Powder Load testing my new McGowen 260 Ackley Improved - And some questions

[Onewolf]

My new McGowen barrel (28", SS, Shilen #7 profile, 260 Ackley improved, 1:8 twist) was delivered a couple weeks ago (Thanks Dennis!) and I have started doing load development for it. I just started shooting bolt action rifles about one year ago and I started hand-loading early this year. This rifle is intended for 'fun' shooting out to the maximum distance (currently ~1100 yds) of our long range field/match shooting club.

The rifle uses a Manners T5 stock, Savage target repeater action, SWFA 12X fixed mil quad scope, and a Harris bipod.

Based upon prior research I had bought 8lbs of Hodgdon 4831SC because it (and H4350) seem to be recommended frequently for 260AI rifles. I already had 3 lbs of H4350 (which is virtually impossible for me to find these days). I also have about 5 lbs of RL-17 which turned out to be the 'winner' with my other McGowen 24" Rem 260 rifle.

I decided to do a basic powder load test of all three of these powders this morning. All rounds were prepared exactly the same: Rem 260 brass fire formed into 260AI, CCI #200 primers, Lapua Scenar 139, COL @2.802" (0.015 jump to lands).

For each different powder I did a quick barrel clean, and I shot 3 'fouling' rounds before shooting the powder load tests. All shots were fired at 200 meters. The temp was 68-70 degrees and sunny. I shot 3 round groups because I was shooting 22 groups + foulers/zeros.

H4831SC: 46.0, 46.5, 47.0, 47.5, 48.0, 48.5, 49.0

49.0 was showing signs of pressure (flattening primers) and I would have stopped at 49.0 even if I had made some 49.5 rounds.

H4350: 42.0, 42.4, 42.8, 43.2, 43,6, 44.0, 44.4, 44,8

44.0 was showing slight pressure signs. 44.4 was definitely showing pressure signs. I did not shoot 44.8.

RL-17: 41.6, 42.0, 42.4, 42.8, 43.2, 43.6, 44.0

44.0 was showing signs of pressure (flattening primer) and I would have stopped at 44.0.

All shots were fired using a bipod and rear bag from a wood bench with two other shooters bouncing the bench.

Observations:

1) This barrel/rifle appears to be a 'shooter'.
2) H4831SC between 47.5 and 48.5 appears to have a potential accuracy node.
3) The H4350 shot nice groups, but the ES and SD were relatively awful.
4) The RL-17 between 42.0 and 43.6 had great groups and great ES/SD except for 42.4. What happened at 42.4?

Based upon these results should I reject H4350 (since it's very hard to find anyway)? Great groups, terrible ES/SD?

I'm leaning towards further refining the RL-17 load since it seemed to provide nice groups, very good ES/SD _and_ slightly higher velocity than the H4831SC @ 48.0 and 48.5.

Does that seem like a reasonable analysis?

H4350 - Nice groups, terrible ES/SD

link to full image (http://www.onewolf.org/Files/TgtGfx-H4350.jpg)

http://www.onewolf.org/Files/TgtGfx-H4350.jpg

H4831SC - Accuracy node between 47.5 - 48.5?

link to full image (http://www.onewolf.org/Files/TgtGfx-H4831SC.jpg)

http://www.onewolf.org/Files/TgtGfx-H4831SC.jpg


RL-17 - ES/SD at 42.4 seems anomalous compared to all other loads between 42.0 and 43.6.

link to full image (http://www.onewolf.org/Files/TgtGfx-RL17.jpg)

http://www.onewolf.org/Files/TgtGfx-RL17.jpg

[Wildboarem]

If you subscribe to the OCW method your nodes should be around 3% apart. So let's say you have a node at or around 41.8-42 than your scatter node will show up around 42.4- 42.6. Your next accuracy node would be around 43.2- 43.4. I verify my nodes sometimes by using the scatter nodes. If I think I have a node I will load up +/-1.5% (scatter node falls in the middle of accuracy nodes) and see if the grouping falls apart.

I like #5 in you OCW. Mainly because of the trending poi and the nice triangle grouping (nice and even not stringing).

I try and find two powders that shoot just in case one powder becomes har to find ie h4350. Good luck.

[homefrontsniper]

sorry to say this but at 200 yards all the shots should be touching keep trying though .

[Onewolf]

Thanks for the quick response.

I'm not 100% sure if you mean you like #5 in the H4831SC test or #5 in the RL-17 test? The RL-17 groups between 42.8 and 43.6 look pretty good (and the have great ES/SD).

At this point my plan is to perform another RL-17 test with 5 shot groups at 42.8, 43.0, 43.2, 43.4, and 43.6. Does that make sense?

[Onewolf]

sorry to say this but at 200 yards all the shots should be touching keep trying though .

Seriously? Shooting from a wooden bench with other shooters bouncing the bench, using a bipod and rear bag? I will be very happy with a 1/2 MOA rifle shooting 10 shot groups at 300 meters.

[Wildboarem]

Thanks for the quick response.

I'm not 100% sure if you mean you like #5 in the H4831SC test or #5 in the RL-17 test? The RL-17 groups between 42.8 and 43.6 look pretty good (and the have great ES/SD).

At this point my plan is to perform another RL-17 test with 5 shot groups at 42.8, 43.0, 43.2, 43.4, and 43.6. Does that make sense?

Sorry didn't see all the photos. I was referring to the h4831 #5. I would load 48.0 and do a seatin depth test, done.
You narrow around that 48, load 47.8, 48, 48.2 then do seating depth.

Rl-17 I would load +/-.2gr around 43.0 gr then seating depth test.

It must suck having such an innacurate rifle.

[sharpshooter]

First thing I would do is try a CCI BR-2 primer.

[squirrelsniper]

I gotta go with Sharpshooter on this one and suggest trying a different primer (or as he did, at least the "match" version of what you're using).

The H4350 looks good, but that ES/SD is never going to work well at your listed max range of 1,100yds. High ES/SD is often a primer issue.

Both the H4831SC and RL-17 both show vertical stringing. Again, assuming the shooter is doing his job behind the rifle, it suggests a primer issue may be rearing its ugly head.

Personally, the first thing I'd do is play with H4350 and at least a couple different primers. If that doesn't work out, then RL-17 and a couple different primers. Although I can't pinpoint exactly what it is, there's just something I don't like about those H4831SC groups.

[Brent]

Change primers if you can find Federal Match 210. We fought an issue recenlty with CCI and solved it quickly with Federals.

Vertical strings are usually ES issues as already mentioned by primer, load work up issues, or shooter. Assuming it is not shooter eye to scope issues then try a quick primer change. We like the 4831 in the 260's, best speeds, and low ES. But your rifle is indicating a like for 4350. Perhaps take the best 4350, change the primer, or do a quick seating test.

[Onewolf]

Thanks for all the responses.

I have BR-2 primers that I will try (I was planning to save those for my 'real' long range field/match rifle). I have serious reservations about pursuing H4350 as the initial option because I have had an incredibly hard time acquiring it (I haven't been able to find/buy any in over 6 months). My current supply of H4350 would last about one month given that we are currently in the "prime" shooting period of the year.

I think I am going to do my next powder load test using RL-17 and BR-2 primers in the 42.8-43.6 range.

[RiverSink]

43gr-RL17,BR-2, move on to seating depth testing.

[jerry shaw]

You present a great question.
Bottom line up front - don't eliminate a powder that might produce good results without doing a lot more testing.

I would try some BR2 primers (or Fed Gold Medal if you can find them) before eliminating a powder. My own testing showed that BR2s give me results I would not otherwise have expected with a range of powders. I experimented with a number of primers before settling on them. They give better across-the-board accuracy than anything I have tried. Not just smaller muzzle velocity standard deviations but smaller groups overall.

Same thing applies to bullets. The Lapuas are great bullets through most barrels. I get great groups from my .308 WIN guns, but have significantly different recipes. I use AMAX 155s using N150 with my Savage Palma gun - whereas the Berger 155's produce bughole groups through a Shilen Barrel with Varget. The only way to get there is through experimentation and patience.

Good luck.