I loaded and shot NS-CPS' today, 500gr 470NE. I was looking for the best accuracy before going to various FN solids I now have.

Loads are: Federal brass, Federal 215 primers, RL-15: 82 to 87 grains. Please see the photo below.

Any ideas why the left barrel group seems to respond to change in powder charge while the right barrel seems not to?

Brett



[IMG:left] [/IMG]

Is the rear tirgger pull greater than the front? How do other types of bullets shoot in that rifle? I think we need more info to offer good advice.

Is this at 50 yards? If so, I still vote for 500 grains's reply the first time around. Move the rear sight over and call it good.

Agreed...move the sight. You have a small variation vertically...but not unusual. I had a 450 3.25 that did the exact same thing...but it shot 2" groups at 55 yards....about 1-1.5" of that was on the diagonal.
Try 87.5-89 gr with the 500 gr and see what happens. My 470 shoots best at about 2200 fps with the NF's and Woodleighs.

Gary
DRSS
NRA Lifer
SCI
DSC

Will,

This is at 25yd.s. I'm just hoping to work out a better regulating load.

The fact that the left barrel group is larger makes me wonder if there is something simple that might help. I may try to shoot the left barrel first next time. Maybe the bullets are coming unseated under recoil.

Brett

quote:

Originally posted by Brett:
Any ideas why the left barrel group seems to respond to change in powder charge while the right barrel seems not to?

That's what it's supposed to do. When you start low enough, the barrels will shoot wide. As the charge is gradually increased and the velocity rises, the left should walk toward the right. When I run out of powder and have to buy a new lot, reduce, and work back up, that's exactly what my own double rifles do.

Just looking at your diagram, I would suggest loading eight rounds at 85 grains RL 15, and eight at 86. You need enough rounds of each load to tell what it's really doing. Also, I'd shoot at 50 yards, and not waste time at 25.

What kind of rifle is this, and what barrel length? The 87 grain load is probably too hot, as 2125 fps is what a 500 grain .470 is supposed to do in 31" barrels.
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"Serious rifles have two barrels, everything else just burns gunpowder."

quote:

Any ideas why the left barrel group seems to respond to change in powder charge while the right barrel seems not to?

If I can understand your question, you mean that from 82 to 85 gn right barrel point of impacts moves less than one inch but left barrel POI moves 2".
This can bea diference in accuracy or not enough shooting. Try 3R+3R with each charge

BTW: It looks like you need more powder or a lighter bullet IMHO.

Thanks
Martin

quote:

Originally posted by Brett:
Will,

This is at 25yd.s. I'm just hoping to work out a better regulating load.

The fact that the left barrel group is larger makes me wonder if there is something simple that might help. I may try to shoot the left barrel first next time. Maybe the bullets are coming unseated under recoil.

Brett

Brett,

I do not mean to minimize your concerns, but it is difficult enough for me to see anything at 50 yards with open sights. Even at twenty-five yards I still think your rifle is close enough, but then I try not to shoot anything over 25 yards.

I guess it depends on your goal. Pinpoint accuracy out to 100 yards? Try it again and see what happens. Maybe a different outdoor temperature will make it behave differently.

Also I do not believe that one must live with some random or reduced velocity for the sake of regulation. I want my 470 shooting at 2150+ fps and hope it regulates. In my particular case, my 470 shoots pretty much the same regardless of how fast or slow it spits them out. I do not want to have it shoot at 2000 fps just for the sake of regulation.

To my view, the first shot spot on is the one that counts. The second shot doesn't have to be so precise as the critter is probably either clearing off or coming.

If it were me I'd take the loads that are giving me the velocity I wanted (say 87 grs., 2125 fps in your case) and shoot one barrel (the right?) and then the other in fairly quick succession to simulate hunting. Let it cool off, and then repeat 2 or three times.

If it still will not regulate to your satisfaction, I would send it off to JJ or someone to get it re-regulated.

I went back and looked at your first post about this in African Hunting.

I don't understand your worries. It was shooting just fine the first time around.

I have run into the same challenge with a few doubles and NF Solid and CP bullets.

I could get great individual groups, and they would move together as anticipated with increased velociy - but I couldn't safely get enough velocity to bring the two barrel groups together the way I wanted them. Nothing was "wrong" with the bullets or the rifles.

Yours look like they might come together at about 2250 fps, but that's obviously too much velocity and too much pressure.

quote:

Originally posted by new_guy:
Yours look like they might come together at about 2250 fps, but that's obviously too much velocity and too much pressure.

That's what it looks like to me too, which is why I asked about barrel length. Looking back at the old post, it's a Douglass with short barrels. It's already too fast at 2125 in that length and they're still too wide, especially for 25 yards. I think it's time to try a different bullet.
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"Serious rifles have two barrels, everything else just burns gunpowder."

I'm with 400 NE on the 50yds and the four of each load.

I'm with Will on the 87 grain load.

Load eight of those and try them at 50yds. With just one round of each load, there is too much probability of variation from any source, from the shooter to the load itself and everthing in between.

You should be crimping your bullets too, imo. As you know, in the field you may end up shooting a couple of rights before a left. No need to invite the bullet to move. Crimping the NF's isn't difficult so long as all of your cases are the same length and they don't need or want the same crimp pressure you would use for, say, a Woodleigh.

JPK

quote:

Originally posted by 400 Nitro Express:

quote:

Originally posted by new_guy:
Yours look like they might come together at about 2250 fps, but that's obviously too much velocity and too much pressure.

That's what it looks like to me too, which is why I asked about barrel length. Looking back at the old post, it's a Douglass with short barrels. It's already too fast at 2125 in that length and they're still too wide, especially for 25 yards. I think it's time to try a different bullet.
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"Serious rifles have two barrels, everything else just burns gunpowder."

Maybe a different powder. NF's perform well enough better than round noses to try every resort.

JPK

Thanks for all the input. The North Forks seem to be more consistant than Woodleighs in my rifle. Once I get the best NF cup point load I'm going to try the NF-FN. I have some of Jay's banded FNs to try after that and again some GS Custom FNs. Hopefully something will work really well.

BTW, I trim to lehgth so the cases are uniform.

I think I'm going to try sooting groups with 85gr and 86gr. Seems to give the best tradeoff between velocity and regulatiion.

I posted this time mostly because the left barrel seemed to be responding to changes in poweder charge while the right barrel wasn't. I still wonder if that barrel is really responding to changes in powder charge or if it is something else. I may experiment with fireing order or replace the round in the left barrel with a fresh one after fireing the right.

Will, you're probably right that it's fine. I just can't help trying to find a load that gives really good accuracy at a reasonable velocity.

Brett

quote:

Originally posted by Brett:
I posted this time mostly because the left barrel seemed to be responding to changes in poweder charge while the right barrel wasn't.

Again, that's normal.
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"Serious rifles have two barrels, everything else just burns gunpowder."

400,

Is it normal for one barrel to change POI with changes in powder charge but not the other??

Brett

Yes. As the charge is increased, it's normal for the POI of the left to move to the right and for the POI of the right to not move much, or at all. That's what all of mine have done, as well as many others I've developed loads for. I've run across a few that shot wide, and increasing the charge had no effect at all - and those had to be re-regulated. As new_guy said, sometimes you can't get the barrels together without loading too hot. Then you just have to try something else.
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"Serious rifles have two barrels, everything else just burns gunpowder."

400,

That is really helpful. Thank you.

You recommend a different bullet. I have NF-FN 500gr. and Jay's banded FN in 475gr. as well as Woodleigh soft and solid 500gr. Also some GS Custom FN 500 gr on the way.

How would you go forward from here?

Brett

You could try a different powder. I wouldn't go faster than RL 15 in that case. In my experience, if a double is shooting wide with RL 15, a slower powder usually doesn't help, but it's worth a try. Perhaps 4831, either IMR or H.

Personally, I always work up with Woodleigh softs, then back off a few grains and work up with their solids. I'm afraid I can't be much help with the monos. I tried monos in a double just once, got burned bad, and will never do it again, "banded" or not.
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"Serious rifles have two barrels, everything else just burns gunpowder."