Converting a Musgrave to a 556

[Cameron Mc]

It is dangerous if the back end of the case is not surrounded by the bolt head, or in case of a rimmed round, the chamber. Ideally, there is very little gap between the end of the bolt, and the end of the barrel in the action. For example, in my Paramount, there is only 0.0035" gap (three and a half thousandths of an inch) between the bolt and barrel.

A rifle may well be shot for years without a problem with the bolt face larger than that specified, but why take the risk?

Other than the above, it would be pretty poor practice for any person to undertake a conversion, and leave the bolt face out of spec as mentioned. I have never seen any rifle converted like this, and hope I never do.

Woody, the chambered case in combination with the bolt face and barrel contain pressure while the projectile travels down the barrel.

The bolt head rim aligns the case and is there for some protection in case of a head separation.

Mauser bolts do not offer full case head support. I am not a Mauser fan but they have quite a following. The Musgrave bolt is a Mauser copy.

Cameron

[Woody_rod]

Mate, I have only been playing with engineering on and off for 29 years, I am only learning about this stuff.

I have only worked on 4 different Musgraves in the past 3 months, maybe I missed something. It is hard to make any comments about your post, and stay within the new posting rules

[Robert Chombart]

Robert
The only mod that I can see that Keith done to my Musgrave to convert it to 223 is to let the extracter claw reach the shell rim to be able to extract the shell, no welding or other metal involved, works well.
PeterH.[/quote]

Peter,

One of the functions of a bolt head recess is to serve as a support for the case body to be maintained in the extractor without having the possibility to move sideway. If originally made for a 12mm case head, it will not work well for the 9,6mm of the .223.
The adaptation could be made, I have seen even worse than that, but will result in cases falling in the action before being fully extracted, not to mention a stuck case that the extractor will override without extraction....
If you are happy with this, and if someone undertakes such ''modification'; feel free to have it done and use it...full point.

One might comment that the Mauser system does not have a full recess in the bolt head. This is intended for feeding from the magazine only, with the groove of the case sliding UNDER the extractor. Feeding a Mauser system by allowing the extractor to slide over the rim is not recommended, and even impossible with the origial Mauser calibers such as the 7,92 or the original 7x57 of the Musgrave. This disposition allow also the Mauser system to have the shortest bolt head recess (2,4mm as compared to the some 3,5mm and more of some unthought designs. This is important in order to contain an eventual case blow.
Also, when closed, the half dameter recess protects in the right and performs its function of maintaining the case head when open.
Peter-Paul has done it completely right the century before last, no more I can or will say, except that such 'modification' would have some chances to not pass the CIP after-proof check if made under the normal CIP test protocol... Also, if the pressure-test round does not extract, this led to rejection and ni acceptance.....But you do not have this problem in OZ !!!!
Robert Chombart

[Robert Chombart]

Woody, the chambered case in combination with the bolt face and barrel contain pressure while the projectile travels down the barrel.

Too simple an explanation. There is a gap between the bolt face and the barrel rear. If the bolt head recess is too deep and if the gap is too large, the lain bottom of the case in not fully chambered, and only the thin wall of the case ahead of the head ensures limited resistance.
If there is no recess, or if the bolt head recess is too large for the case head diameter, the problem is even increased.


The bolt head rim aligns the case and is there for some protection in case of a head separation.

Strictly technically speaking, I would very much prefer the contrary, this is to say the bolt contributing to align the case in the chamber!!!

Mauser bolts do not offer full case head support. I am not a Mauser fan but they have quite a following. The Musgrave bolt is a Mauser copy.

I am one of hois fans. I think I have already expressed that.....

Cameron[/quote]

Robert Chombart

[Woody_rod]

Robert, your last post is a bit confusing due to missing quotes. If I may you might have wanted it to look like this:

Cameron Mc said:

Woody, the chambered case in combination with the bolt face and barrel contain pressure while the projectile travels down the barrel.

Too simple an explanation. There is a gap between the bolt face and the barrel rear. If the bolt head recess is too deep and if the gap is too large, the lain bottom of the case in not fully chambered, and only the thin wall of the case ahead of the head ensures limited resistance.
If there is no recess, or if the bolt head recess is too large for the case head diameter, the problem is even increased.

Cameron Mc said:

The bolt head rim aligns the case and is there for some protection in case of a head separation.

Strictly technically speaking, I would very much prefer the contrary, this is to say the bolt contributing to align the case in the chamber!!!

Mauser bolts do not offer full case head support. I am not a Mauser fan but they have quite a following. The Musgrave bolt is a Mauser copy.

I am one of his(edited) fans. I think I have already expressed that.....

Robert Chombart

[AlanF]

Rod,

This thread seems to have gone a long way without much foundation. We have someone saying that they think a modification was done in a certain way, and you are implying it is unsafe without knowing exactly what was was done, or how much expertise with this type of work the gunsmith has. I believe it would be best to give the official NRAA gunsmith the benefit of the doubt? After all he would hardly be likely to prepare an unsafe firearm for the Chief Range Officer??

Alan

[balcom]

Rod,

This thread seems to have gone a long way without much foundation. We have someone saying that they think a modification was done in a certain way, and you are implying it is unsafe without knowing exactly what was was done, or how much expertise with this type of work the gunsmith has. I believe it would be best to give the official NRAA gunsmith the benefit of the doubt? After all he would hardly be likely to prepare an unsafe firearm for the Chief Range Officer??

Alan

Thank you alan, I was going to make further comment but you said it well.
Cheers
PeterH

[KHGS]

Alan,
Not only would he not do it for the Chief Range Officer, he would not do it for anyone else either! He has worked on one or two rifles & shotguns & pistols in the last 30 years.
Keith H.

[AlanF]

...Not only would he not do it for the Chief Range Officer, he would not do it for anyone else either!...

Now you'd think I would have seen that coming ... . I try to tell others to think carefully what they write. Ah well, its all good fun.

Alan

[Woody_rod]

Keith,

I take your sarcasm in the right spirit. I apologise if there was any misconception that I was inferring that KHGS was doing any unsafe work, which I never intended. I dont know what happened with the conversions, as I have already said.

Anyway, lets get on with it.

Maybe people should write what they mean, not mean to write....would make it easier to understand what posters are on about.

[KHGS]

Rod, I can take then, that you will now check read your posts so that you write what you mean. Good advice for others too, I might add.
From the perspective of a full time professional gunsmith such as myself any hint of criticism will be picked up by third parties to the detriment of that gunsmiths reputation, not a small matter & one I am justifiably touchy about. So any time my name is linked to an unfounded criticism in a thread, the facts had better be accurate.
O.K. Now it is time to move on, put this behind us & continue our common interest.....shooting!
Keith H.

[Robert Chombart]

Rod, I can take then, that you will now check read your posts so that you write what you mean. Good advice for others too, I might add.
From the perspective of a full time professional gunsmith such as myself any hint of criticism will be picked up by third parties to the detriment of that gunsmiths reputation, not a small matter & one I am justifiably touchy about. So any time my name is linked to an unfounded criticism in a thread, the facts had better be accurate.
O.K. Now it is time to move on, put this behind us & continue our common interest.....shooting!
Keith H.

I take the point to put an end to this.

I think however the commets and the indents were to my adress, therefore, I use my right to reply..

Some others might also have backgrounds allowing them to have pertinent opinions on certain subjects and, without having an over-dimensioned ego, I can modestly say mine show also some experience and graduations, mostly in metallurgy, metalworking and metal flowing and deformations.. Not to count a german degree in Safety and accident Prevention and Industrial Risl management. I however do not consider myself as a gunsmith, as I have no degree in this branch, just some experience, I think...

End of the matter for me.... No aplogies, and consider I always say (or write for the mater) what I think..

Robert Chombart

[KHGS]

Robert, that is all very well indeed.....saying what you think.
You will do yourself a great service if you take care that what you say in print does not reflect on others also well qualified.
My right of reply, also with no apology.
Keith H.
Graduate of The North American School of Firearms.
Trade certificate in fitting & turning.
ACT Chief Safety Officer.
Honorary NRAA Gunsmith.