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[ArtR 0]

7mm on Gun Broker could be one that went to Chile...as SN looks like 47XX (may be either 4709 or 4792.. hard to know... time will tell)

B2159 on Gun Broker 

Unknown SN on Gun Broker 

 SN 4034 (Miltech) on Gun Broker

 

[Whitpusmc 0]

Are the external dimensions of the 7mm barrel the same as a 30 06 barrel? 

[ArtR 0]

My understanding is that they used standard .30-06 barrels and just bored and reamed for 7mm

[Ed Johnson 0]

In looking at ammunition diagrams in one of Dad's books, it would appear that the 30:06 case length and distance from base to shoulder were longer than the 7mm Mauser. Can't be too sure about actual bullet size, as i don't have any 7mm to measure against my 30:06 ammo. Not sure how all of this might affect a re-bore and re-ream procedure.

[Whitpusmc 0]

Thank you!

[Joseph Scott 0]

The 7mm barrels were purchased from Mexico and are Mauser stepped design.  They have Mexico proofs.

[ArtR 0]

Thanks Joe

[eb in oregon 0]

On 2/18/2021 at 2:26 PM, Ed Johnson said:

In looking at ammunition diagrams in one of Dad's books, it would appear that the 30:06 case length and distance from base to shoulder were longer than the 7mm Mauser. Can't be too sure about actual bullet size, as i don't have any 7mm to measure against my 30:06 ammo. Not sure how all of this might affect a re-bore and re-ream procedure.

7mm = .275

30.06 = .308

7mm 

Case length	57.00 mm (2.244 in

30.06 

Case length	2.484 in (63.1 mm)

7x57 can be re-bored and re-chambered to 30.06, but the expense would be terrific and trash a good barrel for 7x57 mauser.

[matconcrete 0]

The unknown on gb is b7763, 

Im quite sure O.D. Is same on 06 and 7mm, on both the same barrel locking collar and site is used.

interesting story accompanying A0009, not sure gun is actually the one they think it is though. Google search the serial number it should come up.

[ArtR 0]

2 hours ago, matconcrete said:

The unknown on gb is b7763,

Where did you pick up that info on SN?

[Ed Johnson 0]

OK, not to belabor the subject, but based on EB in Oregon's figures, it would seem that you could re-bore and re-chamber a slightly smaller bored 7mm barrel into a larger bore & chamber 30:06, but going from 30:06 down to 7mm might be a problem. I bow to anyone who has more direct experience with this subject. The only experience I have is with our conversions of existing .30 cal. M1 Carbine barrels down to smaller bore 5.7mm (.2235 - .224) barrels. We tried using inserts, but found it was more cost effective to install new 5.7 barrels and gas port assemblies.. In short, you can always drill and/or ream a smaller bore into a larger one, but not vice-versa, I would think.

[Whitpusmc 0]

I really appreciate the responses! I believe I’ve been fortunate enough to locate a 30 06 barrel so I’m going to pass on the 7MM and allow someone else to acquire it.
 

I was both thinking of acquiring that 7mm barrel and 1) using the external parts to unsporterize my 30 06 barrel and 2) if that failed, attempt to ream out the 7mm barrel to 30 06. I was concerned that any mistake would as said above, trash a good 7mm barrel. 
 

Now does anyone have a buttplate they are willing to preferably sell or if not, loan to me to allow me to create a reproduction that would fit a Winfield buttstock? Your buttplate would not be harmed in any way, just measured. My reproduction would have my name permanently on the inside and would be easily determined to be a reproduction. 

[matconcrete 0]

Hi Art,

 I msgd the fella on gb.

Any thoughts on whether a0009 is actually a usmc used rifle?

https://www.galesburg.com/article/20140303/NEWS/140309932

[Brian Alpert 0]

It is for real.  Well documented provenance.  Simpson's knows what they are doing.  It is their business.

[Whitpusmc 0]

12 hours ago, Brian Alpert said:

It is for real.  Well documented provenance.  Simpson's knows what they are doing.  It is their business.

How did he manage to get the rifle back from where he was wounded? Normally you can’t maintain possession of a firearm through the medical evacuation process? 

[Brian Alpert 0]

From the accompanying article:  

 

"The Johnson M1941 was a latecomer to the war. The one with serial number A0009, was issued to Dunlap. His comrades in arms knew how much he valued the rifle and saw that it was returned to him when the war ended."

[eb in oregon 0]

On 2/18/2021 at 5:28 PM, matconcrete said:

Im quite sure O.D. Is same on 06 and 7mm, on both the same barrel locking collar and site is used.

Merely an observation, but as the rifle was designed and manufactured to be able to interchange barrels of different calibers it sort of makes sense that barrels would be identical with the exception of caliber. Which is essentially of bore size and cartridge case diameter and length. And essentially cases within the .003 difference in diameter of the two wouldn't mean a bolt change was necessary. The 1941 Johnson was designed to be able to handle different cartridges.

On 2/19/2021 at 1:11 PM, Whitpusmc said:

Now does anyone have a buttplate they are willing to preferably sell or if not, loan to me to allow me to create a reproduction that would fit a Winfield buttstock? Your buttplate would not be harmed in any way, just measured. My reproduction would have my name permanently on the inside and would be easily determined to be a reproduction. 

The sporter stock looks thinner than the military stock. You might consider getting some dimensions before going much further.

You know, that rifle is collectible on it's own merits, I'd leave it alone and just enjoy it.

[Whitpusmc 0]

8 hours ago, eb in oregon said:

Merely an observation, but as the rifle was designed and manufactured to be able to interchange barrels of different calibers it sort of makes sense that barrels would be identical with the exception of caliber. Which is essentially of bore size and cartridge case diameter and length. And essentially cases within the .003 difference in diameter of the two wouldn't mean a bolt change was necessary. The 1941 Johnson was designed to be able to handle different cartridges.

The sporter stock looks thinner than the military stock. You might consider getting some dimensions before going much further.

You know, that rifle is collectible on it's own merits, I'd leave it alone and just enjoy it.

I appreciate your response.

Are you saying that I could use my same rifle and merely by swapping barrels I could shoot 7mm and 30 06? If so I’m mildly disappointed I did not bid on that 7mm barrel that just sold for $175... 

I understand what you are saying, and it is tempting to not mess with my rifles stock at all. If I could get a replacement stock I would just swap them out and retain both so as to have both the Sporter version and the original as the metal on the rifle is unchanged and I now should have a Sporter barrel to shoot and a military one to display. I’m just not a fan of that recoil bad, it just doesn’t look like it belongs! 
I will keep looking, but so far zero leads on a replacement stock.

[eb in oregon 0]

4 hours ago, Whitpusmc said:

Are you saying that I could use my same rifle and merely by swapping barrels I could shoot 7mm and 30 06? If so I’m mildly disappointed I did not bid on that 7mm barrel that just sold for $175... 

What I'm saying is that after researching the differences in cartridges there is only a .003 difference in diameter between 30.06 and 7x57 Mauser in base diameter. I'm pretty sure that difference falls within manufacturing tolerances in the bolt face. Changing the outside working dimensions makes no sense in manufacture of barrels of different caliber as that places an undue burden on the manufacturing facility. I was once a Journeyman machinist for over 25 years and changes in the barrels outside dimensions would be silly. That would necessitate different diameter barrels and the inside of the receivers front end. Not cost effective or sensible for a rifle touted as having the ability to run different cartridges. And it makes little sense to change barrel profile as the differences in caliber are miniscule. That too would increase manufacturing cost as those changes would require engineering changes. I'm conjecturing in this belief, however my conjecture is based on solid experience. I don't have either to measure at this point, but I'll bet money on my thinking. That does require though the question if there were multiple magazines for the 1941 Johnson, but that too would increase manufacturing costs of an already expensive rifle. And as the difference between 30.06 (3.34 OAL) and 7x57 (3.071 OAL) was was only about 5/16ths I'm positive the magazine could accommodate both as the 7x57 was only a bit shorter. It is possible that a spacer of some sort was made to account for the difference in cartridge length, not having a 7mm rifle I can't answer that, but I think it probably wasn't necessary.

And as Joe Scott mentions the barrels were subcontracted to a firm in Mexico (I'll take his word for it, I don't know) which also makes sense as 7x57 Mauser was a well used cartridge in Mexico and I think the tooling for making the Johnson barrels in 7x57 was readily available. I'm pretty sure Cranston Arms was pretty much tapped out for tooling costs and focused on the rifles in 30.06. Much of this is difficult to prove without the original drawings, but much can be reliably conjectured with the knowledge of manufacturing processes and tooling requirements. Remember that Johnson and Cranston Arms was struggling to be able to sell and supply any rifles regardless of caliber and changing the design and components for different calibers wouldn't have helped their efforts. I might be entirely wrong, but I'm thinking not. Oh, and remember that it was mentioned in another thread that 7mm barrels had 30.06 stamped on their barrel collar, that suggests that Cranston Arms made the barrel blanks and shipped them to Mexico for boring and chambering.

As to the matter of reboring or re-lining barrels: you can make a small hole bigger and then re-rifle it, and a short chamber longer, but these days that is rather expensive for a one shot deal. It does require specialized equipment to rifle a barrel. And re-lining high pressure rifle barrels isn't a recommended process and such work is usually only done for low pressure straight walled rifle cartridges. Having done some barrel re-lining in pistols I can honestly say it isn't the easiest of tasks.

[Brian Alpert 0]

JSAR bbl are interchangeable.  The guide collar and locking collars are identical, thus the 30/06 markings.  Cranston (Johnson) produced them in 30/06 and 7mm Mauser using blanks from Mendoza in Mexico.  Winfield offered 270 WCF sporter bbls.  Winfield made standard sporter bbl using Garand bbl.  Others were made for them by Apex.  I have or have had JSAR bbls in 308, 7mm Mauser, 8 x 57mm Mauser, 270 WCF as well as 30/06.  They have supposedly also have been made in 7.65 Argentine Mauser. 

Joseph Scott has replacement butt plates.  If you are adapting them to Winfield sporter stocks, which are thinner, they need to be trimmed to fit.

[ArtR 0]

Hi Brian (and Joe)

Thanks again for all your input. I was just 're-reading'   'the book' on another matter and saw where I had missed where the 7mm barrels had been purchased from the National Arsenal in Mexico. Early on I had just assumed  that they would take standard blank barrels and bore and ream for the 7mm cartridge. But I now understand that by buying pre-made barrels from the National Arsenal, they did not need new tooling or have to do a separate barrel setup, and they also would not be 'stealing' from the Dutch contract metal.

I still contend, that if an unassuming  NOOBIE JSAR purchaser unknowingly gets a 7mm rifle, and sees the receiver and  barrel collar marked .30-06 and inserts a .30-06 cartridge in a 7mm barrel, they will be in for a very rude surprise. And it very well could happen. If a family member seeks to dispose of dad or grandpa's  JSAR and delivers it to a gun shop who does not know the gun or does not thoroughly inspect the gun, there could very well be someone buying what they assume to be a .30-06 rifle. Some of the 7mm markings that I have seen shown on the Chilean contract rifles do not 'stand out' and the barrel must be removed to even see that marking.

ArtR

[eb in oregon 0]

3 hours ago, ArtR said:

I still contend, that if an unassuming  NOOBIE JSAR purchaser unknowingly gets a 7mm rifle, and sees the receiver and  barrel collar marked .30-06 and inserts a .30-06 cartridge in a 7mm barrel, they will be in for a very rude surprise. And it very well could happen.

And too there is always the chance of getting hit by lightening, a meteor, or an astroid. I don't think we'll ever agree on this issue. But then again, how many rifles have blown up by a malfunction where the case didn't eject or the case separated and only the rear portion extracted and the rifle tried to feed another round?  Have any M1 Garand's chambered for .308 blown up from someone not familiar with the rifle putting a 30.06 round in it by mistake? Is what you contend possible? Anything is possible. Probable? About as much as that bolt of lightening.

[ArtR 0]

1 hour ago, eb in oregon said:

And too there is always the chance of getting hit by lightening, a meteor, or an astroid. I don't think we'll ever agree on this issue. But then again, how many rifles have blown up by a malfunction where the case didn't eject or the case separated and only the rear portion extracted and the rifle tried to feed another round?  Have any M1 Garand's chambered for .308 blown up from someone not familiar with the rifle putting a 30.06 round in it by mistake? Is what you contend possible? Anything is possible. Probable? About as much as that bolt of lightening.

I think that if you carefully reread my post, never once did I say or imply 'blown up', only they  might be in for a very rude surprise...I.E., the .30-06 cartridge will not chamber in a 7mm Mauser  barrel, and that there might be momentary confusion until the realization is made that the cartridge and the chamber do not match. 

[metrotps 0]

Just for clarification from the SAMMI website. 7x57  vs  30/06.

ANSI-SAAMI-Z299.4-CFR-Approved-2015-12-14-Posting-Copy_(1).pdf 

https://en.wikipedia.org/wiki/7×57mm_Mauser

ANSI-SAAMI-Z299.4-CFR-Approved-2015-12-14-Posting-Copy.pdf

https://en.wikipedia.org/wiki/.30-06_Springfield

[eb in oregon 0]

6 hours ago, ArtR said:

I think that if you carefully reread my post, never once did I say or imply 'blown up', only they  might be in for a very rude surprise...I.E., the .30-06 cartridge will not chamber in a 7mm Mauser  barrel, and that there might be momentary confusion until the realization is made that the cartridge and the chamber do not match. 

I read your post, several times. In another post you implied that more than a stoppage (which is all we're talking about) could occur. Stoppages aren't rare or uncommon, so "very rude surprise. And it very well could happen" is, in my opinion, suggesting more.