Ok here goes, well last night I got a bug up my butt and decided to slug the barrel of my Trapdoor to see how close the bore was to the bullet size I have been currently shooting. Well much to my suprise the bore is bigger then the bullets. I am currently shooting a 500 gr RNPB sized to .458 , well the bore measured .461. Am I atill in tolerance with the bullet to bore marriage. I know alot of guys preach about having the bullet match the bore exactly, but come on its 3 thousandths difference. Any thoughts on this ????

I've never had good luck with bullets under groove diameter. I prefer them .002 over myself, but at least groove diameter. This is particularily true with smokeless.

In my 32-40 Groove Dia. .320 a .321 cylindrical plain base bullet works for me. 
Any Larger or Smaller and performance suffers.
Alloy 1-23

J.Louis

being a machinist I simply used a Avil Mic and measured it. That is how it is done with odd numbers groove barrels, the traditional method with even groove barrels will not work. I am currently using a 500 gr RNPB bullet, so you are saying that the bullet will deform enough to accommodate the bore size????

Redwing give's good advise. The most accurate load in my 40/50 SS which has a .410 groove diameter is a soft 400 gr bullet. It measures .402. 45 grains of swiss 1.5.  Prone, from cross sticks it shoots consistent three inch groups at 200 yards. 

                                                                Joe.

Good advice so far a few things to add.  Wolf's book is about essential for Trapdoor shooters.  Have had and campaigned several.  Generaly with Black powder and 1/25 bullets they will bump up to bore size when fired. Sometimes the bore is so large a "correct"  bullet won't fit in the case.

You run into trouble when trying to shoot them with Smokeless charges. Because of the actions limited strength charges are light and most people use hard bullets. this makes proper fit essental to good results.  I only had one trapdoor that shot smokeless and hard bullets well and it was a H&R reproduction Officers model.

The Cadet model Trapdoor I am shooting now with black powder is accurate for a Military rifle and has done well in competiton.   As you say the sight is not a target sight.  You can use a Merritt disk that sticks on your shooting glasses, has the same effect of a close to eye peep sight. They are intended for pistol shooters but work well at barrel mounted sight distances.

I switch out the Arsenal sight for a 03 blade, higher and sharper plus had room for filing down.   Shoot the rifle with a Arsenal front sight hood in place too.  My rear sight on this particular rifle was a little loose and have shim stock under the bar to tighten things up. Big advantage is to set elevations with a dial caliper allowing much more precise settings.  You can also zero at your regular distance and use a brass bar spacer filed to suit correct starting sights.   

Not target rifles but a lot of fun to shoot.

Boats

WOW, we could talk about Trapdoor’s till the cow’s come home !!!

Boat’s mentioned the Armory front sight cover which is a great place to add a shotgun bead (on its top) to bring down the POA when shooting under 250 ft.. Pick them up at Al Frasca’s great site along with ton’s of load info, parts and gun’s.

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Also a good source of info is the CSP site:

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But then you already know that !!!

Ed…

2nd Grampa, Not much reason to size bullets for your trapdoor. Pan lube them as cast.   

Boats