity and could be promising.

[Richard]

No, the N-110/N-120/H-322 is one that has given me excellent results in the past. Actually it shot a .054" three shot group a couple of months back. I just feel its in the quality of these pistol bullets. Besides the fact they are being shot and spun at velocities and rpms they are not intended for. A pistol shooter would probably never know the difference but in our case it really showcases an imbalance bullet.
Richard

[Deleted]

Richard, you sure are persistent and call them as they fly. cant ask for more than that!

[edge]

Richard I might suggest that it may be more sabot related than bullet related, but a lathe cut monometal bullet would answer that since center of gravity would be assured.

Perhaps the next time you cut the crown on a rifle you might take a piece of stock and cut it to 0.400 diameter by about 2 inches long...or a gage pin if you have one.

With the barrel indicated you could load the rod into the barrel and check concentricity and straightness with a couple of different sabots. I suspect that they will not be very consistent and the rod will be pointed in different directions by several thousandths....but i may be wrong.

edge.

[Richard]

Not quite following you Mark.........When I crown, I use a gage pin to indicate the bore both fore and aft in the headstock.
Richard

[edge]

Exactly!

Now you know that the bore is on the centerline of the chuck.

Now insert a 0.400 gage pin or turned material into a sabot and "load" it into the bore.

If you indicate the projectile ( the gage pin or turned material ) it should be perfectly true to the bore... it should run just as true as the gage pin that you indicated the barrel...but I bet it won't.

Actually if you have a helper I bet they can wiggle the "projectile" at least 0.020 in the bore because the sabot is so soft. The higher the temp the more it will distort.

edge.

[cuda]

But it is still better than a patch and ball! To keep it all lined up in the barrel you would need a full bore bullet. And that can be started off center too. You just have to hope you do your job and do the best you can to keep it lined up.

[edge]

You missed the point.

Richard stated that a problem is bullet imbalance and I contend that the greater problem is sabot irregularities and the sabot construction.

I am not so sure that from an alignment standpoint that it is better than a patch and ball!

edge.

[wilmsmeyer]

The larger the bearing surface the easier it is to align. The smaller it is the harder it is to align......until you get to a perfect sphere....then it's almost impossible to mis-align.

[Richard]

Edge.............OK Now I see what you mean! Don't thin k I really want to pull the barrel now for that test but you are probably right.
Let me run this past you................Since the bullet is not engraving the bore, it is not being distorted.........maybe misaligned slightly as it is being seated..............In the case of CF, when a bullet is not lined up dead center in the bore, it enters the throat and starts engraving the rifling "off center". This continues down the bore until it exits the muzzle..........where it leaves still distorted and not out of balance? The saboted bullet, on the other hand, is not being distorted and "maybe" has the ability to straighten itself by the centrifical force being exerted (spinning). Possibly, this force can help to realign itself prior to exiting? Maybe I'm just rambling? ;D
Richard

[edge]

IMO, if it is off center it probably stays off center until it exits.
As it exits it is thrown off axis to the bore but rotates true to the target from that spot.
If this is correct then it could result in a smaller MOA at distance than at 100 yards as with a crown defect.

I think that it was Lilja that used to have a program to calculate how far the spin would throw an off center CG bullet. Basically it advocated for the slowest twist to stabilize your bullet.

edge.

[Richard]

Unfortunately, we don't really know if it does or does not stay off center?.........obviously, it is best if it starts out straight!
The benchrest community is definitely of the opinion that the slowest twist that will reliably stabilize your bullet is about where you want to be.
Richard

[deadon]

May 14, 2011 20:04:04 GMT -5 Richard said:

Unfortunately, we don't really know if it does or does not stay off center?.........obviously, it is best if it starts out straight!
The benchrest community is definitely of the opinion that the slowest twist that will reliably stabilize your bullet is about where you want to be.
Richard

Richard, Is that due to the torquing thingy you spoke of a hundred post ago? Rusty

[edge]

Richard if a bullet tends to center itself then your inaccuracy would be due to bullet construction and then wouldn't a monometal lathe turned bullet achieve near benchrest accuracy?


edge.

[Richard]

Edge..........you would probably be right! That is kind of why I am disappointed in Leheight bullets and why they don't work...........besides drilling sabots. What we need is an outfit like Berger Bullets to produce quality semi-custom .40 bullets with a lower BC on J-4 jackets with good lead cores................vs. these pistol bullets that have their "poured molten lead cores!"..........along with jackets that "who knows" how many ten thousandths the wall thickness varies
Unfortunately, the amount of smokeless shooters looking for this type of accuracy do not number enough for them to produce these bullets .........Oh, and Parker has to get real with his prices! If Berger can produce a hundred 108 gr. boat-tail bullets that I can buy for $28/100, I am sure a box of 100 .40 flat base LD bullets could easily be produced for under $40 since a boat tail is more labor intensive than a flat base.
Richard