seating question
- Thread starter rebs
- Start date
ligonierbill
New member
Have you loaded a dummy round and tried it in your rifle? (Or is that how you got the 2.444?) If it just won't fit, you could have a gunsmith modify the throat.
First I would determine the length of the chamber from the beginning of the rifling to the bolt face. If there was any subject in reloading that has been talked to death this is one of them.
The first thing I want to know about a chamber is the length of the chamber from the beginning of the rifling to the bolt face. I have checked rifles that did not belong to me, nothing surprises me but when asked "What happened, what caused this?" I have had to respond with "I do not know".
And be leery of answers that start with "All you got to do is...".
F. Guffey
Rebs,
How did you measure 2.440? If you did it with another bullet, it won't be valid for such a long one. If you did it with the same bullet, I will wager the bullet hanged up on its way into the throat and wasn't actually against the lands when you tried to measure it. That happens in my AR all the time. It took me a little while to learn to wiggle things just right to get the bullet fully forward against the throat. I usually have to have the barrel upright or straight down while I wiggle it until I feel the bullet slide in.
How did you measure 2.440? If you did it with another bullet, it won't be valid for such a long one. If you did it with the same bullet, I will wager the bullet hanged up on its way into the throat and wasn't actually against the lands when you tried to measure it. That happens in my AR all the time. It took me a little while to learn to wiggle things just right to get the bullet fully forward against the throat. I usually have to have the barrel upright or straight down while I wiggle it until I feel the bullet slide in.
2.260" is the SAAMI Max OAL for .223 regardless of what bullet is used.
If you have not worked up the load for the 80 grainers, you can forget about the off-the-lands stuff altogether. It's a load tweaking technique not done until you have worked up the load. And only then, if you feel like fiddling with the OAL. Doing so is 100% trial and error.
Which rifling twist your Tikka has matters too. They come with 1 in 8 or 1 in 12. Has to do with stabilizing the bullet.
If you have not worked up the load for the 80 grainers, you can forget about the off-the-lands stuff altogether. It's a load tweaking technique not done until you have worked up the load. And only then, if you feel like fiddling with the OAL. Doing so is 100% trial and error.
Which rifling twist your Tikka has matters too. They come with 1 in 8 or 1 in 12. Has to do with stabilizing the bullet.
Your measurement of 2.444 is that from base to ogive ? Sierra measurement of 2.555 is from base to ogive or OAL. Do you know your base to ogive measurement .? Just as important is base to datum or shoulder measurement. Once you know that measurement you can any bullet with a .020 jump and work up to see what shoots best . OALis important when loading more then one round for proper feeding . Most likely your rifle won't have alot of free bore like Remingtons .
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CW , any book measurement will always be COAL or base to meplat. Any variation in the diameter of the hole in the comparator would cause a change in OAL or base to ogive. You, Uncle Nick, and myself could all measure base to ogive on a round and have three numbers and all be right just because our three comparators were different. That is why BTO should only be used as a reference for your own reloading reference
dawg
I know I just wanted rebs to see he was comparing two different measurements . 2.444 and 2.555 ogive and OAL. rebs measurement of 2.444 was with the comparator and Sierra is OAL of 2.555 .If I remember right his rifle is a 1 in 8 twist so using the 80 grain would be fine .
I know I just wanted rebs to see he was comparing two different measurements . 2.444 and 2.555 ogive and OAL. rebs measurement of 2.444 was with the comparator and Sierra is OAL of 2.555 .If I remember right his rifle is a 1 in 8 twist so using the 80 grain would be fine .
rebs said:
Rebs,
CW308 is right that the 2.550" number from Sierra is COL and not Base To Ogive, which is what the Hornady bullet comparator attachments for a caliper will measure. However, my Hornady comparator meets the ogive half an inch below the tip of the 80-grain SMK bullet. If you measured 2.4440" with the comparator, the 80-grain Sierra would be completely outside of the adapter case. But if you used a bare caliper to measure the Hornady OAL gauge from the head of the caliber adapter case to the tip of the bullet and you got 2.4440", that almost certainly means the bullet did not go fully into the throat when you pushed the rod of the gauge in. It cocked slightly and jammed at the edge of the neck step into the freebore.
I suggest you remove the comparator attachment from your caliper. With the 80-grain bullet in the Hornady OAL Gauge and caliber adapter case, adjust the rod until your bare caliper measures very close to 2.5500" from the base of the case to the tip of the bullet. Lock the adjustment rod in place. Now feed the gauge slowly into your chamber. If it doesn't go all the way in, wiggle it to clear the bullet cocking until it does slip in. When it does, then carefully loosen the rod thumb screw (so the rod doesn't slip) and push the rod until the bullet stops and then tighten the screw again. This will be correct for your rifle. You can then go back to the comparator attachments on your caliper and get the desired measurement for adjusting jump to the lands.
AVirginian
New member
I have the same rifle (Tikka T3X Varmint in .223.) and am shooting the Berger 80gr VLD Match bullets. My chamber also measures 2.450 COL with that bullet touching the lands.
I worked up a load with the COL at 2.430 and am getting about 2800 fps, and yes, you can ring steel with it a 1,000 yds.
Start low and work up. Be careful out there.
I worked up a load with the COL at 2.430 and am getting about 2800 fps, and yes, you can ring steel with it a 1,000 yds.
Start low and work up. Be careful out there.
Run dummy load long, test, push back, test, push back ( .010 each time ) until it quite sticking.
That is your Length. Drop off another .020 for the first firings
If the load looks good drop it back and sneak up on the original good measurement where it did not stick.
Keep in mind you will find some misformed bullets that are way off (Hornady so far but that is the only ones I am shooting now)
That is your Length. Drop off another .020 for the first firings
If the load looks good drop it back and sneak up on the original good measurement where it did not stick.
Keep in mind you will find some misformed bullets that are way off (Hornady so far but that is the only ones I am shooting now)
I did some looking at the bullet dimensions in my CAD software. I used Bryan Litz's numbers for the ogive radius of a 77 grains MatchKing, which is designed to comply with magazine feed length, and the radius he has for the 80-grain SMK. The total ogive length difference is 0.145". If I draw them in my CAD software with Litz's ogive radii, and then overlap the two bullet profiles at the bore diameter, I get a difference of just 0.14". So if the 77-grain SMK is seated to 2.250" COL, the 80-grain SMK will have the same amount of bullet jump seated to 2.390". A 2.444" COL is 0.054" greater than that, so it seems it is just a case of a tight throat and not a measuring error after all.
Try seating the bullet to 2.414" as a trial spot to start loads.
I confess I am astonished that Sierra published such a long number, but their test guns were a Colt AR15A2 HBAR and a Remington 600 Mohawk rifle, and not SAAMI standard test barrels, and their throats may just have been long.
Try seating the bullet to 2.414" as a trial spot to start loads.
I confess I am astonished that Sierra published such a long number, but their test guns were a Colt AR15A2 HBAR and a Remington 600 Mohawk rifle, and not SAAMI standard test barrels, and their throats may just have been long.
I like to start with a bullet at the manufacturers recommended OAL for my initial powder test. Once I have a good load I tune it with the seating depth. Then sometimes you don't need to. This was shot using Varget, 100 yards, using Sierra recommended seating at 2.260 COAL in a Savage action with a Criterion 8 twist barrel.
For comparison purposes when I use the 80gn SMK in the same rifle I load them at 2.460, a full .2 longer and a soft jam into the lands. Both bullets group about the same out to 600
For comparison purposes when I use the 80gn SMK in the same rifle I load them at 2.460, a full .2 longer and a soft jam into the lands. Both bullets group about the same out to 600
Attachments
In this instance, the Sierra recommended COL of 2.550" for the 80-grain SMK apparently would have jammed the lands before chambering is complete in the Tikkas. Indeed, looking at the SAAMI drawing it appears that even with a SAAMI standard chamber about 2.400" would be contact COL using a fireformed case. Again, I'm surprised at Sierra's published number, given that fact.
Rebs,
what gun did you use and what COL did you wind up with?
Rebs,
what gun did you use and what COL did you wind up with?
Sorry to make you repeat the gun. I forgot it was at the top.
The bullet I measured here made contact with the Hornady comparator 0.502" below the tip. If your comparator is exactly like mine (and they don't all have the exact same mouth radius), that particular bullet would have had a COL of 2.420". Since you had 2.444", that suggests to me that your comparator is hitting lower than mine does. Mine is twenty years old, so it may have been changed since mine was made. But also, the SMK tips can vary 0.015 without much effort, so that could account for a big part of the difference, too.
The bullet I measured here made contact with the Hornady comparator 0.502" below the tip. If your comparator is exactly like mine (and they don't all have the exact same mouth radius), that particular bullet would have had a COL of 2.420". Since you had 2.444", that suggests to me that your comparator is hitting lower than mine does. Mine is twenty years old, so it may have been changed since mine was made. But also, the SMK tips can vary 0.015 without much effort, so that could account for a big part of the difference, too.