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Posted: 8/21/2010 8:25:09 PM EDT
Im not sure re-port is possible or what the cost difference is... id prefer not to have to switch buffers for different barrels on my LMT MRP... running an H. 6.8 is still ejecting at 1:30 / 2 with H2. Its a 14.5" with carbine gas.
Link Posted: 8/22/2010 12:20:50 AM EDT
adjustable gas block and choke 'er down.
Link Posted: 8/22/2010 7:48:56 AM EDT
Switch to a slower powder...
Link Posted: 8/22/2010 8:19:42 AM EDT
[Last Edit: 8/22/2010 8:22:11 AM EDT by pavlovwolf]
What ammo are you shooting? What weight and velocity? If handloads, give the same info but also powder choice. Some rifles were overgassed to handle the most loads that were available when the standard was the slower ammo. That should feed fine in over gassed guns, but some hotter loads such as the tactical or combat loads from SSA won't have enough time for the brass to shrink away from the chamber which keeps the extractor from having a easy job because it's dragging the case out, resulting in the 1 o'clock patterns and sometimes failures to extract. Also, what spin are you using? Try out the extra power springs from Springco if you're not already using one. The Tubbs css flatwire spring may be just as good or better, since I know it gives you the ability to tune it by cutting coils if necessary. My upper is throwing the 110 Prohunters at the 1 'oclock position, but all other loads, my hotter handloads and all SSA that I've run through it, including the 85tsx and the 110xxx combat loads eject at 4 o'clock, most hitting the shell deflector and landing a good 3 to 5 feet away. The prohunters were landing less than a foot away at one o'clock, and out of 250 or so, I had three not eject at all, but lay on top of the mag in the breech. Switching to the Palmetto State Armory H2, I've increase the extraction to about 2-3 feet away, but still between 1 and two o'clock. My next thing is the spring.
If you're using 4198 in your hand loads in anything over 90-100gr, that can be too fast and cause those problem. Re7 is probably the best for under 95gr, and H322 seems to be the best for anything over 100gr, with 10x being really great is some of the 6.8s out there.

My upper is 16", but everything should still apply.
Link Posted: 8/22/2010 9:48:33 AM EDT
Originally Posted By pavlovwolf:
What ammo are you shooting? What weight and velocity? If handloads, give the same info but also powder choice. Some rifles were overgassed to handle the most loads that were available when the standard was the slower ammo. That should feed fine in over gassed guns, but some hotter loads such as the tactical or combat loads from SSA won't have enough time for the brass to shrink away from the chamber which keeps the extractor from having a easy job because it's dragging the case out, resulting in the 1 o'clock patterns and sometimes failures to extract. Also, what spin are you using? Try out the extra power springs from Springco if you're not already using one. The Tubbs css flatwire spring may be just as good or better, since I know it gives you the ability to tune it by cutting coils if necessary. My upper is throwing the 110 Prohunters at the 1 'oclock position, but all other loads, my hotter handloads and all SSA that I've run through it, including the 85tsx and the 110xxx combat loads eject at 4 o'clock, most hitting the shell deflector and landing a good 3 to 5 feet away. The prohunters were landing less than a foot away at one o'clock, and out of 250 or so, I had three not eject at all, but lay on top of the mag in the breech. Switching to the Palmetto State Armory H2, I've increase the extraction to about 2-3 feet away, but still between 1 and two o'clock. My next thing is the spring.
If you're using 4198 in your hand loads in anything over 90-100gr, that can be too fast and cause those problem. Re7 is probably the best for under 95gr, and H322 seems to be the best for anything over 100gr, with 10x being really great is some of the 6.8s out there.

My upper is 16", but everything should still apply.


Thanks for the info! Shooting Sierra and Nosler HPBT 115s behind 27.7 of H322... I have not checked velocity but was hoping to go a bit higher because don't think Ive hit an accuracy sweet spot. This barrel is 1x10 LMT SS that was cut down from 18"... previous owner did the work and reamed the chamber to SPC II.
Link Posted: 8/22/2010 1:38:47 PM EDT
My advice at this point would be to pick up some factory loaded ammo in those weight classes with those projectiles and see how they cycle. If you have no chronograph, you can't be sure that you have enough power to cycle properly, but you have the right powder for that weight range. It may or may not be the most accurate load for your rifle, but you will find that out with more testing. My concern is cycling, and that powder is right for that. With 28.2c, ( compressed load), being shown as the max load for your combo, and 26.0 being the min, I would say that it would be cycling correctly as far as the load is concerned. Are you seeing swipes, flattened primers, cratered primers around the firing pin indentation, bulges just above the case head, extractor or ejector marks, etc.? The load data I put up there is from Hodgon, and is for saami chambers and 1/10 twist. You should be able to get a little more with the spec II chamber, but I would be sure that it is indeed a spec II seeing as how the previous owner did the work. You would have to be sure of his competency. If he had it done, I would personally like to see the receipts for the work if it were me.
Back to the ammo issue. I would recommend Palmetto State Armory, they have the SSA 115 gr Sierra for 18.95. I would also say get a box or two of something lighter, under 100gr to test for cycling.
Using an old formula for estimating velocity, you should be around 2560fps or so, which should be good pressure wise and cycle normally.
Link Posted: 8/22/2010 4:32:35 PM EDT
AR10 Buffer Springs work wonders !
Link Posted: 9/9/2010 11:05:04 PM EDT
I bought an upper that the seller stated was 'overgassed' from the factory with certain SSA loads. He put a JP adjustable gas block on it and dialed it in. I have not had a bit of problem with it.
Link Posted: 9/10/2010 2:17:25 AM EDT
Originally Posted By Ironnewt:
I bought an upper that the seller stated was 'overgassed' from the factory with certain SSA loads. He put a JP adjustable gas block on it and dialed it in. I have not had a bit of problem with it.


I'm glad the upper is working out for you. How's the brass looking?
Link Posted: 9/10/2010 2:51:06 AM EDT
Great, just great. I just drilled out my gas port. I was having a problem with failure to cycle and exhausted all other remedies before resorting to a drill bit. And the first thing I read, after getting back from the shop, is this thread
Link Posted: 9/10/2010 5:30:19 AM EDT
Originally Posted By Gardner:
AR10 Buffer Springs work wonders !


How does that help an oversized gas port? The problem is too much gas, and yes, playing with buffer and springs makes it "feel" better and eject better, but you're going to be beating the hell out of some brass I think.

Adjustable gasblock would probably help out a bit...
Link Posted: 9/10/2010 2:05:19 PM EDT
[Last Edit: 9/10/2010 2:05:57 PM EDT by jrswanson1]
Which brass are you using? I use SSA small primer brass, and have used 29.0gr of H322 behind that same bullet. I've gone higher and gotten good results, but higher than 30.0gr of H322 I start getting swipes when I go higher.

Jim
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