I am specing a reamer for a 7mm cartridge. I have some Cauterucio bullets to shoot and these bullets measure .285. I was wondering if I need to make my lead at least .285 to shoot the Cats? Will I be able to shoot other bullets like Berger, JLK, Sierra without any ill side effects like loss of velocity and accuracy?
If I spec the lead for the other bullets at .284 will I be able to shoot the Cats without experiencing extreme pressure? Will I even be able to chamber the Cats?
When I draw up my reamers for what will be a "match" reamer meaning extreme accuracy and somewhat controled conditions(not dirty hunting conditions) I will go with a diameter of 0.003" over what ever bullet diameter I will be using. This is about as tight as I really like to go. I have done 0.002" but found that even in same lot some bullets will vary enough to rub the lead solidly.
To be honest, you need to be taking measurements in the 0.0001" range to get a good idea of what diameter you will need.
For a big game or any reamer that will be used to chamber rifles that will be used in dusty or dirty conditions, I open things up to 0.0005" over bullet diameter just for the slightly looser fit allowing a bit more variation in ammo which there generally will be with big game hunting ammo compared to fully prepped match ammo.
If the Cauterucio bullets are running an honet 0.2850" diameter I would go with a 0.2853" dimension on your reamer. The smaller diameter bullets will certainly not be the perfect fit but if everything is true they should still shoot very well.
I have built some rifles using SAAMI spec reamers that were sub 1/4 moa rifles. Machining quality is every bit as important as reamer specs.
That said, I would rather error on the side of being a bit loose by a few ten thou then to be to tight as pressures will increase as will copper fouling just ahead of the throat.
You will be able to shoot the fatter bullets in the tighter chamber but you will see minor pressure increases. Just be sure to work up loads with each bullet for that specific chamber.
It is tricky setting a rifle up for use with only one bullet. Sometimes that one bullet does not shoot well in the finished product. For that reason it is generally better to set the chamber so it will be compatible with as many different bullets as possible.
Allen Precision Shooting
Home of the Allen Magnum, Allen Xpress and Allen Tactical Wildcats and the Painkiller Muzzle brakes.
Fiftydriver thanks for the response. I am not going to set the reamer up for specifically one bullet. In fact, I doubt I will shoot a bunch of Cauterucio bullets. I just want to try to cover all the angles when I spec the reamer. I would rather spec the reamer for the majority of the other bullets I would shoot and have the Cats a bit tight. Still hoping I can shoot bullets like JLK, Berger, and Sierra and have the Cats chamber without any trouble.
Let the reamer guys (I reccommend Dave Kiff at Pacific) do the reamer specs.
I have built a ton of 7 WSMs for customers and 3 7mm Dakota's for our own Len Backus- none of which the reamer was set for a specific bullet. I simply call up Kiff and order a match reamer, MAYBE specify what neck. But I have never worried about what bullet, lead, throat angle etc. He is the expert and I trust his ability. I have shot the Cauterucio's in these set-ups and had awesome results.
The reason I say this is because I use a lot of Rock and Obermeyer barrels in 30 cal that are .307" in bore diameter, not .308 like a Hart, Krieger, etc. This has the same effect as pushing a 285 bullet down a 284 bore.
My advice is don't sweat the small stuff, and don't get hung up on a particular bullet- cause like Kirby said your barrel might not like it.
Get a match reamer in your caliber choice and maybe with your choice of neck if you want to neck turn and spend time sending lead downrange and less time at the loading bench!!!!
I guess I should have just asked if anyone had had any trouble shooting Cauterucio bullets when the reamer was not specifically ground for Bob's fatter bullets.
I will certainly get Dave to grind my reamer again. Just want to make sure I do not run into any problems that should have been considered before the reamer was ground. I am asking these questions to give my self as many bullet options as possible. [img]/ubbthreads/images/graemlins/smile.gif[/img]