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 25 Krag Bore Size Question (Read 5781 times)
Texas10
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Krag Bore Size Question
Nov 4th, 2019 at 3:05pm
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I have a low serial number Krag that I took out of the safe the other day to prep for winter. My new endoscope camera revealed a much better than anticipated bore, better than even my low round count Shilen Select Match 308 barrel.

Almost no firecracking, perfect lands and grooves, very few rust pits. But after cleaning two 308's, I tried to put the same jag and patch down the Krag to oil the bore, and it would not fit! I had to drop down a jag size, and that confused me.

Is the 30-40 bore smaller than the 308 Win?
  
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FredC
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Re: Krag Bore Size Question
Reply #1 - Nov 4th, 2019 at 4:07pm
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The first Krags had an issue with bore size variation. My recollection is not perfect on this but I think most were too large and many of these work better with cast bullet sized a little on the large size.
Later Krags should have been held to a tighter tolerance, and should have a .300 bore and .308 land to land measurement just like your Shilen.
No copper fouling buildup?
  
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Texas10
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Re: Krag Bore Size Question
Reply #2 - Nov 4th, 2019 at 4:34pm
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Yes, it does copper foul a bit, but I've not put more than about 30 rounds down it since I started shooting it, but it shoots very well. 

It's serial number 133937 and professionally sporterized probably sometime in the 20's. Was purchased around 1940 from a pawn shop by my Dad.

I don't recall him ever shooting it when I was young, and I put one round down it about 1969 during a pig hunt. It sat until 2015 when I shot it again, and bought dies for hand loading.
  
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butlersrangers
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Re: Krag Bore Size Question
Reply #3 - Nov 4th, 2019 at 6:13pm
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'Texas10' - Your Krag, #133937, was assembled around October, 1898. Therefor, it is not really a "low number" Krag.

What is your barrel length? Both model 1898 carbines and rifles are found near your Krag's serial number.

If you 'slugged' your bore (with a soft lead oversize slug), you could easily measure your bore's land and groove diameter.

FWIW - I have generally found my model 1898 Krag barrels to run about .3085 to .3095 inches in groove diameter.

My rifles in .30-06 and .308 Winchester & NATO calibers have 'tighter' bores.

My Krag barrels shoot .308" diameter commercial jacketed bullets well.

If you are going to shoot cast bullets, it is important to know your actual bore dimensions. Cast bullet shooters generally use projectiles sized .001" or .002" over barrel groove diameter.

Most of us would enjoy seeing photos of your 'Family Krag'.
  
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Texas10
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Re: Krag Bore Size Question
Reply #4 - Nov 4th, 2019 at 8:49pm
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Thanks, Butler,

I'll take some photos and post. I actually did post some when I first started down the Krag road back in 2015. My pics are still on the sporterized page. I just looked them up.

Two years ago I took my first deer with it, on the 75th anniversary of when my dad took a deer on the family farm in Oregon during Christmas leave from the Army. He'd just bought the gun at a pawn shop in Waco, TX. I have a pic of him standing with the deer, Krag by his side.

I've got some Hornaday 220 gr. RN, and a bunch of different powders, so I won't be casting my own.  I'll chase up some Hornaday brass and see if I can load some rounds that shoot as well as the factory loads I have.

I would like to learn to use the elevation adjustment on the peep. Last time I tried, I sent one over the berm at 500 yds and I don't want to repeat that experience.  Shocked

One nice thing about the serial number and manufacture date is it isn't classified as a firearm.  Cool
  
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Magilla26
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Re: Krag Bore Size Question
Reply #5 - Nov 9th, 2019 at 9:46pm
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The barrel on my 1901 Model '98 Krag, slugs at .309"  It shoots all factory and handloaded ammo using .308" bullets just fine.
  
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Texas10
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Re: Krag Bore Size Question
Reply #6 - Dec 19th, 2019 at 3:54pm
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Any links for "how to slug a barrel" would be appreciated. Bore looks mighty fine using my new Teslong bore scope.
  
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Whig
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Re: Krag Bore Size Question
Reply #7 - Dec 19th, 2019 at 6:02pm
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The easier way to do it is to take a pure, round soft lead fishing weight and insert it into the chamber of your Krag. Then tap it with a wood dowel slightly smaller in diameter than your bore to push it into and down the length of the bore. When it taps out the muzzle, you will have a resized lead weight that reflects the smallest diameter of the bore that it traveled down. If you drip a little oil on the weight before tapping it down the bore, it'll go a little easier.

One disadvantage of this approach is if your bore is pitted bad, it will chew up the lead weight a lot before it drops out the muzzle. It will also leave behind small chunks of lead in the pitted areas, similar to shooting a cast bullet in a badly pitted bore.

I use a Hawkeye Bore Scope. That was the best investment I have ever made for my gun collection. I love looking into bores before and after cleaning. Really teaches you what works and what doesn't work with cleaning your guns. Also it's irreplaceable for examining older military firearms for bore condition and damage.

I have done the lead weight approach but now I use Cerrosafe to make an actual casting of my chamber that gives me measurements I need for reloading. Each chamber can be slightly different. But, it's a good and safe way to get a lot of info about your rifle or carbine.

Brownell's sells Cerrosafe. It melts at a real low temperature and hardens quickly. Safe to use.

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Re: Krag Bore Size Question
Reply #8 - Dec 19th, 2019 at 10:58pm
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Nix on the "fishing weight".  Those things are made of unknown alloy, including scrap with plenty of scratchy contaminants. Use something intended to be passed through a gun barrel, like buckshot.

And while a wooden dowel is OK for starting the slug the first couple of inches, NEVER attempt to drive a slug all the way through with wood - which can split, splinter, and wedge itself most horribly! Use a smooth solid steel rod with a flat face for pushing the slug through.
  
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Texas10
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Re: Krag Bore Size Question
Reply #9 - Dec 21st, 2019 at 1:53am
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Ok now, that was just too easy! OO buck, an Oak dowel, and a stiff cleaning rod perhaps?

What are the dimensions I'm looking for? Groove and bore?

The barrel looks beautiful inside, so this should be a piece of cake.
  
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Parashooter
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Re: Krag Bore Size Question
Reply #10 - Dec 21st, 2019 at 5:23am
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Texas10 wrote on Dec 21st, 2019 at 1:53am:
Ok now, that was just too easy! OO buck, an Oak dowel, and a stiff cleaning rod perhaps?

What are the dimensions I'm looking for? Groove and bore? . . .

Bamboo chopstick makes handy starter. Best is a brass rod about 7mm.

Nominal US Krag barrel is .300"x.308" - some a bit larger, few smaller.
  
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Texas10
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Re: Krag Bore Size Question
Reply #11 - Dec 22nd, 2019 at 11:14pm
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Slugging it was a walk in the park. OO buck measured .300 across the lands, and .306 in the grooves. However across one set of grooves, it measured .301.

Any comments welcome.
  
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Parashooter
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Re: Krag Bore Size Question
Reply #12 - Dec 23rd, 2019 at 5:14am
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.301" or .306" groove diameter is likely incorrect. Clean bore thoroughly, grease bore and new buckshot, try again. Use micrometer if available. Be gentle when taking readings. Shot is soft, requiring light touch.
  
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Whig
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Re: Krag Bore Size Question
Reply #13 - Dec 23rd, 2019 at 9:16am
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Is your Krag barrel an original Springfield Armory barrel? Has it been changed on your Krag? Pictures might help. Might not be original and measurements might be different than expected.

Just a thought.
  
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FredC
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Re: Krag Bore Size Question
Reply #14 - Dec 23rd, 2019 at 3:55pm
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I like Parashooter's advice on this, I am thinking the round shot rocked a little going through the bore. Make sure the rod you use to push the slug through is flat and square on the end. Using a file and square can accomplish this.
Two other less likely possibilities are some of the grooves in the barrel are filled with copper alloy which would be a little harder than lead or a rough spot in the bore scrapped off some of the lead.

If the .301 measurement was real you would barely be able to see the rifling in the barrel .0005 per side would nearly be invisible. The fact that the .301 measurement is probably so wrong makes your .306 measurement suspect also which is a good thing now.
  
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