Bore Diameter versus Factory Ammunition

[PeteDavis]

I talked to someone last weekend that has been using powder coating on cast bullets to bring them up to the .3095 diameter of the Krag bore.

I have three boxes of Remington factory Krag rounds that are made from.308 bullets. They seem to shoot accurately in my 1898.

What are the various fixes for this disparity? Is the difference critical in real terms?

PD

[PhillipM]

I never knew that! Hopefully jon or someone will chime in.

[Johnny P]

Typo? That is just 5 thousandths off being .40 caliber.

[bruce]

Re: Op. Cast bullets must be fitted to the actual bore diameter for best results. The nominal bore diameter of a .30 Krag rifle is .308 measured groove to groove. It is .300 measured land to land. A worn bore will be larger. With common loads using a standard service weight flat based bullet, results with a good bore will be excellent. Once the bore is worn from use, poor cleaning of corrosive primer residue, etc., then results will be less than ideal. However, using cast bullets one can fit the bullet to the bore and often obtain extremely good results. Using a coating to get a bullet up to the required diameter sounds like a very workable solution to getting good on target results shooting a Krag with a worn bore. JMHO. Sincerely. bruce.

[jon_norstog]

Pete, powder coat is a kind of thermoplastic resin that gets baked onto things. It is popular because it is so hard to chip or knock off. Are you sure you want to melt that stuff into the barrel of your rifle? I'd say, let someone else try it and see how it works for them. If you are having problems with jacketed bullets but you can still see rifling in the barrel, maybe the best thing is follow Bruce's advice and fit up a cast bullet. Guys on this list are loading them up to 2,000 fps with good results.

Good luck!

jn

[mannparks]

I'm still in the r&d stage with regards to polymer coating rifle bullets ,but have had good results so far 30/40 and 30/06.
No ill effects in the bores.they are gas checked.not much different than shotgun wads or plastic sabots in muzzle loaders
One coat Gaines 1.5 to 2.0 thousands b4 your size die of choice .
Also about a 6% increase In velocity with same powder charge.

Charles

[mhb]

The nominal bore diameter...

of the U.S. Krag rifles is .300", in common with other U.S. caliber .30 military and sporting arms. The bore diameter is that diameter which is established by reaming before rifling the barrel. Because properly dimensioned, sharpened and maintained reamers do not cut much oversize, if at all, the bore diameter in Krag barrels does not vary much from the nominal .300". The land-to-land diameter in the rifled barrel is, in fact the bore diameter, as the lands are the remaining portion of the original reamed bore after the grooves are cut.
The groove diameter in Krag barrels, however, is not nearly so consistent in maintaining the nominal .308" dimension. I've measured many original Krag barrels in otherwise excellent condition, and the average groove diameter is much closer to .310", with some running considerably larger and only a few actually close to .308" - this variance cannot be readily explained, since the barrel makers at Springfield should have been easily capable of maintaining the tolerance within .001", with any attention to QC, but apparently did not bother. The variation was well known to serious competitors (such as Townsend Whelen) in the Krag's service days, and the knowledgeable ones took care to select or acquire rifles and/or barrels with groove diameter as close to .308" as possible.
Whatever the actual groove diameter of a given Krag barrel, any bullets, cast or jacketed, should be as close to that dimension as available, for best accuracy, and cast bullets should never be undersized at all.
Factory and military Krag ammunition has always been loaded with jacketed bullets of the nominal .308" diameter, and they perform reasonably well in most Krag rifles, but better in barrels of closer to that in actual groove diameter.

mhb - Mike

[PeteDavis]

Thanks for the insightful comments and, excuse me that's .3095. He said the next factory bullet available was .3011. He was taking about cast rounds and said that Krag bores ran .3095 with some regularity. PD .

[Mark Daiute]

Many of the members here will think of me as a broken record and deservedly so BUT

I had a Krag that, at less than 50 yards, would spray bullets all over a 24X36 sheet of paper. Literally, not figuratively.

Switched to .312 bullets and all of a sudden it shot. Switched to cast and it shot even better and had no problem at all holding the black at 200 yards.

[Dick Hosmer]

Mark, you don't say how much "less" than 50 yds was meant, but at very short range, a bullet - especially if (as later events apparently confirmed) it is undersize - will not yet be "asleep", as in settled in its' spin. That fact can sometimes contribute, at least to some small degree, to poor short-range grouping, but the major problem is almost surely the loose fit.

[Sunray]

Powder coating is usually just powdered paint. Isn't always thermoplastic.
"...next factory bullet available was .3011..." .3105" from Hornady. 174 grain FMJ they pretend is for the .303 Brit. Loaded ammo would be a .311", but not in .30-40 Krag.
When in doubt, slug the barrel.

[madsenshooter]

With jacketed a bit of looseness doesn't seem to matter much. I was surprised when I shot a group close to 1" out of my .310 groove diameter rifle using Nosler .308 168gr match bullets. But it really likes the hole plugged rather than gas blowing by and shoots even better groups with .310 and .311 bullets, even the little short ones! Here's a 10shot, iron sight, 100yd group shot with the .310 diameter Hornady 123gr V-max that I shot last week.

[mannparks]

Powder coating is usually just powdered paint. Isn't always thermoplastic.

Sunray ,respectively not so.

We get so many posts in the “Coatings & Alternatives” and their real question is powder coating worthwhile and why should I give it a try. With the help of others I have compiled a list of my reasons to powder coat and I am sure there are more:

WHY POWDER COAT?

· Lubed bullets are simply that, grease applied to the bullet alloy to reduce leading; Powder Coating (PC) is more than just another lube or coating providing lubrication. A properly applied and cured PC actually creates a Polymer Jacket that does not leave any leading or copper fouling in your barrel, so cleaning time is significantly reduced and money spent on exotic cleaners is not needed. The fact is lubed lead bullets leave lead residue and copper jacketed/plated bullets leave copper residue in barrels

· Since PC does not leave a lead residue it can be shot in polygonal barrels such as Glocks. Firing lubed lead bullets is a safety issue posted by Glock as the polygonal rifling swages the bullet causing sever leading. However, shooting any reloaded ammunition voids Glocks warranty. PC save the expense of purchasing a non-polygonal barrel just to shoot lubed lead bullets.

• PC is a superior bullet lubricant at preventing lead deposits. In a recent test of identical loads where several different lubricants were compared, PC bullets chronographed approximately 4% higher velocity over all conventionally lubed bullets with no lead deposits.

• Powder Coating add thickness the cast bullet diameter, which can be of benefit for bullet molds that cast undersize or for oversize barrels.


· Powder coating creates a very tough and 2H+ hard chemically bonded Polymer Jacket that can totally encase the lead making it safer to handle and to shoot than lubed lead bullets.

· The Polymer Jacket (PJ) created by the powder coating process virtually eliminates feeding problems in semi-autos, both rifle & pistol. A PJ bullet will reliably feed when bare lead, plated, coated and metal jacketed bullets will not because the entire PJ is a lubricant.

· Powder coating is hard, but more than hard it is tough. A bullet alloy can be hard, but lacks toughness and with the increase of alloy hardness other problems increase, like brittleness and inaccuracy.

· Typical PC creates a polymer jacket similar in thickness and hardness of pure copper plating, but PC does not have the velocity restrictions (1250 fps) of a standard copper plated bullet. Due to the chemical bond and toughness of the Polymer Jacket the coating does not flow back under pressure like copper plating. This can be easily verified by recovered bullets.

· The polymer jacket created by PC resists the stress force created by chamber pressure allowing PC bullets to use a much softer alloy that lubed bullets. PC pure lead bullets can be fired at handgun velocities without leading. I as well as others on the Cast Boolits site have coated and fired PC pure lead with no leading at velocities far greater than an identical lubed bullet would allow.

· PC saves money, by eliminating the need for copper plated/jacketed bullets for handgun calibers and many rifle calibers.

· PC bullets do not leave a grease residue in reloading dies, eliminating the time and materials needed for cleaning. Also eliminating the constantly changing Cartridge Overall Length (COAL) as lube residue builds up in the bullet seating die.

· PC does not pick up and trap contaminates (dirt/sand, etc.) that can then be loaded into a cartridge.

· PC bullets function in a bullet feeder, lube bullets do not, allowing those with a progressive press and bullet feeder to increase the speed of production.

· When tumble coated and cooked base down PC flows into the imperfection on the cast bullet’s base creating a much more uniform flat base for accuracy similar to a gas check. The imperfections due to the cut sprue on the base of the bullet remain on standard lubed bullets. The coating on the base of the bullet also insulates the bullet from the heat of ignition, resisting gas erosion, similar to a gas check and the tough coat appears to have a much higher shearing resistance than the lead substrate.

· Powder coating may eliminate the need for gas checks, but more high velocity testing must be performed. Lubed lead bullets and other coatings offer no protection against gas erosion, necessitating the need for gas checks at higher pressures.

· PC does not burn, altering the chamber pressure/velocity as bullet lube can do when ignited. With PC there is no infamous lube burning smoke cloud that obliterates the view of the target, annoys others and has the indoor range office asking you to leave the range or shoot something other than lubed bullets.

· PC bullets are accurate. My Ransom Rest testing of PC handgun bullets indicates accuracy equal to jacketed bullets. Others are finding excellent accuracy in rifle calibers.

· PC bullets will store indefinitely with no special care. Storage temperature is not an issue as it is with lubed bullets.

· Powder coating in different colors allows quick identification not only of a particular bullet design; it can be used to define a particular load. A 44 magnum cartridge loaded at maximum for a rifle looks just like a 44 magnum cartridge loaded for a pistol. If one load has a red bullet and one a blue bullet it makes identification easy and could save damage to a gun and possible injury.

· PC can be achieved with a minimal investment in time, materials or equipment.

· PC eliminates the boredom of the casting process and opens up new venues of creativity and enjoyment of a hobby. PC is a good topic of conversation for range talk, generating more associates and friends. Powder coated bullets are prettier than lead bullets; Women love PC bullets and detest ugly, sticky lead bullets.
. And I can now use a bulletfeeder die on my progressive press.
Last edited by Dragonheart; 02-24-2016 at 10:22 AM. Reason: additions
This article was written by dragon hart

Charles

[madsenshooter]

When you put it that way, I could see some possibilities. I gotta get away from buying and shooting those jacketed things! I got too many very good moulds sitting idly by! Maybe I could get through a match without the problems I've encountered using lubed bullets.