Anyone good at reading borescope pics?

[lugerstew]

I took about 30 pics of my 243 barrel this morning, and would like to know if anyone can interpret them, I can't,.
I'm only going to try to upload the first ten of the chamber end, that I think has problems.
This morning at the range I had bad powder blowback down the brass, all the way to the rim and 2 out of 15 primers blew out. Either I need to super clean the throat of my barrel or maybe it is damaged.
This is 100 rounds since cleaning and about a thousand rounds on a 2 yr old Shaw barrel.
Thanks for any advice.

 

[lugerstew]

3 more borescope pics

3 more pics

 

[lugerstew]

3 more pics

3 more pics.

 

[lugerstew]

last borescope pic

1more pic.

 

[MarkCO]

Sooting of cases past the neck is typically indicative of a load issue and not really a chamber issue. Pressure too low, brass too hard, etc. Sure, a really loose chamber will soot cases more, but it would have to be really loose.

I do forensic analysis of firearms and know how to read the inside of a barrel (I also manufacture barrels) and I avoid borescopes in my own personal barrels. It just causes undue worry.

Blown primers too? Sure sounds like a case issue.

Factory or reloads? If reloads, what brass, how many firings, annealing process?

 

[lugerstew]

Thanks MarkCO

It was funny at the range this morning, I shot same bullet same powder but with RP brass and there was no blowback, then I shot 15, same bullet, same powder, only difference was Hornady brass that had been loaded many times and had very bad powder blowback. I also shot a different bullet with different powder, but with starline brass, and all shot good, no blowback.
So I guess I can safely assume that the hornady brass might be ready for the trash after a dozen or so loadings.
My reloads, never annealed.

 

[jetinteriorguy]

Get the Sinclair tools for checking primer pockets. A worthwhile investment, much safer than blowing primers due to undetected oversized primer pockets.

 

[lugerstew]

jetinteriorguy
I have had these tools for a few years, used them when something didn't feel right, but I just started using them on my freshly sized brass just a few months ago, they have helped me find a few oversize pockets, but mostly so far in my RP brass, the hornady brass so far has been fine. But I will continue checking.

 

[tangolima]

What do you mean by blown primer? The spent primers fell out pocket after firing, or there was holes in the primers and gas leaked out?

-TL

Sent from my SM-N960U using Tapatalk

 

[lugerstew]

Sorry I didn't explain it better, the primer was blown completely out of the pocket, and now the pocket measures about .015 bigger than a new primer diameter.
Also I checked the other 13 brass of that bunch that was sooting, and found out every single one,except for one, had loose primer pockets after shooting them.

 

[MarkCO]

Hornady is soft brass. Primer pockets open up sooner than on other brands of brass. Given that they were reloaded several times in Hornady brass, that is surely the culprit.

I use Hornady brass only a few times, and anneal it, but use it mostly when I won't be able to save my brass.

 

[Unclenick]

I would guess the primer pockets were already pretty loose when you fired these. Did you notice any difference in feel seating the primers? Cases can grow primer pockets gradually over successive firings. At firing, you probably had enough pressure bleeding out around the primer to prevent the case from sealing normally, and hence the soot line down the side from gas blowby.

Before he retired from the lab, board member BobCat45 did some micro-Vickers hardness testing of a number of new pieces of .308 Win (mostly) brass I sent him, and Hornady was softest in that round of testing.

As far as the borescope images go, the bore looks no better or worse than a number of commercial bores I've looked at. Pretty rough, but functional. The main nuisance with a rough bore is the tendency to accumulate more metal fouling than a lapped bore surface would. If you want, you can firelap it. If it shoots well, I wouldn't overdo that, though. You might consider trying just a dozen very light lapping loads with a few grains of Bullseye or other fast pistol powder driving a cast bullet impregnated with something pretty fine, like 600 grit silicone carbide just to take down the worst sharp edges.

In images 7 and 8 you can see some carbon glazing of deeper spots beginning to happen. This can be removed with Slip 2000 Carbon Killer, if you want to bother. If you aren't going to shoot again for a week, a patch or bore mop wetted with Gunzilla can be pushed through and the bore left wet with it for that week, after which the carbon will likely just patch out.

 

[tangolima]

It is impossible for the primer be blown out of the brass when firing, as it is being backed by the bolt face. It fell out during ejection.

It does sound like soft brass. The pocket opens up during ignition, leaked out gas and lowered the pressure inside the brass. The brass couldn't seal the chamber and hence the soot. Did you notice loose pocket when seating the primers? I have a batch of factory ammo that spent primers fell out during the 1st firing. Worthless.

Consider yourself lucky. You don't want any gas leakage during firing, especially gas going rearward.

-TL

Sent from my SM-N960U using Tapatalk

 

[hounddawg]

https://ballistictools.com/store/small-and-large-primer-pocket-gauges

23 bucks is cheaper than having a etched or pitted bolt face repaired

 

[Unclenick]

The primer would not be displaced in the closed breech, but gas can still leak around it as I described. When a pocket is blown open, the gun owner frequently reports a puff of smoke coming up from the bolt, though it is likely actually coming up around the bolt from a vent hole.

 

[lugerstew]

Houndawg,, I have those two primer pocket tools, I am using them now all the time when I size brass, especially if they have several firings.
Do you keep shooting the brass as long as the no go gauge does not go in?
Or toss them because they have too many loadings, even if the no go gauge doesn't go in the primer pocket?

 

[hounddawg]

These days I only use premium (Lapua, Peterson) and Lake City and try and stick with middle node loads. I have some Lapua SRP .308's that have close to 30 loadings on them.

Back when I was using Hornady, Federal and such I did not own the tools and just went by feel when seating the primer. I think it is a judgement call, if it does not feel right then it probably isn't

 

[jetinteriorguy]

https://ballistictools.com/store/small-and-large-primer-pocket-gauges

23 bucks is cheaper than having a etched or pitted bolt face repaired

Oops, my bad. In my previous post I said Sinclair, these are the ones I meant. Getting old, I used to have a memory like a steel trap, it’s just getting pretty rusty now.

 

[lugerstew]

Thanks Unclenick for checking the borescope pics, I am going to clean the heck out of it today, bore, throat and chamber, going to use Boretech first on the bore and then maybe try some slip 2000 on the chamber and throat, I have had it for a while but never used it.
I guess I just stated it wrong, I understand a primer can't blow out while up against the bolt face, but they did fall out of the gun when I opened the bolt, hope it doesn't happen again, I don't like it at all.

 

[Unclenick]

You've discovered why the military crimps primers. Having one fall out on ejection can jam a weapon, and full-auto weapons, in particular, can start to eject before chamber pressure is zero, and that encourages primers to pop loose.