Extractor scaring under side of casing rims

[Phantom30]

Hi have built 3 aero precision LR308 uppers 2 6.5 Creedmoor and one 6mm.  I have two bolt carriers and four bolts I share among them.  All leave extractor scars on the underside of the casing rim.  May be this is normal, but haven't noticed it before.  What I have noticed is that LR308 BCGs have tight bolts.  You can flick an AR BCG to put the bolt forward when installing in receiver.  You can't do that with these 308s.  I suspect pressure build up in BCG is causing scaring of cases, because of tight gas ring fit.  Theory, anybody know facts?

[jtallen83]

I have noticed the same scaring and seen a couple changes lessen it, heavier buffer and an adjustable gas block. A heavier carrier gives the case more time to shrink back from the chamber walls making it extract easier. Lowering the gas has a similar effect slowing down extraction. I would imagine loose gas rings would also slow down the gas impulse giving the case more time to extract. Check out these JP gas rings for their take;

https://www.jprifles.com/buy.php?item=JPEGR-308

[98Z5V]

1 hour ago, Phantom30 said:

I have two bolt carriers and four bolts I share among them.  All leave extractor scars on the underside of the casing rim.

Please post pics of what you're talking about.  If it's what I think it is, I have a cure for you, and it's simple. Pics please, of the brass damage.

[Phantom30]

Here is pic requested.  Hope you can make them large enough to see what I talking about.

As for JP stuff I just ordered from them so it will be awhile until my account settles there.  I use their recoil eliminators not so much for recoil but to keep the scope on target and it works really well, especially with 6mm Creedmoors.  These builds are basic battle rifles with a 1,000 to 1,300 yard long range capability.  Any way to smooth out the rings I have?  or just buy the good ones and get on with it.

Why are these things so tight?  is that typical of 308 or is it a problem?

[98Z5V]

I'm betting this is the issue - test it out, and tell me if that's it. I went through this with 6.5 Grendel.

By the way, from your pics, that is very, very minor.  VERY minor.

 

[Phantom30]

OK minor, but Creedmoor ammo is not cheap so I was planning to reload these casings.  Accumulated damage could result in ripping a rim after a couple of these imprints.  Just being cautious, probably over cautious

Nice video.  Good stuff.

Still why are the rings so tight, normal or not?

[98Z5V]

4 minutes ago, Phantom30 said:

OK minor, but Creedmoor ammo is not cheap so I was planning to reload these casings.

Shoulda went .260 Remington, man.  I'm making my own brass from Hornady .308 Match Brass. 

[Phantom30]

Yes but my daughter likes the no recoil 6mm

[Phantom30]

is the tight sticky bolt in the BCG normal or not???

[98Z5V]

7 minutes ago, Phantom30 said:

Yes but my daughter likes the no recoil 6mm

That's exactly what a .260 Remington is, man...  

[98Z5V]

Just now, Phantom30 said:

is the tight sticky bolt in the BCG normal or not???

It better be.  If your gas rings are sealing like they should.  Benchrest guys will tell you different.

Extend the bolt.  Stand the BCG up on it's face, on the bolt face, on the table. Did the BCG collapse, or stay there, bolt extended?

You want it to stay there, extended, standing on it's face.

It's new, right?  It'll break in, too, and push in and out of the carrier, too - after a few hundred rounds. It still better stand up on it's face after a couple hundred, too...

[Phantom30]

OK after a couple hundred rounds my KAK-Davidson BCG is still standing on its face extended.  So that is normal. which means that the extractor imprint is due to an overpressure some where else in the system.  6mm has an R+2 gas system and has the strongest but as you say very minor imprint.  So my solution is just keep blasting away and be careful to inspect them for rim cracks before each reload and have a nice day.  I can live with that, so thanks for the support and good answers.

PS SOCOM rejected the 260 REM for the 6.5 Creedmoor, so I have a better chance of seeing fresh lake city MILSPEC production in the future.  I have also fired hundreds of thousand 7.62x51s and left all that brass on the ground for you to pick up and reform.  Enjoy.

[Phantom30]

 

19 hours ago, jtallen83 said:

I have noticed the same scaring and seen a couple changes lessen it, heavier buffer and an adjustable gas block. A heavier carrier gives the case more time to shrink back from the chamber walls making it extract easier. Lowering the gas has a similar effect slowing down extraction. I would imagine loose gas rings would also slow down the gas impulse giving the case more time to extract. Check out these JP gas rings for their take;

https://www.jprifles.com/buy.php?item=JPEGR-308

I have a stiff 458 SOCOM  buffer spring but if I slow down recoil I speed up recharge.  I have proven that semi-auto chambering will cause an asymmetry in bullet tips of SP, BTHP, OTM and ELDs which will reduce accuracy.  More energy will exacerbate this effect.  S&B FMJ is least effected in this way.  I bought ADK BCG from Delta Tactical for $99 a real deal but it didn't help or add any weight.

[jtallen83]

42 minutes ago, Phantom30 said:

 

I have a stiff 458 SOCOM  buffer spring but if I slow down recoil I speed up recharge.  I have proven that semi-auto chambering will cause an asymmetry in bullet tips of SP, BTHP, OTM and ELDs which will reduce accuracy.  More energy will exacerbate this effect.  S&B FMJ is least effected in this way.  I bought ADK BCG from Delta Tactical for $99 a real deal but it didn't help or add any weight.

An adjustable gas block may be your best option if you want to fine tune the system for a specific round. Just remember the closer you get to minimum pressure needed the more likely you are to see a malfunction, doubt it would add much life to the brass though, yours actually looks pretty good. The Tubbs flat wire spring runs pretty smooth for me, applies a more even pressure through the whole cycle. He has a low powered spring I run in 300 BO and on a low reciprocating mass 5.56 build, nothing like that for the big boys though.

[Phantom30]

tanks

[98Z5V]

If you're ripping into the rims, it's one of two things (could be a third thing).

1.  Sharp teeth on the edges of the extractor, just like that video I linked above shows.  File them down.

2.  Overgassed.  Can't make a smaller gas port in the barrel, but you can add an adjustable gas block, as JT stated above.

(Possible) 3. Under-recoiled, from a bad recoil system, that's too light.  Make the buffer heavier, make the recoil spring stronger.  Use a matched recoil system with KNOWN-GREAT components.  Never "trust" a manufacturer in what they say for recoil parts, unless they're a proven, solid, known recoil system manufacturer.

^^^  The "aftermarket" routinely fuks up #3...  Routinely.

Edited October 17, 2018 by 98Z5V

[survivalshop]

     I see nothing to worry about with those case Rims , looks normal , even below normal marks . You have to realize is Brass has never been meant to be reloaded & its not the Brass its Firearms , they are made to function reliably with factory loaded Ammo . Its only us reloads who want to extend & give a service life to fired Brass .You can polish parts to lesson the imprint of Extractors or Ejectors , but there is still going to be pressure from a Steel component on a softer brass Case , its going to leave a mark .

[Sisco]

3 hours ago, survivalshop said:

     I see nothing to worry about with those case Rims , looks normal , even below normal marks . You have to realize is Brass has never been meant to be reloaded & its not the Brass its Firearms , they are made to function reliably with factory loaded Ammo . Its only us reloads who want to extend & give a service life to fired Brass .You can polish parts to lesson the imprint of Extractors or Ejectors , but there is still going to be pressure from a Steel component on a softer brass Case , its going to leave a mark .

I am pretty sure ammo manufacturers could invent a near indestructible case that could be reloaded multiple times but they have no financial incentive to do so. They would just lose sales. I wonder if a method has ever been developed to successfully reload steel cases? Would have to start from scratch on a system, though.

[jtallen83]

5 hours ago, Sisco said:

I wonder if a method has ever been developed to successfully reload steel cases?

People do it, not sure it is a good thing but it is done.

http://www.gunsholstersandgear.com/2013/02/14/reloading-steel-cases-reload-steel-case-ammo/

[survivalshop]

9 hours ago, Sisco said:

I am pretty sure ammo manufacturers could invent a near indestructible case that could be reloaded multiple times but they have no financial incentive to do so. They would just lose sales. I wonder if a method has ever been developed to successfully reload steel cases? Would have to start from scratch on a system, though.

https://www.ammoland.com/2016/05/first-new-technology-ammunition-cases-decades-shell-shock-technologies-llc/#axzz5UKpxzNCn

 

Up to 40 reloads , no Rifle, that I could see though .

Edited October 19, 2018 by survivalshop

[308kiwi]

2 hours ago, survivalshop said:

https://www.ammoland.com/2016/05/first-new-technology-ammunition-cases-decades-shell-shock-technologies-llc/#axzz5UKpxzNCn

 

Solution looking for a problem IMO.

"up to 40 reloads", heck I've got .40, .45 and 9mm brass that's probably getting up to that count and it still loads perfectly fine without proprietary dies, I would go as far as saying that you would loose the cases before you got anywhere near reloading them 40 times.

Hey I'm all for innovative ideas but I really don't buy into this one.

[survivalshop]

6 hours ago, 308kiwi said:

Solution looking for a problem IMO.

"up to 40 reloads", heck I've got .40, .45 and 9mm brass that's probably getting up to that count and it still loads perfectly fine without proprietary dies, I would go as far as saying that you would loose the cases before you got anywhere near reloading them 40 times.

Hey I'm all for innovative ideas but I really don't buy into this one.

Ya , but just think if you could get forty reloads on a 308 case .I would like to see that, may never happen, but  its why I posted it in response to Sisco's post .

[308kiwi]

9 hours ago, survivalshop said:

Ya , but just think if you could get forty reloads on a 308 case .I would like to see that, may never happen, but  its why I posted it in response to Sisco's post .

Oh absolutely, if they come out with 308 I'll be in, but as far as pistol, nah.

 

 

 

[Phantom30]

Well on range Thursday was snap shooting a string of 200 yard plates, miss matched bolt dropped a casing in receiver instead of ejecting it.  Next feed action drove casing neck up into the gas tube pushing it forward an inch as it hard jammed.  So new R+2 gas tube on order.  These non-standard suckers are tough to get right.  Every time you try to save a buck it costs more in the end.

Edited October 20, 2018 by Phantom30
spelling

[Phantom30]

Jtallen83 - I like Tubbs' 115gr RBT Closed tip (CT) for the 6mm, if I can get the rifle to work reliably.  CT format has nearly same toughness needed in a semi-auto bullet to reduce chambering effects, hopefully as well as S&B FMJ does in 6.5.  Plus it has great ballistics with potential to take battle rifle class hardware and give it accurate long range capability.