Major Velocity Uniformity Difference With Powder in 223

[CharlieNC]

Started shooting 223 in Savage 1 1/2 years ago, and could achieve 1/3 MOA at my 200 yard range using 69SMK and Varget. I was so impressed I ordered a Brux barrel replacement (22" 1:8 twist) to hopefully achieve this more consistently, plus have a nice barrel to last the rest of my life (I'm not young). Cheap to shoot plus great accuracy = primary training weapon.

About the same time I got the new barrel I scored on a lot of IMR4064, which looked suitable for the 69-75gr bullets, so based on Optimum Barrel Times I did an OCW comparison vs Varget and it looked better. But with additional fine-tuning I have not been able to get consistent groups, most in the 1/2 - 1 MOA range. So I got a chrono (first one) and it showed quite a velocity spread with SD around 28 (ES over 60)! Thought it may be the "new" LC brass so tried recently fire-formed LC and new Lapua; no improvement (Lapua actually worse).

Maybe the wrong powder? Found the following:
4064: SD = 28 Varget: SD = 35 RL15: SD = 7 CFE223: SD = 13
So now I will work on the RL15 and work up the OBT and OCW.

Apparently this barrel does not like the faster powders. Although I have defined good nodes, the accuracy is just not there with 4064 and the high velocity variability of 4064 and Varget will not shake out too well at longer ranges.

Anybody else had a similar experience? I am surprised at such a major difference and would like to understand WHY if at all possible.

 

[1lnbrdg]

I've always had issues getting the .223 into the low SD numbers that I can get with my .308. I don't think I've ever had under 40fps max deviation with a .223.

I think it has more to do with the recoil impulse than the powder burn rates. My $.02 on it anyways.

 

[CharlieNC]

Looking at the pressure and velocity curves in Quick Load, I see hardly any difference in the faster vs slower powders I compared. I'm trying to get a lead on what to look for to better understand how to choose a powder, and reduce the amount I'm burning up.

 

[Drifter™]

Have you experimented with different primers and bullet seating depths?

Both can potentially have an effect on consistency.

 

[gstaylorg]

.223 Rem has only about half the case capacity of something like a .308 Win cartridge. Therefore, a small discrepancies in powder weight will give you almost double the change in velocity relative to a .308 (ie. extreme spread) because the variation will be almost twice as large as a percentage of the total charge weight. You want to weigh powder as accurately/precisely as possible for a small case like the .223. How are you weighing your charges? I typically weigh powder to +/- 1/2 kernel using, which is less than 0.01 gr. Few have either the desire or patience to do that, but it pays off in terms of extreme spread. I typically see ES values around 15-20 fps for .223 Rem, with single digit SD values. You may not need to go to that length, but I would be weighing to at least +/- 0.1 gr, if possible. Your SD values indicate extreme spreads that are pretty large, even larger than factory ammo (in the case of Varget or 4064), which typically show ES values of over 50 fps in my hands.

I'm not sure it is fair to conclude that your rifle "doesn't like" faster powders solely from the info you posted. Although that is one possibility, there are many other potential explanations. Ideally, you want to use a powder that will give you the best efficiency and put you where you want to be for that bullet/barrel combo in terms of pressure and velocity. The best efficiency will usually be found at slightly under max pressure, meaning somewhere in the neighborhood of a 95% fill ratio up to slightly compressed. In a .223 Rem case, that likely means a powder with smaller kernel size in order to get enough in the case to achieve the kind of velocity you're after. It is also much easier to measure charge weights accurately and precisely using powders with smaller grains, IMO. Some people have also reported that changing primers can have a huge impact to help lower ES/SD.

A 22" barrel is not extremely long like some of the barrels seen in F-Class rifles (30"+), so a slightly faster burn rate ought to be good for that setup. The R15 looks like it might work for you, but if not, I would suggest something like H4895 or 8208 XBR. Both are relatively fine grained, temp stable, and should work very well for your setup.

In any event, all of the powders listed here or in your original post have been used with great success in .223, so it should be possible to generate a load for your rifle with at least one of them that works well. For the 69 gr SMK, I would start it at around 0.015" off the lands, and I would work up your charge weights in 0.2 gr increments for the initial testing (0.3 gr increments are too large IMO for the small .223 case). Then go back and find the center of the node using 0.1 gr increments. Once you have your charge weight, do a seating depth test from .009" to .025" off the lands in .003" increments. You should end up with a load that shoots very consistently and has less than ~ 30 fps ES and SDs in the 10-15 range, depending on how accurately you can weigh the powder. Good luck with it and let us know how it works out.

 

[CharlieNC]

Being less particular when loading I had better groups with the 20" Savage barrel and Varget than I have achieved so far in the new name-brand custom barrel, even with going to extra pains now. I recently got a tuned balance beam from Scott Parker, and the performance in other loads is great. The load development was in 0.2 gr increments across a wide range, and identified good nodes, then worked with seating depth. Loads were slightly compressed. The OCW procedure for charge and seating depth identified the best load with this powder, but even at a node the results were not satisfactory for groups or velocity uniformity. This is not so unexpected, and it does not come as a surprise that some powders are certainly better than others in this regard.

The lower velocity SD with the RL15 (slowest powder) is statistically significant at a high level, and since I loaded the different powder groups at the same time with the same components, and all were shot at one setting, it is conclusive that the improvement is from the powder. This is not to say that my loading techniques cannot be improved, but they were the same for all the powders in this case.

So my question is not how to improve any given load, but how to select a better powder to work with in advance? Why did Varget, a known good performer, work well with the same bullets in one barrel, and terrible in this one? Perhaps there is not a good answer. One factor that is different is the jamb length on the Savage was quite a bit longer, so the chambers are different. Well I'm scaling up for OCW testing around the OBT nodes using RL15 now, and we'll see how that turns out.

 

[Drifter™]

One factor that is different is the jamb length on the Savage was quite a bit longer, so the chambers are different.

The best COL for each chamber / barrel will likely be different. And they might not like the same jump either.


Varget is a reasonable powder to try, but it's not necessarily the best in every barrel. Be sure to test different primers with any powder you try in each barrel, regardless of what combination has worked well in other barrels. The results can sometimes be surprising.

The fact that a barrel might show a preference for RL-15 over Varget, of vice versa, is not surprising.