Help me understand precision bullet seating

[hydro556]

On other boards a lot of guys recommend 6MMBR for good reloading advice. So, here I am. I started reloading about 3 months ago and am loving it. I have been having good results so far. I shoot a Savage 10FCP HS Precision. I have been loading mostly 175SMK's and 155 Scenars in fromt of Varget using Lapua brass. I have gotten results as good as 1/2" with all of them. I am perfectly satisfied with this, but would love to decrease variance. I am wanting to start trying to seat bullets a given distance from the lands. I have,or am waiting on) the following tools and would like advice on properly using them to get the best results.

Hornady LNL OAL gauge with modded 308 case.
Hornady Comparator with inserts.
Hornady headspace gauge,400).

Anybody using these tools care to share their process?

 

[billmo]

hydro, the instructions that come with the tools are very easy to
understand. You basically, just thread the modified case on the tool, stick your bullet in the case, put the modified case into the chamber, push the rod in until everything is bottomed out in the chamber.,bullet and case) and lock it down with the thumb screw. Sometimes the bullet will stay in the lands and you have to retrieve it by dropping a smaller caliber bullet down the bore to dis-lodge it. CAUTION - DROP THE SMALLER BULLET BASE FIRST INTO THE BORE TO AVOID WEDGING OF THE TWO BULLET POINTS.It is best to take a few readings and then go with your average test length. The comparator works in conjunction with the former tool and of course is attached to your dial caliper. After attaching the comparator with the appropriate insert installed, your dial caliper will need to be zeroed. Mine is very close to being 1 " off with all inserts.
The headspace gauge will fasten to your dial caliper also and you will simply measure your fired brass before sizing and afterwards and adjust your die down deeper in the press slightly until you see the amount of bump that you desire. This is a brief overview but I am sure you will be able to follow the instructions with each tool. You may also get different opinions as to exactly how the tools are manipulated to accomplish the task at hand by other users here on the site. I hope this helps. Bill

 

[hydro556]

Thanks, Bill. So far the only tools I have my hands on are the Hornady OAL gage and the modded case. I bought them used and they dont have instructions, but they are pretty easy to use. When I first tried it, the results were inconsistent. So, I ordered the comparator/inserts and headspace gage. I was told these would allow me to accurately use the OAL gage/modded case to find the distance to the lands and, ultimately, the best OAL for my rifle.

My caliper is digital, you keep referring to a "dial" caliper. This is probably just the verbage you typically use, but to be sure, these items will work with a digital caliper, right?,I know that was probably a silly question, but I just want to be sure)

Could you please elaborate on what I am trying to accomplish with the headspace gage? I bought it because I was told it would assist me in this process, but am unsure what exactly I am trying to get done. I hope I dont come across as dense, I am not, I am just trying to break things down to their simplest terms. I want to understand exactly why I do each step to maximize my understanding of each new process.

 

[billmo]

Yes Sir, I will try. You are correct concerning the caliper. Both do the same thing. But nothing wrong with asking questions to learn. The headspace gauge is used to help maintain that precise amount of clearance and in order for your bolt to close on your re-sized brass without binding or your bolt scraping brass from the case heads. Further, headspace is very important and you can read all about it in your reloading manual if you have not already done so. Mainly, neck sizing will cause the need to bump the shoulders back. F/L sizing dies will move the shoulders back usually. You are on the right track by asking questions. And you are definitely on the right web-site to learn from a vast majority of BR shooters, long distancs shooters, long distance hunters, and folks like me that just shoot quite a bit more than the average dude. I have learned many lessons and still learning from this fine group of shooters. Ask questions. Somebody will answer. Bill

EDIT: One note concerning the .308 caliber. I have read some articles concerning bullet seating depth and have actually experienced it myself. Sometimes seating your bullets to the advertised 2.800 OAL or close to that will give you just as good and sometimes better accuracy than jam seating or seating closer to the lands. Remember, I said sometimes.

 

[hydro556]

Bill, on the seating depth issues, I understand what you mean. I have been seating from 2.70 to around 2.9. To be honest, I havent noticed much difference in group sizes with the various OAL's. The rifle seems to shoot around .5" to .75" at 100 yds with each load. The one thing I am not happy with is the inconsistency. Some of it may be the shooter, but I get more variance than I think I should be, even when I feel that the shot was executed properly. Could be the rifle also. It is a bone stock Savage 10FCP with HS stock and a Zeiss Conquest. At any rate, by tweaking the OAL and finding the "best" for my setup, I can at least remove one more variable in the process.

 

[rayjay]

You need some sort of windflag. Even a stick stuck in the ground with some surveyor's tape tied on the top.

 

[hydro556]

If you are suggesting the wind is causing my inconsistency, I dont think that is it. I have no doubt that the wind will make groups get big, but I have had issues on calm days. I dont expect this process to make my groups go into one hole, I am just trying to remove or at least minimize variables. The more variables I can remove, the more I can narrow all my problems down to the shooter. I guess that is a good thing, right?LOL

 

[rayjay]

Once you start using windflags you will realize that there are no calm days. If there is a slight breeze to the left that is 1/8" or more of movement from 'calm'. If this slight breeze reverses then the 1/8" goes the other side of calm. 1/8" plus 1/8" equals 1/4". 1/4" of improvement is what it sounds like you are after.

Let the wind pickup to 10 mph and it's more like 1/4" each way, 1/2" worst case shooting into a full reverse. There is the inconsistency that is dogging you.

Flags tell you when not to shoot as much as they tell you when to shoot. 'Dead calm' is the worst time to shoot.

 

[treeman]

just thought i'd throw this in the modified case must be the same length from case head to shoulder datum line to get accurate measurements. thats just something that i ran into in my search for more accurate reloads_____treeman

 

[Forum Boss]

just thought i'd throw this in the modified case must be the same length from case head to shoulder datum line to get accurate measurements. thats just something that i ran into in my search for more accurate reloads_____treeman

Treeman is correct--if the modified case is slightly different, you may think you are at .000" land contact, when you're really +/- .002 or .003 etc.

However, in my opinion, it doesn't really matter, as long as the readings you get are repeatable. The reason is that you are going to do testing and record, empirically, the corresponding number that shoots best. If you're ten thousandths ahead of indicated .000" contact with your modified case, it really doesn't matter if that's truly .010" into the lands or .013" -- because it is a length you can duplicate each time and its proven to shoot well.

I recently used my Stoney Point tool, using 4 scenar bullets and measuring each twice. Every measurement came out an .x89 or .x90, and that was consistent with previous measurements. Hence I know I can go five thou or ten thou deeper than that point every time, and this is confirmed by measuring base to ogive on the loaded rounds.

 

[hydro556]

Thanks for a ton of great info. A lot of it is going over my head a bit, but I will make sense of it this weekend when I actually start trying to load some rounds with the new tools. Everything came today. Moving too MO is a double edged sword. I had to pay sales tax on my order for the first time, but I got my box within 48 hours of placing the order.

 

[hydro556]

Alright guys. I am going to sound really dense here, but I need help. I have used the tools mentioned and determined,apparently) that in my chamber, the max Length To Ogive is 2.238". That is the measurement from the case head to the bullets ogive when my bullet is pressed into the lands. That measurement is different than all other measurements I am able to take. The rest of my measurements are from the bullets tip instead of ogive.

If I remove the comparator, and re-zero the caliper, and then measure the same case/bullet still in the OAL gage, I get a measurement of 2.835". If I subtract the two measurements, I get a difference of .597". But this measurement will vary from bullet to bullet, since I am no longer using the ogive as a,consistent) point of reference.

If I use this info and compare it to other COAL's I have used in the past, such as the 2.80 I have used with success, it tells me that at 2.80 I was roughly .035" from the rifling, is this correct?

Assuming it is correct, how do I remove the "roughly" from the equation? In other words, how do I use this info to seat bullets a certain distance from the lands? Do I just load to a COAL of 2.835 and then work backwards in .010 increments? Can I assume the 2.835" is an accurate max length to lands? I am confused. Sorry.

 

[Shootndig]

Hydro-
hell you had me confused for a while there...but I think I understand where you're at now, and you're almost there. The reasons you are trying to find the base to rifling,ogive contact) distance are 1)it is after all where the rifling starts and 2)the ogive of the bullet is far,far more consistant than the tip length of a bullet,any bullet,s)). So at the point where you have carefully and accurately determined the base to ogive length of your rifle,you can and probably should stop measuring COAL. The base to tip measurement is now totally moot,beyond whether it fits in your magazine or not. And you don't need calipers for that.
One last thing or two. The base to ogive length is for your rifle only, and is a snapshot in time. As the throat wears the length will increase. Also if you have and continue to measure very carefully and consistantly, using the same tools every time, the base to ogive meaurement can be used for different weights and brands of bullets,in this rifle only, without having to go thru the entire process again. You may want to pick up a hex comparator from Sinclair at some point though, as they are cut with an actual for caliber reamer. FWIW.

 

[billmo]

Hydro, I agree with Shootndig. You are to a point now that COAL to bullet tip has lost it's importance unless you are loading to fit a certain mag. length. Your measurements now should be from base to ogive with any bullet that you may want to try. A fellow member says to load your test in this manner. Five bullets at .015, five at .010, five at .005 out of the lands, skip just touching and repeat the above numbers with five bullets each into the lands for a total of 30 bullets. If you start your test with the .015 out of the lands and work inward with your test, you will be able to watch for signs of pressure. I have done my testing this way since I was told this and it works fine for me.
In my opinion, it is best to figure out which powder or powders that you are planning to use first. That way you are changing only one varible at the time which is one of the most important issues while trying to find your most accurate load. Bill

 

[Shootndig]

Hydro-
Read it again some more, and before we blow your gun up, theres a couple of more things Do you have all the parts for this comparator set? If so, then when you knock the bullet out of the barrel after measuring the ogive contact point, you put the bullet back in the modified case and then theres a two piece gizmo, one piece that clamps to one jaw of the calipers and a second caliber specific piece that locks into the first piece. Both pieces together measure 1") that slips over the bullet and stops at ogive contact point,theoretically). This is where you get the base to ogive measurement,less the 1" for the measuring gizmo). As you touch or jam into the lands, your chamber pressures can rise dramaticlly. I usually take the ogive measurement and back up at least .020 to start with.
Make sure you have all the pieces for your kit. If you don't, all is not lost..I use a combination of two or three different things anyhow. But you have to have the right pieces to get the right information. Keep us posted.

 

[hydro556]

[/IMG]

Here is a picture of what I am doing to get the measurement. I have yet to use the headspace gage. Does this look right?

 

[billmo]

Yep that looks correct to me. Bill