Thread: 6.5x55 SE Sanity Check

Originally Posted by Magnetite

I had a look at how pressure and velocity increase in relation to charge weight in both the 260 and 6.5x55. Looks my initial figures where too high. Assuming a linear relationship (I know it's not but there's only two data points) and target pressure of 58,000psi (the same as the 260).
New maximum charges:
2209 47.5gr @ ~2800 w/ 24" barrel
2213SC 50.5gr @ ~2800 w/ 24" barrel

I will be reducing them by 10% and working up in 0.5gr increments.

Pressure and velocity do not run hand in hand. A lower velocity load may have higher pressure, or even a pressure spike, for a number of reasons.

Originally Posted by Jhon

Pressure and velocity do not run hand in hand. A lower velocity load may have higher pressure, or even a pressure spike, for a number of reasons.

Just some clarification on my prior statement. It is specifically referring to two cases with similar volume (<10% difference) running the same powder. Correct me if I'm wrong but unless you have an under fill situation (below book minimum) or are seeing pressure signs the relationship is close to linear. I know there are some powders which are notorious for pressure spikes but I believe 2209 and 2213SC aren't.

PS: Also haven't jammed the bullet into the lands, or compressed the load.

Originally Posted by Magnetite

Just some clarification on my prior statement. It is specifically referring to two cases with similar volume (<10% difference) running the same powder. Correct me if I'm wrong but unless you have an under fill situation (below book minimum) or are seeing pressure signs the relationship is close to linear. I know there are some powders which are notorious for pressure spikes but I believe 2209 and 2213SC aren't.

PS: Also haven't jammed the bullet into the lands.

To be honest mate I'm quoting something I learned elsewhere rather than by experience. The point made was that pressure can vary widely and separate to velocity for a number of technical reasons. That is, you cannot rely on an increase in powder that gives a linear increase in velocity to also give a linear increase in pressure. This is the key issue of going beyond published data. If the published data gives a velocity that one would like to improve on, and the indicated pressure is below published max for the cartridge, folk tend to assume a few steps above published load data will increase velocity and pressure at the same relative rates. This is not necessarily the case. While US liability realities might mandate large margins for error, we clearly go beyond published data at our own risk. Without being able to see what happens to pressure there is a real risk of crossing the line if we assume a linear relationship. Of course we still do it. Hopefully with a piece of string operating the trigger lol. I made the comment because I think its important to acknowledge in a forum, where the risk lies. There is no telling who will come along and read a thread and get the wrong end of the stick. Hope you don't mind. Watching with interest. J.

Originally Posted by Jhon

I made the comment because I think its important to acknowledge in a forum, where the risk lies. There is no telling who will come along and read a thread and get the wrong end of the stick. Hope you don't mind.

I don't mind at all. Hopefully I have been clear enough (In my first post I mentioned it's over max and again when I posted over max data).

Originally Posted by Jhon

The point made was that pressure can vary widely and separate to velocity for a number of technical reasons. That is, you cannot rely on an increase in powder that gives a linear increase in velocity to also give a linear increase in pressure.

When venturing past max, my new approach is to cross reference with Gordon's Reloading Tool and data from previous testing. But yes it is very much at your own peril.

Sounds about right. What's the rifle? I've a Ruger 260 and a husky 1640 6.5 on the way.

2209 is a good choice for your bullet and barrel imo. But i would stop at 44.02grains and choose the 143gn eldx for hunting. I kinda dont see the point of light projectiles whatsoever unless your gun hates heavies (like my 243).

If your shooting a tikka I'm getting out standing results with 143 eldx in front of norma brass fed 210m and 44.8 of 2209 validated at 2720.
I cant shoot any better than that load

Sent from my SM-G950F using Tapatalk

I did check the group sizes at 100yards but I don't trust them entirely as the wind was up.

Grains 42.5 43 43.5 44 44.5 45 45.5
Max Spread 1.172 0.988 1.290 1.926 1.337 1.496 1.136
Group Height 0.961 0.985 1.283 1.817 1.108 1.462 0.872
Vertical Offset -0.785 -0.105 -0.529 0.332 -0.325 0.610 -0.249

The plan is as follows:
Work up a load with 2213sc. Shoot best load from 2209 and 2213sc and compare. Then move on to seating depth testing.

I botched some of those numbers. Corrected below:

Grains 42.5 43 43.5 44 44.5 45 45.5
Max Spread 1.172 0.994 1.287 1.926 1.326 1.496 1.135
Height 0.961 0.991 0.648 1.817 1.174 1.462 1.039
Vert Offset -0.785 -0.108 -0.200 0.332 0.318 0.446 0.503
Mean Rad 0.496 0.442 0.580 0.696 0.625 0.506 0.47

Greetings Magnetite,
I tried 49 and 50 grains of AR2213SC behind the 129 grain SST which gave 2,720 and 2,780 fps respectively. You may get a little more. As far as your accuracy figures go you could shoot that string again and get completely different results. For accuracy testing the average of three, three shot groups would give you a better idea.
Regards Grandpamac.

Obligatory disclaimer: What you put in your chamber is your business. Some of these loads are over ADI's maximum.

2213SC powder 4 shots each charge:

Grains fps SD ES
46.0 2475 29.9 63
46.5 2486 34.1 73
47.0 2538 29.3 58
47.5 2570 3.7 8 (Several chrono errors in this group)
48.0 2603 15.6 37
48.5 2632 9.7 23 (ADI Maximum)
49.0 2645 13.3 32
49.5 2677 8.4 19
50.0 2709 10.3 23
50.5 2749 8.3 18
51.0 2769 14.7 34



It looks to me that 49.5-50.5gr should be pretty good. The node seems to be a bit wider than the 2209 but you sacrifice 100fps. I didn't see any pressure signs and it's under expected velocities. I not sure what I should call maximum. What's everyone's thoughts on the 2213sc vs 2209 data?

2209 data for easy reading:

Originally Posted by Magnetite

Grains fps SD ES
42.5 2693 23.3 52
43.0 2726 12.6 28
43.5 2750 10.4 19 (only 3 shots)
44.0 2761 16.8 39
44.5 2780 9.9 24
45.0 2805 9.5 22
45.5 2842 21.8 43

I’ve always been a group or ladder shooter when looking for new loads. However following Erik Cortina I would now look more closely at ES to zero in on the node.

Originally Posted by Dicko

I’ve always been a group or ladder shooter when looking for new loads. However following Erik Cortina I would now look more closely at ES to zero in on the node.

I like Erik's explanations, and I've cobbled together some form of hybrid method. First off I'm assuming Erik is correct with the charge determines the combustion characteristics (ES/SD) and the seating depth determines harmonics. It seems to me when developing a load your either going for precision or stability. Erik is obviously going for precision, where as the ladder/OCW test are looking for stability. I think with the small sample sizes using SD is preferred. If the samples sizes were larger ES would be preferred.

Using the 2209 data as an example:

Having thought about the data some more it looks like the best way to asses the loads for precision is using the mean ±2SD to estimate the ES for a given charge (IIRC 2SD should cover 95% of the probabilities). Initially it looks like 44gr may be good with the best ES of 17fps. However when using SD the estimated ES(eES) is 67fps. Choosing 45gr with the worse ES and tighter SD gives a better eES of 38fps.

Now with searching for stability like the ladder/OCW test, it seems the best assessment is to look at two charges next to each other. To do this I take the mean of the higher charge +2SD and subtract the mean of the lower charge -2SD. This gives attempts to simulate an under charge on a cold day and an over charge on a hot day (I don't know how much variance this will give but I think 0.5gr should be fair). The ladder/ocw method as I understand it would select the flat spot in the curve (either looking at velocity or vertical shift doesn't matter). This is 43.5-44gr. Using the above method this gives a shifted ES(sES) of 67fps. However the SD of 44gr isn't that great. Looking at 44.5-45gr even though it isn't a flat spot the sES is 63fps which is better.

One final caveat is because we are dealing with small sample sizes I think that the chosen charges will need to be verified. I don't know who said it but I tend to agree with: 3 shots with show you a bad charge not necessarily a good one.

As for my selected charges here they are in order of preference:
2209 44.8gr ~2790fps
2209 43.8gr ~2755fps
2213sc 48.8gr ~2640fps
2213sc 50.8gr ~2760fps

An interesting point I noticed there may be a shared node at ~2750fps with both powders.
Also if anyone has a better understanding of statistics please chime in (I'm not a statistician by any stretch of the imagination).
Let me know if this makes sense or is closer to the ramblings of a lunatic.

Magnetite,
Years ago I got a distinction for biometrics. However I am pleased I didn’t read your post last light half gorged on Shiraz!

While I’m not totally sure I followed your path as you walked it it think you arrived at the right place.

If I followed Erik right after testing for ES and in particular two loads a increment apart worth low Ed he then drill into the space just under the higher load to check precision and then works on seating depth if needed.

Stability I think is determined upfront by powder selection? Burn rate and temp stability. All being equal slow burning and higher case fill% more stable. Your experience may differ?

The other powder to try in the Swede with 140s if available is RL22. It can be rocket fuel in some cases. I really like RL powders despite the supposedly greater temp sensitivity.

Originally Posted by Dicko

However I am pleased I didn’t read your post last light half gorged on Shiraz!

The ancient Persians would debate an idea twice: sober and drunk.

I was combining two ideas with stability. Tolerance to temperature, I think that all powders will be affected by temperature just to what extent will vary. And the other idea is tolerance to charge variation. I intend to throw the charges which hopefully should be ±0.1gr. As for my experience: none. I'm just going off what I've read while I gather my own.

I was planning to try RL19 and RL22 but availability pushed me to ADI. The other nice thing with Alliant is they have data for modern 6.5x55s.