You ALWAYS measure base to ogive. That's the consistent measurement....base to tip varies too much from bullet to bullet to be accurate
-
Having trouble using the site?
Contact support
Hunting & Fishing New Hunting Bullets Available
- Thread starter bohem
- Start date
You ALWAYS measure base to ogive. That's the consistent measurement....base to tip varies too much from bullet to bullet to be accurate
I said I could wait for the 160gr class competition bullet, but that was January. Starting to think about it too much now lol.
This is correct for swaged bullets however this is generally not true with machined projectiles. The base to tip dimension consistency on my bullets as well as many other solids, is less than a thousandth variance. I can say with mine that it's under half a thou.
This is also a problem for bore-rider designs because ogive measurement comparators are typically about 1-2 thousandths under the size of the bullet max diameter. Bore riders drop through them to the sealing surface location, which doesn't allow an appropriate measurement on something with a pilot band like my bullets have. The ogive comparator drops clear into the sealing surface, past the pilot band and that won't give an appropriate number to work from because the pilot band touches the throat first.
Working on programming the 8tw 161-ish right now.
The heavy 6.5mm 7tw bullet is being tested now, I've got some initial numbers on it and I'm pretty excited. I need to make sure it's stable and accurate at all distances. So far I've only tested it to 700yd.
For those chuckling at the twist rate: I would have laughed a few years ago to however now I have 7tw barrels in stock, about 47 of them on last count, and folks shooting the heavy 6.5's from other companies are going 7.5, 7.25, and now even to 7's in 6.5mm chamberings.
161gr
BC ~0.380-0.385 I think based on testing so far. It might be a little higher but I don't want to push out a bad BC
I know I said I was interested in 160 class 7mm, but I have to back out due to health issues. Sorry.
COAL is a measurement used to determine if a cartridge will fit inside of the magazine. Cartridge Base to Ogive is used to measure the distance the bullet will travel before encountering the lands of the rifle bore. MANY times you are limited by COAL and are unable to get even close to the lands.
Here's a copy of what I said above regarding this topic:
This is correct for swaged bullets however this is generally not true with machined projectiles. The base to tip dimension consistency on my bullets as well as many other solids, is less than a thousandth variance. I can say with mine that it's under half a thou.
This is also a problem for bore-rider designs because ogive measurement comparators are typically about 1-2 thousandths under the size of the bullet max diameter. Bore riders drop through them to the sealing surface location, which doesn't allow an appropriate measurement on something with a pilot band like my bullets have. The ogive comparator drops clear into the sealing surface, past the pilot band and that won't give an appropriate number to work from because the pilot band touches the throat first.
Help me understand...
For sake of argument, let's say your magazine will hold a bullet/casing combo no more than 3" long. This same bullet/casing combo sitting against the bolt face leaves a full .25" away from the lands and too far away from the lands for good accuracy.
Now what?
I don't understand how this pertains to measuring off the ogive as opposed to measuring base to tip with solids.
Bore rider designs, as a rule, don't work with the ogive comparators that have been made for a given jacketed bullet size.
If you pin gauge the inside of a 6.5mm ogive comparator they typically fall between 0.2630-0.2635
If the front end of the bore rider is 0.256 and the pilot band is 0.260, you're not going to touch anything with a comparator until you're up on the full diameter area.
However, since the throat angle comes down from 0.264 groove size to 0.256 bore size then the bullet will actually touch the lands and work just fine.
But your comparator won't give you good readings.
Which is why I said that most comparators are going to be worthless and you should measure based on COAL. Since the bullets are machined anyway then the COAL is just as reliable as the comparator numbers.
And, I can state with full confidence from having made about 500k of them so far:
The bullet OAL on our stuff falls within 1/2 thousandth (normally it's +/-0.0003), which is tighter than calipers can consistently and repeatedly measure.
If for some reason you must measure with a comparator then you're going to need to drop down to the next smaller size. For example, measuring 6.5mm bullets that fit in a 0.256 bore you will need to go to at least a 25 caliber, if not a 6mm, comparator.
If you go to the smaller size you'll get something that rides on the ogive. It will give you a reliable, consistent measurement.
You don't NEED a comparator that measures just in front of the bearing surface on a jacketed bullet either. You need something that measures consistently on a reference surface that's reliable, which is why jacketed bullets use ogive comparators instead of base to tip. The tips aren't consistent and you get variation.
You can get reliable loading information with a 6mm comparator on a 6.5mm bullet for machined or swaged type, you just won't be able to tell the guys on facebook your comparator measurement without them scratching their head. It's going to be too long.
On that note, when people offer BTO measurements without any qualification of the comparator size I usually just shake my head knowing that comparators from different brands are different sizes and even from the same brand they vary enough that matching numbers still isn't going to guarantee much more than +/- 0.010" consistency between the two sets of loaded ammo.
How would you determine how far away the bullet is from the lands? Do you just load and shoot a bunch of different length bullets? I mean, that is sort of what I do anyway but I have a real good idea how far from the lands I am for any seating depth of a cartridge/bullet combo.
it's easy to measure COAL to lands, use a hornady modified case gauge https://www.hornady.com/modified-cases#!/
But, with these "new" bullets, the monolithics, by the time the bullet is touching the lands, it has been pushed out of the case completely, or nearly so, right? The portion that is to full caliber diameter is far back on the bullet. I am imagining something like a full inch of jump for some of these projectiles.
If you have alot of freebore yes they will stick way out there with nothing in neck. But if no freebore they are fine and normal. Have to watch but .150 jump isnt bad with these bullets thats what i have to do with the 170 in 7 max that i played with
The COAL to lands for the 6.5 122 Cayuga is about 3.3" with my TRG .260, so it's about 0.34" jump, loading to near magazine length. They shoot very well.
What is the distance from the bearing surface (or whatever you call it), where the bullet becomes full caliber diameter, to where the bore becomes caliber diameter?
If I understand your question, your'e asking what is the bullet jump and based on the Hornady OAL gauge measurement, its 0.34". I'm seating the 122 g Cayuga to 2.96" COAL.
I assume you are limited to that COAL due to the magazine? Out of curiosity, have you tried single feed to try to get closer? If you were say something like 0.005" off the lands, how far into the case would the bullet be seated?
With most of my rigs, there is an accuracy node or 2 or 3 based on bullet jump/jam as well accuracy nodes related to velocity.
I'm asking these maybe dumb questions because I am curious. I have considered trying some mono's but don't want to waste a bunch of supplies right now unless I'm pretty sure I'm going to like them. Actually, no matter what, I will likely wait until the supply and demand thing returns to a more normal state.
My bullets have on them a "pilot band" region.
US10480917B2 - Projectile with enhanced ballistic efficiency - Google Patents
A projectile for use with a firearm having a rifled barrel including helical grooves extending longitudinally along an inner surface thereof can include: a substantially cylindrical projectile body having at a front end an ogival nose section and at a rear end a tail section; a driving band...
patents.google.com
If you look at the first picture on that patent disclosure you'll see a feature labeled "130"
That is the pilot band.
The region labeled as "140" is bore rider
The region labeled as "160" is full diamter
For example, in a 30 caliber bullet and 30 caliber bore we have the following general relationships:
Bore hole is 0.300 (to the land tops)
Groove diamter is 0.308 (to the groove depth)
THe bullet is
Feature 130 is 0.304
Feature 140 is 0.300
Feature 160 is 0.308
The pilot band is very slight and hard to feel but the bullet is aligned in the throat by that feature. It keeps the bore friction down and we get some very good velocities with the reduced engraving pressure.
The pilot band (130) allows us to also align the bullet in the throat without running very short freebores or cramming the bullet way down into the case.
The trouble most people have with the stony point gauge (hornady gauge) is that when they push the bullet into the throat they're feeling for a hard wall like a regular bullet feels like. With the tiny pilot band they push right through it and don't realize that they've found the full bearing surface. The pilot bands are typically 0.12-0.17" ahead of that. So the best way to find it is use the stony point gauge and sharpie the bullet. Push it in until you feel the hard wall and then take everything out and meausure where your throat sits between the hard stop you felt on feature 160 as to where the marks of the pilot band showed up on top of feature 130.
Thanks for the added explanation. GREATLY clears things up in my mind.
I was actually taught a variation of the sharpie trick when I first started reloading. That old man used a candle to blacken the bullet and it was pretty evident where it touched. He would do that 10 times, each time with a different bullet, then he would average the measurements. I use a sharpie but I still do 10 different bullets and average.
Now...when seating these, are you wanting only feature 160 to be in the neck? If one is looking for say, 0.002" of neck tension on that 30 caliber bullet, for instance, I would want the inside of the case to measure 0.306" so everything noseward on that bullet is less diameter. I would think you would not want any "loose" case mouth out there in front of feature 160.
I'm going to have get some of these to test and explore.
Last edited:
You're only seating the full diameter region into the case neck, not any further.
I just finished a somewhat large job in the swiss yesterday so I'm setting up for bullets again now. I'll start with 151's and get some back on the shelf for you in the next day.
Just finished FFL paperwork for the Origin today, and the prefit should be getting delivered this afternoon. Should be able to assemble everything in a few days. Gonna be a 20” 7mmSAW.
I’m a recoil sissy. No magnums for me.
I worked up a 7 Max load for 26" 1:8 Proof barrel with the 170 Cayuga and H1000, avg. 2905 fps, can push faster but it was grouping well, and no pressure signs. At 2500' the G7 0.375 BC from PVA website worked great at 500 and 900 yds. Was maybe 0.2 mils low at 1340, but that could have been headwind. At 1720 vertical dispersion became erratic, possibly from variable headwind, but also velocity is falling & probably transonic. I loaded more of these and hope to get back out there soon.
Just ordered some 7mm 151 grain bullets, just put together a 7 saum to shoot 180 ELDm's. Chambered long will be about 3.1 OAL in a tikka, will I need to jump these a large amount to keep the bullet in the band area?
Last edited:
Yes and no, as 260284 said, all Tikka actions are the same, it's just a bolt stop change between SA and LA, though they aren't a true long action with a long action mag length of 3.56. Works well for seating long bullets in short magnums since you don't have to stuff the bullet deep into the case. It's just a smidge over 3.1 OAL with a 180 ELDm which is .1 longer than the bullets I ordered. I would have ordered the 170's as they're longer than the ELDm by .1, but they're out of stock. Can't use lead to hunt with in Calif, which is too bad since I have 500 ELDx's and 1500 ELDm's.
Last edited:
The reason I ask is that I have a Tikka CTR in 308 that I am thinking of switching calibers on and wondering what options I have for prefits and kind of leaning towards 6GT with a carbon barrel but 7SAUM is near the top of the list as well.
I've seen that guys have had the bolt face enlarged to accommodate the 7SAUM.
I'd just buy another tikka with a mag boltface, it's not like you can have too many rifles.
That's one of my dilemmas. I have a McRee chassis which accepts the CTR mags from the Tikka CTR, which are superior mags if you ask me, for the money that is. The problem is that the overall mag length is 2.958 inches front to back with a mic. In talking with other who seat the longer bullets for 7 SAUM their rounds are 3.1 and 3.2 inches long. That extra tenth of an inch or two tenths makes a difference.
Wondering if it is worth it to switch calibers on the CTR from 308 to 7 SAUM or should I switch to 6GT since the mags will accept the longer bullets in 6GT?
Do you think you can get decent performance from 7SAUM with a mag length of 2.958?
For hunting and long range target shooting are the uses.
Lots of people are shooting a 7 saum in a SA, the 151's are .1 shorter than the ELDm 180's. Depends on what you want to do with it. 6GT is a competition bullet to me. 7 Saum would be a hunting and LR round, look in the reloading section you'll find lots of loads and speeds for the 7 saum. I wouldn't want to carry a McRee chassis hunting, they're heavy, had one on a savage in the past.
Similar threads
