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View Full Version : Barrel Diameter vs Action Diameter



jbhotrod
01-15-2014, 04:17 PM
Hello yall, Blake here. I was just thinking about something the other day and figured yall would most definitely know the answer. So, basically, when you have a rifle with a barrel of say, 1.75" diameter, wouldnt you also want to have atleast an action 1.75" diameter or more? Whether you have a barrel block or not, the barrel threads on the tenon will require an action that ends up being roughly the same diameter as the barrel or more. Am I correct on that statement?

Thanks.

j mckinnie
01-15-2014, 05:44 PM
Hello yall, Blake here. I was just thinking about something the other day and figured yall would most definitely know the answer. So, basically, when you have a rifle with a barrel of say, 1.75" diameter, wouldnt you also want to have atleast an action 1.75" diameter or more? Whether you have a barrel block or not, the barrel threads on the tenon will require an action that ends up being roughly the same diameter as the barrel or more. Am I correct on that statement?

Thanks.

not with a barrel block.and in a stock the barrel protrusion would act as a recoil lug.

jbhotrod
01-15-2014, 07:26 PM
not with a barrel block.and in a stock the barrel protrusion would act as a recoil lug.

So with a barrel block rifle, you can make the threaded barrel shank as small as you need to, to fit the action? For example, could you fit a 2" diameter barrel to a Remington 700? Would there be any disadvantage to having a large discrepancy between the barrel Outer diameter and the threaded shank outer diameter?

Also, when you see thread dimensions, ie 1.062" x 16tpi, is the first number, 1.062", the diameter of the thread shank or is that number the length of the threaded portion?
And would you say that most barrel block rifles are using an action that is smaller in diameter than the barrel?

Thanks for replying.

SGS
01-16-2014, 06:57 PM
So with a barrel block rifle, you can make the threaded barrel shank as small as you need to, to fit the action? For example, could you fit a 2" diameter barrel to a Remington 700? Would there be any disadvantage to having a large discrepancy between the barrel Outer diameter and the threaded shank outer diameter?

Also, when you see thread dimensions, ie 1.062" x 16tpi, is the first number, 1.062", the diameter of the thread shank or is that number the length of the threaded portion?
And would you say that most barrel block rifles are using an action that is smaller in diameter than the barrel?

Thanks for replying.

Yes, yes, and no. 1.062 would be the tenon diameter (approximately). "Barrel block rifles" may be stocked, as is the case with some long range BR rifles; or they may be unlimited class rail guns used in short range BR. I can't answer for the long range guys, but it is quite common for rails guns to use a straight barrel of 1.400 or so, and a standard 1.37 diameter action. No disadvantage that I know of.

Scott Roeder

jbhotrod
01-19-2014, 12:38 PM
Thanks for answering everything sir.

I was looking at a thread the other day in which the OP was arguing bolt actions are behind the times and should have the receiver and chassis/stock be one piece ala the DTA rifles or AR15s. Not only that but he said they should have a bolt head/lugs like the AR15. Personally I disagree as the bolt lift should be real heavy with that many lugs due to such steep camming. And if setup as a straight-pull I personally wouldnt trust it as far as strength after seeing problems with the Blasers.

I dont agree that a rifle setup like this would be any better than what we have now. However, instead of the action and stock/chassis being one part; do you think we`d see any advantage where the action/barrel were one piece of metal? Instead of connected by threading? I could maybe see it being stiffer but machining it would be more difficult/expensive and you`d basically have to get an entirely new rifle when changing caliber and bolt face. So mostly neither of these would offer as many options in customization as current rifles. With that said, do you/yall think a design like either of these would ever make any headway in the market, or offer any accuracy advantage?

Thanks again sir.
Blake.

Boyd Allen
01-19-2014, 01:24 PM
Current action designs are used as parts of rifles that can shoot well under .2" under good conditions. This does not seem to point to a need for different designs, particularly since accuracy is the result of multiple factors. I spend most of my time shooting on public ranges, and believe me, the reason that shooters do not shoot any better than they do has almost nothing to do with the designs of modern actions. Even when considering benchrest competition, there are so many variables, that except in the case of some gross deficiency it would be difficult to pin a problem down to the action. Bottom line, the best of current designs work pretty darn well.

B.Larson
01-19-2014, 01:50 PM
i`ve built a few rifles with barrel blocks.With heavy/long barrels,I think they are and advantage.

jbhotrod
01-19-2014, 04:45 PM
Current action designs are used as parts of rifles that can shoot well under .2" under good conditions. This does not seem to point to a need for different designs, particularly since accuracy is the result of multiple factors. I spend most of my time shooting on public ranges, and believe me, the reason that shooters do not shoot any better than they do has almost nothing to do with the designs of modern actions. Even when considering benchrest competition, there are so many variables, that except in the case of some gross deficiency it would be difficult to pin a problem down to the action. Bottom line, the best of current designs work pretty darn well.

Thats exactly what I thought sir. The AR15 bolt design may be nice for a semi-auto but trying to introduce that into a bolt-action will bring in more problems than advantages I would think.

Thanks for replying yall.

One more thing, on McMillans website in the stocks section, it said something about sleeved actions. Why would you want to do this? And does anyone have any pictures of what a "sleeved action" looks like?

Thanks again.
Blake.

alinwa
01-19-2014, 05:43 PM
rem700 sleeves

14459

al

Vibe
01-20-2014, 10:29 AM
I dont agree that a rifle setup like this would be any better than what we have now. However, instead of the action and stock/chassis being one part; do you think we`d see any advantage where the action/barrel were one piece of metal? Instead of connected by threading? I could maybe see it being stiffer but machining it would be more difficult/expensive and you`d basically have to get an entirely new rifle when changing caliber and bolt face.

Thanks again sir.
Blake.
There were a few economy 22s built that way back in t he 50's and 60's.

jbhotrod
02-08-2014, 02:55 PM
I realize this is off-topic from the original post, but I wanted to ask a few other things, and figured it didnt call for a new thread.

Has anyone here seen/handled the CG Actions? Obviously, they come from the same line as the rest of the CG actions; Millennium, RPA Qaudlite/Quadlock, etc. The older ones are mostly 4-lug while the newer stuff is 3:

http://www.actionclear.com.au/product_list.php?page_id=2

The newer ones especially incorporate some very interesting features, for instance, the CG INCH is rear lug action. The Delta is 3 front lugs. What is pretty cool is the lug design on the Delta almost completely surrounds the bolt head, forming something similar to a truncated triangle with concave sides around the bolt head. It certainly looks like a strong design. All of the CG-design actions are some of the most prevalent custom actions when it comes to Palma and Int`l Fullbore shooting competition, as well as some of the more popular Euro competitions, like 300m, Prone, etc. Obviously though, I havent seen many at all in F-Class/Benchrest use. Here is an article on the older Millennium though, as you can see its a very good shooter as well:
http://www.accurateshooter.com/guns-of-week/gunweek065/

What is yalls thoughts on these actions?

Also, instead of having a traditional flat 90 degree back side on the bolt lug, would there be any advantage to having the contact area of the lug sloped at an angle for more contact surface area with the lug abutment? Or maybe a semi-spherical contact area on the contact side of the lug ala the American Rifle Co.`s M2 action? Just wondering if there is maybe possibly a way to shape the lugs for more consistent extremely-close fit without sacrificing strength.

Another interesting feature is that on the CG actions, they use a Belleville washer spring instead of a coil spring, so the lock time is very very fast.

On a BR rifle though, I cant help but to question exactly how useful small improvements in lock time would be? Certainly I could see it help Palma/High Power shooters, but for BR I dont think you would really notice any improvement, as with the right setup the rifle shouldnt be moving much, if at all, anyway. Then again yall would be in a better position to speak on that. Overall though, I could definitely see the CG actions being very successful in short range Benchrest, but maybe not so much with the heavy stuff because I doubt the CG`s are going to be as stiff as, say a Hall Model B or BAT M 1.55".

With all that said, what do yall think of the CG/RPA design actions? Is there anything in the design of them that would lend themselves to better accuracy than the more traditional stuff?

Thanks everyone.

Dave Tooley
02-25-2014, 05:58 PM
There are bolt action rifles that use a barrel extension just like an AR-15. They are Remington's MSR sniper rifle. They use a three lug bolt. I've had to eat crow as I didn't think it would work. Now I've chambered more barrels for those rifles than anyone at Remington. No complaints so far.

Dave

jbhotrod
02-26-2014, 02:51 PM
There are bolt action rifles that use a barrel extension just like an AR-15. They are Remington's MSR sniper rifle. They use a three lug bolt. I've had to eat crow as I didn't think it would work. Now I've chambered more barrels for those rifles than anyone at Remington. No complaints so far.

Dave

Youve chambered MSRs? I thought those werent available to the public? How did it shoot?

Do you think the bolt locking into the extension offers any consistency advantage?

Dave Tooley
02-26-2014, 03:28 PM
Youve chambered MSRs? I thought those werent available to the public? How did it shoot?

Do you think the bolt locking into the extension offers any consistency advantage?

They're not available to the public yet. How did they shoot - no complaints so far. Extensions are just another way to skin a cat.

Dave