Accurising Rem Bolt Shroud Question

[Ronin]

I recall reading an article many years ago about the negative effect a "loose" fitting shroud has on the accuracy of Remington actions (and clones)

 

The idea was that the relationship bettween the lower two faces of the shroud and the contact points on the action guide rail was improved if there was some kind of bushing "stud" fixed to the two points of the shroud base.

 

Ive been trying to locate the article (it was online) and im damned if I can find it - ive tried the precision accuracy forums stateside, to no avail.

 

 

Can anyone recal the article or point in the right direction.

 

 

Basically I have the plan of fitting two delrin (or similar slippery hard material) studs to the lower contact point on the shroud - machine them down to they are a smooth interferance fit on the guide rail of the action to stop the shroud and bolt twisting on cocking / firing cycle - so alignment is maintained.

 

I may be trying to fix a probnlem that doesnt exist, but the bolt and firing pin cannot be concentric to the centreline of the bore if its a loose fit, having detrimental affect on accuracy.

 

 

Anyone thoughts or have an opinion on doing this?

 

 

 

 

[baldie]

Sounds a good idea in theory Andy, but its going to wear.

 

I think its a problem that doesn't exist.

 

Providing both lugs are square with 100% contact, they can only be square when the trigger is slipped and ignition occurs....especially if the bolt can actually "self centre"

 

I think a little play can be productive.

 

A few years ago, I built a .22Br for one of the shows, and kept it myself. It was made on one of my actions, and I had 2 bolts made for it which were identical in every aspect apart from bolt fit.

 

One ran "benchrest" tolerances of 0.0015" bolt to action fit.

 

The other ran a much looser "repeater" tolerance of 0.005"

 

Headspace was exactly the same on both bolts. I tested them side by side, with the same loads on the same days.

 

Absolutely no difference whatsoever.

 

I remember Hatzi testing the gun at Diggle...he still says its the most accurate rifle he's ever tested.

 

I think bolt tolerances are there to fool the unwary and saves folk bragging about their cars/morgages/dogs/baylocks....

 

It would be a simple test though, as you say, just fit some delrin studs to the guides. I would be very interested in your findings .

[Leeman]

Andy,

 

I can't recall reading about bushings but I have read about using something like PTFE plumbers tape on the shroud threads to tighten up the fit in the bolt. It would have been in precision shooting magazine or maybe on the benchrest central forum, but possibly going back ten years or so. One of my F class rifles is built on a Rem 40x, I can't say it's sloppiness makes any difference as it's just as accurate as the other two I have built on custom actions. By the way, I don't use any thread tape on the shroud, never tried using any either.

 

Richard.

[Scotch_egg]

I have done a bit of a search and come across a couple of references to Tony Boyer. The table of contents refers to bolt shroud modifications.

 

http://www.rifleaccuracybook.com/files/BoyerBook_Sample.pdf

[bradders]

Sounds to me like a solution in search of a problem

[Ronin]

Thanks guys,

 

it is probably a problem that doesnt exist, im modifying one of my rifles at present and having changed bolt shrouds from standard (v sloppy) to PTG, (less sloppy), wondered if accuracy would be affected, thought some more and recalled the article - hence my post.

 

 

 

I may persue this, but given no one else seems to be making modifications (in the accuracy world) agree it may not be a worthwhile pathway to accuracy ("grasshopper")

[Tictac]

Borden have modified their bolt shroud to stop bolt lift. Maybe this does make a difference, but can it be measured on target?

[Ronin]

Borden have modified their bolt shroud to stop bolt lift. Maybe this does make a difference, but can it be measured on target?

 

 

 

No, they made the bolt body slightly oversized at the rear of the bolt head and in front of the primary cam - "Borden Bumps"

 

 

Im talking about the shoud base / interface with the action guide rail itself

[Tictac]

_{They have modified the shroud, Take a Google. "Short video demonstrating no bolt handle jump upon firing and ease of bolt lift with new mods to the Bolt shroud. Joint effort-Borden Accuracy and Alex Wheeler."}

 

_{I cant post a link.}

 

_Paul

[baldie]

Bolt " jump" has nothing to do with sloppy shroud fit.

 

Its caused by the cocking ramp timing being out, and is easily fixed. I'm not going to describe how to do it, but if you give me a buzz Andy, i'll explain [though you probably know ]

[Tictac]

 

According to Borden, a revised shroud does reduce the bolt jump on their action?

[Ronin]

Dave, thank you, you are right - im not trying to correct bolt jump on the firing cycle.

 

Tictac - thanks for the video, Jim is addressing a different issue; though excessive bolt lift on firing with his actions is something I have rarely seen - and I have used quite a few Borden actions in my customer builds and my own rifles

[Tictac]

I have a Borden on order so that's good to hear I thought it was worth mentioning as the subject was bolt shround accurising and "every little helps"

[Ronin]

This is what I was refering to in my original post.

 

 

(after much searching,,,,)

 

2nqquf9.jpg

[Ronin]

Thought id do a test group (witnessed) before I attempted any modification of the bolt shroud.

 

This is a rifle ive used for deer management for the last 13 years (or longer) and on its 3rd barrel in 6.5 x 284 form.... and is a accurised Rem 700, with US made barrel, PTG bolt handle, PTG shroud and modified Tubb spring, trigger is a shilen unit that has fired 000's of rounds, all set in a PSE stock. The bolt handle by the way does not jump on the firing cycle - as per the Wheeler / Borden video

 

All modifications and barrels were done by me, in house.

 

This barrels had 600 rounds through it on the day of the test:

 

test conducted at 130 mtrs in still wind using bipod and rear bag

 

 

 

The group (5 rounds) measured .246", a second witnessed group (5 rounds) measured .250"

 

 

I dont think i'll bother modifying the bolt shroud any further.