I just got my first AR-10 and am beginning to do load development. It is a. 260 and I am specifically interested in knowing when to stop from a pressure standpoint. I am pretty experienced at loading for bolt guns but this is my first long range gasser. What pressure signs should I look for and how much should I back away from the Max. Also COAL is limited by mag lenght now, so start there and back down in length? How much less than my normal load should I expect this to be? Should I focus on powder burn rates on the faster or slower end of the spectrum? Double base powders OK?
- Thread starter Barrel Nut
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Re: How to do load development for gas guns.
I also have a .260 Rem gas gun built by GAP on DPMS receivers. Here's my experiences so far:
I started with N500 series powders, and got pretty high extreme spreads, and was finally informed that the high-energy, double-base powders burn the throats faster, so I stopped using them. N540 gave me some surprises with bent firing pin retaining pins and pierced primers in 100 degree heat during development, so I found that powder to be too hot with the 123gr Scenars when loaded to around 41gr.
I went to H4831, H4350, and RL17, and have had great results accuracy-wise with all 3, although I don't see myself using H4831 anymore due to lower velocities. (Great powder for .270 and magnums, too bulky for .260 Rem)
I've worked with H4350 the most, and it seems to be just the right powder for the 130gr Bergers for me, as I'm getting 2860fps from a 22" gas gun with that load.
I just barely started playing with RL17 and the 140gr Barnes Match Burners, and my first loads were all in .5 MOA, so there is some promise there.
What you will see with the gas system and slower burning powders is that when you push the pressure curve into the gas port, you will get unacceptably violent operation of the reciprocating parts, and it will be clearly noticeable.
Your biggest friend in seeing where you depart from a linear pressure increase will be your chronograph. I'll see maybe an average of 20-40fps of velocity increase, depending on what charge weight increments I'm using, and then maybe a 60-90fps spike, then I know I'm done at that charge weight, and will drop back down where the last accuracy node was.
As far as COAL, I have been able to push out to 2.810" with VLD-type pills with no issues, feeding from 7.62 PMAGS, but I don't need that OAL. All the VLD pills I have fit into 2.800" and feed fine.
If I were you, I would start with H4350, and some bullets. I've tested out...
123gr Lapua
139gr Lapua
130gr Berger
140gr Berger
140gr AMAX
140gr Barnes Match Burners
142gr SMK
I have been able to quickly find 1/2 MOA loads with the 139's, 130's, and 140gr Barnes. Hornady AMAX have shot the worst so far, averaging .75 MOA for 4 rounds, with the 5th opening the group. Maybe I need to mess around with them more, but I'm happy with a few other pills, so no need.
139 Lapua's and 130 Bergers have gotten into .4-.6 MOA 5-round groups consistently, and I like the speed of the Bergers, as the BC's are pretty close, and the 130's do well for me at 500, 750, & 1000yds when I've printed groups on paper yargets.
Because of the gas system, you'll be limited to 100fps slower than guys' hot loads in bolt guns, but I've been able to realize 24" bolt gun book velocities in my 22" gas blaster.
I also have a .260 Rem gas gun built by GAP on DPMS receivers. Here's my experiences so far:
I started with N500 series powders, and got pretty high extreme spreads, and was finally informed that the high-energy, double-base powders burn the throats faster, so I stopped using them. N540 gave me some surprises with bent firing pin retaining pins and pierced primers in 100 degree heat during development, so I found that powder to be too hot with the 123gr Scenars when loaded to around 41gr.
I went to H4831, H4350, and RL17, and have had great results accuracy-wise with all 3, although I don't see myself using H4831 anymore due to lower velocities. (Great powder for .270 and magnums, too bulky for .260 Rem)
I've worked with H4350 the most, and it seems to be just the right powder for the 130gr Bergers for me, as I'm getting 2860fps from a 22" gas gun with that load.
I just barely started playing with RL17 and the 140gr Barnes Match Burners, and my first loads were all in .5 MOA, so there is some promise there.
What you will see with the gas system and slower burning powders is that when you push the pressure curve into the gas port, you will get unacceptably violent operation of the reciprocating parts, and it will be clearly noticeable.
Your biggest friend in seeing where you depart from a linear pressure increase will be your chronograph. I'll see maybe an average of 20-40fps of velocity increase, depending on what charge weight increments I'm using, and then maybe a 60-90fps spike, then I know I'm done at that charge weight, and will drop back down where the last accuracy node was.
As far as COAL, I have been able to push out to 2.810" with VLD-type pills with no issues, feeding from 7.62 PMAGS, but I don't need that OAL. All the VLD pills I have fit into 2.800" and feed fine.
If I were you, I would start with H4350, and some bullets. I've tested out...
123gr Lapua
139gr Lapua
130gr Berger
140gr Berger
140gr AMAX
140gr Barnes Match Burners
142gr SMK
I have been able to quickly find 1/2 MOA loads with the 139's, 130's, and 140gr Barnes. Hornady AMAX have shot the worst so far, averaging .75 MOA for 4 rounds, with the 5th opening the group. Maybe I need to mess around with them more, but I'm happy with a few other pills, so no need.
139 Lapua's and 130 Bergers have gotten into .4-.6 MOA 5-round groups consistently, and I like the speed of the Bergers, as the BC's are pretty close, and the 130's do well for me at 500, 750, & 1000yds when I've printed groups on paper yargets.
Because of the gas system, you'll be limited to 100fps slower than guys' hot loads in bolt guns, but I've been able to realize 24" bolt gun book velocities in my 22" gas blaster.
Re: How to do load development for gas guns.
Great info.......thanks. BTW RL-17 is a double base powder too. I shoot it in my bolt gun with great velocity in the 140 class bullets, but It goes a little flaky on really hot days. I plan on using h4350 in my Gasser and also testing VV-N150.
Great info.......thanks. BTW RL-17 is a double base powder too. I shoot it in my bolt gun with great velocity in the 140 class bullets, but It goes a little flaky on really hot days. I plan on using h4350 in my Gasser and also testing VV-N150.
Re: How to do load development for gas guns.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LRRPF52</div><div class="ubbcode-body">I also have a .260 Rem gas gun built by GAP on DPMS receivers. Here's my experiences so far:
I started with N500 series powders, and got pretty high extreme spreads, and was finally informed that the high-energy, double-base powders burn the throats faster, so I stopped using them. N540 gave me some surprises with bent firing pin retaining pins and pierced primers in 100 degree heat during development, so I found that powder to be too hot with the 123gr Scenars when loaded to around 41gr.
I went to H4831, H4350, and RL17, and have had great results accuracy-wise with all 3, although I don't see myself using H4831 anymore due to lower velocities. (Great powder for .270 and magnums, too bulky for .260 Rem)
I've worked with H4350 the most, and it seems to be just the right powder for the 130gr Bergers for me, as I'm getting 2860fps from a 22" gas gun with that load.
I just barely started playing with RL17 and the 140gr Barnes Match Burners, and my first loads were all in .5 MOA, so there is some promise there.
What you will see with the gas system and slower burning powders is that when you push the pressure curve into the gas port, you will get unacceptably violent operation of the reciprocating parts, and it will be clearly noticeable.
Your biggest friend in seeing where you depart from a linear pressure increase will be your chronograph. I'll see maybe an average of 20-40fps of velocity increase, depending on what charge weight increments I'm using, and then maybe a 60-90fps spike, then I know I'm done at that charge weight, and will drop back down where the last accuracy node was.
As far as COAL, I have been able to push out to 2.810" with VLD-type pills with no issues, feeding from 7.62 PMAGS, but I don't need that OAL. All the VLD pills I have fit into 2.800" and feed fine.
If I were you, I would start with H4350, and some bullets. I've tested out...
123gr Lapua
139gr Lapua
130gr Berger
140gr Berger
140gr AMAX
140gr Barnes Match Burners
142gr SMK
I have been able to quickly find 1/2 MOA loads with the 139's, 130's, and 140gr Barnes. Hornady AMAX have shot the worst so far, averaging .75 MOA for 4 rounds, with the 5th opening the group. Maybe I need to mess around with them more, but I'm happy with a few other pills, so no need.
139 Lapua's and 130 Bergers have gotten into .4-.6 MOA 5-round groups consistently, and I like the speed of the Bergers, as the BC's are pretty close, and the 130's do well for me at 500, 750, & 1000yds when I've printed groups on paper yargets.
Because of the gas system, you'll be limited to 100fps slower than guys' hot loads in bolt guns, but I've been able to realize 24" bolt gun book velocities in my 22" gas blaster. </div></div>
I've had the best results so far on my 6.5 Creedmoor with Varget and next with H4350. My gun likes 130 VLD's and 140 SMK's the best so far. I've shot 140 Amax and 140 Berger Hybrids pretty well so far. I have some RL 17 but haven't tried it. What would you consider a max load according to what you have seen on a 140 grain bullet?
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LRRPF52</div><div class="ubbcode-body">I also have a .260 Rem gas gun built by GAP on DPMS receivers. Here's my experiences so far:
I started with N500 series powders, and got pretty high extreme spreads, and was finally informed that the high-energy, double-base powders burn the throats faster, so I stopped using them. N540 gave me some surprises with bent firing pin retaining pins and pierced primers in 100 degree heat during development, so I found that powder to be too hot with the 123gr Scenars when loaded to around 41gr.
I went to H4831, H4350, and RL17, and have had great results accuracy-wise with all 3, although I don't see myself using H4831 anymore due to lower velocities. (Great powder for .270 and magnums, too bulky for .260 Rem)
I've worked with H4350 the most, and it seems to be just the right powder for the 130gr Bergers for me, as I'm getting 2860fps from a 22" gas gun with that load.
I just barely started playing with RL17 and the 140gr Barnes Match Burners, and my first loads were all in .5 MOA, so there is some promise there.
What you will see with the gas system and slower burning powders is that when you push the pressure curve into the gas port, you will get unacceptably violent operation of the reciprocating parts, and it will be clearly noticeable.
Your biggest friend in seeing where you depart from a linear pressure increase will be your chronograph. I'll see maybe an average of 20-40fps of velocity increase, depending on what charge weight increments I'm using, and then maybe a 60-90fps spike, then I know I'm done at that charge weight, and will drop back down where the last accuracy node was.
As far as COAL, I have been able to push out to 2.810" with VLD-type pills with no issues, feeding from 7.62 PMAGS, but I don't need that OAL. All the VLD pills I have fit into 2.800" and feed fine.
If I were you, I would start with H4350, and some bullets. I've tested out...
123gr Lapua
139gr Lapua
130gr Berger
140gr Berger
140gr AMAX
140gr Barnes Match Burners
142gr SMK
I have been able to quickly find 1/2 MOA loads with the 139's, 130's, and 140gr Barnes. Hornady AMAX have shot the worst so far, averaging .75 MOA for 4 rounds, with the 5th opening the group. Maybe I need to mess around with them more, but I'm happy with a few other pills, so no need.
139 Lapua's and 130 Bergers have gotten into .4-.6 MOA 5-round groups consistently, and I like the speed of the Bergers, as the BC's are pretty close, and the 130's do well for me at 500, 750, & 1000yds when I've printed groups on paper yargets.
Because of the gas system, you'll be limited to 100fps slower than guys' hot loads in bolt guns, but I've been able to realize 24" bolt gun book velocities in my 22" gas blaster. </div></div>
I've had the best results so far on my 6.5 Creedmoor with Varget and next with H4350. My gun likes 130 VLD's and 140 SMK's the best so far. I've shot 140 Amax and 140 Berger Hybrids pretty well so far. I have some RL 17 but haven't tried it. What would you consider a max load according to what you have seen on a 140 grain bullet?
Re: How to do load development for gas guns.
I've been learning load development on a 5.56 gas gun. A lot of reloading material seems to be tailored for bolt guns, so I've stumbled across some of the differences through experimentation and discussion with more experienced reloaders. I'm also interested in seeing what folks will say here.
Loading longer than COAL is more than possible assuming you envision a state (relaxed competition or hunting?) where you can single-load rounds.
It is possible, but slightly difficult, to derive chamber dimensions using typical means (chamber mics). The difficulty is that the bolt mechanism in the AR comes forward with a high amount of force and seems not to fully engage the rebated rim of the precision mic that I've used (the RCBS one), resulting in false readings when the bolt slams close and pushes the mic to its shortest length. I've resorted to slowly closing the bolt with the mic in, then adding the depth of the bolt (from the tip of the bolt lugs to the face of the bolt) and adding it to the average length of the mic across seven readings, discarding high and low.
You may wish to research how you're resizing your rounds. Full length vs. neck resizing have different values for the semi-auto world than the bolt one, from my research, with proponents for each.
I've experienced that my groups close up a bit - 0.1 MOA or so? - when I'm single-feeding bullets versus magazine feeding them, something other AR shooters seem to corroborate. When ladder testing, you may wish to exclusively single-feed rounds.
I've been learning load development on a 5.56 gas gun. A lot of reloading material seems to be tailored for bolt guns, so I've stumbled across some of the differences through experimentation and discussion with more experienced reloaders. I'm also interested in seeing what folks will say here.
Loading longer than COAL is more than possible assuming you envision a state (relaxed competition or hunting?) where you can single-load rounds.
It is possible, but slightly difficult, to derive chamber dimensions using typical means (chamber mics). The difficulty is that the bolt mechanism in the AR comes forward with a high amount of force and seems not to fully engage the rebated rim of the precision mic that I've used (the RCBS one), resulting in false readings when the bolt slams close and pushes the mic to its shortest length. I've resorted to slowly closing the bolt with the mic in, then adding the depth of the bolt (from the tip of the bolt lugs to the face of the bolt) and adding it to the average length of the mic across seven readings, discarding high and low.
You may wish to research how you're resizing your rounds. Full length vs. neck resizing have different values for the semi-auto world than the bolt one, from my research, with proponents for each.
I've experienced that my groups close up a bit - 0.1 MOA or so? - when I'm single-feeding bullets versus magazine feeding them, something other AR shooters seem to corroborate. When ladder testing, you may wish to exclusively single-feed rounds.
