What would you do based on this OCW test? I only have one more range trip before a comp.

[HumbleEinstein]

I did an Optimal Charge Weight type test with my first round of reloads. I used Varget, fire-formed and prepped Norma brass, CCI 200 primers, and 175 SMKs. The rifle is a Remington 700 AAC-SD 20" .308 Win in an XLR Chassis with a PWS PRC muzzle brake. I did three shots at each charge and waited about one minute between each shot. I'm looking for a cartridge that will give me maximum accuracy from 100 to 1200 yards.













The red dots are 2" and the black circles inside are 1". I had setup my Chrony to record all the velocities while I was shooting in prone. The Chrony was on a plastic box and little by little it kept turning. I was hoping it would stop turning but then it shifted big time and I ended up clipping the rods. For that reason, one shot is missing from 43.9, which might have been very telling. I only have reliable chrono data on a couple of five shot test groups, that didn't shoot all that well. With 44.0 grains I got an average of 2549 ft/sec. With 44.6 I got an average of 2593. I was hoping there would be a clear winner in the higher velocity range, but I'm not sure I found that. 43.7 grains grouped at less than .25". That is best I have ever seen from this rifle, although I have always done five shot groups up to this point. The two shots at 43.9 were basically in the same hole, while the third was in the Chrony.

Should I load at 43.7 because it shot so well? Should I load at 43.8 because its in the middle of two good groups (despite the missing shot) and would give slightly higher velocity? Will I get enough velocity in this range for my purposes? If I go with 43.8 grains, do I risk the load sucking since it's untested?

Does anything on the higher end of the charge test warrant further investigation? I'm going to go subsonic before 1200 no matter how I load with a 20" barrel, right? Is chasing higher velocities worth it, in my case?

I HAVE TO DECIDE FAST. I only have one more opportunity at the range to chrono and test final load before a competition I want use my handloads in.

I would appreciate advise from the experienced amongst us.

 

[shoot4fun]

Unless you shot round robin as OCW requires you have not done the OCW. It appears what you have done is either group shooting or a dot drill. From my experience with 308 I would say 44.5 to 44.7 is normally a good accuracy node for the 308 with 175 SMK. The disclaimer here is that I mostly shoot that load in longer than 20" barrels and use only Lapua brass. Your velocity at 44.6 seems pretty low even for the 20" tube. I get 2720 from a 22" barrel. Normally, at this point, you would have a node and just play with seating depth a bit but you really don't have the time for that.
My suggestion is load 44.5 and 44.7 at 2.80 COAL and try it.
I know those weren't necessary benchrest groups like down in the lower loads but there is also more recoil there and that could cause more shooter error.
Shoot at 300 and out to as far as you will in the comp (if you have the range for it). Pick what you prefer at that point and go have fun at the comp. You can drive yourself nuts over the "perfect load" when you have more time.

 

[HumbleEinstein]

I did round robin. Thanks for the advice.

 

[shoot4fun]

I did round robin. Thanks for the advice.

I assumed because you stated "OCW type test" which usually means " I did it but not quite like Newberry said".
Good luck with the load and the match.

 

[HumbleEinstein]

I assumed because you stated "OCW type test" which usually means " I did it but not quite like Newberry said".
Good luck with the load and the match.

Makes sense. I said "type test" because I didn't wait quite as long between shots as suggested. I just didn't have the time.

 

[AtOne]

Personally I'd roll with the 43.8 and go shoot a couple 5 shot groups to confirm.
POI between the 43.7 and the two shots at 43.9 shouldn't change any with 43.8 and should work great.
Load up some more and go shoot a few 5 shot groups to confirm.

I say should because sometimes you get different results on the second time out especially with 3 shot OCW's being the gauge.
Its easy to throw a shot and in a 3 shot group and that makes all the difference in what you think is a good group, where as a 5 shot group you still have 4 to work with, Just my thoughts on it.

It sounds like your pressed for time so just go with that load if it does well, shoot the match and you can come back and work out some higher charge loads when you have more time.

Good luck at the match and have a blast !

 

[Greg Langelius *]

With a longer barrel, I'd back up the suggestions to use the 43.3gr load, but with that short a barrel, I'd hedge it with the 43.9gr load.

I like to ensure that my bullets are at or above 1300fps at target. With the 20" the 43.3gr load may or may not be adequate to achieve such a goal, and 43.9gr is well within published load limits with bullets such as your 175.

That said; trying to advise you under such limited testing opportunities may well be a crapshoot. I would far sooner advise you that basing expectations on a load that has only one group to show for its support is a very thin premise.

Here would be my approach. I would use the 43.3gr load for the shorter distances. Then I would make up an ample supply of both the 43.3gr load and the 43.9gr load for the segments beyond 800yd.

If the 43.9gr load performs well, you're in. If it doesn't, take your best shot with the extra batch of 43.3gr loads.

Either way, continue to redevelop/confirm your load development after the comp.

Greg

 

[Niles Coyote]

Your velocity sounds in line for a factory Remington barrel, I can add 90-100fps to the follow when switching to my 21.75" custom barreled 308...

In my 20" AAC and 20"tactical:
With Lapua brass 43.0g of varget in my AAC is my low node and runs about 2490-2500, the higher node is 44.0 and runs 2540-2550. FWIW, the Tactical likes .1-.2 grains more with Lapua brass and if I use Winchester brass I need to add .1-.2 grains to all those.

I have not used Norma brass in a 308 so I can’t help there. Since you have another range day and you want as much velocity you can get for 1200y I would load up 43.8-44.4 in two tenths steps and retest at 3-4 hundred yards and shoot groups of 5. Pick the one that has the least vertical spread.

There is an even higher node that is also about a grain more but I wouldn’t use it as it was very taxing on brass and depending on the components used and ammo temp, I sometimes saw ejector swipes.

 

[damoncali]

One three shot group per load tells you almost nothing about it. You have to shoot more. Ladder tests (one shot per load) and OCW (three shots per load) are statistically insignificant.

 

[Sig Marine]

Unless you shot round robin as OCW requires you have not done the OCW. It appears what you have done is either group shooting or a dot drill. From my experience with 308 I would say 44.5 to 44.7 is normally a good accuracy node for the 308 with 175 SMK. The disclaimer here is that I mostly shoot that load in longer than 20" barrels and use only Lapua brass. Your velocity at 44.6 seems pretty low even for the 20" tube. I get 2720 from a 22" barrel. Normally, at this point, you would have a node and just play with seating depth a bit but you really don't have the time for that.
My suggestion is load 44.5 and 44.7 at 2.80 COAL and try it.
I know those weren't necessary benchrest groups like down in the lower loads but there is also more recoil there and that could cause more shooter error.
Shoot at 300 and out to as far as you will in the comp (if you have the range for it). Pick what you prefer at that point and go have fun at the comp. You can drive yourself nuts over the "perfect load" when you have more time.

Since time is a concern and does not allow you the opportunity to do much more testing at this point, I'd shoot a couple of 5 round groups of 43.8 and a couple more of 44.5 - 44.7 and take the best one until you get to do more testing. If both shoot about the same, I'd take the higher charge weight for the velocity. And as shoot4fun states, "go have fun at the comp".

 

[gstaylorg]

It looks like you have identified a pretty good charge weight region in your OCW. I would load up 5 rounds each of 43.6 gr to 44.0 gr, and a few extra at 44.6 as sighters/foulers to get dialed in at the start. Total of maybe 28-30 rounds. After sighting in, shoot 5 shot groups for muzzle velocity and grouping. Try to find the upper and lower boundaries of the node. You want to be close to the center of that, if possible. Look for lowest ES and best grouping within that range, even if it's not in the exact center of the charge weight range. As far as 3- or 5-shot groups not being significant, don't worry about it. A lot of top shooters do exactly what you're doing to find their load, without completely shooting out a barrel while they're doing it. If someone can't shoot groups consistently enough to believe what 3- or 5-shot groups are telling them during the beginning steps of load development, no amount of groups is ever going to improve that. Because you only have one more range trip, you'll have to forego the seating depth test and validation at longer range, but that's the best you're going to be able to do in the time you have. Plus, it looks like the 43.7 gr load is shooting very well. One more trip should confirm that that is your load, or possibly suggest 43.8 gr could be a tick better, the test should tell you.

As far as shooting that rifle/load to 1200 yd, I would suggest you're probably going to find that is extremely wishful thinking. Will it get to 1200 yd at that velocity? I'm sure it will. But I think you're going to find that past 800 yd or so, it will drop off in performance pretty quickly. An SMK 175 even at 2750 fps is pretty marginal at 1000 yd if the wind conditions are anything above calm to fairly mild. It will get there, but it will get pushed around a LOT. YMMV.

 

[Tx_Flyboy]

Einstein,

I would retest by loading 43.5 all the way to ~46gr ish...assuming you did not see pressure signs at 44.7.

I would also highly recommend loading 5-shot groups as it is better at telling you where the nodes are. The problem with 3-shot groups is that if you have a shot out there, you don't know whether it is a thrown a shot, or a scatter group. 5-shots will allow you to throw a shot yet still see where the group is centered.

Lastly, keep this in mind. You a shooting a 308. It is a marginal 1,000yard round due to it's relatively small case capacity. The cure for that are:

1. High BC bullets (which the 175SMK isn't)
2. Long barrels (nothing shorter than 24", preferably 28-32")
3. "Stiff" (not overpressure) loads of powder charges.

Anything else is a recipe for frustration and crappy scores at a match when wind is more than 5mph and varying.

I hope you get out there with your 20" barrel. After you do this enough times, you'll be a convert to long barrels...ior as i say "right tools for the job".

Good Luck with the load development and good luck at the match.

 

[Darkside-Six]

based off what you have here, if you did indeed fire this in a round robin style then 43.3 is where it's at.

 

[dariof]

I'd work up another round robin of 5 each at 43.7, 43.8 and 43.9.

Look at the best group and that's your load. Zero in your scope with that load and call it a day.....until you decide to recheck everything.

 

[Darkside-Six]

I'd work up another round robin of 5 each at 43.7, 43.8 and 43.9.

Look at the best group and that's your load. Zero in your scope with that load and call it a day.....until you decide to recheck everything.

OCW is not designed to show you your best group. it's ment to show you your best shots closest to poit of aim.

 

[dariof]

OCW is not designed to show you your best group. it's ment to show you your best shots closest to poit of aim.

Yes. I meant to say best group closest to POA, but typed out the response too quickly.

After looking at the OP's targets, I wold still go with 43.7 - 43.9. I hope the OP lets us know what he ended up with.

 

[HumbleEinstein]

I will certainly let everyone know what I decide to do and report on results. In the mean time, I'm still taking in everyone's advice and thinking it through. I appreciate all the insight so far.

I have just less than a couple weeks before the range trip, so there is still time to decide. The comp is three weeks after that.

 

[jsthntn247]

No need to test anymore. 43.8 is your OCW node, and will shoot well. Your next node will be around 45.1. You are using the wrong bullet for 1200 yards in a 20" .308. Short barrel and a bullet with a low b.c. don't make it to 1200. A 168 hybrid or 185 hybrid would be a better choice.

 

[HumbleEinstein]

No need to test anymore. 43.8 is your OCW node, and will shoot well. Your next node will be around 45.1. You are using the wrong bullet for 1200 yards in a 20" .308. Short barrel and a bullet with a low b.c. don't make it to 1200. A 168 hybrid or 185 hybrid would be a better choice.

You have my attention.

Can you please fill me in on how you projected another node at 45.1? I would be interested in the increased velocity if I can get good accuracy in that range.

Also, can you please tell me more about the hybrid bullets. My barrel is 1 in 10 twist, so I can probably go with a 185. Is there a specific one you would recommend? How much of an increase in BC can I expect by making that kind of switch? Is there a downside?

Thanks.

 

[jsthntn247]

Per the ocw instructions nodes run in 3% increments, so multiply 43.8 x .03 and add it back and you come up with 45.1 which is where your next node will be. As for the hybrids, google jbm trajectory and select the 178 matchking and add your velocity and elevation into the parameters and see when you fall below Mach 1.2. Then do the same for a 185 hybrid and see what you get. The scale will show you where Mach 1.2 is, just look around, you don't want to fall below this number because it's the point where the bullet destabilizes.

 

[HumbleEinstein]

I decided to test 43.8 and 45.1. I only did a handful of groups. The pic below is my best one. Not counting the one outlier it is sub .5 MOA. I'm pretty sure the outlier was me. I'm going to stick with 43.8 for now, but frankly, I think I need to test it again. My kids woke me up at 4 am, I had to drive for a couple hours to the range, and I did a USPSA match that morning. By the time I got to the rifle range mid afternoon I was exhausted, could feel my muscles twitching behind the rifle, and was all around uncomfortable. I got a velocity of 2539 at 43.8. While it would be nice to get a little more velocity, it will have to do. I will use the match in a couple weeks to gather DOPE on the load. I'm really looking forward to it.

Much thanks to everyone for all the advice.

<a href="http://s1349.photobucket.com/user/HumbleEinstein/media/Mobile%20Uploads/photo_zpsf4bdb324.jpg.html" target="_blank"><img src="http://i1349.photobucket.com/albums/p754/HumbleEinstein/Mobile%20Uploads/photo_zpsf4bdb324.jpg" border="0" alt=" photo photo_zpsf4bdb324.jpg"/></a>

 

[29aholic]

I am pretty sure from what I read on Dan's site your load should be the 43.7. It is between the 43.3 and 43.9 and allows for changes in pressure (+/-) which is the whole point of the OCW if I read right.