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Longhair

My Delema...

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I almost don't know where to start. I guess at the beginning.

I'm loading 6.5CM for a factory Howa APC rifle. My components to this point have been Hornady Brass, CCI BR-2 Primers, Barnes Match Burner 140gr Bullets, and IMR4350 Powder.

I know that H4350 is the most preferred powder to use, but I have a lot of IMR4350 on hand and not a lot of time to mess with obtaining and testing anything else before the Armory Shoot.

 

Barnes load data shows a minimum starting charge weight of 38.8gr, and a max of 43.1gr, with a COAL of 2.700". Since I want to push these a fair way past 1000yds I wanted to find a load that would be fast enough to not have a rainbow trajectory, so I started my testing with 41gr, and a COAL of 2.820" (the absolute longest I can fit in the AmmoBoost mags this rifle requires). So far my absolute best ES/SD numbers were with 41gr and 43.3gr, BUT....the 42.2gr load had one anomalous round that skewed the data, so I want to re-shoot that node for verification. Anyway, within that 41-43.4gr range that I tested I found a couple of plateaus that I can work on refining, so I decided that I really needed to see what sort of jump I was starting with.

I don't have a cartridge comparator or a chamber micrometer yet, so I can only go off of other real world indicators. I just resized a neck on a once fired case to barely hold on to the bullet, and then I seated it out to 2.910". I dropped it in and closed the bolt, then extracted it for examination. Not a mark on it. So I slid it out to just over 3" and repeated the chambering & extraction. This time the bullet had the lightest sign of hitting the lands, and it pushed the pill in to where the COAL was 2.990". That's .290" longer than spec!

 

I don't mind loading them out to where I have to drop them in and not use the magazine for loads I'll take out to Raton for the shoot. My opportunities to shoot past 1000yds after the shoot will be virtually non-existent, so at that time I will play with other options because I won't have the current constraints. But for now, I'm inclined to retest my best nodes with seated depths that only have .015 jump to see what that does to the numbers and group sizes, realizing that there will be both velocity and pressure changes that will occur with the additional case capacity and reduced jump distance that could change everything.

 

So what say Ye guru's of the Reloading Armory? Between work and weather my opportunities to test are very limited between now and the shoot. Should I follow my inclination to play with jump distance, or do I just do the best I can with further testing only on the powder side? I'm really torn, because even at 2.820" COAL I'm looking at a jump of .170" and that just seems to me to be excessive.

HELP!!

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Did You use a marker pen on the Dummy rounds bullet  ,so as to verify where your chambers leade is ?  Barnes are copper  In my limited experience with long range and copper  0.030- 0.040 is the jump preferable . Greg would Know far better than I however .

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Welcome to funky profile bullets  and numbers in loading books designed around magazine length.  Most chambers from the factory are pretty generous day in day out so this is not unusual.  Forget COL spec if you have that much room.  First off how well does it shoot?  Are you seeing 0.5" or less or 1.5" on average?  Are you using a chronograph?  If you are chasing the lands are you going to have enough bullet in the case neck. I's want about 0.250 for sure.  

 

Doing the teeter totter of pressures vs. length here that as you get a lot closer to the lands pressures increase but the increased case capacity also drops pressure. It is a balance. Also distance to lands vs.pressure with same same powder charges is a reverse bell cure that starts out high at shortest load drops as you increase COL and then as you star inching up to the lands the pressure. goes back up. If you stick a bullet in the lands you will obviously see a pressure rise but done sanely this can be a benefit. In your scenario it may be impossible to do that and for most applications it's one of the last things you want to do to chase accuracy.

 

Recently in shooting the 6.5's we are seeing that they are tolerating big jumps to the lands. By big I mean 0.30-0.50 when most of the time we are shooting from 0.015 to on the lands with 0.005 being most common.  As  these are copper I would go with 0.050 as most manufactures recommend that as a minimum jump distance.  Accuracy wise we have seen some vast improvements in the results down range pulling back.  I'll discuss that a bit later in the day on my Grendel range report BTW.

 

Me? I'd load me a ladder up at 0.050 off and go shoot it. 

 

Greg

 

Your approach to the DTL acquisition is spot on  if done right and you are doing that. You'll usually find your numbers are just a smidgen, and I mean within about 0.002-3, shorter than actual as you are having to get the bullet into the lands to engrave. Thank goodness for magic markers. I, myself, use a jewelers saw and slit a case neck in to places and size the neck a bit to get my lengths using your method.  The process is a bit hit or miss and I highly recommend investing in a Sinclair Bullet Seating Depth Tool for accurate repeatably and speed.  You use a case fired in your chamber and in five minutes you'll know all you need on a given bullet in that chamber.

 

https://www.sinclairintl.com/reloading-equipment/measuring-tools/bullet-seating-depth-tools/sinclair-bullet-seating-depth-tool-prod35491.aspx

 

 

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10 minutes ago, GLShooter said:

Welcome to funky profile bullets  and numbers in loading books designed around magazine length.  Most chambers from the factory are pretty generous day in day out so this is not unusual.  Forget COL spec if you have that much room.  First off how well does it shoot?  Are you seeing 0.5" or less or 1.5" on average?  Are you using a chronograph?  If you are chasing the lands are you going to have enough bullet in the case neck. I's want about 0.250 for sure.  

 

Doing the teeter totter of pressures vs. length here that as you get a lot closer to the lands pressures increase but the increased case capacity also drops pressure. It is a balance. Also distance to lands vs.pressure with same same powder charges is a reverse bell cure that starts out high at shortest load drops as you increase COL and then as you star inching up to the lands the pressure. goes back up. If you stick a bullet in the lands you will obviously see a pressure rise but done sanely this can be a benefit. In your scenario it may be impossible to do that and for most applications it's one of the last things you want to do to chase accuracy.

 

Recently in shooting the 6.5's we are seeing that they are tolerating big jumps to the lands. By big I mean 0.30-0.50 when most of the time we are shooting from 0.015 to on the lands with 0.005 being most common.  As  these are lead core, I had to look,  I would go with that. If they were solid copper then 0.050 would be my start as most manufactures recommend that as a minimum jump distance.  Accuracy wise we have seen some vast improvements in the results down range pulling back.  I'll discuss that a bit later in the day on my Grendel range report BTW.

 

Me? I'd load me a ladder up at 0.030 off and go shoot it. 

 

Greg

 

Your approach to the DTL acquisition is spot on  if done right and you are doing that. You'll usually find your numbers are just a smidgen, and I mean within about 0.002-3, shorter than actual as you are having to get the bullet into the lands to engrave. Thank goodness for magic markers. I, myself, use a jewelers saw and slit a case neck in to places and size the neck a bit to get my lengths using your method.  The process is a bit hit or miss and I highly recommend investing in a Sinclair Bullet Seating Depth Tool for accurate repeatably and speed.  You use a case fired in your chamber and in five minutes you'll know all you need on a given bullet in that chamber.

 

https://www.sinclairintl.com/reloading-equipment/measuring-tools/bullet-seating-depth-tools/sinclair-bullet-seating-depth-tool-prod35491.aspx

 

 

 

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Thanks a lot Greg! That helps me with my decision.

At some future period I will get a comparator, but for now all I can do is go by COL.

 

After doing some measuring, with these bullets I can seat out to 2.825" and get .250" actual grip in the neck above the boat tail. That will only reduce the jump from where I was by .005". So it's probably not worth the bother.

 

To answer your questions; Yes, I'm using a chronograph. Yes, a few loads I've run get me groups at or just under .5MOA, but the problem is that the best groups @ 100yds with velocities in the neighborhood I'd like have unacceptable ES/SD numbers that will come back to bite me @ 1000+yds, however there are two that I want to re-test that did show some promise.

 

Worst case scenario, I go back to the best group size and numbers that don't give me the velocity I was hoping for, or....I change powders and start over. To date, the absolute best group size and numbers was sub-½MOA w/ES=12.07 & SD=5.74 @ AV=2576fps.

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Based on that speed I would not be afraid to use it as is. I would suggest shooting  five five shot groups at those specs. I don't know what your increments were but f they were big  for grins I would shoot a pair of groups, five per, 0.2 on either side of that magic load.

 

Greg

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I'm loading in 1/10th increments and shooting 5-shot groups, which is why I was looking at jump distance for further refinement.

 

I'll load another set of 5/ea of the two I want to retest to see what they'll do. If one of them pans out I'll be right in the 2770 neighborhood, which isn't too far off what I was hoping for in terms of speed.

 

It's a cooler day today with higher humidity and Baro-Pressure quite a bit lower than my previous test days, so I'll wait until tomorrow to give the retests a fair whirl. I'll report back with the results.

 

Thanks again Greg. :tiphat:

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Sounds like a great plan. Even at the speed you have been getting you a very nice residual velocity at 1000 with plenty of breathing room over trans-sonic activity.

 

Greg

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9 minutes ago, GLShooter said:

Sounds like a great plan. Even at the speed you have been getting you a very nice residual velocity at 1000 with plenty of breathing room over trans-sonic activity.

 

Greg

:thumb: 

At the Armory Shoot I hope to take a crack at a mile. And at that distance, regardless of my load I'll have passed through trans-sonic range, so I expect things to go a bit wonky, but another couple hundred FPS would get me closer before that happens. That's why I'd prefer the 2770 loads over the 2576. please1.gif

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2 minutes ago, Longhair said:

:thumb: 

At the Armory Shoot I hope to take a crack at a mile. And at that distance, regardless of my load I'll have passed through trans-sonic range, so I expect things to go a bit wonky, but another couple hundred FPS would get me closer before that happens. That's why I'd prefer the 2770 loads over the 2576. please1.gif

 

You a funny guy but I see where you are coming from. Don Quixote would have been proud to ride the river with you.  :thumb:

 

Greg

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3 minutes ago, GLShooter said:

 

You a funny guy but I see where you are coming from. Don Quixote would have been proud to ride the river with you.  :thumb:

 

Greg

1320yds (3/4mi) would be okay, but the slower load is likely to be a bit dicey even at that range, as it would go sub-sonic by then.

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5 minutes ago, Longhair said:

1320yds (3/4mi) would be okay, but the slower load is likely to be a bit dicey even at that range, as it would go sub-sonic by then.

 

If you flinch just right you can gain 1 FPS. I know as I've seen it!!Free speed and no pressure.   :lol:

 

Greg

 

BTW I'm writing up my range trip as we converse here.

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I'm starting to feel like I'm chasing my tail.

 

Weather changes are really messing with my test results. The only good thing is that my best performing loads haven't changed with respect to being the tightest groups and the best numbers, but the variance in numbers from one day to the next is notable.

 

My first outing with the 41.0gr load the temp was 68°F, the barometric pressure was 30.05", and the humidity was 72%. The AV=2576, ES=12.07, and SD=5.74.

Today when I shot the same load the temp was 65°F, pressure was 30.12", and the humidity was 63%. The AV=2616, ES=22.71, and SD=9.43.

So I got about a 50FPS kick, but the ES/SD were nearly doubled.

 

Got similar results with the faster load too.

First trip with 43.3gr loads the temp was 73°F, pressure was 30.09", and humidity was 43%. AV=2747, ES=13.12, and SD=5.38.

Today (see above paragraph for weather conditions) the AV=2787, ES=28.85, and SD=11.26.

So these yielded a 40FPS gain, but the ES/SD virtually doubled too.

 

The question now is, "Where do I go from here?"

Do I settle for what I've got? Do I play with DTL? Do I start over with a different powder?

I'm running out of time, and even getting components with enough time to fiddle with them could be a crap shoot.

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LH,

Just looking for info here, not questioning you. I lurk here for tips I can use in the future...

 

Are what I see as small changes in temp. and barometric pressure, with a pretty sizeable change in RH* (which would be expected depending on the time of day),

going to cause the change you show in velocity, and especially with the doubling of ES and SD, due to weather conditions where the only sizable change was humidity  ? 

* I presume that is relative humidity. 

Also wondering if your POI and/or your group sizes noticeably changed ? 

Thanks for the schooling.

John

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27 minutes ago, Retcop said:

LH,

Just looking for info here, not questioning you. I lurk here for tips I can use in the future...

 

Are what I see as small changes in temp. and barometric pressure, with a pretty sizeable change in RH* (which would be expected depending on the time of day),

going to cause the change you show in velocity, and especially with the doubling of ES and SD, due to weather conditions where the only sizable change was humidity  ? 

* I presume that is relative humidity. 

Also wondering if your POI and/or your group sizes noticeably changed ? 

Thanks for the schooling.

John

Actually, I believe that it's "air density" that makes the biggest difference. So it's a combination of condition factors.

 

My POI and group sizes haven't changed notably @ 100yds, but the difference in ES/SD will matter more when I start reaching out to the 800+ yards that I'm going to be shooting. I wouldn't concern myself with it much at all if I was only going to be working 300yds or less.

The gamble at this point is that when I go out to Raton the temps may not be much different, but the humidity will be much less, and the altitude will have an effect on combustion. It could make things better, or it could make things worse.....I just don't know.

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