Onewolf
Member
My new McGowen barrel (28", SS, Shilen #7 profile, 260 Ackley improved, 1:8 twist) was delivered a couple weeks ago and I have started doing load development for it. I just started shooting bolt action rifles late last year 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
H4831SC - Accuracy node between 47.5 - 48.5?
RL-17 - ES/SD at 42.4 seems anomalous compared to all other loads between 42.0 and 43.6.
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
H4831SC - Accuracy node between 47.5 - 48.5?
RL-17 - ES/SD at 42.4 seems anomalous compared to all other loads between 42.0 and 43.6.
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