All this time I was blaming remington brass but I definitely have high pressure signs. The rifle is a DPMS LR 260 with a 24" barrel, the load is 42.5 grs of H4350 topped of with a 142 Matchking. Velocity is 2700 fps. Out of a batch of 50 rds., 2 or 3 cases will lose the primer. The ejector will bite into the case head and the primers are flat and raised where the pin strikes. According to the books this is a mid range load for a 24" barrel. Starting load is 41.5, max load is 44.5 grs. My rifle is showing pressure signs at 42.5 at 2700 fps meaning I may have to back off to the low 2600 fps range (hopefully not more than that) and see if the pressure signs go away. It will be too bad because that load is very accurate in my rifle but I don't want to beat it up. Have any of you experienced this?
-
Having trouble using the site?
Contact support
Pressure signs from a mid-range 260 load
- Thread starter danr
- Start date
Re: Pressure signs from a mid-range 260 load
I run 43.8 in a bolt gun with only moderate pressure signs. This pressure issue of yours isn't normal.
I would examine a few areas.
First, I would ensure that my resized case will chamber without any resistance. I am particularly interested in assuring that the case neck has not grown too long. When a loaded round is chambered and the neck is too long, the bullet gets seriously pinched, and a big pressure spike can arrive from out of left field.
Next, if this does not cure it, the bullet may be getting seated firmly enough into the rifling to create a pressure spike as well.
I would also mic the neck diameter of your loaded rounds and ensure it falls within your chamber's specs.
Greg
I run 43.8 in a bolt gun with only moderate pressure signs. This pressure issue of yours isn't normal.
I would examine a few areas.
First, I would ensure that my resized case will chamber without any resistance. I am particularly interested in assuring that the case neck has not grown too long. When a loaded round is chambered and the neck is too long, the bullet gets seriously pinched, and a big pressure spike can arrive from out of left field.
Next, if this does not cure it, the bullet may be getting seated firmly enough into the rifling to create a pressure spike as well.
I would also mic the neck diameter of your loaded rounds and ensure it falls within your chamber's specs.
Greg
Re: Pressure signs from a mid-range 260 load
This is exactly why the people that write handloading manuals tend to understate everything.
This is exactly why the people that write handloading manuals tend to understate everything.
Re: Pressure signs from a mid-range 260 load
The 44+ grains listed in the Hodgdon manual is a very hot load. With other 140 grain bullets, around mid 42's to low 43's is the normal max load I've found. When you get pressure signs, you have to work back down. You could also switch and try other powders to experiment with different velocities and group sizes. With a 24" barrel and being a gas gun, you will not get the same velocities as a bolt gun.
The 44+ grains listed in the Hodgdon manual is a very hot load. With other 140 grain bullets, around mid 42's to low 43's is the normal max load I've found. When you get pressure signs, you have to work back down. You could also switch and try other powders to experiment with different velocities and group sizes. With a 24" barrel and being a gas gun, you will not get the same velocities as a bolt gun.
Re: Pressure signs from a mid-range 260 load
No Greg, this also happens with new brass, as well as reloaded brass. I don't run it thru the sizer when it's new. I will just have to back off and see at what point the pressure signs stop.
No Greg, this also happens with new brass, as well as reloaded brass. I don't run it thru the sizer when it's new. I will just have to back off and see at what point the pressure signs stop.
Re: Pressure signs from a mid-range 260 load
You can't go by the book for max loads with a gas gun. For the most part max loads in the book are over the top for a semiauto. I learned this the hard way myself when I started loading for my AR10.
You can't go by the book for max loads with a gas gun. For the most part max loads in the book are over the top for a semiauto. I learned this the hard way myself when I started loading for my AR10.
Re: Pressure signs from a mid-range 260 load
Pressure signs are the best indicator.
I topped out at 42.5 H4350 with 139's so I'm not surprised.
Here is a post of mine on a similar topic:
"I have had this happen with a .308 AR10 of mine.
Some cases (about 25%) were overpressure but the others were fine.
I also saw flyers with about the same frequency too.
Here is what was causing it for me:
I loaded 0.010 off the lands and, while single loading, saw that pressure and accuracy were acceptable.
When I let the rifle do the loading was when I ran into the pressure and accuracy problems.
The bullet was sliding FORWARD from kinetic effect (and sometimes) into the lands causing a pressure spike during the violent slamming home of the BCG.
Question:
If you hand fit your ammunition into your chamber, does it fall back out under its own weight?
It should not stick as that may mean that it is jamming into the lands and that will cause an increase in pressure.
Do you know how far off the lands you are to begin with?
If you fully seat the bullet into the chamber and then drop the BCG does the overpressure then disappear?
If it does, like I suspect it will, then you may need to increase neck tension.
A lee factory crimp die and canelured bullets can solve this but may bring up accuracy problems."
Pressure signs are the best indicator.
I topped out at 42.5 H4350 with 139's so I'm not surprised.
Here is a post of mine on a similar topic:
"I have had this happen with a .308 AR10 of mine.
Some cases (about 25%) were overpressure but the others were fine.
I also saw flyers with about the same frequency too.
Here is what was causing it for me:
I loaded 0.010 off the lands and, while single loading, saw that pressure and accuracy were acceptable.
When I let the rifle do the loading was when I ran into the pressure and accuracy problems.
The bullet was sliding FORWARD from kinetic effect (and sometimes) into the lands causing a pressure spike during the violent slamming home of the BCG.
Question:
If you hand fit your ammunition into your chamber, does it fall back out under its own weight?
It should not stick as that may mean that it is jamming into the lands and that will cause an increase in pressure.
Do you know how far off the lands you are to begin with?
If you fully seat the bullet into the chamber and then drop the BCG does the overpressure then disappear?
If it does, like I suspect it will, then you may need to increase neck tension.
A lee factory crimp die and canelured bullets can solve this but may bring up accuracy problems."
Re: Pressure signs from a mid-range 260 load
OK, Dan; good to know.
I just mentioned those things because I had them all happen to me at one time or other, and I think it's all just good practice to check these thing anyway.
I think part of the lack of especially serious pressure signs I'm seeing personally is a product of my general policy of specifying SAAMI chamber specs exclusively. I think it's just a bit more forgiving.
Greg
OK, Dan; good to know.
I just mentioned those things because I had them all happen to me at one time or other, and I think it's all just good practice to check these thing anyway.
I think part of the lack of especially serious pressure signs I'm seeing personally is a product of my general policy of specifying SAAMI chamber specs exclusively. I think it's just a bit more forgiving.
Greg
