How do differently shaped recievers impact barrel vibrations?

4

404tbang

Member
In one of the threads that became too toxic, there was a computer simulation of barrel (and reciever) vibrations and the impact of muzzle devices/tuners on the muzzle.

In decades past there have been a variety of different types and shapes of recievers. I am trying to understand how the reciever affects barrel vibrations.

I have an old BSA #12 Martini custom rifle. I have not had the chance to shoot it yet. In looking at it and differently shaped recievers on classic target rifles, including Ballards, I have wondered whether and how the shape of the reciever would affect the barrel vibrations.

Bill Calfee pointed out that when a factory reciever is heat treated, it will warp somewhat. His explanation made sense to me. Some of the old recievers seem quite symmetrical, and as I understand it, would be less prone to warpage in heat treatment.

Several of those recievers are not cylindrical, would there be a difference in the stiffness of the reciever compared to more modern ones? I realize that there are other issues, the amount of cam they provide, many of them had the forearm mounted directly to the barrel, quality of the available triggers etc., however the International Martini sought to solve some of these issues. Might have created a few issues too.

So, how do different recievers and the stiffness each would have, affect barrel vibrations?

Is the cylindrical reciever the final word on precision, or is it that the recievers that are prevalent today have more research and development in them because that is what is currently used?

Thanks!
Greg

Guys, I'm looking for knowledge, please don't let this turn in to a peeing for distance contest because I mentioned Bill Calfee. I greatly respect his input, and the input of a great many of you as well!
 
In general as a receiver is made stiffer the more it will increase vibration amplitude. This will not be accepted by most shooters but it has to be recognized that if you consider the Varmint Al model of vibration where the vibration originates from the force that is acting against the bolt face, the effect of this force will be more readily transmitted to a barrel by a stiff receiver/barrel joint and thus cause more vibration.

However, as you increase stiffness in a receiver you probably increase it's weight. Adding weight to the receiver will tend to decrease receiver movement and thus it will decrease barrel vibration. The closer you get to a "heavy" cantilever mounting for the barrel the lower will be the vibration amplitude. If the cantilever mounting is heavy but not stiff then again the barrel vibration will be less.

Stiffness and weight of the stock, and how stock is bonded to the receiver, all affect barrel vibration in the same way the receiver alone would act.

The Martini is a stiff action because of it's depth but I'm not sure the barrel mounting area is as stiff as a conventional bolt action. Which receiver is stiffest would be best determined by FEA. Probably a bolt action or a Martini could be made equally stiff but the bolt would be cheaper to build.
 
Fred K, thanks! It might be too good of a question, only have 2 replies so far! This question has been bugging me for a while. I am not an engineer, and I don't have enough experience with different rifles to figure it out, hence the question.

Pacecil, thanks! Your comments raise several more questions for me.
Regarding adding weight to the reciever, specifically in this instance, the Martini, how does the neccesity for a 2 piece stock affect the vibrations?

The Martini requires the buttstock to be screwed into the rear of the reciever. This adds weight. Would different weight buttstocks affect the vibes? If one created some sort of recoil buffer similar to an AR 15, would this not reduce vibes, or at least change them?

Shooting the rifle without the forearm would have to change things as the forearm is mounted to the barrel. On the Martini I have, there is an extra screw hole that has been plugged in the forearm. Only 1 hole in barrel for the forearm. Apparently the shooter, or the gunsmith (Eric Johnson) found the sweet spot for best accuracy regarding the way the forearm was mounted. That may be a stretch, but it is all I can figure out.

These questions do not pertain to the Martini action alone.

As it was related to me by a dealer in exquisite antique target rifles, the reason that the single shot was all but abandoned for a while was the desire to have repeating target rifles for the Camp Perry matches after WW1.

He said that the old rifles are still very competitive, but simply not used that much.

So I ask again, are cylindrical recievers the pinnacle of precision, or do they have so much research and development simply because that is what is being used?

Thanks!
Greg
 
receiver

Greg,

Many years ago Shilen produced a square receivered rifle and the write-ups quoted Ed Shilen as saying they were the most accurate way to go.
In a short time period Shilen again began producing only the round action and the write-ups again quoted Ed as saying they were more accurate. I wrote Shilen a letter over this flip-flop and his final reply was simply that they determined the round action was better.

More years ago Roy Dunlap experimented with square actioned rifles of his own design using a Win.52 bolt (in the case of RF) to check the advantage of a heavy rigid receiver and its affect on accuracy. His conclusion was it was the most accurate. Yet I believe those custom actions sold were round.

One has to wonder about about the cost factor.

Also years ago there was an article on forearm attachment and its effect on accuracy on the two piece stock. It may be worth locating. I'd like to say early AR but can't be sure.

bjm
 
Last edited by a moderator:
I'm sure there is a little different effect of a Martini action on vibrations when compared to a conventional bolt action. There are also differences in stiffness, and precision of manufacture, that might have effect, but these differences, or their total effect, is so slight in a rimfire that for all practical purposes it can probably be considered to have little or no effect on accuracy. Again, we're talking about rimfires.

Both actions, Martini and bolt, can, I believe, be made equally accurate. Any difference in accuracy, when comparing guns, can be attributed to those things the shooter does, or is able to do, or the ammo.

I've compared the accuracy shooters get with the various guns, I've kept track of what I get with my own guns, and found there seems to be a lower limit to average group size. (On another thread I thought mr nobody might be getting accuracy below that limit....then I discovered he was shooting at 25 yards instead of 50....and so it goes!) Bottom line is if you studied the top several hundred rimfires used in benchrest, or position for that matter, I think you would find they are all shooting around that lower limit. This applies whether they have a tuner or not, or whether they are "tuned" or not. If you could compare them over a long period of time and under all the varying conditions you would find the accuracy of all good guns is essentially the same.

I'm not saying there are no differences in the various guns, nor am I saying "tuners don't work"! What I'm giving you is an observation made over many many years.
 
Thanks all around!

BrianJ
Thanks for the info, I have drooled on a Shilen DGA at a gunshow in Louisville that had, if I recall correctly, what appeared to be an almost octagonal reciever. Stunning rifle! Does that mean that the DGA is a round reciever now?

If you can find the forearm article, that would be useful! I have no clue where to look for that. Your resource library must be huge, you come up with helpful stuff! The Dunlap action with the 52 bolt:), left handed even:cool:, Johnson barreled even:D, a rifle sold to get it even:(, a day off work to make SURE I got it even:(, and got beat even:eek::eek:confused::eek:, that one STILL hurts!!

Pacecil, thanks again for helping! If you have studied several hundred top rimfires over a long time, I suspect you could have insight into some interesting trends!

To the Gracious Responder via pm, I cannot thank you enough for trying to help me learn, you have done that more than once. Your answers to every question have been well thought out, insightful, and definitive. I appreciate the help more than you know!

To all who are willing to take time out of your busy day to help me learn, a very heartfelt THANK YOU!

Take care,
Greg
 
You must log in or register to reply here.
Back
Top