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Scratch that....UNDER sized bore in .45 Colt....how much does it matter.


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So I'm looking at an older used Marlin 1894 made by Marlin.  It started life as a .44 mag but at some point it got bored out and rechambered for .45 Colt.  The current owner has taken some calipers to it and as best as he can tell, it is .448 on the GROOVES.  SAAMI spec is .452.  A difference of .004".

 

My question is how much of an issue is .004"?  I've got a bunch of .45 Colt ammo and components.  I really don't want to get into casting something special for one gun.

 

EDIT>  I was talking to him about the lands and he measured hte grooves.  So it is undersized.

 

Thanks!

Edited by smokedawg SASS#60968
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  • smokedawg SASS#60968 changed the title to Scratch that....UNDER sized bore in .45 Colt....how much does it matter.

Unless you can get into it cheap enough to rebarrel it I would run away.

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39 minutes ago, smokedawg SASS#60968 said:

So I'm looking at an older used Marlin 1894 made by Marlin.  It started life as a .44 mag but at some point it got bored out and rechambered for .45 Colt.  The current owner has taken some calipers to it and as best as he can tell, it is .448 on the GROOVES.  SAAMI spec is .452.  A difference of .004".

 

My question is how much of an issue is .004"?  I've got a bunch of .45 Colt ammo and components.  I really don't want to get into casting something special for one gun.

 

EDIT>  I was talking to him about the lands and he measured hte grooves.  So it is undersized.

 

Thanks!

 

A.  You do not know if the current owner even knows how to properly use calipers.

 

B.  Calipers are not a good way to measure rifle bores.

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5 hours ago, Larsen E. Pettifogger, SASS #32933 said:

 

A.  You do not know if the current owner even knows how to properly use calipers.

 

B.  Calipers are not a good way to measure rifle bores.

Agreed.  However I would be buying it from a guy in another state.  No chance for me to slug it. 

 

He is going to take it to the range tomorrow and shoot it with commercial ammo.  I will have to see what the results of that are.

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Howdy

 

In addition to the statements about calipers:

 

I have an old EuroArms 1858 Remington Cap & Ball revolver. Even though these revolvers are called '44 caliber' revolvers, they do take well to conversion cylinders chambered for 45 Colt.

 

A number of years ago I had a 45 Colt conversion cylinder fitted to it.

 

I never measure groove diameters with a caliper, I always slug the barrel. The groove diameter of the barrel is  .449, if I recall correctly.

 

Never had any problem shooting 45 Colt Black Powder cartridges loaded with soft lead .452 diameter bullets through it.

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IF it undersized by some .004", depending on a number of factors, hardness of your lead, actual size of your projectiles, chamber length, diameter, length of leade, and what depth you seat bullet to, it could, possibly, maybe, might, increase pressure somewhat.  Since the 45 Colt factory ammo is relatively anemic, as it's made to be safe in even 1st gen Colt SAAs, and the Marlin IS safe with 44 Mag ammo... I wouldn't worry about it at all.  But, like mentioned above, (at least once), I slug the barrel and take a chamber cast so that I'd KNOW what all the factors are rather than SWAG'n it.   Wait, it'd still be a SWAG... except after the measuring, it'd be a Scientific Wild Assed Guess, instead of a Silly Wild Assed Guess! ;)

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