Home Forums Hunting & Shooting Ask The Gunwriters Mule Deer my 6 Ackley seems too fast

I’ve had a hart barrelled 6 Ackley built on a short 700 for years. It’s a 12” twist and a .270” “tight neck”. It has always shot “fast”. Always beating published 6mm Remington velocities using published 6mm data by 100fps or more. Which would seem odd to me due to the larger case volume “requiring” more powder to reach the same velocity as the smaller case. I don’t have any pressure equipment, only my chronograph. I’ve got a hankering to try it out on deer so bought some 90gr BT’s in hopes they’ll stabilize in the slow twist. I did hot rod it quite a bit in my youth and have loaded ammo that was clearly too “hot” but try to gain wisdom with age which often means asking people who know more than I questions. I have always wondered if the 12” twist built less pressure than the faster twist data which normally is shot in 1-9” twist guns. So, I guess I’m asking you if you have any idea why my rifle shoots so fast and if you could see any reason why as long as I don’t get more than a few (2-3)% over published 6mm Remington data that I should be pushing pressure limits. Thank you in advance.

Ben

I have a 270 wsm, I started 140 grain accubond load development with the book RL 26 starting load, got max load velocity and stopped right there. Fast velocity is a pressure sign. If you don't have pressure testing equipment a chronograph is the next best thing. I always try to stay within book velocity with my loads, as you gain very little by exceeding them. You only get to blow your damn head off one time.

I don't think the 12" twist is less pressure as wouldn't less pressure result in less velocity,? I would guess your probably using a custom barrel and chamber that may be a little tighter than the ones that were used for book velocity

I shoot the 70g Nosler at 4150 in a 26" shilen 14 Twist, zero freebore, Win 760 powder.

Book velocity is darn slow, as they are lawyered up. Look at 4 books and you get 4 different velocity as max loads.I shoot rem 700's where the bolt head alone is tested at 150,000 psi. Brass will fail in the 70,000 psi range.

A pard is shooting a 6/284 with 80g at 3800 and now he is shooting the 55g Nosler at 4400 fps as a coyote hunting load. Another pard is shooting the 80g Sierra bt Blitz at 3800 out of a Shilen like mine cut with my reamer.

6mm Rem AI = the 6/284 in most respects

if you think that your 6 AI is fast, throw out some stats for us to look at, ie. bullet, load, barrel length, throat length or freebore, etc.

My old Remington 700 BDL would shoot 100 grain bullets of all makes through the Chronoraph at 3100 FPS. That was smokin' hot, maybe a shade hotter than I should have been loading them but it would do it. I never shot much lighter bullets than that. Althtough I did shoot a n 85 grain Sierra a few times at over 3300 FPS but that load was usless for me. Just a lot of MV but down stream it lost most of its steam. Just looked good on the Chronograph. But that 100 grain bullet at that speed would flp a deer side ways. He didn't know what hit him.

I have both a 6-284 and a 6mmAI, been shooting both since 2000-2001.
Sorry what you are claiming aint gonna fhuqking happen !!!!!!!!!!!!!
You must have a Shooters Chrony ????

A

Well that is exactly what is happening, hence the question. I’ve shot it over three different chronographs that I can think of and possibly four. One of them was a shooters chronograph. Two others for sure were not.

Ben

Benbo,

I would guess the high velocity has something to do with interior dimensions of the chamber and/or bore, especially the "tight" .270 neck. Can you slide bullets easily into the necks of fired brass?

I like Chronys, but years ago, I found a consistent .22 Mag rifle load ( WW 40gr FMJ) that I use as a "check". Every now and then I'll shoot it over the the thing and see of I'm still getting a good reading. I also do not use a chrony except for "my own enjoyment/curiosity", no long strings, anything that requires alot of calculations. I add this as alot of guys I feel are just like me, and the Chrony is good for what it does. I only like a High B.C. for its wind bucking ability, which I found helpful out on those Godawful, short-grass prairies! ha. I'm also not a LR Hunter so anything less than 400 is in trouble, but beyond, he/she is safe as can be, ha.
Having said that, I used a 6mm/284 and the 90gr NBT for antelope. It was flat, but sure tore up alot of meat. They are "dainty" creatures for sure.

Hey John, thanks for your reply. I just went out and measured a few cases. Loaded rounds necks measure .2665”. Shot cases necks measure about .269”. Flat based Sierra 55Bk slip inside the fired cases easily. I tried to find my old load notes that contained a lot of my “pre level headed” load data but couldn’t locate it. But did look through my current (last 15 or so years worth) notes.

Hodgdon data 58vmax 49.7 H414=3925fps 24” barrel
My load. 58vmax 50.0 H414= 3958fps. 25” barrel

Hodgdon data for 55BT H4895 42=3656: 46.5=4066
My only chrono’d data I could find With 55BT with H4895 is 44.03930fps

Hodgdon 70 grain data with H414 44.0=3305: 49.0= 3693
My load w/70BK was H414 51.0=3750

I wish I could’ve found my original notes. These are all taken after a 1” barrel set back due to throat erosion. Then again maybe the old girl just ain’t as fast as I remembered. Powders I used back then were a lot of RL19 H380/414. I don’t remember the exact additional capacity the Ackley gains over the std cartridge but it seems to have been around 7-9%. Anyway, thanks again.

Ben

I remember when a "fast barrel" wasn't a problem, when it was like cheating. "I used the data out of the manual, and got 100fps more than they did!" I'd like to have that problem. Usually, I have the opposite problem.

Dunno if I got a fast snout or not, 55 gr superformance, 80 gr bt, 3650. 22” 8 twist hart 6 ai, love it

Benbo,

Yeah, looks like your velocities are pretty much normal for the unimproved 6mm! In fact I've gotten similar velocities with a couple of .243 Winchesters that had 24" and 26" barrels.

Have never fooled with the 6mm AI, but have with the .257 Roberts AI, which is a very similar case. The improved version had about 8.5% more powder room.

>>>i will back that up too ! > my 6mm-284 `s both shoot those same velocities as above and are very accurate too.Pete53

These days I don’t fret over velocity nearly as much as I used to when I was more velocity crazed. I have shot loads that were hotter. Used to shoot 55 BTs at 4300 FPS. But after a few years was setting the barrel back. But, to this day I’ve never seen anything dismantle varmints so viciously!! I feel like my current load, used the last several times in the dog towns, a 70BT at a lazy 3600 FPS, does just fine and won’t be burning the barrel nearly as quickly. It just always perplexed me how 9% more case capacity was getting the numbers I was seeing with loads that “should’ve “ been much lower in pressure and theoretically velocity than what I got....I did throttle it up a few times... primer pockets loosened and I’d get shiny spots on the heads where the brass pushed into the ejector port... but turning necks on brass is a pain in the A.... so I try staying away from all that.

I bet Pete’s 70BT @4150 is a real lightning bolt! I’d love to see that thing at work on dogs or chucks or yoties!

I took my 6AI on a deer depredation “shoot” a few weeks ago and it killed like lightning and got me to thinking I’d retire the ol girl from the dog towns and just use her for the deer culls from now on. Trying the heavier bullet just gave me a reason to tinker and try something new.... maybe even add a little knowledge. Thanks again John and everyone else for your thoughts.

Ben

Jeez, mine is almost the same as yours. My 6AI was built 25ish years ago, and was also a short action 700 26" Shilen (I think 12T). Shot a bunch of stuff with it 55, 70 BT's, and finally settled on the 87 Horn. BTHP, and 87 V-Max (IMO one of the best intermediate range vmnt. bullets ever). A buddies kid killed a doe antelope at 400+ yds. several yrs. ago after a nice crawling stalk, and fell in love with the gun. It was originally going to be a 6-284, and then at the last minute changed to 6AI from Bob Jourdan's article on 6AI in Precision Shooting many years ago now. Gun sits mostly in the safe now as I don't like fireforming brass as much as in yrs. past, but it was a great killer in it's day.

Had a 6-24 Burris Ballistic Mil-Dot years ago and killed my 1st long-range coyote with it somewhat beyond 400. Now it wears a 4-12X Burris Mini Ballistic Plex. What optic did you put on yours sir?

I have been loading for a slightly tight necked 6 AI and 2-3% over standard 6mm loads is about it. When I hit peak pressure it comes up fast with only a half grain or so more powder resulting in stuck cases. I can slide a bullet into a fired round but it has a little more feel to it than I like. PPU cases would max out about a grain or grain and a half faster than Winchester cases. I am going to try skim turning the necks on the PPU brass as an added safety factor but it may just be the heavier brass and lesser capacity. With 100 grain bullets my comfort zone stops at around 3,350 fps. although others have reported 3,400 fps. I don't believe these were pressure tested loads. R26 gets there easily but hits a peak pressure (probably close to 70,000 psi.) at 3,400 fps which several other powders can reach too: H4831, H1000, 7828, VV 560, R22 etc.

I do believe there is such a thing as a fast barrel but more typically it is a tighter chamber. At some point I will check it out more thoroughly and maybe do a chamber cast or see if I can get the reamer specifications (borrowed from a silhouette shooter). My 1-8 twist has a short throat too which can increase pressure. I may extend the throat and open up the magazine but it shoots so well with 95-105 grain bullets I have little need to try this.

Could be my imagination but it seems to shoot flatter and get more of a reaction from deer when hit than the 243 Win does. And I am running the Winchester pretty fast at around 3,150 fps with 95 Noslers and R26.

Hi Benbo,
This is off topic from what you sought in your OP, but, when you went on that deer cull what bullet did you shoot? The OP implies you've not yet tried out the 90 gr BTs. You might also consider the 80 gr TTSX. I have heard glowing reports on their deadliness on deer and pronghorn. I got a bunch on sale and have just been doing load work so far. May hunt them this fall.
And if the 90 BTs shoot well, consider the 90 AB for a little tougher bullet at those velocities you're getting.
Best of luck with your "problem" rifle! LOL.
Rex

Mine currently has a 8.5-25 Leupold 1” tube with turrets. I shot 70BT’s that were still loaded from a p dog shoot I was just back from. All were small southern white tails and ranges were all 371-491. All lasered. Except one that was so close I just shot her...best guess 225 or so. It killed like lightning. I think my initial question was perhaps misunderstood. I found it perplexing that my 6 Ackley was shooting essentially the same velocity as a std 6 mm rem using std 6 mm data. What I mean is a 300 mag can be shot at 3006 velocities but it is still going to require more powder to do it

For instance, using Nosler data, both rifles 24” barrels:
3006 165 gr bullet W760 56.0=2882fps
300 win mag 165 W760 63.0=2866

Essentially the same velocity but the larger case requires more powder to get there.

I’ve tried 85 partitions but they shot poorly. I’ve shot 85 bthp sierras and they were very accurate. I’ve also shot 87 VMax and it also shot very well. .3 moa out to 300 yards. The farthest I shot it. It would not shoot 100 Sierra flat base. If it shoots the 90 BT’s I will probably put a 4.5-14 Leupold w/turrets on it and just let her ride it out easy shooting deer and coyotes. When it gets a new barrel probably go 9/10” twist and just keep using it in the same roll. But probably thread it and put a suppressor on it.

Ben