What does the barrel bore look like?

I recently dealt with a damaged barrel of one of the weapons and after inspecting the bore with a camera it turned out to have defects from the production. So I took a few new and used weapons and looked into their bore...

This is what the bore of one of our school rifles Remington 700 Sendero II in caliber .308 Winchester looks like. This is a rifle with a stainless steel barrel which we have been using since 2014 and has fired about 3,000 shots. This barrel is in perfect condition and gives great results.

The pictures always show from the left:

Transition edge from the chamber to the bore, the leade transition and then after about 10 centimeters further to the muzzle of the barrel.

Another stainless steel school Remington 700 in caliber .308 Winchester. We have been using this since 2012 and it has fired about 6,000 rounds. It's significantly more used but still shoots great.

The rifle mentioned at the beginning with a defected barrel also shoots great in terms of accuracy. But due to defects in the barrel it has low muzzle velocity and high chamber pressure which is simply not good. It is a 6.5 Creedmoor Tikka TAC. Unfortunately I don't have pictures due to a technical defect ...

This is another example of rifle with defected barrel. This is another of our school Remington 700 with a stainless steel barrel in caliber .308 Winchester which shoots noticeably worse. And now we know why... Both of these bad barrels are manufacturing defects not damage caused by the user.

This is what the target quality stainless steel barrel looks like. It is Proof Research in caliber 6.5 Creedmoor with a count of about 650 rounds. Loads are at the upper limit of pressure and speed. A cracked transition edge is common in this caliber and it doesn't have any impact on accuracy.

In addition to these used weapons I also looked at new rifles. However it should be noted here that although they are "new out of the box" they have several test shots at the manufacturer and also at the proof house. After these few shots of course no one cleans them properly. So they can show cooper fouling and of course dirt...

Daniel Defense Delta 5 in caliber 6.5 Creedmoor surprised me quite nicely. The material of the stainless steel barrel is free of defects and traces of machining. This was a pleasant surprise. On the other hand this weapon is far from being a cheap model... Of the new weapons this bore looked the best.

Ruger Precision Rifle in caliber 6.5 Creedmoor. The material is carbon steel without defects. Machining also very nice. Given that we know what performances he can give I expected it.

Remington 700 Sendero II caliber .223 Remington. The stainless steel barrel showed signs of increased cooper fouling. Otherwise it was flawless and nicely machined.

Remington 700 SPS caliber .308 Winchester. The material is porous the machining is relatively nice. A minor decay was on the edge of the transition from the chamber to the bore. It would not affect accuracy or durability.

Savage Axis II in caliber 6.5 Creedmoor. The material is porous. Traces of machining are visible and they should disappear within about 200 shots. However the transition to the borehole is nicely machined.

CZ 557 Lux II in caliber 8x57 IS. The material is porous and there are noticeable traces of machining. Unfortunately the machining of the chamber and the transition to the bore is weak...

Proof Research target barrel in .30 caliber, 1/10. In this case it is not yet a barrel as such but only a semi-finished product without a chamber. So it doesn't have a single shot fired yet. The material is stainless steel and is manufactured using a different technology than the previous one. It is not a forging, but a so-called "single-point cut rifling" ie machining in the direction of firing. Traces of machining are possible to recognize but they will disappear after a few shots. This is a very high quality and precise stainless steel target barrel which can be seen above what it looks like used...

At some barrels it is possible to see, for example, the porosity of the material and small traces of machining. And that's why the Break-in of the barrel is so important. It aims to get the new barrel to perfect condition as quickly as possible. The traces of machining are smoothed and the pores are healed with cooper from the jacket of the projectiles. But the cooper fouling on the surface form extremely fast especially with the new barrel and they need to be disposed of... Large cooper fouling in the bore have a negative effect on the accuracy and service life of the barrel. In the extreme case there may be an increase in chamber pressures and for charges operated at the limit of maximum pressures this may even be problematic ...