COAL problem

Able · 03-13-2005, 06:34 AM

I am trying to work up a load for my Rem 700 270. I am using Sierra matchking SBT's. The problem is the book states I should have a coal of 3.315". The bullets are slightly different in length and when I use the same seating depth in my die they come out up to .01" different. How do you determine what is the proper seating depth. Also having a problem getting a tight group so far.

HighDesertWolf · 03-13-2005, 09:56 AM

you can either invest in some stoney point COL gauges or not worry about it, what i do is take about 20 to 30 of the bullets measure them all with calipers, take the average length and find a pill which is closest or exactly to the average length and set my dies with that pill and just go with it. I have never had any problems or accuracy issues doing it this way. good luck

stubblejumper · 03-13-2005, 10:13 AM

Quote:

The problem is the book states I should have a coal of 3.315".

That is the first problem.The people writing the manual have no idea how long the throat in your rifle is so their published OAL is basically meaningless.You need to determine a starting point for a particular bullet in your rifle by using dummy rounds or a specialized tool like the one from stony point.Once that is done you can then vary the OAL to see what shoots the most accurately in your rifle.

driftrider · 03-13-2005, 10:20 AM

Bullet lengths, from base to tip, are rarily completely consistant. I've measured Hornade V-Max and SST bullets and seen as much a +/- .003" variation, but the accuracy is still very good. I've found Nosler BT's are much more consistant than the Hornadys.

When the load manual says the COL should be X, as long as you're not too much shorter or longer than that number you should be just fine. You don't want to be too much shorter because you could have pressure problems, but you can seat them out longer as long as the bullets don't hit the lands and you work up like you should you should be fine. If you want to have really accurate and repeatable measurements, you need to measure the bullet off the ogive not the tip. Stoney Point makes a set of bullet comparators that clamp onto your dial/digital caliper and do just this. This really helps a lot if you're playing with seating depth to find an accurate load. I stopped worrying about base to tip COL beyond ensuring that they aren't too way too deep or way too shallow. What I do is measure a number of loaded rounds and average the measurements, and as long as the average isn't below the stated COL in the book, and no one cartridge is more than .003" shorter that the recommended COL, I call it good. I also like my loads to fit in the magazine, so I test fit them there too. Then I measure them with my comparator and write down the measurement, which seldom varies more than .001". I then use this measurement to set and adjust my seating die in the future.

Mike

HighDesertWolf · 03-13-2005, 10:46 AM

I use sierra BTHP gamekings in my 308 and the bullets varie in length asmuch as .005, and if you call .5 inch groups at 100 yards a accuracy problem....... I sure dont, aslong as your COL is within saami specs or set to your rifles throat a little variation is not a big deal at all.

mossy33oak · 03-13-2005, 02:26 PM

Quote:

ORIGINAL: Able

How do you determine what is the proper seating depth. Also having a problem getting a tight group so far.

Well since you are shooting a bolt action, finding your oal can be accomplished two ways, with the Stoney Point OAL guage like mentioned above or you can use the old method of putting a bullet in a fireformed case (slightly pinching one side to hold the bullet some) and placing in your gun and closing the bolt. Repeating this several times and taking the average number you get. When you get a number this is what you should work from. Try seating your bullet from .005 to .030 deeper than this number to start. I have seated some bullets as much as .080 and found my most accurate load. Varying this number may also be the answer to your accuracy problem. If changing seating depths doesnt improve accuracy, change bullets, or powder. I ALWAYS use a Stoney Point comparitor guage when I am doing this, (this is different from the OAL guage.) It is a cylindical part that fits onto your caliper and measures from the ogive of the bullet (the part of the bullet that actually comes in contact with the lands of your rifling first.) When I am doing this, I take 2 measurements, 1 with no comparitor, and 1 with, write both numbers down, and check against these numbers during the reloading process. The comparitor aleveates any question of inconsisentcy in lead tip bullets.

Rebel Hog · 03-13-2005, 05:08 PM

Able,

I have three Stoney Point Gauges. The one to check Free bore in bolt actions and one for Levers
Also the one to check case OAL.
Before I purchased them I did it like HighDesert or many times like Mossy.
I also have the Redding Comp Die, .001 at a time.

"Italian tanks had two Foward gears and 9 Reverse gears." -Gen. Rebel Hog.

Rootsy · 03-13-2005, 05:22 PM

since lead tipped bullets can easily be deformed in packaging and production it's not going ot be uncommon if measuring from the end to the base for them to be different lengths...

as said you can invest in the stoney point gauges... or if you have access to a drill press or lathe you can make your own... all i do for a given caliber to gauge off of the o-give rather than the tip is take a piece of aluminum or mild steel round stock, face both ends and drill a hole through the middle that is about 0.100 smaller than the diameter of the bullet. I then drill a hole about half the way through that is a thou or so larger than the bullet diameter... once you seat, slip it over and measure with the calipers, etc...

for my bolt guns i do the ole dent the mouth, blacken a bullet seat lightly in the case... chamber it and eject.. generally i have to pop the bullet out iwth a cleaning rod... reassemble in the case to the mark made on the bullet, then measure to achieve a datum measurement... and seat deeper accordingly...

Jamie

Slamfire · 03-13-2005, 08:02 PM

I determine bolt face to lands length with a cartridge containing a flat based bullet loaded upside down. Then mark the ogive of the bullet I'm going to use by inserting it into the muzzle and twisting it until a mark is made on it. Now I adjust the seating die until it seats this bullet, base to mark, whatever distance I want, short of the oal of the dummy cartridge described above. Hard to say, easy to do.

Highpower · 03-14-2005, 07:29 AM

Buy a Stoney Point Guage and don't look back. Some of the best money you'll spend.