Stag 10 bolt wear

greg olmstead

greg olmstead

CGN Regular
Rating - 100%
27   0   0
Location
alberta
I have a lantac E-BCG in my stag 10 chamber in 7mm-08. Not running hot loads. No signs of pressure 38.5 gr varget behind a 162 eld m in a 8 twist barrel. I'm just cleaning it and noticed wear on the lugs of the bolt. I dont think it's anything serious as it's not like it's missing half the lug or anything. It's a custom barrel with a bat machine barrel extension.

Its not over gassed. I have a superlative arms gas block on it and a jp enterprise h2 scs with the the stiffest spring out of the builders 3. Its tuned to just catch the bolt catch on the last round. Brass ejects at 4 o clock every shot.

Here are some pictures

https://drive.google.com/folderview?id=1bhf-aNAp0o0gPunFboiKTK7u57_kf3aL

Thanks for you input in advance
 
Your Google drive is asking for permission before I can view.
From what I see on Hodgdon site, that is a starting load at about 2500 fps.
I am just wondering if you have an adjustable block, why are you running a heavy buffer and spring?
Is the wear on the lugs at the rear? The front?
You would think with their NiB coating you wouldn't see much of any wear as they claim 82-85 Rockwell.
I just wonder with the heavier buffer and spring if you are still getting a hefty dose of gas?
How long is the barrel and gas system? Not like a 24" barrel with a mid length gas or something?

"The entire carrier assembly is NiB, Electroless Nickel Boron coated with the patented, advanced UCT EXO process, unlike standard NiB coatings. This offers extreme lubricity with a friction coefficent of .02 and surface hardness of 82-85 Rockwell C. The carriers patent pending design features unique shrouded and forward facing gas ports that have also been re sized so that gas is vented differently to a standard carrier. This results in a system that runs flatter with a smoother energy pulse. In addition the system also runs cooler and cleaner, there is also less pressurization of the upper receiver when running a suppressed barrel. The flared boss at the tail of the carrier enhances the BCG's lock position within the upper and makes it more consistent, resulting in an accuracy improvement.
The E-BCG's forward porting and unique shape assist in reducing pressurization inside the upper receiver that can be caused by short barrel rifles running suppressors. However, it should be noted that the E-BCG is not a complete solution for this issue and all rifles are different. 'Over Gassed' guns will suffer to a larger extent from this problem."
 
Last edited:
I'm running a 24 inch barrel with a rifle length gas system. I'm running the h2 because with the standard buffer weights i had to have the gas block adjusted to far out for my liking and bleeding off to much gas and was getting wild es numbers. With the h2 I was able to waste less gas and get my speed up and more consistent. The way it is right now I have an sd of 3 and es of 7. I'm bleeding off way less gas and getting 2566 fps with a very reliable bolt lock back.
 
The wear is on the back corner of the lug where it contacts the barrel extension on unlock only on 5 out of 8 lugs on the right side and bottom of the bolt where the brass hits on chamber and eject
 
Last edited:
I can see them now.
Ya on that rear corner I would agree its during bolt unlock if I have things orientated correctly in my mind.
I wonder about excess dwell time with a lot of barrel after the gas port? I see some other guys running rifle length gas +2" or more sometimes. I personally don't as all my NR AR style rifles are all 19" IBI with rifle length gas. But I will try to go and look at my Stag titanium BCG when I get home to see if there is any similar wear. Although I dont have too many rounds on mine as I'm just waiting on a new Odin BCG so I can steal the bolt with small firing pin hole before I start handloading for 308 and 6mm Creedmoor.
Those are fantastic SD and ES numbers.
I have only gotten numbers like that from bolt guns with Alpha brass.
What brass are you using?
 
Ya I have always greased lugs on bolt guns but never on a semi....maybe I should...or read into it anyways.

I would just keep an eye on it.
Inspect it whenever cleaning and if it gets worse contact Lantac.
 
Last edited:
looks fairly normal, variances in machining tolerances especially from different manufacturers, there will be some initial wear at first it will stop after once the parts gets settled in after a couple of hundred rounds, unless you start seeing large chips missing, otherwise rounding of edges and corners are expected.
 
Last edited:
scourge18a said:
I can see them now.
Ya on that rear corner I would agree its during bolt unlock if I have things orientated correctly in my mind.
I wonder about excess dwell time with a lot of barrel after the gas port? I see some other guys running rifle length gas +2" or more sometimes. I personally don't as all my NR AR style rifles are all 19" IBI with rifle length gas. But I will try to go and look at my Stag titanium BCG when I get home to see if there is any similar wear. Although I dont have too many rounds on mine as I'm just waiting on a new Odin BCG so I can steal the bolt with small firing pin hole before I start handloading for 308 and 6mm Creedmoor.
Those are fantastic SD and ES numbers.
I have only gotten numbers like that from bolt guns with Alpha brass.
What brass are you using?
Click to expand...

I have a very long dwell time with all the mass in the bcg and h2 buffer along with the suparms gas block. During the wait for my reciever set I read as much as I could find on how to make an ar accurate and dwell time was right up there with a high quality barrel and ammo. I have this rifle tuned to hold a 1 inch waterline at 800 yards and can print sub half minute groups that far out. I dont build anything unless I build it to be accurate. Dwell time reduces the variation in muzzle velocity that plagues some ars because my cases stay put in the chamber long after the bullet has left the muzzle. I'm running lapua brass hornady eld m bullets (the eldx 7mm bullets SUCK!). This gun is more accurate than me and runs so smooth. I'd just hate to have to start replacing parts this soon as I only have 600 rounds on it. I understand that ars have consumable parts in them and I'm prepared for that day. I just didnt expect to see wear this soon as I'm used to bolt guns
 
For the record my use of the term dwell time is different than BCM's and other manufactures. I use dwell time in reference to how long the case dwells in the chamber before extraction. BCM refers to dwell time as how long the bullet stays in the barrel after it passes the gas port. A longer dwell time referring ti the time the bullet is in the barrel provides more reliable extraction and ejection. My dwell time provides better accuracy. And lower es and sd numbers.
 
greg olmstead said:
For the record my use of the term dwell time is different than BCM's and other manufactures. I use dwell time in reference to how long the case dwells in the chamber before extraction. BCM refers to dwell time as how long the bullet stays in the barrel after it passes the gas port. A longer dwell time referring ti the time the bullet is in the barrel provides more reliable extraction and ejection. My dwell time provides better accuracy. And lower es and sd numbers.
Click to expand...
Your issue doesn't look like it has anything to do with extraction/dwell time, it's a chambering issue. The bolt lugs hit the barrel extension lugs sideways when the bolt slams a cartridge in the chamber and wants to rotate into battery. That's normal, however...

Looking at the dings, either the bolt is too soft, or the barrel extension is too hard/has machining burrs.
 
greg olmstead said:
For the record my use of the term dwell time is different than BCM's and other manufactures. I use dwell time in reference to how long the case dwells in the chamber before extraction. BCM refers to dwell time as how long the bullet stays in the barrel after it passes the gas port. A longer dwell time referring ti the time the bullet is in the barrel provides more reliable extraction and ejection. My dwell time provides better accuracy. And lower es and sd numbers.
Click to expand...

i'm glad you explained your use of the term dwell time.
your posts make perfect sense.
I am also nearing assembling my 7mm-08 stag-10 so I am following along and appreciating the information.
 
Dietz said:
Your issue doesn't look like it has anything to do with extraction/dwell time, it's a chambering issue. The bolt lugs hit the barrel extension lugs sideways when the bolt slams a cartridge in the chamber and wants to rotate into battery. That's normal, however...

Looking at the dings, either the bolt is too soft, or the barrel extension is too hard/has machining burrs.
Click to expand...

My bolt is carpenter 158 steel that is heat treated and shot peened as per normal. The barrel extension is 4140 heat treated steel. That's is the only difference. It's not 8620 or whatever most other extensions are made from 4140 is harder to start with than the other steel that is used. I think it's just normal wear and tear. I did shoot some pretty stout loads in the beginning trying to get the 150 eldx 7mm bullets to shoot. I've since switched and backed it down on powder.

Also the dings on the lugs are on the back corner that is the last contact point when un locking. The front face of the bolt lugs are still pristine
 
I had to Google it before I made a fool of my self arguing with some one. I've only played the auto loader game for a year and still have lots to learn but I'm not a noob
 
greg olmstead said:
My bolt is carpenter 158 steel that is heat treated and shot peened as per normal. The barrel extension is 4140 heat treated steel. That's is the only difference. It's not 8620 or whatever most other extensions are made from 4140 is harder to start with than the other steel that is used. I think it's just normal wear and tear. I did shoot some pretty stout loads in the beginning trying to get the 150 eldx 7mm bullets to shoot. I've since switched and backed it down on powder.

Also the dings on the lugs are on the back corner that is the last contact point when un locking. The front face of the bolt lugs are still pristine
Click to expand...
Deep dings like that are not normal wear and tear. Surface finish wear is, but that's not it, your pics show obvious material loss/ impact peening.

Like I said, those dings are made during the locking phase, not the unlocking phase. The bolt lugs hit sideways (counterclockwise) on the extension lugs (due to the cam pin hitting the locking cam track of the carrier) when the cartridge bottoms out in the chamber but hasn't entered the bolt face/pushed down ejector/pushed extractor outwards yet.

I'd look at the respective inside corners of the extension lugs that face the chamber. That's where your wear is coming from.

EDIT: the burrs may have flattened out by now too if it's seen enough rounds.
 
Last edited:
Dietz said:
Deep dings like that are not normal wear and tear. Surface finish wear is, but that's not it, your pics show obvious material loss/ impact peening.

Like I said, those dings are made during the locking phase, not the unlocking phase. The bolt lugs hit sideways (counterclockwise) on the extension lugs (due to the cam pin hitting the locking cam track of the carrier) when the cartridge bottoms out in the chamber but hasn't entered the bolt face/pushed down ejector/pushed extractor outwards yet.

I'd look at the respective inside corners of the extension lugs that face the chamber. That's where your wear is coming from.

EDIT: the burrs may have flattened out by now too if it's seen enough rounds.
Click to expand...


What you are saying makes more sense. I follow now. The bolt is trying to cam shut before the case is fully seated and the corners are catching on the barrel extension. That makes more sense now that I've thought about it.
 
You must log in or register to reply here.
Back
Top Bottom