Anyone have experience/luck reloading for ar10/15 accuracy by adjusting bullet jump?

[Morndorff95]

I just got into reloading and have an AR10 (308) and AR15 (5.56) and was wondering if anyone has had any luck in regards to accuracy by adjusting bullet jump, or if the magazine is enough of a limiting factor to where length of the bullet seating depth to the leads would make it not be worth it to mess with jump at all. Ex. Not being able to seat the bullet further up and there by not fitting in the mag. And if I should just focus on the powder load for the best reasonable accuracy.

I know every chamber is different and jump is more of a term/applicable for bolt rifles, but if there are people who have had success or even failure with adjusting jump for ARs then I would like to hear about your experience with it before I invest in the tools to pursue it instead of just using measurements from factory match loads. I would definitely pursue that after developing a reliable powder load if people have had luck with it.

My ARs are stock Diamondback DB10BGB and DB15BGB if it matters. I also various bullets for my twist rates and powders based off of several relaoding sources to test so im good there. I know I'll never achieve BR rifle accuracy or probably even bolt rifle accuracy with them but I'm looking to make loads for them as accurate as possible so when I hunt with them I know I will be as accurate as possible at ranges 300-500 yards max so shots will be as clean as possible.

 

[Koda_]

using a Hornady OAL gauge I compared the jump to my lands with a handload set to saami oal and it had a .100" jump. There are AR15 magazines you can buy that handloaders use which allow for about .030" more room, PRI mags and ASC steel version. I bought the cheaper ASC mags and they work great but have not yet tested to see if an extra .030" reduces my group. If I use the extra room in the ASC mag I will be stuck with those mags only if its worth it, but will still have about .070" of jump so my guess is its not worth it and will just load the oal to fit any AR15 magazine and just accept the best accuracy for powder load.
Pay attention to projectile length since you cant load longer than the magazine allows the rest of the projectile might compress your powder load if you choose a really long for caliber bullet. Im not certain what the limitation is for how far a bullet to protrude inside the case but can say Barnes 55g TTSX worked for me on my first ladder test.

 

[captrjc]

I have 22 creed, 257 roberts, 6.5 creed, 308and 338 federal in AR10 platform. Non of them have any significant accuracy change by the small COAL adjustments limited my the magazine. For me, brass prep and not running hot loads had the greatest effect. YMMV
I run standard type bullets like ballistic tips, hornady sst in most. But both the creeds I'm running vlds and coal has little effect. Of course all of them are not bolt action accurate. 1MOA accurate. I know people say they get .5 out of their autos but I haven't been able to get that consistent enough to claim it.
Definitely look for pressure when working up, it probably will show up sooner then your bolt action load.

 

[WildRose]

I just got into reloading and have an AR10 (308) and AR15 (5.56) and was wondering if anyone has had any luck in regards to accuracy by adjusting bullet jump, or if the magazine is enough of a limiting factor to where length of the bullet seating depth to the leads would make it not be worth it to mess with jump at all. Ex. Not being able to seat the bullet further up and there by not fitting in the mag. And if I should just focus on the powder load for the best reasonable accuracy.

I know every chamber is different and jump is more of a term/applicable for bolt rifles, but if there are people who have had success or even failure with adjusting jump for ARs then I would like to hear about your experience with it before I invest in the tools to pursue it instead of just using measurements from factory match loads. I would definitely pursue that after developing a reliable powder load if people have had luck with it.

My ARs are stock Diamondback DB10BGB and DB15BGB if it matters. I also various bullets for my twist rates and powders based off of several relaoding sources to test so im good there. I know I'll never achieve BR rifle accuracy or probably even bolt rifle accuracy with them but I'm looking to make loads for them as accurate as possible so when I hunt with them I know I will be as accurate as possible at ranges 300-500 yards max so shots will be as clean as possible.

Mostly I just set OAL by how much room there is in the mag and to allow smooth feeding.

If everything is right you should be able to just load to SAAMI standard and tune things in with powder charge.

 

[Darryle]

Find you a copy of Competitive AR15 Builder's Guide and go over your rifles. There are more ways to accuracy than taking an off the shelf AR and playing with COAL. I have been able to squeeze a bit of accuracy out of factory rifles with a complete disassembly and reassembly.

Once you have verified that the rifles are in the best shape, then get to playing with your reloads.

 

[Morndorff95]

Thank you all, I greatly appreciate the replies and information

 

[jbs2014]

With 135 grain ATIPs and the powder primer brass combination I use I have achieved a significant increase in accuracy and decrease in ES when seating the bullet .030 deeper than the Hornady load book COAL. From what I am beginning to understand ATIPs in 6.5 & .375 caliber like to be seated deeper.

 

[budlight]

Find you a copy of Competitive AR15 Builder's Guide and go over your rifles. There are more ways to accuracy than taking an off the shelf AR and playing with COAL. I have been able to squeeze a bit of accuracy out of factory rifles with a complete disassembly and reassembly.

Once you have verified that the rifles are in the best shape, then get to playing with your reloads.

In my search on how to build competitive Ar's I came across things like a upper grinder to true the upper receiver to the barrel before you assemble the upper. The use of the best heavy full auto bolts. Using rifle length or even better the plus 2 inch gas port barrels. messing with springs and buffer weights to cycle the easiest possible.

I played with case length and careful trueing and found that 1.78 length works. The minimum a SAAMI 223 chamber can be is 1.772" (and most are longer). My paper rounds use on the same lot Lake City brass. I machined my RCBS case holders .003 down and use competition dies on my single stage to resize the cases and then wet tumble polish to remove all oils and blemishes before reloading. Wet tumble cleans out all the carbon to keep the case volumes consistent

I have single shot bolt guns where attention to seating length really matters in long throated rifles. AR15 I just stick to 2,26 and work on everything else

 

[del2les]

Depending on several factors, playing with OAL in an AR may be the least effective way to increase accuracy. I do want to state one potential exception, and that is when firing the 600 yd slow prone and single loading the "long and heavies" to reach the lands in a typical 5.56 throat. But even here, all other accuracy factors need to be in place first.

I've ran everything from minimum 223 Match chambers, 223 Wylde and some 5.56 throats, and without exception, seating depth was not the improvement that gave me the greatest accuracy increase.

 

[Darryle]

I have never lapped an upper receiver, but I have bedded every single upper I have assembled with Loctite 620. I also have used quality uppers, the biggest majority Aero Precision. I have paid exorbitant prices for quality barrels and I have paid bargain basement prices, but I have always stayed with manufacturers that had good reputations and offer slightly faster twists per caliber.

I have tried PSA and Diamondback rifles, more luck with the PSA rifles than the DB rifles, although I had one DB 6.5 Creedmoor that was extremely accurate after a disassemble, reassembly and a CMC 2.5lb 3 Gun trigger.

Don't get caught up with playing with seating depths or data until you know the initial potential of the barrel. Some quality ammo that has proven it's accuracy in similar twist rifles. I doubt you will find a bad barrel, quality barrels are fairly easy to manufacture with today's processes.

Good luck and keep us informed.

 

[HSmithTX]

I've shot a lot of handloads in a lot of AR rifles, I have never changed OAL to try to improve accuracy. My rifles and the others I have loaded for either shot well or they didn't after a velocity ladder and loading the highest flat spot before any pressure signs were seen. I run them fairly hard in 5.56, 308 less so but still factory plus velocities looking for low SD's. I also tear them down before doing any load work, true the uppers, bed the extension, etc. It's been rare for anything of reasonable quality to not shoot under 1.5MOA after doing the work. Those that didn't shoot well after the work shot great after changing the barrel out to a good quality barrel, some of them easily sub minute.

 

[ARlife4me]

I would change powders and/or charge weights, before changing coal if feeding smooth. In the Berger manual (223rem) they show 2.260" for the 90gr vld-tgt bullet. I bought 5 boxes, tried a dummy round (no primer, no powder), seated to length, stood facing up and the bullet fell inside the case. Called Berger about it and thy stated the caol was wrong listed. They made good on an xchange, so it was nice having good people to work with!

 

[Earnhardt]

Yes, adjusting bullet jump can/will effect accuracy in an AR...just as it does in a bolt gun.

But if you are starting out in reloading (learning the ropes) in the AR platform...good luck

As Darrlye said, start out by accurizing the AR itself before you work on the your reloading for the gun

 

[Kansaswoodguy]

Jump can have an effect on accuracy as has been stated. I do not however fool with it in gas guns I load the bullets mag length and forget seating depth after that. Just adjust powder charge for best accuracy if that fails to give the accuracy you find acceptable change powders. There are some bullets that simply don't shoot well out of some guns also. In AR-15 with light bullets 50-55gr try Benchmark powder for heavies 75-77gr try IMR 8208 XBR powder. If you can achieve MOA with a gasser your doing well. Also a trigger upgrade from Mil spec will help achieve MOA accuracy.