Help with Ransom Rest group?

I would ditch the Destaco toggle clamps and put something more secure. The recoil may be slightly moving your base.

I would not dismiss the clamps as being a source of the problem, but a couple of points: 

·       The 4 clamps each put down 500 lb of pressure making a total of 2,000 lb total down pressure.

·       The front of the board holding the RR has a screw that goes through it and attached to the bottom board (you can see the large screw in the photo), it serve as a pivot point to adjust windage.  That screw would also make movement difficult.

·       Assuming the board holding the RR moved laterally, how would that translate to a vertical stringing group?

Again, I do not dismiss this out of hand but based on the above, a bit hard to rationalize, but I do have a plan to test it.  

In the meantime, other ideas of why the groups happen would be helpful and appreciated.

A. fire at least 10 rds to settle the rest before you start real testing. sometimes more.. you should check the pistol for shifting

B. recheck Nuts A, B and C for being finger tight

C develop a rhythm and method for return the rest to the starting spot each time..( watch Steve Huff of accuracy Xs videos on his ransom testing)

if you are going to only test 5 rounds groups. load with 6 rds in the mag. fire the 1st round away from the target then shoot the five for your test.
Repeat this for each test.

doesn't hurt to monitor each shot through a scope so you know which round goes where in the group.

Have you tried a 22 yet? Something you know should group well. Then if that's gives good results go to a larger bore pistol again.

Presume U R careful not to touch the gun when resetting the RR? Pulling trigger?Perhaps raise gun all the way before lowering? Someone suggested to me to put a glass of water next to the RR. Watch what happens when you fire, let water settle if disturbed. 

 Have you tried some top notch factory ammo?

With respect to group shape - 5 shot groups won't tell you anything. 50-shot groups, maybe. 

Imagine you shoot a 100- shot group.  Now randomly select 5 shots from that 100-shot group.  Then randomly select another 5 shots, and so on.  Some of those 5-shot group will have a vertical pattern, some will have a horizontal pattern, and so on.

Patterns happen by chance.  If there is a tendency for stringing, it requires many, many shots in one group to determine if it is real, or just a chance event. 5 shots are meaningless.

As a former outdoor master who owned and used a Ransom Rest regularly in the past, I'd say, although it is somewhat hard to determine the size of the groups by the photo only, it looks like your groups aren't too bad for a "tactical" 9mm pistol. My testing was limited to accurized 1911's, accurized Beretta 92 FS and target .22 pistols. I always attached my wooden platform (raised like yours) to a steel plate that was mounted on the concrete base using steel C clamps. You appear to have extra layers. That may or may not make any difference. I did my testing at 50 yards and fired 10 shot groups, although I disagree that "5 shot groups won't tell you anything". They still give you a trend. It is a good idea to fire some "seating" shots before recording results, but I have actually fired 10 shots without seating and gotten very good groups. Heed the advice of not touching the pistol any more than necessary. Many RR users take off the lever that pulls the trigger and prefer to use their own trigger finger. When doing so, it is advisable to still use proper trigger control. Use the "tab" on the RR to put it back into position after each shot. Basically, I don't see any problem with your RR setup, but having extra screws and bolts adds the increased chance of something getting loose. There is a good chance that your "tactical" pistol will not lock up the same and that can cause vertical stringing. Unless your pistol is custom and came with an accuracy guarantee, you really have no basis for your expectations on how it will group. This may be about as good as it gets.

+1 on trying a 22.  There are techniques you learn that work well on a RR, so starting out with a gun that is known to group well will help you figure out what works well and what does not with the RR.  Right now you have an unkown setup, an unknown gun, and little experience, so it's going to be difficult to clear away the smoke....

Good advice.

Try a 22 or Revolver in 38 Special to develop your RR technique.

That said, in these groups presented I’m not seeing significant vertical in all cases. You have 2 vertical, 3 horizontal, and one square. They are large compared to a Bullseye pistol. But this is (I presume stock) tactical pistol, probably with a polymer frame. With the exception of the two vertical groups, all of these loads are likely good enough.

I’d load fifty of the “best” load then shoot 3 15-round groups.

A precision 22 is a good idea but mine is not a precision 22 and of course I don't have a grip for it.

For now, I will get some Atlanta Arms ammo to evaluate the precision potential of the gun.

Another possibility is to pick one of the vertical groups with the tight SDiv and do load development by adjusting seating depth.


I also plan on evaluating the potential movement of the RR platform.

What gun are you shooting?

Also, what size are those groups measuring the extreme spread? It would help to have some numbers to go with this.

And what is your load data?  Especially what powder and charge weight are you using?

Al wrote:

jlow wrote:The two vertical group with low side dispersion is also interesting because they were the ones with lowest MV SDev.  At least in precision rifle, we commonly find the most precise groups most frequently (but not always) have the lowest MV SDev.

Precision rifle & bullseye are two entirely different animal.

PR we're shooting from a solid rest at ranges up to 1000 & beyond. BE we shoot with one hand @ 50 yds.


That being said, early on I extensively Ransom tested over my chronograph. I found some of my most accurate loads had the highest SD. I quit using the chronograph & went entirely on group. The paper doesn't care how much energy the bullet has when it goes through. However, long range shooting with my prairie dog rifles is a much bigger factor. Best accuracy with sufficient speed to reliably expand is extremely important.
Al

Just to add to this, an article at the link below found no correlation between velocity variation and group size in the typical handgun at 25 yards fired from a Ransom Rest.

https://americanhandgunner.com/handguns/exclusive-consistent-velocity-accuracy/

Were all those groups with the same load? Or were there 6 different loads?

Sorry I missed that. 

Any information on the gun, gunpowder, charge weight, group size measurements?

When you say a tactical pistol, do you mean one with a plastic frame?  What is the pistol?  Plastic frames can be harder to mount properly in the rest.

Also, a torque wrench helps get even tension on the grips.

Mounting system looks fine.

As for diagnosing your groups, not much to say.  It looks like what you would expect from a 9mm tactical pistol, which is 5-6” groups that are not all that consistent.  I didn't have to see a million shot group to decipher that from your targets.

A high level accurized pistol can tell you a lot with just five shots.

5-shots on a dinner plate will look randomly dispersed and inconsistent.  5- shots on a $0.50 piece will look tight and beautiful, no matter how randomly they are dispersed in that group.  

if those are 115's crank up the velocity to the 1100-1150 range and report back...

Did you find a good accuracy node up here?