What is "excessive" bullet jump ?

[armorydoc]

I am using a Hornady Lock-n-Load OAL straight gauge and comparator and finding that if I load to the recommended cartridge oal of 2.260 (can't go much longer - mag restrictions), my chamber has .040 "jump, or leade" from the bullet ogive to the lands. The bullets I'm using are Hornady 123 gr. ELDM and Hornady 123 gr. SST.

Reading the comparator with these bullets, the CBTO (Cartridge Base to Ogive) measures 1.6875. My question is, "is .040 too much leade, or clearance since most manuals recommend .015~ to .020~ jump ? I ask because I'm having trouble getting my group size down below 1 moa. For information, this barrel is fairly new with about 300 rounds down the tube.

Thanks for the input !

[GLSHOOTER]

Sept 25, 2017 15:23:05 GMT -8 armorydoc said:

I am using a Hornady Lock-n-Load OAL straight gauge and comparator and finding that if I load to the recommended cartridge oal of 2.260 (can't go much longer - mag restrictions), my chamber has .040 "jump, or leade" from the bullet ogive to the lands. The bullets I'm using are Hornady 123 gr. ELDM and Hornady 123 gr. SST.

Reading the comparator with these bullets, the CBTO (Cartridge Base to Ogive) measures 1.6875. My question is, "is .040 too much leade, or clearance since most manuals recommend .015~ to .020~ jump ? I ask because I'm having trouble getting my group size down below 1 moa. For information, this barrel is fairly new with about 300 rounds down the tube.

Thanks for the input !

Every bullet/barrel combination will tel you what it wants and they are not always the same from barrel to barrel. 0.040 is not excessive for many. In fact a FACTORY 223/556 is maybe twice that in many cases. We shoot many bullets up to 0.125 off the lands in some chamberings.

Powder choice can make or break any load. You may want to swap some powder, change bullets and buy some ASC magazines for longer loading. You don't say what the chambering is so that would help to know BTW.

I have some barrels that hate XXX bullet but YYY of the same weight shoot lights out. It's all a trade off in this hunt for accuracy.One size never fits all.

Greg

[sandman799]

I recently started handloading for all my guns, but most of what I load is for my .223 which has a BHW 16” Poly Rifled Barrel, I noticed on some projectiles, especially the heavier ones of 80 grains or heavier they say these bullets require a fast barrel of 1:7 or 1:8 or even 1:6.5 barrels, but the BHW boasts improved balistics on these barrels so if I have a BHW Polygonal Rifled 16” Barrel is it faster or slower then standard barrels with standard lands and grooves with the same twist rate? Mine has the 1:8 twist so is the end result faster or slower then standard barrels?

When handloading for my BHW is there differences between the way I would measure for the best OAL on my cartridges and my chamber? Because when I do it for my Olympic Arms AR it seems different then with my AR that I built with the Black Hole Barrel, any tips and tricks you guys can give us on how to handload the best possible rounds for Black Hole Polygonal Rifled barrels would be greatly appreciated and would help us to get the most out of our barrels

Also I am starting to try and develop rounds for this build and I bought a Hornady LNL OAL gauge to find the chamber depth and depth to the rifling, are there any considerations I need to take into account with my BHW Barrel compared to standard barrels? I want to develop ammo for my Black Hole Barrel on my AR build and test its range and accuracy out past 500 meters so I want to make sure I am loading correctly for the Black Hole Barrel..

Is there anywhere on the Black Hole Weaponry website where we can find information to aide us in making better handloads for the BHW barrels?


Anything else you guys can tell me to make handloading for my BHW Rifle more efficient and for better accuracy, yes I know each Barrel is different and so are the bullets but black hole barrels are a whole different class then other barrels so I just want to make sure I am doing everything right for this barrel

Sandman

[GLSHOOTER]

The barrels have the twist as marked but they run at lower pressure hence faster speeds than the standard rifled barrels and they seem t shoot about one twist faster bullets than they should on paper? I have no idea exactly why but I'll take it.

There are about 15 different 223 chambers out in the wild. Many variations and you just load for what you got. Go check a Colt and a DPMS and they will be different in head space and chamber design. BHW chambers tend to small in size in diameter in many chamberings and that is a plus for accuracy you will enjoy. 223 is one of them. I don't use small base dies BTW at all on the 223..

Accuracy on these seems to really show up at the top end of the loading levels. Some love to be drive as hard as you can go. There will be a lower accuracy node in most set ups but I don't worry about that. I want performance at speed so on a loading table I lean to the far right as opposed to the far left.

I shoot them off the lands in some at 0.010, some at 0.005 and some in the lands 0.005. It just varies from bullet to bullet. No hard fast rules. I start as close to the lands I can get and then start shortening them up as I find loads that want to work for me. That way you only have to go one direction.

I basically use magazines that allow me to load longer than 2.260 as this gives me more flexibility. Mostly ASC's are taken to the range as they allow 2.316 nominal in the Stainless Steel versions. This really pays off in the bigger cartridges like the LBC's and 6.8 variants.

Greg

[sandman799]

So I took my BHW build to the range again recently and I shot 150 or so rounds of mixed ammo, some PMC bronze and some Winchester and a lot of handloads, the results were very interesting especially when trying to zero a second optic to the rifle, I have had eyes so shooting at 100 meters with a 3.5x ACOG I can’t really see the target clear but I can still get good groups, so I swapped out the 3.5x ACOG for the scope on my DPMS Panther LR-308/AP4 AR10 because it has a LOT more magnification, HOWEVER trying to resell the scope to my BHW rifle was a nightmare and nearly impossible because I’ve had the scope so long and o don’t know the click values anymore so it was hit and miss on adjusting it, I finally went back to the ACOG and now have to readjust the AR10 scope when I go out again.... so anyways with bad eyes at 100 meters and barely able to see the smaller targets (used the targets that have one large target and four smaller targets on one piece of paper, I adjusted the scope a few clicks and was doing really good at groupings and after I made final adjustments I was on bullseyes..... anyway the Barrel seems to shoot factory loads as well as it does custom hand loads, I typically stay on the low end of the load charts while I am still learning and after I’ve got some experience I’ll start playing with different powder loads, i shoot mostly hornady projectiles, and occasionally some soeer that I got in a trade a month or so ago, it’s a lot of fun loading, and I love shooting, I just hate the cleaning afterwards 🤕 so here’s one of the targets and keep in mind there are two big groups, that one was a full mag of mixed factory loads and hand loads and all were within the same 1/2” to 3/4” group hole and the smaller was 15 rounds of PMC bronze through about a 1/2” Hole so they all seemed to perform the same, the scattered holes were when I was adjusting the scope

Attachments:

[GLSHOOTER]

That's some good shooting right there. Looks like you got a good tube.

What brand of scope on the AR10? When you take the caps off is there anything written on the knobs?

Greg

[rps]

Sept 25, 2017 15:23:05 GMT -8 armorydoc said:

I am using a Hornady Lock-n-Load OAL straight gauge and comparator and finding that if I load to the recommended cartridge oal of 2.260 (can't go much longer - mag restrictions), my chamber has .040 "jump, or leade" from the bullet ogive to the lands. The bullets I'm using are Hornady 123 gr. ELDM and Hornady 123 gr. SST.

Reading the comparator with these bullets, the CBTO (Cartridge Base to Ogive) measures 1.6875. My question is, "is .040 too much leade, or clearance since most manuals recommend .015~ to .020~ jump ? I ask because I'm having trouble getting my group size down below 1 moa. For information, this barrel is fairly new with about 300 rounds down the tube.

Thanks for the input !

I am also using the Hornady device to prepare an accurate long-range load for my Remington 700 in .22-250.  I had been using the Hornady factory 40 grain cartridges that rocket out at 4150 fps but was worried about throat erosion.  Using the comparator, I got a reading of 2.054" and backed that off to 2.034" to provide for jump.  Then I measured a factory-fresh round with the comparator and got 1.9935."  So my barrel is telling me that it likes a longer round than factory-loadings.  Any suggestions on what to do now?  Which should I believe?

Thanks for any assistance you can provide.

[GLSHOOTER]

Mar 11, 2018 3:33:46 GMT -8 rps said:

Sept 25, 2017 15:23:05 GMT -8 armorydoc said:

I am using a Hornady Lock-n-Load OAL straight gauge and comparator and finding that if I load to the recommended cartridge oal of 2.260 (can't go much longer - mag restrictions), my chamber has .040 "jump, or leade" from the bullet ogive to the lands. The bullets I'm using are Hornady 123 gr. ELDM and Hornady 123 gr. SST.

Reading the comparator with these bullets, the CBTO (Cartridge Base to Ogive) measures 1.6875. My question is, "is .040 too much leade, or clearance since most manuals recommend .015~ to .020~ jump ? I ask because I'm having trouble getting my group size down below 1 moa. For information, this barrel is fairly new with about 300 rounds down the tube.

Thanks for the input !

I am also using the Hornady device to prepare an accurate long-range load for my Remington 700 in .22-250.  I had been using the Hornady factory 40 grain cartridges that rocket out at 4150 fps but was worried about throat erosion.  Using the comparator, I got a reading of 2.054" and backed that off to 2.034" to provide for jump.  Then I measured a factory-fresh round with the comparator and got 1.9935."  So my barrel is telling me that it likes a longer round than factory-loadings.  Any suggestions on what to do now?  Which should I believe?

Thanks for any assistance you can provide.

Well I'm not sure what the question is but as long as you have enough bullet in the neck and aren't in the lands and can load to fit the magazine you can load as long as you like. The barrel will tell you what it likes. Surprisingly you may see a factory load jump 0.100+ in some rifles and shoot lights out. Remember it has to run in every chamber out there and you get to "fix" that. Moving it to 0.050 jump and its poor and moving it to 0.005 and it's super again. The vagaries of bullet shape, throat erosion and the loading means that one COL, or Base to Ogive , measure won't work. We have to move things out constantly to get top[performance when we get a different round. Many rifles love them 0.005 off, some like them 0.005 in the lands and others just ask you to put a bullet in a case and pull the trigger with no nevermind on length.

Greg

[rps]

Thanks, Greg.  I made a couple of dummies at 2.433" COAL, which is what the comparator suggested, with allowance for jump.  Both fit the 700's magazine and chambered with no problem.  The next step will be to load some test rounds and take them to the range, then make adjustments as needed.