105 hybrids not shooting in 243win?

[Jca57jd]

I just read through a thread from last year talking about stabilizing the 105 hybrids. It talked about the twist rate to stabilize them mostly with a little talk about velocity. My new build is a ar 10 chambered in 243win with a 26" custom match grade Krieger barrel with 1-8" twist. I have been working on load development with the Berger 105 hybrids only. I started off doing the seating depth test and the bullets did best with a .050" jump. From there I started doing lader tests with different powders; Imr4350, h4831sc, h1000, and h100v. So far the h100v has produced the highest velocity at roughly 2950fps (41.6gr), and the rest of the charges and powders have been in the mid 2800's. None of the loads I have tried have had a consitant es under 30fps. I separate all of my cases and bullets by weight length, ect; and when I load them I manually weigh every charge and set each bullet to exactly .050" off of the lans measuring the ogive. I just can't get anything better than a 1.5" group at 300yds and that only happend once and I did another group with the same load the next day and it was 4"?! Ive shot 97 total load development shots with the 105 hybrids so far and I just received 200 more today. Do you think that I'm not getting enough velocity to stabalize them, 1-8" isn't fast enough twist rate, or my gun just doesn't like them?

I finally found some h4350 that I'm going to buy on Monday to try but Im really starting to get discouraged with these bullets or even worse my new gun! I also looked and Berger twist calculator and it says that my sg is 1.42 wich is rated on the high end of marginal stability but not in the comfortable stability. What would be your next step if you were in my shoes?

Thanks!

 

[Jca57jd]

Oh and by the way I'm using hornady brass and fed 210 primer. I'm going to go ahead and pick up 1000 fed 210gm to see if that helps on future loads!

Thanks again!

 

[mac37]

Do you think that I'm not getting enough velocity to stabalize them, 1-8" isn't fast enough twist rate, or my gun just doesn't like them?

Take it for what it's worth but if the Hybrids are that finicky in your rifle don't waste any more time and effort on them.

 

[SDDasher]

Maybe I missed it but what exactly are you wanting the 105's to do? Shoot with low ES/SD? Shoot at a specific velocity? Shoot for accuracy? If your bullets are not blowing up en route or Key Holing on target they are stabilized. 1x8 is great for the Hybrids.
I suspect your powder choice on the ES. Try some H4895 or RL15 or Varget.
If you are looking for match accuracy from the AR 10 good luck. I had one and gave up after a lot of trial and error. JMTCW

 

[rcw3]

Jca57jd

Reading your post, here's what I see:

1. You don't know if your gun is accurate
2. You don't know if the loads you're shooting are accurate
3. You don't know if 105 Hybrids shoot well in your rifle

Having done a lot of work with AR-10's, I can say for a fact that most people are also not "dialed in" to AR-10's and what's possible from them in terms of accuracy or how to get it - bolt guns are a "piece of cake" compared to semi-auto AR-10's (and I include in the definition of "AR-10's" the DPMS LR's) so be careful following bolt gunner's advices on AR-10's. Also, just because an AR-10 has a Krieger barrel on it does not guarantee it will shoot well. In terms of potential accuracy, there's a lot going on with AR-10's and going through the rundown of the possible accuracy issues with one is beyond this posting.

One thing is clear, if you're "in the dark", you're likely not going to get where you want to go with your project.

If it were me, here's where I would go:

1. Start with a "no brainer" milder .243 Win load with a bullet that is extremely forgiving (like the Berger 108 gr. BT) to see if you can get something running accurately in your rifle. If it were me I would start with something like around 37 - 38 gr. of H4350 or IMR 4350 to see what you get. If that will not shoot, then I would try a mild loading with a faster burning powder (like Varget - - maybe 32 gr or thereabouts) and see if you can get something going). If you can get something going then you can step up the load until things start coming apart and that's the top end of your accuracy window (and it may be a lot lower than you want in terms of velocity) but it's a semi auto rifle and a lot starts going on with them while the bullet is still in the bore.

2. I shot AR-10's in highpower for years, and some of them were chambered in .243 Win, and I did very well with them but most of the time I was running the 105-108 gr 6mm bullets in the 2750-2800 fps range because that's where they shot well. Most "hot rod" loads in an AR-10 shoot like crap! If your thinking you're going to find a load that runs 2950+ fps with the 105 Hybrids that's a true .5 MOA shooter - good luck - I would "take odds against that all day long. Also a lot of the slower powders shoot poorly in AR-10's because they cause extremely high port pressures that advance the cycling of the action while the bullet is in the bore, to the point that it disrupts accuracy.

3. If you get something going, then "play" with the 105 Hybrids and see what you can get out of them and go from there.

Good Luck!

Robert

 

[Jca57jd]

Thanks for the advice gentleman! Robert you are a scholar to take the time to go over some details like that with me. I'll move on and try some 95gr nosler ballistic tips to see what she is capable of (those bullets have shot good in anything I own, however they ain't a good long range round in my book). Then proceed to try some 105 a max. What bullets and powders were you shooting in your 243 ar10s? Many thanks!

 

[rcw3]

H4350 was my favorite in the 243 Win AR-10 but IMR 4350 will do well too. For bullets XTC I used the 105-108 gr bullets (Bergers mostly, sometimes Sierra 107's but I found the Bergers more consistently accurate). The Berger 108 BT is a very accurate designed bullet and about as forgiving a bullet as you can get for something like a semi-auto.

 

[joshSloThree]

what is your COAL??, bc my 105 hybrids are fine in a AR platform bartlein barrel 1/7.5 twist 24 in

 

[CaptainMal]

An inch-and-a -half group at 300 yards with that thing is BAD???

You wrote that.

Man what kind of benchrest accuracy do you want with that gun? No clue what scope you have or how good you are but if you get sub 3" groups at 300 yards with it, I think it's great.

 

[jsthntn247]

I've done allot of load development with a couple 243's here lately. They all have a high node around 44.9gr of H4831sc and 42gr H4350. All of the guns tested with H4350 had lower nodes around 40.6-40.9 as well. I probably would not try for the upper node in an AR. All shot best .010 to .015 off the lands as well.

 

[MOShooter]

I'm running a 7.5 twist in my 6slr with the hybrids and it shoots great. My 6br with a 1-8 didn't shoot them as well at the 95vld.

Scott

 

[searcher]

Not being able to get low ES's with various loads out of an A/R usually points to bullet movement in the case when loading or varying neck tension due to unturned and or ununiform neck thickness. Without adequate tension to hold all bullets in the same position through the loading cycle, you will have different pressures on each round. I'd suggest going another .001" more neck tension if you are using bushing F/L dies. I'd go about .003" MINIMUM under loaded round neck O.D.. What has worked even better is using moly AND very tight neck tension. Moly without adequate neck tension will simply push the bullet into the case when loading a lot of times. With adequate tension and moly, the bullet will hold well without moving and the release is much more uniform if your brass is not. Additional enhancement is made by doing a 75% coverage neck turning skim to better uniform the brass without weakening it. Do these and your ES's will go down.

 

[Heman]

In my .243 I'm jumping the Hybrids 0.020" The other thing I've found in my rifle and its been both barrels the loads shoot best when I'm running them fast. I run Whidden's load of 45.2gr N160 molly coated. Now slap a 105gr Nosler/Hornady on there and they shoot great too and I use the cheaper bullets for mid-range. I tried finding a lower velocity node around 3,050 for mid range and I found it but none of the bullets shot as well as they do when i'm running them up around 3,300fps. BTW, 1,758 on the first barrel and it is still shooting, although put the new barrel on for Perry for this year.