6.5x47 - tell me about barrel set-back

[AR Shooter]

My Bartelin 5R rifled barrel is "tired" after ~3200 rounds of F-Class (became a solid 9-ring shooter, which is not competitive). I'm thinking of having it set-back 2 inches and shooting at 26" length as I shoot at 600yd. One of my fellow shooters said that is not a good idea, that it will never be a 10-ring shooter after being set-back.
Is he speaking the truth or am I good with setting it back?

 

[Doug Beach]

Set backs are a step into the unknown. It might act like new again, for another thousand or more rounds, or it might have no result. Probably won’t make it worse. If you’re paying for the work, on an f gun, I’d get a new barrel.

 

[Walt Krafft]

If doing it yourself, have at it. I have never been able to make a good shooter out of a bad one and won't do it for a customer.

 

[Kurz]

One thing I suggest first is to have an experienced gunsmith use a high quality borescope to examine the interior of the barrel. If appropriate, you should take a look to see what he is seeing and commenting on. You may find that the barrel is significantly used far enough to not allow for the set back. On the other hand, you may find that it has possibilities.

The gunsmith may have some hesitation about running his expensive reamer into the carbon still existing in the barrel even after the setback. Then too, there is no guarantee as to how many quality shots you can expect for your investment.

I prefer to opt for a new barrel in order to get the most performance for the expense.

 

[AckleymanII]

Bore dia will taper from throat forward on used barrels. Most high quality barrels will have the same bore dia from end to end when new. So, how much do you have to cut off to get the new throat back to new bore dia? Reamer pilots graduated in .0002 can be used on a Grizzley rod to determine the bore dia wear, it is interesting to say the least.

Depending on the powder used, rounds fired, you are probably looking at 3-5" to be cut off. You can't just pick a number of inches to cut off, which would be helter skelter in the least.

 

[whatwind?]

Make is fire forming or load development or practice bbl is another choice

 

[Lefty Trigger]

Setting back might not get you out of the bad area, ask me how I know this... money waisted that could have almost paid for new barrel.

 

[AR Shooter]

Time for a good look thru my friendly local gunsmith's bore-scope.

 

[AckleymanII]

or buy a Teslong bore scope and hook it up to your phone or old lap top or computer.

Nothing new about how to determine how much a barrel should be set back.

Grizzley rod with a large variety of sizes of reamer pilots



Muzzle dia of this Hart barrel measures .2186, so I want to locate the distance from the breach where the dia. is that dia., eliminating throat dia wear.



Notice how the throat had worn in dia





End of new Chamber, will be a 223 Match chamber, zero freebore, .250 neck



You hear all kinds of things like, "set backs do not last as long as the first chamber, set back not shoot well", etc.

This method was developed in the late 1800's for the military and if you see a Swedish mauser with the coin in the side indicating the quality of the barrel, this coin indicates the bore size.

If you stay ahead of the wear and not let the wear get too bad, then set backs to original accuracy of the new barrel is often very successful. If you do not measure the Bore dia and set back the barrel where the throat is located in New barrel bore dia, the set back is questionable.

This barrel started off as a 26" max heavy varmint and is down to 23" with the barrel now shooting in the 2's without much effort with a variety of powders.

I cut the threads on this barrel with a Carmex carbide insert, BXA grade made for low speeds and tough stainless materials.

Lately, I have been shooting a 6 BRA with H4895. This powder is pure hell on barrels. Bore dia has increased for 10" in the barrel, set backs are difficult when you are dealing with a powder that burns up barrels. Many calibers have similar effects on a barrel.

 

[AR Shooter]

Interesting. What was the distance to the 0.2186" diameter on that barrel?
Thanks.

 

[X-Caveman]

3,200 rounds is getting your money's worth.

 

[AckleymanII]

I don't know the answer to your question, AR shooter...I am sorry. It is a 223 case, threads are approximately .875 long.

When we were shooting the 243 AI's with 48-48.5g of Win 760/70g bullets, we would get around 1700-2000 rounds before a set back where the leade had grown from zero freebore to .070-.100 of leade growth. We learned to shoot unturned blanks, started out with 29" finished length, and by the time they were on their 4th chamber, they would be chambered with a zero freeobore 6 BR reamer. Total shots fired on a barrel was 14,000 with 6000 being fired with Win 760 in the 243 AI zero freebore chambers(3) and the one 6 BR zero freebore chamber with usually 8000 rounds using H335 with 60ish grain bullets. Stick powders seemed to eat bores.

 

[AR Shooter]

3,200 rounds is getting your money's worth.

Indeed. No complaints. If I go with a new barrel it will be another 5R rifled Bartlein.