Holy cow!!!

[Sniper260]

Granted it's an AR-15.... If my numbers are right... For my Satern Custom 6.5 Grendel Barrel... My MAX overall length for a loaded round is 2.557 where the bullet touches the lands. My loads are 2.283 overall length due to AR-15 magazine length issues to fit them in the mag... This means when fired, my bullet is jumping .274 before it comes in contact with the rifling... THAT SEEMS HORRIBLE!!!!! THATS A HUGE GAP!!! Granted I've been up all night, am I missing something here??Does this seem like a problem to anyone else??

 

[dawson08]

How many rounds fired? I was thinking throat erosion and alot of it. But you should try switching to an OTM type bullet it might get you closer.....MAYBE>

 

[Red_SC]

The original barrel on my .308 had a jump in the 1/4" range as well, it shot just fine.

 

[dustinoif3]

Ill have to check one of my ar's. Always did mag length like you've been doing. I can tell you that my 700 jumps .125 and shots fine. Can't get to the lands due to ogive to tip off my bullets being longer than smk's and won't go into my mag. How many rounds have you fired in it?

 

[Sniper260]

This is a new barrel... it has at most 200 rounds through it... I havent got past developing a load for it...

 

[dawson08]

here is the real million dollar question. How well does it shoot?

 

[Sniper260]

I don't know what to think.. that's a big jump... big enough that it seems like the bullet could jump into the rifling crucked at times.. this could possibly explain why its taking so long to find a good load.... and why I don't get pressure signs out of hotter loads.. because the way I understand it your highest pressure would be with the bullet touching or jammed into the lands...???

 

[Sniper260]

I've got two .3 something 3 round groups. Not consistant though. I've had hell getting it under half an inch at a hundred many times.

 

[dustinoif3]

I don't know buddy. In my ar's if I shoot .75 I'm happy. Just don't expect a whole hell of a lot out of those scary rifles. Now the bolt guns I'm chasing the ragged hole. I've got a friend that has a 6.5 AR. Ill pick his brain. Mine are chambered in 556 so it may be way different as far as tolerances.

 

[gvanhyning]

I had an Alexander Arms GDMR which shot sub 1/4 MOA. I never worried about bullet jump. I'd start testing with max COAL and once the charge was identified then I'd play with seating depth. A lot of bolt guns will have jump without custom chambering.

 

[Deadshot2]

I don't know what to think.. that's a big jump... big enough that it seems like the bullet could jump into the rifling crucked at times.. this could possibly explain why its taking so long to find a good load.... and why I don't get pressure signs out of hotter loads.. because the way I understand it your highest pressure would be with the bullet touching or jammed into the lands...???

Take a look at a design drawing for a rifle chamber. Bullets don't "go crooked" as much as everyone thinks. When you chamber a round, the bearing surface that is exposed is lined up with the freebore area. Even if it hasn't engaged the lands yet, just how "crooked do you think it can get considering that the freebore is the same diameter as the groove diameter in the barrel?

I have a Remongton that has just short of .200" of freebore. Funny thing is that it shoots best when I load to magazine length. Trying to reach the lands is futile yet groups out of this .308 "Factory Barrel" can amaze even some Bench Rest Shooters. Yesterday, in the wind, I shot four groups of less than .3 MOA at 300 yards.

With that kind of accuracy I don't care if the bullet travels half way down the barrel before it hits the "throat".

 

[Sniper260]

That makes since deadshot. I've heard some people have AR-s that shoot some tight groups... This one is all custom.. It's a satern barrel, and other parts are les bear. I just kind of built it thinking this combo would turn out some good accuracy. I havent been wow'ed by it in a good way yet though. I may have to just stick with my custom bolt guns.. Who knows, I could just be still missing the right bullet powder combo...

 

[jeff1383]

I used to own the same barrel in 20". That cartridge can be very picky about powder charge as well. I had great results with imr 8208xbr 123 amax and lapua brass. If my memory serves me right I loaded 28.3 with a coal of 2.255. That combo would bughole every time for me at 100.

 

[Sniper260]

I have some 8208 and cfe 223 I can try with it. I haven't ran ladder test with those yet.

 

[dustinoif3]

I have some 8208 and cfe 223 I can try with it. I haven't ran ladder test with those yet.

I've had great results with CFE in my .223 and .308. Shoots clean and offers good velocity but I've really noticed pressure signs when close to book max where as I usually don't with other powders. Also if you don't like that CFE be sure to PM me and I'll sure take it off your hands.

 

[Sniper260]

Haha sounds good

 

[GentleBen]

I found the same thing in my Tikka T3 Varminter .223 bolt gun. I was trying to get the OAL and found a jump of almost a quarter inch when loaded to magazine length. Have not yet fired it, will be interesting.