My 308 always shows high pressure signs.

[Justintoxicated]

My 3rd trip out with this rifle, finally got past all the bolt catch issues and got a replacement adjustable gas block.

 

Even my starting loads show high pressure signs.  I have read that primer cratering and flattened primers and ejector smear are normal for LR308's.  But I just can't get over that.  My rifle has a rainier arms ultra match barrel and its very accurate but it must have a tight chamber or something?

 

 

pressure signs by Glamisduner, on Flickr

 

The loads with the mil brass were not starting loads, I used hard tula primers.  This piece was probably from one my my hotter loads 43 grains varget behind a 175 SMK.

The ruptured gold colored winchester primer however was just a hair above the starting load recommended for 155's.  It uses 155 grain Palma SMK, behind 44.5gr varget.

This found burned a small hole in my brand new JP bolt. (I say new but it has about 100 rounds or so shot out of it_.

 

bolt damage by Glamisduner, on Flickr

 

You can see the pit right next to the ejector.

 

Not sure what I could be doing wrong here, or maybe its a defective primer because my friend had the same thing happen with winchesters we bought around the same time on his 1903a3 with a light load as well.

Edited September 16, 2013 by Justintoxicated

[survivalshop]

The firing pin hole mark on the spent primer, that's cratered, is of some concern , but those primers do not look all that flattened . Could be the angle we are looking at them .

 

If you see what you believe are high pressure signs , drop the powder load ,I don't care what the manual states as a starting load .

 

A Chronograph would be helpful to determine Velocities . 

 

Blown primer ? Could be a fluke , but I would go over my loading procedures  , to make sure .

 

New tight build ?

[Justintoxicated]

Thanks for the insight.  I never really see all these pressure signs in any of my guns.  Cratering, Flattening of primers, ejector smear, but I keep reading it is normal for LR308 and want to confirm that this is the case.  The cases were not bulged at all either.  

 

Hodgdon online lists 

155 GR. SIE HPBT  Hodgdon  Varget  .308"  2.775"  44.0  2759  41,300 CUP  47.0C  2909  49,400 CUP 

 

I was just reading about several other people having this problem with Winchester primers.  http://www.calguns.net/calgunforum/showthread.php?t=623587  This guys primer ruptured at the same point.

 

My Friend had one (WLR Primer)  do the same thing in his starting loads on his 1903A3 bolt, and it pitted it in the same way as my JP bolt.  

 

I have a Chronograph but I haven't figured out an easy way to set it up at the range.

 

The damage looks minor, but is there anything I should be worried about to warrant buying another JP bolt?  I guess I didn't notice the Gases being blown back which I think is strange too.

 

Yes the build is new, this was my first time out since I fixed the bolt stop issues.

[texas30cal]

It most likely ruptured at that point bc that is the thinnest part from being formed and due to cost they probably try to use as thin material as they can, I always use cci 34's for my military rifles that is what they were meant to use. Not real sure about the signs but is it normal for that much metal to flow into the gap between the firing pin and bolt?

[survivalshop]

Was headspace checked ? 

 

I have not used any WW primers of recent production , but have not had any problems with them in the past & still use the old ones I have .

 

AS said , check your loading procedures , COL ,case sizing & charge weighing , all can cause problems if not to spec's. 

 

Where is the spent ejected brass ending up ?

 

The primer cratering is showing high pressure signs , with the primer cup material flowing into the firing pin gap in the Bolt. I would not worry about the Bolt ,but if you have blown out primers often , the bolt could be part of the problem or a victim of them .

 

Have you tried factory ammo & if so, how do the cases look ?

Edited September 17, 2013 by survivalshop

[mineralman55]

You're loading way too high. Don't use Hodgdon's numbers. They are extremely high loadings for gas rifles. Use Sierra's numbers, they seem to be far more in line with reality. Sierra says the MAX for a gas rifle is one loading below their MAX listed for a powder/bullet combination. For instance, for the 155 HPBT Palma MatchKing, Varget MAX loading is 43.8 grains, therefore you should max out your loading at the one lower, 43.1 grains Varget (2700 fps). For the 175 BTHP, Varget MAX is 41.7 grains, therefore you shouldn't exceed the listing of one lower at 39.9 grains Varget (2400 fps).

[Justintoxicated]

You're loading way too high. Don't use Hodgdon's numbers. They are extremely high loadings for gas rifles. Use Sierra's numbers, they seem to be far more in line with reality. Sierra says the MAX for a gas rifle is one loading below their MAX listed for a powder/bullet combination. For instance, for the 155 HPBT Palma MatchKing, Varget MAX loading is 43.8 grains, therefore you should max out your loading at the one lower, 43.1 grains Varget (2700 fps). For the 175 BTHP, Varget MAX is 41.7 grains, therefore you shouldn't exceed the listing of one lower at 39.9 grains Varget (2400 fps).

 

Well that sucks because my rifle does not like those charges.  I'm not sure that's 100% though cause I have used their numbers before in my other semi autos, granted I have never needed to approach their maximums to get an accurate load.  In fact I find sierras numbers to be too conservative in almost all of my rifles.  Actually usually I typically use my Hornady reloading manuals numbers since they start out the very conservative.  Their starting loads so far have ALWAYS been weaker than factory ammo.  And even with their starting load I get high pressure signs on the LR308 with both 155s and 175s. The adjustable gas block has been adjusted to eject brass properly if not a bit weakly but once I find my accuracy load I will dial it in more right now it looks like 43gr varget under a 175gr smk is the best (using military cases), and 44.5gr varget under a 155 smk (commercial brass).  With the adjustable gas block I should be able to fire stouter loads if anything.  Hodgdon lists 155's with 44grs at 2759 fps which is on par with other good factory ammunition.  But like I said I get the same pressure signs with only 40gr of varget under a 175 smk, granted the primer isn't quite as flat.

 

 

Was headspace checked ? 

 

I have not used any WW primers of recent production , but have not had any problems with them in the past & still use the old ones I have .

 

AS said , check your loading procedures , COL ,case sizing & charge weighing , all can cause problems if not to spec's. 

 

Where is the spent ejected brass ending up ?

 

The primer cratering is showing high pressure signs , with the primer cup material flowing into the firing pin gap in the Bolt. I would not worry about the Bolt ,but if you have blown out primers often , the bolt could be part of the problem or a victim of them .

 

Have you tried factory ammo & if so, how do the cases look ?

 

 

Yes I checked headspace.  The rifle passed both a go and no go SAAMI gauges.

I haven't seen any 308 ammo for sale in over a year around here.  Pretty sure it would do the same thing though I will pick some up if it is ever back in stock.  I used hornadys numbers which have thus far always been on the light side compared to factory ammo.  

 

As far as reloading I'm using Redding National Match sizing dies, and sometimes a small base FL die if needed (was for the Black Hills Brass, but was not needed for the LC).  COL was checked to be consistent with a comparator, and each round was individually weighed and trickel up to the nearest .1gr\

 

I think I am going to contact winchester about a bad batch of primers.  My friend bought his WLR primers around the same time and had one do the exact same thing in the exact same place.  His load was 42gr varget under a 168gr bullet, but in a 30-06 case which isn't a very stout load for a bolt gun.  It showed no pressure signs other than the pinhole that pitted the bolt on his very nice 1903a3.

 

 

It most likely ruptured at that point bc that is the thinnest part from being formed and due to cost they probably try to use as thin material as they can, I always use cci 34's for my military rifles that is what they were meant to use. Not real sure about the signs but is it normal for that much metal to flow into the gap between the firing pin and bolt?

 

I love CCI primers but haven't found them for sale at a reasonable price in years ($45 for 1000 is not reasonable to me).  Actrually I take that back I have found tons of #41s for use in my other ARs.   CCI so far is my favorite primer manufacturer.  The tula primers seem to be working well too but they are a bitch to seat.  I don't know if ejector smear and cratering is normal for 308 ars.  Maybe someone can post some pics of what their brass looks like after firing?

Edited September 17, 2013 by Justintoxicated

[Justintoxicated]

I can try 40.0 gr again, but the group was a little tighter with 43 grain.  I think I will have to move the target back to 200 yards to get a better indication.  Luckily the 43gr load does show signs of high pressure but nothing too terrible IMO (just enough that I'm not comfortable going higher). Again the brass looked similar with 40.0gr varget but the flattening of the primer was slightly less, and slightly less ejector smear and cratering.  Both are 5 shot groups.

 

lr 308 100 yards by Glamisduner, on Flickr

 

As for the 155gr loads, I think I will try them again but with different primers next time.  These were loaded in commercial brass so the loud does not sound too over the top to me, but I have yet to find factory ammo for comparison.

Edited September 17, 2013 by Justintoxicated

[survivalshop]

 

 

With the adjustable gas block I should be able to fire stouter loads if anything.

 

Chamber pressures are at there peak before the bullet pass's the gas port in the barrel , so, no matter how you adj.  the gas block , the pressure on the case has already maxed out for the load formula .

 

Nice shooting , by the way .

 

One more thing while I'm thinking about it . The metal thats cratered around the firing pin hole , its not just deformed , it could be displaced material from another part of the primer & could have weakened it .

Edited September 17, 2013 by survivalshop

[Justintoxicated]

Chamber pressures are at there peak before the bullet pass's the gas port in the barrel , so, no matter how you adj.  the gas block , the pressure on the case has already maxed out for the load formula .

 

Nice shooting , by the way .

 

One more thing while I'm thinking about it . The metal thats cratered around the firing pin hole , its not just deformed , it could be displaced material from another part of the primer & could have weakened it .

 That makes sense.  I think the Winchester primers are just from a bad batch after doing some research.  Seems they moved their primer production facility and were having some teething problems  Once I contact winchester I will update.  I'm going to look for the firing pin gap too.  Maybe JP bcgs are overated..

[unforgiven]

5 shot groups?? Nice shooting brother.Lots of info on reloading,great.

[Justintoxicated]

5 shot groups?? Nice shooting brother.Lots of info on reloading,great.

The Bushnell XRS is a bit overkill at 100 yards :)

[seasprite]

I've read on other forums where Winchester primmer have had issues of blowing out just like yours so you may have gotten a bad lot of primers as far as the blown one goes. But the cratering and ejector swipe would give me some concern I would back it down some. 

[Justintoxicated]

I've read on other forums where Winchester primmer have had issues of blowing out just like yours so you may have gotten a bad lot of primers as far as the blown one goes. But the cratering and ejector swipe would give me some concern I would back it down some. 

 

So your 308 AR does not produce ejector smear marks with factory ammo?

[seasprite]

Nope, It did at one time when it was over gassed but I put an adjustable gas block on and that eliminated all my issues as far as that goes. How do your rims look any bending like you might have some early extraction going on.

[mineralman55]

If you are still getting cratering and other anomolous primer effects when you back down the load, and you've checked the headspace AND the brass seems to be intact along with all the other checks you've made, then you've probably narrowed it down properly to the primers. Too bad you cannot find some commercial match ammo or some military ball. Great shooting BTW. 

[Tripledeuce]

   What do you mean it "passed" on both the go and no go gauges?

   Does that mean that the bolt "closed" on the go gague, and DID NOT close on the no-go?

   Did you strip the bolt of both the extractor and ejector?

   Respectfully

   Terry

 

   Again, I ask these questions with respect.   I don't know your level of gunsmithing experience.

Edited September 18, 2013 by Tripledeuce

[texas30cal]

 That makes sense.  I think the Winchester primers are just from a bad batch after doing some research.  Seems they moved their primer production facility and were having some teething problems  Once I contact winchester I will update.  I'm going to look for the firing pin gap too.  Maybe JP bcgs are overated..

It could also be a undersize firing pin, or a case of tolerance stacking, have no experience with the jp bolt or carriers but always read good things about them. My ejector pin was smearing a semi circle on the case everytime the chamber was rough and the ejector needed deburring.

[Justintoxicated]

   What do you mean it "passed" on both the go and no go gauges?

   Does that mean that the bolt "closed" on the go gague, and DID NOT close on the no-go?

   Did you strip the bolt of both the extractor and ejector?

   Respectfully

   Terry

 

   Again, I ask these questions with respect.   I don't know your level of gunsmithing experience.

Yes that would be the proper way to test :)  Getting the ejector back in was a real bitch.  That isn't a 223 ejector spring in there!  The trick was using a piece of 45acp brass and a vice to keep it together while I tapped the roll pin back in.

 

The firing pin, bolt carrier, gas rings were all JP, so I doubt it is tolerance stacking.  Must just be high pressure signs.  I guess I will have to stop using Varget. If that does not work I guess I will part out this rifle as it won't group like I want it to safely.  I figure if I can't load for a decent velocity then there is no point in having a 24" heavy ultra match  barrel.  Maybe I'll convert it to a light weight 16" barrel plinker or something.  I guess on the bright side I didn't order a custom barrel yet like I was initially going to.

Edited September 18, 2013 by Justintoxicated

[MikedaddyH]

After reading this thread , Points I have noticed:

A: You can back down the powder charge .5gr and test fire again.

B:  Winchester changed primers the end of 2012.

C:  The Chamber could be polished to relieve some pressure.

D:  Adjust the seating depth of the bullet in the case. By increasing COL the pressure inside the case will go down. BUT THIS WILL CHANGE THE POINT OF IMPACT!

That's my opinion , results may vary. Good luck.

[texas30cal]

Could overall be too long putting the bullet against the lands? won't this cause high pressures? It seems like I read about it somewhere and thought it may be worth mentioning.

[Justintoxicated]

After reading this thread , Points I have noticed:

A: You can back down the powder charge .5gr and test fire again.

B:  Winchester changed primers the end of 2012.

C:  The Chamber could be polished to relieve some pressure.

D:  Adjust the seating depth of the bullet in the case. By increasing COL the pressure inside the case will go down. BUT THIS WILL CHANGE THE POINT OF IMPACT!

That's my opinion , results may vary. Good luck.

 

-  Sure already fired a bunch at .5gr less for the 155 palma (a few times now) , they just don't group as well, pressure signs are about the same I actually went up to I think 46gr with this load (wish I would have recorded it)

- I wish I knew which batch of primers I was using, it could be the ones I picked up in December, or they could be from a year earlier.

- I believe the chamber is polished but maybe I could look into it.

- Can't load them any longer and fit them in the magazine.

 

I do not believe the bullets touch the lands.  I can check though.

Edited September 19, 2013 by Justintoxicated

[texas30cal]

Sorry, double posted somehow

Edited September 19, 2013 by texas30cal

[survivalshop]

Still would be nice to see some Chronograph results on your reloads , might answer some questions.

 

There are a lot of good powders for the 308 cartridge , I would try others , you can get different results & may find a sweet load .

[Justintoxicated]

Yea I'm wondering right now if I want to load up the same thing for next time I get to the range.  It will be a while though..