TargetTalk

Looks like the author finally found a good use for that Financial Accounting textbook from his college days.

is it just me or does that lot of ammo seem very inconsistent?

i hope that remington box was for throwing the empties away in...!

Am I misunderstanding something here? Did he take 25 shots for each set while going from one target to the next? He had to move the rifle 25 times for the 25 shots? If so, it is a worthless test.

Joel

joel wrote:Am I misunderstanding something here? Did he take 25 shots for each set while going from one target to the next? He had to move the rifle 25 times for the 25 shots? If so, it is a worthless test.

Joel

Well given that he is not actually clamping the action in a vice, but shooting from a relativly normal benchrest rig he is having to reset the gun for each shot anyway. If you are resetting the rifle it makes no difference if you go around the aiming marks, or just shoot one hole. Actually the single shots make it much easier for the scanning software to read each individual shot location in relation to the aiming mark, which for this type of BR target is likely to be the 0.0625" X ring which is a dot about the size of the one used for the 10m AR bull, but at 50 yards. The software can then very easily plot each shot in the 25 shot group to show the overall group size/shape. It can also calculate the actual score, and the best possible score had the group been correctly centered. This is useful as of course for ammo testing you do not want to adjust the sights once you have started, but knowing how a group will score, in points matches, is just as important as group size.

Alan

BigAl wrote:

joel wrote:Am I misunderstanding something here? Did he take 25 shots for each set while going from one target to the next? He had to move the rifle 25 times for the 25 shots? If so, it is a worthless test.

Joel

Well given that he is not actually clamping the action in a vice, but shooting from a relativly normal benchrest rig he is having to reset the gun for each shot anyway. If you are resetting the rifle it makes no difference if you go around the aiming marks, or just shoot one hole. Actually the single shots make it much easier for the scanning software to read each individual shot location in relation to the aiming mark, which for this type of BR target is likely to be the 0.0625" X ring which is a dot about the size of the one used for the 10m AR bull, but at 50 yards. The software can then very easily plot each shot in the 25 shot group to show the overall group size/shape. It can also calculate the actual score, and the best possible score had the group been correctly centered. This is useful as of course for ammo testing you do not want to adjust the sights once you have started, but knowing how a group will score, in points matches, is just as important as group size.

Alan

Hi Alan,

I'm the owner/builder of the test tunnel linked to in the opening post and I wanted to thank you for the comments above. Other than a few technical details, your explanation of the testing methodology and its validity for advanced analyses of firearm precision is correct.
It's unfortunate, but It's not often that others understand proper testing without lengthy explanations which I usually don't have the time or patience to provide.

Landy in Nebraska, USA

PS The Remington garbage on the test bed was intentionally placed there for the photos because Evan and I thought it would be interesting to see how many might notice it.
We were shooting batches of Tenex and Match. LOL

Whew! Had me there for a minute.

What was the std dev individual lots or across multiple lots?

Were there stamped fps on each and now did they compare?

fieldsj66 wrote:
What was the std dev individual lots or across multiple lots?

Were there stamped fps on each and now did they compare?

The chart below lists a few stats for the testing session being discussed. The Eley batch #'s are on the top with the Eley V, Actual V, and Standard Deviation hi-lited in red:



This chart is a visual representation of the same data/testing session, and a calculated Pearson Correlation reveals there is no statistically significant link between Eley Bx V & the Actual V.



This chart contains a much larger data sample for one of my rifles and also shows the problem of using Eley V's for any practical purposes.
Take special note of the 4 data points (3 batches) in the bottom right of the chart. They are all below 1,030 fps as marked on the boxes, but the actual V in all but one case was the highest V of all batches tested in this rifle. This is a little unusual but after chronographing approximately 40,000 rds over 2 paired/calibrated chronos I built and modified....I see a lot of anomalous results.

Landy

Thank you for posting that!

I've been an Eley fan, and my guns generally like them a lot. We recently acquired an older case of tenex and its is doing very well. I've been researching ammo to see if I could find an out of the box consistent performer. I really don't like the idea of excessive measuring for length, rim thickness, weight, etc. With the types of games we shoot those std dev are what i feel are some of my flyer problems. We know quite a few people that are moving to Lapua and RWS. My best rifle still likes the Eley EDGE though.

Would your data effect shooting with a tuner considerably? or is that variation non-significant for tuner applications?

IMO a tuner's primary purpose is to compensate for velocity variation and reduce the vertical dispersion at the target below what the ballistic calculations imply, but I've been unable to set tuners effectively without expending a sometimes impractical number of rds.
I've never found it as easy to do as most and I'm fairly confident a large percentage of rifles using tuners aren't really "tuned". I wish I had a fool-proof method for tuning that only required a couple of boxes of ammo, but I've been unsuccessful at accomplishing that goal and I'll usually end up shooting a couple of bricks at least before I'm confident I've made a "real" change in rifle precision rather than an "imaginary" one.

YMMV, but if my premise is correct, shooting a minimum of 50 rds across a "RELIABLE" chronograph and choosing the ammo with the lowest Standard Deviation in velocity might be a workable/faster solution for narrowing down your choices when lot testing ammo. It should also be obvious that gathering group size data in conjunction with the chronograph data is the better solution, if possible.

Landy

@Landy

If im right you test a lot in the bench rest circles.

Did you ever do any work/research with the PRX formula that was all the rage a while back? What were your findings opinions in relation to its effects/effectiveness as a method?

remmy223 wrote:@Landy

If im right you test a lot in the bench rest circles.

Did you ever do any work/research with the PRX formula that was all the rage a while back? What were your findings opinions in relation to its effects/effectiveness as a method?

Yup, you're right, I'm fairly well known among the BR crowd but everyone seems to know who I am regardless of the shooting discipline and I often wonder if that's a good thing or a bad thing! LOL

Tony Purdy is a friend and I recently met him face to face for the first time while at the ARA Nationals this past summer. I find myself constantly apologizing to Tony for not finding the time to test his acoustic length theories, but there are just too damn many things to test with my available time and I've gathered far too little data to have an informed opinion. Sorry!

Landy