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Old January 29, 2011, 11:50 PM   #1
JDTech
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What caused this?...LR-308/ammo question

Took my DPS LR-308 out today to sight in my new scope and had some ammunition problems. I dont have access to any match grade ammo atm so I had to use what I could find at Walmart. I picked up a box of Win powermax to sight it in and some cheap fedral power shock to plink with. About 1 in 4 shots with the Win ammo, the primer blew out and jammed the bolt. I have never seen this before but this is my first autoloading rifle. Surprisingly the cheap Fedral ammo fed and fired perfect. Its not consistantly accurate but at least it was not blowing apart in the chamber. Attached some pictures of the aftermath of both casings so that maybe someone can advise me. Not sure if its the ammo or if something like the gasblock needs adj for that specific ammo. Thanks in advance!
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Old January 29, 2011, 11:59 PM   #2
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that not cool how many of the win. did that or did u shoot any more after that
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Old January 29, 2011, 11:59 PM   #3
rezmedic54
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Bad Cases

I had this problem a few months ago with some Privi .308 ammo. First thing we thought was head space but that was not it. Turned out to be some bad cases the primer pockets were almost over sized to start with so when they where lit off it was just enough to finish stretching out the pockets. You may have got some of that bad brass.
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Old January 30, 2011, 12:21 AM   #4
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thats what i was thinking
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Old January 30, 2011, 01:00 AM   #5
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Clean dry barrel. Tight chamber. new rifle

IMHO Dpms SUX
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Old January 30, 2011, 01:24 AM   #6
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I'm quite happy with my DPMS LR .308 L.I would like for the DPMS bashers to show me some inspection reports for non conforming parts.
Did you run a patch through your bore to make sure it had no anti-rust grease in it?That would raise pressure.Something like a 180 hunting bullet may have driven into the rifling,that could be a problem.The bores get the same oxide treatment as the outside of the barrel.it can be a bit toothy the first several rounds,that can raise pressure.
Is the WW Powermax some super performance ammo that may have a long pressure curve?While aftermarket adjustable gas blocks may be available,probably you don't need them.When ammo like Hornady superformance gets more velocity without raising peak pressure,they lengthen the peak pressure curve.Are the pockets blown way oversize,or did the primers blow out due to residual pressure after the rifle unlocked?Is this a carbine with a short gas tube?Even the fine,reliable,venerable Garand can be damaged and taken out of action by firing bolt gun safe 180 gr hunting loadswith slow powder.Gas operation requires proper ammo.
WW has increased the sensitivity on their primers and they may be less suitable given the floating firing pin.BTW,Armalite has a firing pin retraction spring,DPMS does not.
if any primers pierced,the cookie and some crud went inside the bolt.Disassemble it,clean and lube.If the ejector works in and out smoothly,you may want to leave it in place,same with the extractor little roll pins,springs,etc.
Frankly,high quality handloads are the practical solution to feeding an AR in 308

Last edited by HiBC; January 30, 2011 at 01:40 AM.
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Old January 30, 2011, 10:49 AM   #7
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Quote:
Is the WW Powermax some super performance ammo that may have a long pressure curve?
I thought it might be as well, but from looking at Winchesters web site it is just a standard .308 with a velocity of 2500 fps at 100 yards. Winchester states this is ammo designed for the White Tail hunter, using a bonded core bullet. Nothing like the Hornady Superformance or Light Magnum ammunition that were pushing the pressure limits.

Did you shoot all the ammunition? When you have something like this happen contact the manufacturer and file a complaint. Usually they will ask for the unfired ammunition to be returned and they will credit you the purchase price or send you a new box to shoot.
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Old January 30, 2011, 11:22 AM   #8
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headspacing?

Can't tell for shure due to alot of glare in the photo. But, that second photo looks like the shoulder is blown out a little also. May be a problem chambering that winchester amo. Bullet enguaging rifling-something like that.
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Old January 30, 2011, 02:37 PM   #9
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The rifle has the the 24" SS fluted bull barrel. I had put one box of WW White box through it before this trip and I cleaned it good before and after that. I had no problems with any of those. And yes the shoulder is warped from the extracter ans the casings seem to be pretty scratched, not sure if that's normal from extraction. They were both 150gr loads. Out of 15 casings I recovered 7 are blow out and all but 1 have a black ring around the primer from leaking gas. Adding a pic of this.
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Old January 30, 2011, 08:43 PM   #10
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What was the outside temperature where you were?
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Old January 30, 2011, 08:54 PM   #11
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Win Powermax is intended for hunting purposes, and is not everyday plinking ammo. It is loaded to a little on the MAX side for optimal energy and speed.

I wouldn't shoot Powermax in your LR-308 very often. It tends to be a little hot for the gas guns.

The only thing I could figure on the case blemishes .... the timing on your bolt blowback is off. Do you have an adjustable gas block, or is it standard?
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Old January 30, 2011, 09:56 PM   #12
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The temp was a wonderful 70deg and sunny...awsome for kansas in January...and the reason we were out....I got the power max because i wanted something closer to match grade for sighting in my scope.....What then defines "match grade" other than those words on the box?? And I believe it came with the upgraded adj gas block but will have to double check on that. If it just the hot loads then I just wont buy them anymore
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Old January 30, 2011, 10:34 PM   #13
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Quote:
Win Powermax is intended for hunting purposes, and is not everyday plinking ammo. It is loaded to a little on the MAX side for optimal energy and speed.
Power max isn't loaded to max pressures, it is just a bonded core bullet in the cartirdge. 2500 fps at 100 yards with a 150 grain bullet isn't even coming cloes to max pressures in a .308 cartridge. This is what Winchester has to say about it:

Quote:
Super-X® Power Max Bonded™ is specifically designed for the whitetail deer hunter and takes the time-proven jacketed bullet design to a new level of performance at an affordable price. Key features of the Super-X bullet include: Protected hollow point PHP design, lead core bonded to jacket with proprietary process, massive frontal area of mushroom is more than double original diameter, lead remains bonded to jacket after impact.
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Old January 30, 2011, 10:37 PM   #14
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What was the grains of the bullet, you are not supposed to shoot anything over 175 grn out of the DPMS LR308 models. To much pressure, that could cause primer flow, which, from the picture that is what it appears to have happen.
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Old January 30, 2011, 10:44 PM   #15
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I saw that they were 150 grn loads, inn the previous post, something to do with the ammo. If it was the gun, it would have done it with both loads.

Last week, a customer bought some Remington 150gr 308 wins from Walmart, which caused a squib load. he brought the gun in for me to take the bullet out. He also brought the the ammo in too. I pulled the remaining bullets left in the box, and three of the bullets had no powder in them. A phone call was made to remington.

I heard Walmart sells factory seconds, I DO NOT KNOW IF THATS TRUE, but this sure does appear good.
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Old January 30, 2011, 10:46 PM   #16
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Quote:
Originally Posted by taylorce1
Power max isn't loaded to max pressures, it is just a bonded core bullet in the cartirdge. 2500 fps at 100 yards with a 150 grain bullet isn't even coming cloes to max pressures in a .308 cartridge. This is what Winchester has to say about it:

Max pressures in a bolt gun are different from those in a gas gun.

If it were my rifle ... I'd stay away from commercial hunting ammo altogether.

Also, just because Winchester doesn't admit to it being a MAX load ... doesn't make it so. I've known them to push the limit with a lot of their factory ammo. A perfect example is their .223 Federal 55gr. FMJ ammo. It is loaded beyond what most reloading data manuals would consider to be safe. I've seen pressure signs out of every other cartridge during most plinking sessions.
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Old January 30, 2011, 11:25 PM   #17
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Do you have any of the ammo left? I'd call Winchester and tell them what happened. Sounds like the ammo has very loose primer pockets and the case is rocketing itself out of the bolt. I reload and notice a big difference in primer pressure into the primer pocket when loading the primers. Never had one do that though.

I've got the same LR-308 and never had a problem. I did have one punctured primer on a factory Fed powershok 150gr. That's the only problem out of about 700 rounds.
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Old January 31, 2011, 06:43 AM   #18
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the only ammo my lr 308 has ever seen is that cheap federal 150 grain stuff, never had a problem in 400 rounds or so
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Old January 31, 2011, 07:38 AM   #19
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Quote:
Max pressures in a bolt gun are different from those in a gas gun.

If it were my rifle ... I'd stay away from commercial hunting ammo altogether.
It is a .308 rifle not a 7.62X51, hence the DPMS LR-308 not LR-7.62. This gas gun is built to handle the same pressure levels as a bolt gun in the same chambering. That is why it should be able to shoot the ammunitinon, and I say 2500 fps at 100 yards is no where near max pressure for either type of rifle.

Best I can tell the Win PM should have a muzzle veloicity around 2850 fps which is the same as the 155 grain Match ammunition offered by Hornady. Plus it seems checking Federal and Hornady's web sites seems 150 grains with a MV around 2850 is pretty much the standard. So if the match ammo and hunting ammo runs at that speed I don't know where he is going to find something that opperates at lower pressures.

I'm sure there is an ammunition problem here, with this box of ammunition. I wouldn't say that he is going to run into this problem if he uses it every time. This is why I said he shouldn't have shot it after the first time he had a primer blow. That way he could have sent the ammunition back to Winchester so the ammunition could have been pulled apart and the problem found.
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Old January 31, 2011, 08:01 AM   #20
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Have you checked the head space? That would be the first thing to do. 7.62 head spaces a few thousandth different than .308, be sure and use the correct gauges for your chamber.
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Old January 31, 2011, 10:27 AM   #21
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Have you checked the head space? That would be the first thing to do. 7.62 head spaces a few thousandth different than .308, be sure and use the correct gauges for your chamber.
Again he has a .308 chamber not a 7.62X51. He was using the correct ammunition for the rifle. If other brands of .308 ammunition functioned correctly in his rifle I doubt it is a headspace issue. I still beleive it is a ammunition problem, he might have had under charged or over charged powder loads, or oversized primer pockets.

The bullets ogive might have been engaging the lands like one poster suggested which can jump the pressure up as well and cause some of these problems. Unfortunately the OP shot up all the ammunition so he can't put a caliper to it and measure it against the other Federal ammunition he shot as well. He can however compare his fired cases with a caliper to see if they measure any different.

His best bet would have been to stop shooting the Winchester ammo as soon as a primer blew and ship back the unfired ammunition to Winchester to find out what the problem was. I would still contact Winchester and see if they want the fired cases back to inspect. Who knows they might have had a bad run of ammunition that they need to recall.
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Old January 31, 2011, 09:09 PM   #22
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Thanks for the info guys!!, next time ill know to stop with the first misfire. I am just not use to have this kind of problem. I come from 20yrs of shooting trap and skeet and reloading 1000's of shot shells but honestly this is my first centerfire rifle. Never have I seen something like this before.
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Old February 1, 2011, 09:08 AM   #23
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Why not call DPMS?

Anyway - DPMS on 308 vs. 7.62x51 in their rifles.

Quote:
It is a .308 rifle not a 7.62X51, hence the DPMS LR-308 not LR-7.62.
Well, an "LR-308" could have either 308 and 7.62 chambers. In this case, the OP has a 24" barrel, which means 308 chamber.

Lee
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Old February 1, 2011, 09:37 AM   #24
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In my experience, commercial ammo usually is not crimped sufficiently and with soft point ammo sometimes the bullet is set back into the case as it hits the feed ramp or the magazine lip, causing a spike in pressure and blown primers. Run the ammunition through something like a Lee Factory Crimp die and try it again.
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Old February 1, 2011, 09:48 AM   #25
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Quote:
Quote:
Have you checked the head space? That would be the first thing to do. 7.62 head spaces a few thousandth different than .308, be sure and use the correct gauges for your chamber.


Again he has a .308 chamber not a 7.62X51. He was using the correct ammunition for the rifle. If other brands of .308 ammunition functioned correctly in his rifle I doubt it is a headspace issue. I still beleive it is a ammunition problem, he might have had under charged or over charged powder loads, or oversized primer pockets.

It could very well be ammo related but until you physically check the head space you are just guessing. It takes ten minutes to check and then you have a positive answer.
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