Im running 43 grains of H414 and 120 gr a-max and on every case i am getting these swipe marks. Is this pressure signs or more like over gassed? I am new to the semi auto game and dont know exactly what means what yet. Thanks for any help!!
DPMS LR-260 Over Pressure Signs?
- Thread starter STI_1911_Guy
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Im running 43 grains of H414 and 120 gr a-max and on every case i am getting these swipe marks. Is this pressure signs or more like over gassed? I am new to the semi auto game and dont know exactly what means what yet. Thanks for any help!!
Re: DPMS LR-260 Over Pressure Signs?
I have same rifle DPMS 260lr and am also seeing this on a few rounds would also like to hear from someone in the know? doesnt look like case is over pressured? looks more like a hard extraction mark?
I have same rifle DPMS 260lr and am also seeing this on a few rounds would also like to hear from someone in the know? doesnt look like case is over pressured? looks more like a hard extraction mark?
Re: DPMS LR-260 Over Pressure Signs?
Pressure curve is such that the chamber pressure is just a little too high when your bolt is trying to extract the spent cartridge. Nothing to worry about if it is not tearing your brass up too badly. If you want to get rid of it, try running a little faster powder.
Pressure curve is such that the chamber pressure is just a little too high when your bolt is trying to extract the spent cartridge. Nothing to worry about if it is not tearing your brass up too badly. If you want to get rid of it, try running a little faster powder.
Re: DPMS LR-260 Over Pressure Signs?
I agree with bowslngr. I had the same problem with my 260. I have been working up a load with BL-C2 and having much better results and less punishment on the brass. You can always drop your load down maybe a half grain and see what kind of a change there is. I also use the Nosler brass and love it.
I agree with bowslngr. I had the same problem with my 260. I have been working up a load with BL-C2 and having much better results and less punishment on the brass. You can always drop your load down maybe a half grain and see what kind of a change there is. I also use the Nosler brass and love it.
Re: DPMS LR-260 Over Pressure Signs?
I do have a jp adjustable block on it. By adjusting that could it help it or no effect?
I do have a jp adjustable block on it. By adjusting that could it help it or no effect?
Re: DPMS LR-260 Over Pressure Signs?
Restricting the gas flow a bit might help, but it is hard to say. While it might slow the bolt unlocking process slightly, it doesn't change the chamber pressure.
Restricting the gas flow a bit might help, but it is hard to say. While it might slow the bolt unlocking process slightly, it doesn't change the chamber pressure.
Re: DPMS LR-260 Over Pressure Signs?
Just about every Semi Auto does that, Drive on. 260, and 243's are the worst as chamber pressure is greater
Just about every Semi Auto does that, Drive on. 260, and 243's are the worst as chamber pressure is greater
Re: DPMS LR-260 Over Pressure Signs?
Go a step faster in burn rate.
H414 is going to give you higher port/chamber pressure (peak is no more, possibly less) at time of extraction then a slightly faster burn rate powder. H414 is fine with the heavier bullets but for the 120s, go faster burn rate.
Adj gas block might help, might not.
Heavy up buffer a bit.
Go a step faster in burn rate.
H414 is going to give you higher port/chamber pressure (peak is no more, possibly less) at time of extraction then a slightly faster burn rate powder. H414 is fine with the heavier bullets but for the 120s, go faster burn rate.
Adj gas block might help, might not.
Heavy up buffer a bit.
Re: DPMS LR-260 Over Pressure Signs?
you got to bush the pin
i had a headache having the same problem. I talked to allot of people about my possible solutions , i changed primers , pins , ect, but bushing the pin fixed my problem.
its the 6.5mm bullet , those have a tendency to cause cratering at a low pressure , even pierce your primers
the solution is to bush your firing pin , im not sure who would be willing to do that on an AR , you can try dropping Greg Tannel a line , i can't say he'll do the work but i would try begging him before i even thought about going to someone else.
if your not piercing primers then it's something you can live with. But i'll bet your pierce a few, eventually.Bushing your pin will stop cratering completely and will make it sort of impossible to judge pressure signs from fired cases.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Tannel</div><div class="ubbcode-body"> Bushing the firing pin hole and turning the firing pin sounds small but this one operation to the bolt has so many benefits it's hard to believe. The biggie is it has to be done correctly to work as a total benefit. It took two years to perfect my system to get all the good out of this operation.
What can it do for you? The most noticeable that you can see is for the cratering and or primer piercing problem for PPC comp rifles, varmint rifles and the high performance 17's, 20's, 6mm's and 6.5 but not limited to them. The part you can't see that took two years to finally figure out is to make the bushing long enough in side the bolt to guide and support the firing pin.
Cratering and piercing is not a problem with firing pin fit to hole diameter fit. It has to do with pressure control. The smaller the hole the more pressure it takes to blank out a washer from the same thickness and hardness material. So when your 20 Tactical or any other cartridge craters bad and your load is 2 grains light, the primer round and brass has barely formed the problem is not fixed by a larger firing pin! The correct course of action is to reduce the firing pin hole diameter.
The reason you want Gre'-Tan Rifles to do the installation is because of the consistency of ignition by my bushing. This is accomplished because of the longer bushing in the bolt. When you cock and load the firing pin it stays encapsulated. This guides the firing pin back and forth. It keeps it centered in the bolt helping to prevent the spring from rubbing on the interior bolt body. The pin doesn't drop down into the large ramp area behind the firing pin hole in the bolt causing the tip to wear and have different initial vibrations started before the primer ignites. This all adds up to consistent primer ignition and getting an accurate rifle consistently accurate.
So what size is needed? I always strongly recommend .062 for all comp, varmint, and hunting rifles. For the guy that has to always take his gun apart in hunting camp it's a .068.
For the person looking for just the repair, all I need is the complete bolt. Turn around time is 2-3 days.
Price $75.00
Return Shipping $7.00
For a total of $82.00
We can do Remington, Winchester, Savage, Sako, Kimber, Cooper, Nesika, Stiller, Bat, Kelbly, Lawton, Surgeon, Borden, Wichita, Hall, CZ, Ruger, Mauser, Howa, Weatherby, Dakota, Pacific Tool, Phoenix, & Defiant bolt action rifle or pistol. Case hardened style bolts (Mauser, CZ, ect. will run extra with broken tooling to get the job done. I cannot do AR's, Accuracy International, Desert Tactical Arms, Rim fires, Falling block, Break open, Lever, Pump rifle.
How to send your bolt in to be bushed:
You can send your bolt snail mail, priority mail, UPS, Fed-Ex. What ever you prefer. Please include your name, phone number, and return shipping address. Turn around is 1 to 3 days. We usually do them the day that we get them in. The total cost is 82.00 for 1 bolt or 157.00 for two (This includes return shipping, priority mail.) Three or more will be sent back to you UPS and we will have to calculate extra shipping. We can overnight them at your expense. Check, money order, or credit card is fine with us.
Send to: Gre'-Tan Rifles, 24005 Hwy. 13, Rifle CO. 81650</div></div>
http://www.gretanrifles.com/services/viewEntry.jsf
you got to bush the pin
i had a headache having the same problem. I talked to allot of people about my possible solutions , i changed primers , pins , ect, but bushing the pin fixed my problem.
its the 6.5mm bullet , those have a tendency to cause cratering at a low pressure , even pierce your primers
the solution is to bush your firing pin , im not sure who would be willing to do that on an AR , you can try dropping Greg Tannel a line , i can't say he'll do the work but i would try begging him before i even thought about going to someone else.
if your not piercing primers then it's something you can live with. But i'll bet your pierce a few, eventually.Bushing your pin will stop cratering completely and will make it sort of impossible to judge pressure signs from fired cases.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Greg Tannel</div><div class="ubbcode-body"> Bushing the firing pin hole and turning the firing pin sounds small but this one operation to the bolt has so many benefits it's hard to believe. The biggie is it has to be done correctly to work as a total benefit. It took two years to perfect my system to get all the good out of this operation.
What can it do for you? The most noticeable that you can see is for the cratering and or primer piercing problem for PPC comp rifles, varmint rifles and the high performance 17's, 20's, 6mm's and 6.5 but not limited to them. The part you can't see that took two years to finally figure out is to make the bushing long enough in side the bolt to guide and support the firing pin.
Cratering and piercing is not a problem with firing pin fit to hole diameter fit. It has to do with pressure control. The smaller the hole the more pressure it takes to blank out a washer from the same thickness and hardness material. So when your 20 Tactical or any other cartridge craters bad and your load is 2 grains light, the primer round and brass has barely formed the problem is not fixed by a larger firing pin! The correct course of action is to reduce the firing pin hole diameter.
The reason you want Gre'-Tan Rifles to do the installation is because of the consistency of ignition by my bushing. This is accomplished because of the longer bushing in the bolt. When you cock and load the firing pin it stays encapsulated. This guides the firing pin back and forth. It keeps it centered in the bolt helping to prevent the spring from rubbing on the interior bolt body. The pin doesn't drop down into the large ramp area behind the firing pin hole in the bolt causing the tip to wear and have different initial vibrations started before the primer ignites. This all adds up to consistent primer ignition and getting an accurate rifle consistently accurate.
So what size is needed? I always strongly recommend .062 for all comp, varmint, and hunting rifles. For the guy that has to always take his gun apart in hunting camp it's a .068.
For the person looking for just the repair, all I need is the complete bolt. Turn around time is 2-3 days.
Price $75.00
Return Shipping $7.00
For a total of $82.00
We can do Remington, Winchester, Savage, Sako, Kimber, Cooper, Nesika, Stiller, Bat, Kelbly, Lawton, Surgeon, Borden, Wichita, Hall, CZ, Ruger, Mauser, Howa, Weatherby, Dakota, Pacific Tool, Phoenix, & Defiant bolt action rifle or pistol. Case hardened style bolts (Mauser, CZ, ect. will run extra with broken tooling to get the job done. I cannot do AR's, Accuracy International, Desert Tactical Arms, Rim fires, Falling block, Break open, Lever, Pump rifle.
How to send your bolt in to be bushed:
You can send your bolt snail mail, priority mail, UPS, Fed-Ex. What ever you prefer. Please include your name, phone number, and return shipping address. Turn around is 1 to 3 days. We usually do them the day that we get them in. The total cost is 82.00 for 1 bolt or 157.00 for two (This includes return shipping, priority mail.) Three or more will be sent back to you UPS and we will have to calculate extra shipping. We can overnight them at your expense. Check, money order, or credit card is fine with us.
Send to: Gre'-Tan Rifles, 24005 Hwy. 13, Rifle CO. 81650</div></div>
http://www.gretanrifles.com/services/viewEntry.jsf
