Gunsmithing Bedding for COLD BORE

[C Snyder]

I just chambered a 6mm BR in an AISC stock. The barrel is a 27" H&S fluted and the action is an RSR surgen. On load development I noticed from a cold clean bore it would take 3 rounds to walk the shots into the "sweet spot" and it would shoot .25 -.4 once warm. 1st shot 1.5 low .75 left 2shot 1 low .5 left all other shots withing one ragged hole group.

From a dirty cold bore the first shot would always go .75 low and .25 left.

I just got done bedding a 2" barrel pad infront of the recoil lug and bedding the tang of the action. It now has no cold bore deviation and shoots 3/8 moa.

While I have no real scientific data to back it up I do belive the lack of bedding infront of the recoil lug may have been a major factor in the cold bore shot deviation.

 

[coldboremiracle]

Re: Bedding for COLD BORE

Interesting. I'd like to here more discussion about that.

 

[Youngjoonni]

Re: Bedding for COLD BORE

General consensus has always been that in order for a barrel to be completely free floating the area before the recoil lug should NOT contact the barrel in any way.

However, if it works for you, all the better!

What is the grouping AFTER the barrel gets to temperature?

 

[jephs422]

Re: Bedding for COLD BORE

I have no idea about the science behind this, but my smith has bed the first 2 inches or so of my barrels in all the rifles he's built or worked on for me.

 

[C Snyder]

Re: Bedding for COLD BORE

Once warm it will put 10 shots in 1/2 moa. (If I do my part) That is off a Harris bipod in prone or off a bench with sand sock. If one is out of the group it is because of the loose nut behind the trigger.

 

[Lowlight]

Re: Bedding for COLD BORE

GAP beds my chassis with a small 1" pad in front of the lug.

 

[BlackOps Tech]

Re: Bedding for COLD BORE

+1....I always bed with a pad and I determine the length of the pad by the breech length of the barrel....

 

[wnroscoe]

Re: Bedding for COLD BORE

Skim bedding an AI Chassis front & rear would go a long way, especially when a Rem700 is being used in one.

 

[coldboremiracle]

Re: Bedding for COLD BORE

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Okiecop</div><div class="ubbcode-body">
From a dirty cold bore. . . . . . </div></div>


Good bumper sticker

 

[swd]

Re: Bedding for COLD BORE

I doubt the pad had anything to do with it. The bedding was probably just not right. I never bed with a pad on a floated barrel. The F class guys are hanging 32" 1.25" straight bull barrels on Remmingtons with no pad. If a barrel like that doesn't need a pad well why bother.

 

[Terry Persing]

Re: Bedding for COLD BORE

Could it be from oil in the bore. Try passing a couple of patches with alcohol on them to clean out the oil, then dry patch it and then test shoot it.

Let me know how it goes.

 

[Greg Langelius *]

Re: Bedding for COLD BORE

A) I theorize that bedding under the chamber, using a resilient compound like RTV, could have benefits.

B) I would suggest trying a clean bore that has been pretreated with a patch soaked in alcohol and graphite, and the alcohol allowed to dry off.

Greg

 

[C Snyder]

Re: Bedding for COLD BORE

All cold bore shots were from a "dirty" bore. I have only cleaned the bore twice and that was withing the first 50 rds.

Every rifle I have shot will have a differnt cold bore if fired "wet". If I store a rifle I push a few patches with "REM Oil" down the bore. If shooting for the first shot as you say Alchohol, carb cleaner or Acetone works great to pull all oil out of the bore and first shot will be dead on for "dirty cold bore"
I now have about 300rds down the barrel and with an 80gr berger it will put 5 shots in 1/4 moa and 10 under .6 MOA. Dirty cold bore is always dead center or 1/4 to left. After that it is up to the shooter to place them into one ragged hole. I am not sure if it was the barrel pad or the bedding that did the trick since both were done at the same time.

Just a good note that bedding can effect cold bore in a quality setup

Pictures coming soon of the build in gunsmithing forum