High SD w/ RL17 and 185 Bergers (308)

[blue_ridge]

I've been working up loads for a new 308 and almost everything shoots sub 1/2MOA at 100yds. At first I wasn't using a chrono, but decided I better look at velocity and SD numbers to help decide which load to concentrate my future efforts on.

I've shot Berger 175BT's and Lapua 155 Scenars with Varget. Tried some XBR8208 w/ Scenar 155's and some RL17 with Berger 185BT's.

What I found with the chrono was the RL17/185 loads had somehwat poor SD's. In the 25-40 SD range for three 5 shot groups (46.6, 46.9 and 47.2 gr). Velocity averaged 2550 to 2600 out of my 24" barrel. (chrono 15 ft away)

However, using the same once fired brass, prepped exactly the same way (FL re-sized to bump shoulder back .001-.002, primer pockets drilled, flash hole, neck chamfered w/VLD tool, BR2 primers) I got 4-6 SD using 8208 and 155's. The only other difference besides the powder and bullet was I seated the 155's into the lands .005. The 185's at max mag length (2.860) give me .020 off the lands.

Is RL17 known for having higher SD than other powders? I've read people saying 8208 is very consistent. So maybe it is what it is. 8208 showed better consistency than RL17 across three 5 shot strings of each. I like the idea of shooting the 185's but I also want low SD because I intend to shoot at 600-1000yds once I settle on a load.

So, I have a bunch of questions. Should I abandon the RL17/185 load and stick with 8208 and 155's? Or should I try another powder with the 185's? I have Varget, 4064, RL15 and N540 on hand. Or possibly change the seating depth to more than .020? Maybe a different primer than BR2's w/ RL17/185?

 

[esorensen]

Re: High SD w/ RL17 and 185 Bergers (308)

You might want to try a different primer, or change the seating depth or both. I have had pretty good luck with the CCI BR2's though. I was however putting the bullet into the lands.

 

[MALLARD]

Re: High SD w/ RL17 and 185 Bergers (308)

25-40 isnt that bad. 4-6 is great dont you think ? I might settle with the 155s , or try another powder with the 185s, i might change the seating depth to , sorry i couldnt be of help. It seems like you got it figured out though. I wouldnt change the primer but thats one idea.

 

[customones]

Re: High SD w/ RL17 and 185 Bergers (308)

I have also had issues with reloader 17 in the sd department in the 6.5 284 with the 140 class bullets, velocities were better than 4831 sc but the sd was 20-30 fps variation. Also noticed it is extremely sensitive when you approach the higher end of the loading recommendations.

 

[blue_ridge]

Re: High SD w/ RL17 and 185 Bergers (308)

Thanks for the replies. I'm happy with an SD of 4-6. I've loaded up some more 8208/155 loads to narrow down which one looks best for my rifle and see if the SD stays that low in the 2nd test. In the first outing, I worked up from 43.5gr 8208. At 45.0gr things started tightening up with a 1/4 MOA group and SD of 6, at 45.5gr. group was 0.4", SD was 5, at 46.0gr. group was also 0.4" and SD was 4. So I've loaded up some more starting at 44.9 and working up in smaller increments to 46.2. (no pressure signs at 46.0, checking base of case with shell holder and looking for primer signs)

But I had wanted to find a 185 load. I'm sure I can if i try enough combos, but I'm on the fence about pursuing it now since 8208 seems to do so well. So I was wondering if others thought RL17 has a tendency to run somewhat inconsistent. If so, I would drop the RL17 and start testing some Varget or N540 with the 185's. But, if people say RL17 has worked great for them, with low SD's and good accuracy, I'd be more inclined to stick with 8208/155's for now. RL17/185's did shoot okay, with 0.41" and 0.45" groups at 46.9 and 47.2gr.

 

[blue_ridge]

Re: High SD w/ RL17 and 185 Bergers (308)

Was also wondering to myself, what SD should I find acceptable? So I took my velocities recorded from one RL17/185 load and used it in JBM for a ballistic comparison at 1000 yds, zero'd at 200, std weather conditions. My 47.2gr of RL17 and 185 Berger BT averaged 2594fps with a low of 2562 and high of 2626. Here's what JBM says:

2562fps - drop=369.2", 10mph wind=76.0"
2626fps - drop=348.4", 10mph wind=72.8"

So with an SD of 25, I could expect to see shots that varied 20.8" vertically and 3.2" horizontally in 10mph sidewind. That doesn't sound too good to me. I know you need a larger sample for sound statistics, but I think this gives me a rough idea of what to expect at 1000yds.

Now if I take one of my 8208/155 loads, that averaged 2968fps with SD of 4, a low of 2963fps and high of 2974fps in JBM I get this:

2963fps - drop=303.0", 10mph wind=79.8"
2974fps - drop=300.3", 10mph wind=79.3"

So this load would vary 2.7" vertically and 0.5" in a 10mph sidewind.

Unless I am oversimplifying something important here, it seems SD is pretty critical for a 308 at 1000yds. I would think an SD in the single digits to be the goal, with an SD of below 15 a requirement. I'm open to suggestions, opinions and criticism.

 

[Super-X]

Re: High SD w/ RL17 and 185 Bergers (308)

Are you looking to use a single powder for all of the bullets you use? If I remember right the M1A guys I used to shoot Highpower with used RE19 with the heavier bullets and something else for the lighter ones... don't remember what though. You might try a slightly slower powder than RE17 w/ the heavies.
Just a thought........TM
I used RE22 but then I had 28 1/2 in. barrels in 6/284 and 22/250AI. I went on the assumption that velocity can overcome BC numbers w/ less time of flight.

 

[blue_ridge]

Re: High SD w/ RL17 and 185 Bergers (308)

No, I'm not worried about using same powder. Seems like many have been using RL17 for 200+ gr pills, so I'm not sure it is too fast for 185's. Mostly I'm wondering if others have notice Sd issues with RL17.

 

[blue_ridge]

Re: High SD w/ RL17 and 185 Bergers (308)

Tried some N540 and got better SD than RL17 w/185's. Out of four groups I had one single digit SD (9) and the other three were all under 15 SD. Good accuracy too, but this rifle built by Walker Custom Rifles shoots everything well.

I was also surprised to see slightly better velocities from N540 than RL17. I think it is a pressure thing. I think RL17 loads are probably not pushing pressure limits in this case, whereas N540 probably is. Could see some ejector marks on the highest N540 load I tried (45.0 w/185's). That load gave me an average of 2655fps out of a 24" barrel. 47.2gr. of RL17 gave me an avg of 2594fps with same 185's at same 2.860 COAL.

 

[tatemarb]

Re: High SD w/ RL17 and 185 Bergers (308)

I think the 185 bullet is on the lower end of the weight spectrum for Reloader 17 in a 308 win. The 17 is best in short, fat magnum calibers but seems to work well in .308 win if the bullet is heavy enough or barrel long enough. The jump of .02" may allow the neck tension to affect the SD/ED more as well. The powder charge needs to be a little compressed as well I believe. If you aren't seeing pressure signs then continue to increase the load (cautiously of course) until you see pressure signs or you have a tightly comressed load. And try to anneal the brass if you cannot load into the lands.

Try the same workup you have done to date but single load at lengths that put the bullet in the lands to see if that helps with the spread.

A magnum primer works well for some with RL-17 and will probably give more uniform ignition with high load densities.

Just some ideas I have gleaned from others here. I haven't tried 17 yet. I plan to try it though since I have a 300 SAUM that could use it as well as the 308.

tater

 

[shoepop]

Re: High SD w/ RL17 and 185 Bergers (308)

Not 185 but 210 # 30419 Berger's out of a TRG 22 1x11 twist, aac cyclone suppressor, 49 grains RL17, Win brass, 210 Berger, Fed 210 GM primer. 61 degrees, DA 5563 ASL, 5 shots over an Oehler 35P ave. 2675 FPS, SD 5. No pressure indications.