Marlin Firearms Forum banner
1 - 8 of 8 Posts

·
Registered
Joined
·
7,301 Posts
Discussion Starter · #1 ·
Anyone ever try to cut Ballard rifling into a micro groove barrel in order to more easily cast bullets? Seems it should save $$$ over a rebarrel?

I'm one of those who have not been able to get anything better than 3" groups at 50 yards from my '77 vintage 1895.


Would this be a reasonable thing to attempt? Any thoughts how it might be done?

Thanks.
 

·
Registered
Joined
·
97 Posts
You might consider using bullets that are sized larger than what you are using if you have not done so slug your barrel and use bullets that are 2 to 3 thousandths larger than bore diameter. For a re-rifling job the bore will have to be cut to a larger diameter. You didn't state the caliber but I am guessing that it is a 45-70. This means that it will need to be bored to something exotic or a 50 caliber if it is a 45-70. The reason being that the old rifling has to be removed to cut new rifling.
 

·
Registered
Joined
·
1,005 Posts
Something is wrong with your loads (bullet diameter most likely) or your gun. A micro groove barrel will shoot as well as any other barrel but the bullet has to fit. In answer to your specific question, no. A rerifling job won't work. If you are determined to spend un necessarily, contact John Taylor to have a liner installed.

To help you shrink your groups, answer the following questions:

. What is the bore diameter of your rifle? (slug the bore)
. What is the diameter of your bullets?
. What kind of sights are you using?
. What kind of groups do you get with jacketed?
Finally, what do your groups look like, round, vertical, horizontal or a shotgun pattern?

Your problem can be fixed.
 

·
Super Moderator
Joined
·
9,322 Posts
Too many microgroove barrels shoot too well to believe it is the style of rifling giving you problems. Follow the tips suggested above and all will work out.
 

·
Banned
Joined
·
1,761 Posts
From an article at Beartooth Bullets > Home

First let us look at those Marlin Barrels. The chambers in both the Micro Groove models as well as the newer Ballard style rifled guns have chambers with fairly generous proportions in the throat area of the chamber. Typically the throats, while being fairly short, are larger than most folks expect, with the diameter running .4325"-.433" on the average in most guns. For best results using cast bullets, that large throat diameter needs to be filled up for best performance, facilitating bullet alignment with the bore prior to ignition of the cartridge. An undersize bullet has the propensity to yaw or tip in the throat before engaging the lands of the rifling, thus causing the projectile to enter the bore off-center.
As mentioned earlier, the Micro-Groove barrels very typically have a generous helping of machine marks in the bore which, for best cast bullet shooting need to be lapped to some degree. Fire lapping is the easiest and most efficient way to deal with this aspect of bore preparation. (Complete instructions for fire lapping are contained in The Beartooth Bullets Technical Manual. Click here for more information!) While the new Ballard style rifled barrels have bores of a much better condition in regard to machine marks, they too need lapping for best results when shooting cast bullets.
Why do those nice new Ballard barrels need to be lapped? Because of constrictions in the bore! Both the Micro-Groove models as well as the new Ballard style rifled barrels have constrictions in them. These constrictions are located under the dovetail cut on the underside of the barrel for the magazine tube hanger, under the dovetail cut for the rear sight and again under the roll-stamp engraving of the barrel markings on the left side at the rear of the barrel. While the severity of constriction varies from one gun to another, they are there none-the-less on all of these big bore rifles (both .444 and .45-70).
Of the two guns used for testing in this article, the Micro-Grooved .444S model rifle was fire-lapped over fifteen years ago, relieving the barrel of not only the bulk of the machining marks in the bore, but all traces of constriction in the locations mentioned above. However, the Marlin .444P "Outfitter" model used for testing in this series had not been lapped, and had seen only cast bullet use. Using a number eight oval egg sinker (see our FAQ pages for instructions on slugging, or Beartooth Bullets Technical Guide for complete instructions. Egg sinkers available click here.) we slugged the barrel of the new .444P. Actually we used several sinkers, and slugged just the muzzle, then drove a sinker as far as the forward dovetail for the magazine tube hanger, then removed it to measure the constriction at that point, then repeated the process from the breach end shoving the egg sinker as far as the rear-sight dovetail and once again removed the slug to determine extent of constriction under the sight dovetail. Finally we inserted another egg sinker and shoved it to the central point under the roll-engraving of the barrel markings at the left rear of the barrel. From the measurements obtained from each of these slugs, the amount and location of the constrictions in the barrel were determined as illustrated below.


This helped me understand what's up. You might already know it, but you didn't mention slugging your barrel, so...

Good luck,

Brockyhttp://beartoothbullets.com
 

·
Registered
Joined
·
2,957 Posts
I think if you experiment with your rifle you'll find what it likes.
As others have said slug your bbl & size bullets a bit over the size of your bore.
Let us know how it turns out for you. I don't think you have to scrap your bbl, just size to fit your bbl.
 

·
Premium Member
All kinds. Enamored of their mechanisms!
Joined
·
11,353 Posts
Recutting will not work with Marlin's Micro-Groove due to the 'BORE' (not GROOVE) diameter being too large. A standard .308 bore is .300" with a groove diameter of .308". A Micro-groove still uses a .308" GROOVE diameter, however, the grooves are much shallower, meaning the bore is larger than .300" SAAMI Standard. The metal is just not there to 'Re-Groove. AC
 
1 - 8 of 8 Posts
Top