Advice for rifle that likes light and very heavy loads

[cabelasken]

I have a 6.5 CM that shot very well during break in with bottom of the chart loads. As I started load development, groups grew and grew until top of chart loads were 1 MOA or bigger. So I procured some Hammer Hunter 124s and when I got well above the charts, the groups shrank the faster I drove them. So I went back and tried the same with the Barnes LRX 127 i was using and the same thing happened. Groups shrank to below 1/2 MOA. So far most of my testing has been with these two hunting bullets, but both needed to be driven hard (sticky bolt) to shoot well. So, I went back and loaded up some light loads in these two as well as other bullets and again the groups shrank to below 1/2 MOA. Everything in between was disappointing. Help!!!

 

[biednick]

Sounds like the bit in between is at an antinode. Have you tried different seating depths? A tuner or muzzle device with a different weight could help too.

 

[cabelasken]

Sounds like the bit in between is at an antinode. Have you tried different seating depths? A tuner or muzzle device with a different weight could help too.

7 different powders, seating depths from .010 to .075 in .020 increments. I do have a donut that I could put on the barrel the next time out.

 

[biednick]

7 different powders, seating depths from .010 to .075 in .020 increments. I do have a donut that I could put on the barrel the next time out.

I've never had to try that many combinations, so it could be something else. I'd give the donut a try with a range of seating depths and a charge near book max and see what happens.

If you can load your bullets deeper I'd also test another 2 or 3 steps deeper. I've had a couple that needed more than .1" of jump to really shoot well.

 

[cabelasken]

I've never had to try that many combinations, so it could be something else. I'd give the donut a try with a range of seating depths and a charge near book max and see what happens.

If you can load your bullets deeper I'd also test another 2 or 3 steps deeper. I've had a couple that needed more than .1" of jump to really shoot well.

Thanks - I'll try your suggestions

 

[Rich Coyle]

Try one of those rubber donuts on the barrel. If two aren't close move it 1/8" and try two more. If two are close fire another. If not move it 1/8" again.

I have dialed a couple rifles right down to 1" three shots at 300 yards. That's three hundred yards.

 

[bmicek]

It's likely more related to bullet length and not weight. Kinda along the same lines of why it's said you need a fast twist for heavy bullets, it's mainly for the length.

So that being said, maybe you need to just try different bullet lengths, which sounds like I'm saying "try more bullets" which I kinda am but maybe you need to dive into bullet length a little more since all bullets vary a bit based on structure.

 

[med358-boise]

But what is the velocity on the low end? Run the ballistics - Do you realy care if the low end load drops 12 inches more at 600 yards and is a 175 fps slower but still above minimum impact velocity. Knowing the trajectory is more important the trajectory itself. At 500 yards, the difference is about 8 inches.

I realize that this an LR forum but even 750 yards starts to reach minimum impact velocity for a ~130 grn mono-metal bullet in 6.5 crd.

 

[JakeC]

When I had a creedmoor it was very similar. It shot well at pressure, and it shot well quite a ways back, like a grain or more. In between it was fairly erratic. This was with 140 class target bullets and light sierra varminters. I think I've heard of it elsewhere too with creedmoors, I assumed it was just a creed quirk and shot mild.

 

[cabelasken]

But what is the velocity on the low end? Run the ballistics - Do you realy care if the low end load drops 12 inches more at 600 yards and is a 175 fps slower but still above minimum impact velocity. Knowing the trajectory is more important the trajectory itself. At 500 yards, the difference is about 8 inches.

I realize that this an LR forum but even 750 yards starts to reach minimum impact velocity for a ~130 grn mono-metal bullet in 6.5 crd.

My low end velocity was right at 2550 to maybe 2600 with 120 gr bullets and my high end was 2850 + with the same bullets With 127 to 130 gr bullets low end was 2500 and high end was 2800+

 

[cabelasken]

When I had a creedmoor it was very similar. It shot well at pressure, and it shot well quite a ways back, like a grain or more. In between it was fairly erratic. This was with 140 class target bullets and light sierra varminters. I think I've heard of it elsewhere too with creedmoors, I assumed it was just a creed quirk and shot mild.

I just picked up some 140's so I'll try those next. And mild may not be so bad either. I once picked up a bargain basement 270 that shot one hole groups with a 130 pill at 2650. I took many bucks with it up to about 350 yds. All perfect or near perfect hits. But soon after starting to reload for it, I discovered it had a chamber that was way bigger (longer) than spec and not perfectly round. With a bent paper clip, a grove at the case head was present on first fired factory ammo cases. Even with just neck sizing, cases would only last 2 reloads. But with reduced loads, it never got above 1/2 MOA for any 5 shot group and most were at 1/4. At some point cases became too expensive and the gun was so cheaply made, that I just replaced it instead of having it rechambered or installing a new barrel.

 

[med358-boise]

cabelasken,

You should run your own caluclations and use your own criteria but by my way of thinking a 127 @ 2825 has a max effecting range of ~750 yards and 127 @ 2500 is about 550 yards. My criteria (yours and others may have different criteria) for effective range for that bullet is ~1700+fps of impact velocity and 800+ ft lbs of energy.

Then the next question I would ask myself is can I hit a 10" target at those distances ~8 of 10 times under field conditions; i.e., if I can't hit a 10" target 8 of 10 at 550 yards prone then I don't need to worry about getting to 2825 fps.

Also, I would add Barnes bullets like a lot of jump to the the lands, I start at 60/1000 and then go deeper to tune a load. So maybe there is a load, that is in the mid to high 2500s that you can tune with seating depth and you get a good compromise.

 

[cabelasken]

cabelasken,

You should run your own caluclations and use your own criteria but by my way of thinking a 127 @ 2825 has a max effecting range of ~750 yards and 127 @ 2500 is about 550 yards. My criteria (yours and others may have different criteria) for effective range for that bullet is ~1700+fps of impact velocity and 800+ ft lbs of energy.

Then the next question I would ask myself is can I hit a 10" target at those distances ~8 of 10 times under field conditions; i.e., if I can't hit a 10" target 8 of 10 at 550 yards prone then I don't need to worry about getting to 2825 fps.

Also, I would add Barnes bullets like a lot of jump to the the lands, I start at 60/1000 and then go deeper to tune a load. So maybe there is a load, that is in the mid to high 2500s that you can tune with seating depth and you get a good compromise.

The LRX bullets are supposed to be good down to 1300 FPS for reliable expansion. Last year i took a cow elk with the 280 AI with the 145 LRX at an impact velocity of about 2350 and performance was perfect. I have a self imposed max range of 500 yds for elk so most of the loads and calibers I shoot will easily have an impact velocity north of 2000 FPS so bullet performance of the LRX bullets or the hammers should be acceptable. As for looking for the upper velocity range for a particular bullet, I just want to hit an elk or deer with everything the cartridge is capable of. If the creedmore doesn't do it, I'll try something else. But I have memorized my ballistic charts up to 500 yds and beyond for nearly all my rifles as I tune the loads to almost be identical out to 500 yds. My problem now, and it is a good problem, is that Hammer bullets are significantly faster than what I'm used to so I may have to adjust my "typical" charts.
In response to the accuracy part of the equation, I've never experienced a problem in the field shooting accurately and for a very long ways. I know and have seen close friends that can put 1/2 moa 5 shot groups on paper all day long but have trouble with a 200 yd broadside shot on a buck. I have lost one cow elk because I elected to take a bad location shot and the caliber and bullet did not penetrate like I expected it to. The shot location was not the problem, it was just a poor decision. I did miss one 800 yd shot attempt at a wounded mouflon that was walking. I only took the shot because the game warden asked to try to put down the wounded animal. I missed it twice.
I will try more seating depths and the donut when I return home and I was able to pick up a variety of different burn rate powders that may help. It's getting close to hunting season so I'll have to make a decision soon on what to make for the next couple of months. Thanks for everyone's comments as I have learned a lot here in these forums.

 

[med358-boise]

Ken - where did you see the 1300 fps? I have not been able to find a a published number from Barnes I hae seen internet comments of 1500 and I like to add a marging of error but that is just me.