OAL vs Ogive length? Distance to lands vs seating depth. What say you?

[Stuck]

I ordered up a new batch of bullets. Same brand and model Ive been using. Hornady .264 140g BTHPs. I reset and rechecked my dies because I loaded a bunch of .300 sav and I wanted to make sure everything was right. My bullet seater uses the ogive to set depth. I loaded a few dummy rounds to check lengths and my OAL is coming up short. My original load is 2.90 the new bullets are coming up at 2.71.

I checked the bullet lengths and the new ones are about .013 different. My concern is the seating depth. From what I can tell without a ogive comparator Im seating about .006-7 deep. How much of a difference is this gonna cause in pressure? Im guessing enough to throw off my consistency.

Any thoughts?

 

[Splib]

Just a snarky off the cuff comment but that's one reason Hornady bullets do not win any benchrest or even precision shooting that I am aware of. As are you

Lucky to find any bullets right now. Do you have and use a chrono, even occasionally ? No way to really measure pressure but you can reliably measure velocity and related characteristics. I think the bigger effect of any bore/bullet/case position change, bigger than a velocity change, is simply on the result on target, the accuracy. Try to keep all your other shiat consistent. The 0.19 difference in OAL is huge. Huge.

 

[300sniper]

Hornady bullets have been used to will plenty of precision rifle matches. Maybe not BR, but they are plenty accurate for most precision shooting matches including PRS and ELR type matches.

Bottom line, any rifle reloader needs a way to measure to the ogive. Solids may be better, but any pbcu bullet is going to vary from lot to lot.

 

[kf4zht]

Enough to throw off consistency, probably fine for pressure unless you are on the top of the curve already. Regardless of pressure effects it will throw off your POI at least, if not group size by changing the jump distance.

The basic Ogive kit is pretty cheap: https://www.midwayusa.com/product/101273351?pid=231904 or if you have a lathe one can be made very easily

 

[Stuck]

Just a snarky off the cuff comment but that's one reason Hornady bullets do not win any benchrest or even precision shooting that I am aware of. As are you

Lucky to find any bullets right now. Do you have and use a chrono, even occasionally ? No way to really measure pressure but you can reliably measure velocity and related characteristics. I think the bigger effect of any bore/bullet/case position change, bigger than a velocity change, is simply on the result on target, the accuracy. Try to keep all your other shiat consistent. The 0.19 difference in OAL is huge. Huge.

My chrono is down right now. Its not displaying for some reason. Got to send it back. This is the first time Ive had this much variance.

 

[Stuck]

Hornady bullets have been used to will plenty of precision rifle matches. Maybe not BR, but they are plenty accurate for most precision shooting matches including PRS and ELR type matches.

Bottom line, any rifle reloader needs a way to measure to the ogive. Solids may be better, but any pbcu bullet is going to vary from lot to lot.

Enough to throw off consistency, probably fine for pressure unless you are on the top of the curve already. Regardless of pressure effects it will throw off your POI at least, if not group size by changing the jump distance.

The basic Ogive kit is pretty cheap: https://www.midwayusa.com/product/101273351?pid=231904 or if you have a lathe one can be made very easily

Yeah I dont have a comparator but I know my ogive length is the same. My bullet seater uses the Ogive, not the tip" to set the bullets so they should be exactly the same I also did the empty case over the tip of a loaded cartridge method and ended up with same overall measurement with both batches of bullets. The empty case should be the same as using a store bought comparator. The case i used has a fairly consistent ID of .262 so it should be very close to the actual Ogive of the bullet

 

[Splib]

Yeah I dont have a comparator but I know my ogive length is the same. My bullet seater uses the Ogive, not the tip" to set the bullets so they should be exactly the same I also did the empty case over the tip of a loaded cartridge method and ended up with same overall measurement with both batches of bullets. The empty case should be the same as using a store bought comparator. The case i used has a fairly consistent ID of .262 so it should be very close to the actual Ogive of the bullet

My original load is 2.90 the new bullets are coming up at 2.71.

Sounds like you are self correcting and aware of the concepts. Perhaps better than I am I havent use my "comparator" in years, and would have to go into storage to find it. But it simply a fastening plate for one arm of a caliper, and another with a specific diamter hole which lands on the ogive. where, exactly is not critical as it lands on all projectiles at the same outer bullet diameter. I think (?) I got bored after measuring about 200 Sierra Match Kings and eneded up with five piles based on that Ogive landing of the comparator.

So, where did the whopping 0.19" inch go ? That material had to be distributed somewhere. Can you accurately weigh them ? I ask as that is one element I cannot check with a 25 yo lee 0-100g balance beam

 

[Roc Doc]

I use the Forster Datum Dial comparator to set seating depth/jump. I was weighing bullets, (.264 147g ELD-M), but in listening to Brian Litz he recommends sorting bullets by base to ogive length, so that's what I'm doing now. Erik Cortina has some good videos on seating depth and how "chasing the lands" is stupid, what you're really trying to do is to find the seating depth that works best with the harmonics of your barrel.

BTW, with the new 6mm GT barrel on my chassis rifle I shot 2 3-shot groups that were 3" c-c, and one 2.4" group at 750yds. Virgin brass, not even prepped, just seated a primer and used very exact powder charges and precise seating. Now that it's been fired once, I've trued up the primer pockets and will full length size and trim to length.

 

[Stuck]

I use the Forster Datum Dial comparator to set seating depth/jump. I was weighing bullets, (.264 147g ELD-M), but in listening to Brian Litz he recommends sorting bullets by base to ogive length, so that's what I'm doing now. Erik Cortina has some good videos on seating depth and how "chasing the lands" is stupid, what you're really trying to do is to find the seating depth that works best with the harmonics of your barrel.

BTW, with the new 6mm GT barrel on my chassis rifle I shot 2 3-shot groups that were 3" c-c, and one 2.4" group at 750yds. Virgin brass, not even prepped, just seated a primer and used very exact powder charges and precise seating. Now that it's been fired once, I've trued up the primer pockets and will full length size and trim to length.

Ive watched Cortina a bunch thats why I was questioning the seating depth being different while using the same ogive length. Using a seater that sets by ogive should give the same jump to the lands from batch to batch. Im concerned with the increase in pressure and speed throwing me off. 2 tenths of a grain of powder gave me a huge spread in group size. Im sure a .001 or two of seating depth could give me the same issue.

 

[Roc Doc]

Have you read these articles? Bullet Jump: Is Less Always Better?

 

[Stuck]

Have you read these articles? Bullet Jump: Is Less Always Better?

Yeah Ive read similar before. Especially the ladder test and OCW. Theyre essentially the same thing youre just varying the pressure by either changing the amount of powder or changing the case capacity by varying the seating depth.

 

[Stuck]

Went to the range today. I went through and picked out 10 of the shortest OAL rounds. 2 5 shot groups at 100yds, both with all holes touching with the exception of a first shot flyer (.4 out from the rest of the group)
Not horrible considering my workup for the load was at 80° and it was 25° today. Plus I was shooting at a 2" bull instead of the crosshair targets I normally use for load workup so I may not have been holding as dead on as I normally would have.
So this leads me to believe that land jump maybe more important than seating depth. I expected the opposite.

 

[Splib]

Went to the range today. I went through and picked out 10 of the shortest OAL rounds. 2 5 shot groups at 100yds, both with all holes touching with the exception of a first shot flyer (.4 out from the rest of the group)
Not horrible considering my workup for the load was at 80° and it was 25° today. Plus I was shooting at a 2" bull instead of the crosshair targets I normally use for load workup so I may not have been holding as dead on as I normally would have.
So this leads me to believe that land jump maybe more important than seating depth. I expected the opposite.

All holes touching at 100 yards is done and out. I would have trouble doing that with my 6mmBr. I saw Cortina's comments referenced on another forum. He is big, I am small but WTF ? The bullet relationship to the rifling engagement affects pressure. ie jammed 0.010 creates a different pressure than a 0.010 jump. And so on. If the pressure is inconsistent, the harmonics are also, and so the grouping is affected. I guess Lapua gives him new barrels on a regular basis. At any rate, the barrel/land erosion is slow and gradual so I kinda see his point.

 

[Splib]

 

[Stuck]

All holes touching at 100 yards is done and out. I would have trouble doing that with my 6mmBr. I saw Cortina's comments referenced on another forum. He is big, I am small but WTF ? The bullet relationship to the rifling engagement affects pressure. ie jammed 0.010 creates a different pressure than a 0.010 jump. And so on. If the pressure is inconsistent, the harmonics are also, and so the grouping is affected. I guess Lapua gives him new barrels on a regular basis. At any rate, the barrel/land erosion is slow and gradual so I kinda see his point.

You need to work on your load for 6mm BR. The guys at the club shooting 6mm BR are making one slightly large hole. They make me feel like Im shooting a scattergun. Of course they take 20 minutes to run a string, have little flags every 10 yds to the target and use a micro adjust gun rest and 2oz triggers. When Im working up a load I shoot off a bipod with a squeeze bag.

I went back out this morning and shot a 10 round group with assorted OALs all set with same bullet seater off the ogive. Same brass, primers and 39.1g of imr4350. 21° and no wind. Again the first cold bore shot was a bit of a flyer the other 9 were .51 center to center. I can live with it.

 

[Splib]

The BR guys are cult shit. I have a Pac Nor barrel on a 1912 Mauser action. I learned a decade ago I could not compete, but FT/R at 800/900/1000 yards is doable. 6.5-06 Douglas barrel for that shooting. Bench rest is way too competitive for me. Always fun and met great people.

 

[Stuck]

Yeah BR is way to OCD for me. If anything Im a little ADD BR requires way too much attention to detail. I can buy match ammo as or more accurate than my handloads. I do it so I can afford to shoot. If I can put multiple rounds on steel from whatever position they expect me to contort my big ass into at the given distance Im happy

 

[Roc Doc]

All holes touching at 100 yards is done and out. I would have trouble doing that with my 6mmBr. I saw Cortina's comments referenced on another forum. He is big, I am small but WTF ? The bullet relationship to the rifling engagement affects pressure. ie jammed 0.010 creates a different pressure than a 0.010 jump. And so on. If the pressure is inconsistent, the harmonics are also, and so the grouping is affected. I guess Lapua gives him new barrels on a regular basis. At any rate, the barrel/land erosion is slow and gradual so I kinda see his point.

I think that video is about getting a good seating depth for harmonics for mag fed guns, PRS, etc. He starts by finding jamb, then backing off .020 and then loads at .023, .026. 029 and .032 looking for the one that gives the best accuracy. It's what I did with the GT and it worked for me. I did have to do the jamb test with 5 test cartridges, (no primer or powder) and then take an average, when you're using a caliper, even a good one from Mitutoyo or Starrett, you're never going to get exact into the thousands so it's better to get an average. IIRC I had 3 that were the same and one above and one below. The targets I'm shooting at are generally larger than MOA, so as long as I'm 1/2 -3/4 MOA I'm happy with that, and yeah, those BR guys are way down the rabbit hole.

Oh, and Cortina uses Brux barrels and is probably sponsored.

 

[Stuck]

I think that video is about getting a good seating depth for harmonics for mag fed guns, PRS, etc. He starts by finding jamb, then backing off .020 and then loads at .023, .026. 029 and .032 looking for the one that gives the best accuracy. It's what I did with the GT and it worked for me. I did have to do the jamb test with 5 test cartridges, (no primer or powder) and then take an average, when you're using a caliper, even a good one from Mitutoyo or Starrett, you're never going to get exact into the thousands so it's better to get an average. IIRC I had 3 that were the same and one above and one below. The targets I'm shooting at are generally larger than MOA, so as long as I'm 1/2 -3/4 MOA I'm happy with that, and yeah, those BR guys are way down the rabbit hole.

Oh, and Cortina uses Brux barrels and is probably sponsored.

That is exactly how I got my land depth except I used fired brass with the primer still in it. I put the cases into my crimper and just barely bumped it to give a tiny little bit of neck tension so i knew the bullet wasnt sliding too easy. Set the bullets long and then put em in the chamber. I took measurements then I screwed the seater in till I was .020 short. Then I went with a ladder test for powder weight.

I still dont understand using both depth and weight. Technically if you want to get the best group size you should be ladder testig with powder and depth. Say a 3 grain range and maybe 10 different seat depths per tenth grain difference, by the time your done youve knocked a few thousandths out of the throat and need to start over. I say pick one and work your load from there.

Thinking about it I dont see where land jump is going to make much of a difference as long as the bullet is still stable in the case neck when it hits the lands. In other words if the bearing surface is still in the case neck between .020 - .030 off it shouldnt make alot of difference. Im sure there is some other factor attributed to the same thing that does but I think the speed down the barrel has more to do with working the harmonics than when it hits the lands.