Help with .243 TTSX load development - long post

[Aletheia]

"Going on the assumption that since I had two previous groups under an inch there had to be some way of doing it again"

You have to understand that a load that is a 2" load will sometimes put three bullets into less than one inch just by chance. A small sample is not a good predictor of very much. You may be working on assumptions that aren't actually true.

 

[Howa 9700]

Having found myself in the midst of doing something similar to the OP, I will offer yet another possibility.

OP mentions shooting off front and rear bags.......but what are the optics? Historically, I have been a hunting shooter. If I hit what I was aiming at, gun was accurate enough. What I found when I really tried for tight groups, the actual act of shooting those is not as easy as some make it seem. Even with what was best front and rear rest I could muster, scope cranked up to 16X....it's maximum......cross hair was wobbling all over a 1/2" circle. Depending on when the gun went off, my shooting abilities alone would have accounted for at least 1/2" error......and unless you are actually aimed at the exact same spot on the paper, which requires exceptionally good optics and a steady hand, it would be very easy to be off by 2 inches when the gun goes off. You could be sending each bullet exactly to the point where you are aimed.

I'm not sure my 3X9 hunting scopes, even if cranked up to 9X.....will allow me to aim to the pinpoint precision needed to shoot a sub MOA group at 100 yards.

 

[barnfrog]

"Going on the assumption that since I had two previous groups under an inch there had to be some way of doing it again"

You have to understand that a load that is a 2" load will sometimes put three bullets into less than one inch just by chance. A small sample is not a good predictor of very much. You may be working on assumptions that aren't actually true.

Oh, I understand that now. I probably should have written "Going on what I now know to be the erroneous assumption that since I had two previous groups under an inch there had to be some way of doing it again...." Loading up those second batches of the loads that grouped small taught me that. While reading a thread on another site today I saw the following saying, which you long-timers have probably heard many times: Good groups MAY repeat, bad groups ALWAYS repeat. Ain't it the truth.

Having found myself in the midst of doing something similar to the OP, I will offer yet another possibility.

OP mentions shooting off front and rear bags.......but what are the optics? Historically, I have been a hunting shooter. If I hit what I was aiming at, gun was accurate enough. What I found when I really tried for tight groups, the actual act of shooting those is not as easy as some make it seem. Even with what was best front and rear rest I could muster, scope cranked up to 16X....it's maximum......cross hair was wobbling all over a 1/2" circle. Depending on when the gun went off, my shooting abilities alone would have accounted for at least 1/2" error......and unless you are actually aimed at the exact same spot on the paper, which requires exceptionally good optics and a steady hand, it would be very easy to be off by 2 inches when the gun goes off. You could be sending each bullet exactly to the point where you are aimed.

I'm not sure my 3X9 hunting scopes, even if cranked up to 9X.....will allow me to aim to the pinpoint precision needed to shoot a sub MOA group at 100 yards.

I can dig that, daddy-o. I suspect those first two supposed sub-MOA groups were just flukes. That's why we load a second batch to confirm the results, right? But I'm fairly confident that my gun and I are capable of producing decent groups. To give you an example, I worked up a different load with some 75 gr HPFB bullets and IMR4350. I chose a charge weight low in the range specified and tried seating depth adjustments first. I loaded five 3-shot groups starting at 0.010" off the lands and going up to 0.050" in 0.010" increments. Group sizes were as follows from longest COL to shortest: 2.48", 1.05", 1.67", 0.74", 0.67". So I loaded five more rounds at 0.050" and they also grouped under an inch. Since that recipe was just for trigger time and I didn't expect to shoot them at much longer range than that, I called it good. But the fact that the groups tightened up pretty steadily and the best load repeated tells me the precision of that load was real, not just random chance.

Thanks again for all the continued input. I'm going make a decision in the next day or two, load up my next test rounds and fire them this weekend, and report back.

 

[JimKirk]

Eight 80 grain TTSX. 243 Win in that dot(1/2") .... 43.3 grains Reloder 17

 

[JFrank]

@barnfrog I'm torn between staying in my lane or contributing, but I felt like I had not helped earlier as I could have so perhaps another effort on my part but please feel free to disregard this post if it doesn't apply to your program. I have tried this in the past with poor results, finding that it doesn't help with load development as conditions change too rapidly to maintain consistency.
Example:
Shot 1 is blown high left from a 2:00 wind the 60 seconds later the wind lets up and round 2 impacts center bull.
Shot 3 is blown to 4:00 from now a slight headwind

Result- Shooter analyzing incorrect information..

I have the best results with a warm not hot barrel and shoot in a smooth steady pace with and eye on the wind flag that way if I do get an errant round I know why and can take that into consideration.
Shooting over soft bags or a bi pod also adds a layer on complexity, the preference is a front rest and rear bag.

My understanding of OCW load development the shooter is comparing the center of POI on a horizontal plane similar to a sin wave not group size, I'm no expert , I have used it a few times but that's the basics.
Positive Compensation tuning is a technique im partial to is essentially the same thing but shot at a single point of aim with emphasis on not adjusting your set up for each target, the incremental charges climb the ladder (they can go any direction btw..l) than ultimately overlapping prior to breaking out of the quadrant heading for Jupiter or Mars.
I've attached an overview from a previous conversation as well as a couple of examples from my SILs first attempt at load development with his 270wsm choosing magazine length seating depth and a good amount of bullet hold/neck tension.
You may notice that the black sharpie colored loads overlap green and blue prior to the clear breaking out or becoming erratic.
All the groups with the exception of blue are on relatively the same horizontal plane , nothing wild...re test 58.5 -58.6 to confirm both will impact the same location, one slightly smaller yet both result in repeatability and dead deer.
Thanks for posting and please report back so that others may learn from your experience.
J

 

[barnfrog]

Jim:

Most importantly, thank you for taking the time to post your reply. I asked for advice from anyone willing to offer it and I appreciate anyone taking the time to post it up. I believe it is all offered in the spirit of trying to be helpful. Not all of it will be consistent, and it's up to me to decide which bits to heed, and I suffer the consequences if I choose the wrong bits. And regardless of my results, putting them up here may help someone gain a couple more data points to use in their decisions, as you suggest.

Allowing the barrel to cool as I described is just something I found online. Your approach seems to make sense too, as it sounds like you're trying to avoid getting to the point of a "hot" barrel but also not going all the way back to a cold bore. If one were really obsessive I suppose they might use an IR thermometer to take barrel temperature readings after warming up the barrel with foulers and try to maintain as steady a temperature as possible. Come to think of it, I might just try something like that. One question I've never seen answered is how hot is too hot? The closest I've seen is "too hot to touch is too hot to shoot." Only marginally useful, in my mind.

As I mentioned earlier, my "shooting range" is pretty well sheltered from the wind. I'm shooting up a draw behind our barn. The banks are 60' high, so cross winds tend not to be significant. Still, it wouldn't hurt to put up a flag or some other indicator to try and note wind direction and the possible effects on points of impact. I may find the air currents are more significant than I thought.

Unless I'm totally off base, OCW, Positive Compensation and ladder tests all seem to be getting at the same thing: determining the effects of powder charge on point of impact. They all just go at it a bit differently, and whichever one is easiest for someone to interpret may be the best one for them to try, although ladder tests are usually done at longer ranges and typically involve using a chronograph as well. A question I would ask about shooting at one POA in Pos Comp instead of multiple POAs in OCW: If my OCW POAs are 8" apart 100 yards away from me, I'm moving my muzzle somewhere in the neighborhood of 0.01 inches between groups. How likely is it that making that adjustment is really going to skew my results as opposed to shooting all groups at one POA? It seems like a minor effect, but perhaps there is something I'm missing.

Last night I decided to work up an OCW test using IMR4350. Looking forward to shooting them. I suspect that, despite my earlier claim that I would give up and sell the remaining box of bullets if I can't get a load to work, it's more likely that I'll give one of the other three powders in the closet a try if the 4350 doesn't prove promising.

Again, thank you very much for your time. It is greatly appreciated.

 

[AJC1]

The idea of shooting a string is big in the precision world. Finish a string before conditions change and make small wind correction as necessary. Depending on the length of your test string and the weight of your barrel you may learn other things like the question of to hot. If you have the smallest amount of stock clearance when things start heating up you may notice a large poi shift due to contact somewhere on your barrel. For your testing a string of 5 should be sufficient before you test a change on another target. The focus is always on group size not poi so in the second or subsequent strings if conditions do change they can be evaluated as a different event.

 

[lordpaxman]

Last night I decided to work up an OCW test using IMR4350.

I use the OCW method as well with a few changes. Others on this forum suggest 300 yds instead of 100 yds. I also have a Labradar so I can record velocity as well as POI. While V isn’t a factor in OCW I just wanted to have that data at the same time for future reference. Good luck.

 

[JFrank]

Just being aware of the potential for error should be enough, interpreting results seems to be the difference, poi is key in either method. When bullets impact the same horizontal plane and or over lap the Chrono should reveal very little variances in fps despite the increase in powder ( that's a node) size and shape can be manipulated to the potential of the components through fine tuning. Some combos just don't get along....
J

 

[barnfrog]

Well, based on the initial returns, it looks like 243winxb might be the winner. He suggested a load of 42 to 43 grains of IMR4350. Here are the results of the OCW test I ran today with that powder.

Charge.......Vert. from POA.......Grp. size
41.8...............0.66".....................1.62"
42.2...............0.50".....................0.68"
42.6...............0.54".....................1.02"
42.9...............0.14".....................1.40"
43.3...............0.54".....................1.14"
43.6...............0.70".....................1.60"
44.0...............0.14".....................2.52"

So at first glance, I think I'll try five rounds loaded at 42.4 grains and see what that looks like. If it groups right in that 1 MOA ball park I think I'll leave well enough alone and not even bother tinkering with seating depth.

Also, I picked up an inexpensive IR thermometer and Lowes and checked the barrel temperature between shots. Once it was warmed up, waiting 2 minutes or so between shots kept it at about the same temperature for each shot, +/- 5 degrees F. I think that's better than the routine of 1 minute between shots and 5 minutes between groups, because using the 1 and 5 configuration the barrel temp is rising with each shot in the group. At least in my gun.

In case anyone is wondering, the verification group I shot with Hybrid 100V was over 2.5", verifying that Hybrid 100V and Barnes TTSX 80 grain bullets aren't a great combination in my gun.

I want to say thanks again to everyone who offered advice and opinions. For those who suggested other powders, they might have performed as good or even better. I'll probably never know. But I appreciate the time folks took to weigh in.

 

[JFrank]

Can you post pictures of the targets please ?

 

[barnfrog]

Here you go. The target squares are 5/8" inside the lines and 7/8" outside. I find it easier to hold centered on the squares than on circles.

 

[JFrank]

The center of groups 41.8 and 42.2 are almost identical with the latter actually smaller, I would would put my money on 42.0 and 42.2 repeating, after that they start moving around.
J

 

[barnfrog]

The center of groups 41.8 and 42.2 are almost identical with the latter actually smaller, I would would put my money on 42.0 and 42.2 repeating, after that they start moving around.
J

Just to make sure I understand what you're saying: even though there is a bigger difference in the group size as well as the vertical location of the group centroids between 41.8 and 42.2 than there is between 42.2 and 42.6, you're suggesting I try a load between 41.8 and 42.2? Not necessarily questioning your advice, just want to be sure I have it straight, but also understand the reasoning. Certainly makes sense to dismiss everything above 42.6.

 

[JFrank]

Your powder increments are quite large and easy to go past a node. Just a note...
The center of the group ( point of impact ) in relationship to the group poi in each side of that particular group is what we are looking at. When exit timing is optimized rounds will impact at or very near the same location despite the increase in charge weight prior to breaking out of the quadrant and getting erratic. Nodes are stable not erratic, I can manipulate a groups size and shape with seating depths and neck tension and i can adjust my scope once load development is complete to what ever zero I want.

 

[JFrank]

D

 

[barnfrog]

Your powder increments are quite large and easy to go past a node. Just a note...
The center of the group ( point of impact ) in relationship to the group poi in each side of that particular group is what we are looking at. When exit timing is optimized rounds will impact at or very near the same location despite the increase in charge weight prior to breaking out of the quadrant and getting erratic. Nodes are stable not erratic, I can manipulate a groups size and shape with seating depths and neck tension and i can adjust my scope once load development is complete to what ever zero I want.

Thanks for your continued help, Jim. I used those powder increments based on the OCW instructions I found here: https://www.twincityrodandgun.com/docs/Dan Newberry - OCW.pdf. If I am reading it correctly, the increments should be around 0.7% of your chosen max load. But I can also see how a node could get passed over using increments that large.

I get the stability of nodes, and the optimization of exit timing. The sentence I'm having trouble understanding is this: "The center of the group ( point of impact ) in relationship to the group poi in each side of that particular group is what we are looking at." I just can't make sense of it. Is there a way to re-state it? Sorry if I'm being dense, but to me it reads as if you're saying look at the center of the group in relation to the center of the group.

Thank you again for sticking with this. I know it's frustrating to try and explain something to someone who's just not grasping your meaning.

 

[ms6852]

But I'm fairly confident that my gun and I are capable of producing decent groups.

Have you considered the fact that your rifle just does not like this bullet. My brother was having difficulty getting group shots he liked using the barnes ttsx. Rifle twist was supposedly a 1:10 but when I ran a patch to check it , it measured 9.5. Anyway he switch to Hornady and Sierra bullets and heavier 95 to 100 grain it consistently got bug holes.

 

[barnfrog]

Have you considered the fact that your rifle just does not like this bullet. My brother was having difficulty getting group shots he liked using the barnes ttsx. Rifle twist was supposedly a 1:10 but when I ran a patch to check it , it measured 9.5. Anyway he switch to Hornady and Sierra bullets and heavier 95 to 100 grain it consistently got bug holes.

This is most definitely a possibility I have considered. I thought I would give it a go with a different powder to see if I could get better results, but there may come a point when I just go with a different bullet.

I have verified the twist of my barrel to be 1:10.

 

[JFrank]

no worries mate'
I'm just not explaining it very well.

 

[lordpaxman]

The sentence I'm having trouble understanding is this: "The center of the group ( point of impact ) in relationship to the group poi in each side of that particular group is what we are looking at." I just can't make sense of it. Is there a way to re-state it?

I think, I’ll be corrected if I’m wrong ., he’s saying you check POI shift of the current group by looking at the previous group and the next group. At least that’s how I interpret it and do OCW. The first and last groups don’t have a left side and right side respectively.
It almost looks like you might have another node in the 43.3 - 43.6 area. If the high impact of 43.6 were a bit lower it and prior group center would be pretty close.
When I do OCW I try to get a piece of cardboard wide enough to put all targets in a line so it makes it a bit easier to try to check vertical changes. Good luck.

 

[JFrank]

With this horizontal example, the groups on each side of the red mark are stable and impacting on the same vertical plane despite an increase in powder.

 

[barnfrog]

View attachment 999501With this horizontal example, the groups on each side of the red mark are stable and impacting on the same vertical plane, ( in your case near identical horizontal as well) loading in between those two charges the rounds will continue to impact that poi despite the increase in powder.

Thanks, that makes perfect sense and comports with my understanding of OCW methods.

So looking at the groups again, even though there is less vertical shift from 42.2 to 42.6, there's less overall shift between 41.8 and 42.2.

 

[JFrank]

D

 

[barnfrog]

Well, I finally got a chance to load up a few more rounds and shoot them. After some additional consultation with my boss and quasi reloading mentor, I decided to just load another group of the 42.2 grain load instead of tinkering with something in between groups. Here are the results, which I am very happy with for a deer hunting load. Thanks again to everyone who offered advice and insight.