New to LRH

jkad57

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Joined
Nov 23, 2018
Messages
7
Location
Aurora
Hi Folks, New to LRH and have a general question about the 7mm Mag caliber. Bought a new factory 7mm Mag barrel for my TC Encore and noticing my group size deteriorating after about 30 rounds through the barrel. The group change is so extreme, from less than one inch to over two an a half inches, that I thought my scope bases had loosened. After I had cleaned the barrel with copper remover the accuracy returned to normal. I have never experienced this with my 223 or 308 barrels with so few rounds fired. Is this common for this caliber?
 

Heavyiron

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Joined
Apr 11, 2016
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1,008
Location
Danielsville georgia
Welcome to Lrh, great to have you on board. I have a 7mm rem also, i do not let one it go over about 30 rounds before cleaning. If your barrel is new, it needs to go thru a break-in process.
There are many different thoughts on a new barrel how long to go before breakin is complete. Were you usuing one of the all cooper bullets by the way.
There will be some residents with more experience that will weigh in on this. My experience is limited on new barrel break in but usually when first starting i clean it after about every 5 rounds. For maybe twenty rounds or so then go to about 20 rounds after then. Everybody has a different thought on barrel breakin and will get you on the right path.
 

jkad57

Member
Joined
Nov 23, 2018
Messages
7
Location
Aurora
Thanks Heavyiron for your reply. Barrel break in was one shot, clean, two shots, clean and so on up to ten shots. This was all done with factory rounds using Hornady SST and ELDX, Winchester Power Point Bullets. Was using TTSX for a majority of the 30 rounds I mentioned in my post. Think cleaning more often after using all copper bullets maybe the answer.
 

Hand Skills

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Joined
Nov 1, 2017
Messages
834
Location
Canada
Welcome Jkad, that's a good question. Sometimes rougher bores foul more than smooth ones. Premium barrels are often lapped to reduce tooling marks and increase consistency. A couple of suggestions to look into;

-try cleaning with an abrasive. One of the more popular ones is JB Compound. It's about 1000grit abrasive suspended in a paste. This can not only help clean the barrel, but helps smooth it as well

-Tubbs final finish. Similar idea, but instead of manually pushing a patch you press incrementally finer abrasive into some bullets and fire them through

-take it to a gunsmith, have him take a look with a scope and possibly slug your bore and lap it properly.

What I find interesting is many custom barrel makers who double lap their barrels claim no break in is necessary.
 

jkad57

Member
Joined
Nov 23, 2018
Messages
7
Location
Aurora
Welcome Jkad, that's a good question. Sometimes rougher bores foul more than smooth ones. Premium barrels are often lapped to reduce tooling marks and increase consistency. A couple of suggestions to look into;

-try cleaning with an abrasive. One of the more popular ones is JB Compound. It's about 1000grit abrasive suspended in a paste. This can not only help clean the barrel, but helps smooth it as well

-Tubbs final finish. Similar idea, but instead of manually pushing a patch you press incrementally finer abrasive into some bullets and fire them through

-take it to a gunsmith, have him take a look with a scope and possibly slug your bore and lap it properly.

What I find interesting is many custom barrel makers who double lap their barrels claim no break in is necessary.
 

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