Stag 10 7mm-08 or add A.I.?

D

Dave&Dar

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Looking at scratching a couple itches in one go. Stag 10 and 7mm-08 in one scratch. Discussion with a buddy who owns a bolt gun in 7mm-08 Ackley Improved (AI) has me looking at that as a possible option for just a bit more zip. Not a lot, I understand that, but why not right?

Looking into the AI cartridge has me asking questions I can’t find answers for so looking to the forum for thoughts -

1. The steeper shoulder angle on that AI. Do you see potential feeding issues?

2. Some research indicates the modest volecity gains come with increased chamber pressures. Some estimate an extra 10,000psi and that the AI cartridges tend to show pressure signs later in the pressure curve. While that definitely has me looking at the value of going AI. Do you think the Stag 10 chamber would be considered strong? This would be compared to the traditional AI recipient of a bolt gun, so I’m thinking probably not. School me here as this one is safety related. I’ve grown fond of seeing.

3. Looking to keep the barrel as short as NR will allow. Would a shorter 18.6” or so barrel negate the benefit of AI? Obviously I’ll handload, and we all know barrel lengths and finding the right powder(s) is just part of the process. The majority of those extolling the benefits of going AI seem to have barrels in 24” range.

Just some questions my Google skills haven’t found discussion on.

Thanks.
 
You want more zip but you want the shortest barrel possible? Is this to be a long range rifle or CQB? You need to compromise something.
I wouldn't bother with AI, maybe feed problems, maybe not, why risk it in a rifle you're handicapping with a short barrel

Also, you should consider more than the chamber being strong enough, you need to work with the action, it was designed for a certain pressure and weight of projectile, if you go away from that you will have cycling problems unless you compensate by changing the gas system and recoil system to balance the system back out.

I would just do a 20 inch barrel and realize that an inch and a half is not a problem in real life with an AR-10 style rifle.

It would also be easier to give you advice if you mentioned what type of shooting you'll be doing.
Do you plan to sit at a range shooting targets?
Is it going to be a long range target rifle?
Hunting rifle?
 
Thanks CR5! All great points.

Use as I see it today -

Not a long range rig, I have other items to cover that day. Also don’t see it coming with on CQB courses etc.
Mainly a fun range and back country rifle that will see hunting in the form of mule deer, black bear and maybe elk at the most. The driver behind shorter barrel length was hunting thicker bush.

Mostly a Jack of all Trades, Master of none. But not asking it to reach out there, for sure, so no heavy profile barrel here. Figure 300m would be a long poke for this one.

Naturally I want a do it all with the shortest barrel possible, who wouldn’t. But, if 20” is the happy length for the 7mm-08 family that’s certainly workable. I’m thinking of projectiles in 140gr range.

You’re echoing my concerns on chamber and action with AI pressure. I have yet to find one example of a 7mm-08AI build on the AR10 platform. Might be a reason. I’d prefer not to be the crash test dummie.

I am expecting to have to sort out the gas and recoil systems on this build anyway.
 
I can only comment on barrel length. I agree with CR5's comments. I have not noticed any physical handling benefits or advantages of a 18.5" barrel vs a 20" barrel.
 
I have a stag with a MRA 20”. It handles just fine and doesn’t dip too far into the performance spectrum. Even with the muzzle brake on, adding to the overall an additional 2”, it handles very very well at 8lbs before optics.
 
Also coming from the 7-08 fanboy club, might want to look at the 145lrx Barnes. High BC, incredible performance and I was getting 2710 at 22”” and was plenty of rifle.
 
You might try looking at Italy for the gas system specs - they used to sell all of their "308" rifles in 7mm-08 because civilians weren't allowed to own military calibres, it's possible that someone there has the gas port and recoil spring/buffer specs for AR actions. Same deal in Greece. No point in re-inventing the wheel.
 
And I will argue with everyone........ Keep the barrel short. If it's going to be a rifle that sees the field, shorten it. I definitely notice a 1.5" barrel length difference. Leave your bolt guns long and keep the semi's short IMO. I'd chop mine to 13" if it was legal.
I will ask the other question, is the extra 50-75fps worth an extra 1.5"??? Not to me.
My stag10 is in 7mm-08, I bought a Shilen blank and did the work myself. I have about 250 rounds through it and really like it. I can't comment on feeding issues, I feel like the 7-08AI may feed just fine but can't say with any certainty.
I am running Hornady 150 ELDX at 2580fps, and I think I have another node at around 2680 however it is definitely a bit stiff but the gun runs well.
 
Dave&Dar said:
Thanks CR5! All great points.

Use as I see it today -

Not a long range rig, I have other items to cover that day. Also don’t see it coming with on CQB courses etc.
Mainly a fun range and back country rifle that will see hunting in the form of mule deer, black bear and maybe elk at the most. The driver behind shorter barrel length was hunting thicker bush.

Mostly a Jack of all Trades, Master of none. But not asking it to reach out there, for sure, so no heavy profile barrel here. Figure 300m would be a long poke for this one.

Naturally I want a do it all with the shortest barrel possible, who wouldn’t. But, if 20” is the happy length for the 7mm-08 family that’s certainly workable. I’m thinking of projectiles in 140gr range.

You’re echoing my concerns on chamber and action with AI pressure. I have yet to find one example of a 7mm-08AI build on the AR10 platform. Might be a reason. I’d prefer not to be the crash test dummie.

I am expecting to have to sort out the gas and recoil systems on this build anyway.
Click to expand...

I am running rifle length gas system, after looking around on the internet for a bit I went with an .082 gas port, which seems to be near the smaller size recommended for 308 at that barrel length. I am running an AR10 length buffer tube, AR10 flat wire spring, with standard ar15 buffers, the gun cycles with H,HH, and HHH buffers. I was running the H during the winter while hunting. I haven't done too much testing with the buffer weights but am looking forward to doing that this spring as the weather gets nicer.

The gun runs factory ammo and my hand loads just fine.
 
Appreciate everyone’s input.

CanuckR, good to have someone with a 7mm-08 chambering in the platform. First hand knowledge of what the standard 7mm-08 will do helps. Your reasoning on short as possible follows my initial thoughts.

Griffin86, what’s to be said, you’ve built more Stag 10’s than anyone has mentioned on the board. You chip in, it’s worth listening to. Cheers!

So far, nobody has stepped up and said the AI round will not impact feeding negatively. Many have agreed it has potential for concern. It’s just my gut and looking at those sharp shoulders. Between feeding and pressure, getting real close to ruling AI out.

Still wrestling with 20” v 18.6”. Perhaps some Quikload work will help.

Good call on the 145gr LRX. Was considering 140gr TTSX as I do prefer my game unleaded.
 
I meant to say the I think the 7mm-08 AI would have trouble feeding. If you have dummy cartridges, I could try feeding them into one of my Stags to see if it works.

308 left, 7mm-08AI right.

93C85289-1E67-4E81-A11A-E899FB2E0EB7_zpsrvxgq2vo.jpg
 
If it's just for 300 yards or less then I wouldn't hesitate to go with an 18.6 inch barrel and I wouldn't even consider the AI option.
Build a nice 7-08 using the recipe CanuckR listed for parts and enjoy a smooth shooting reliable rifle that easily takes care of all your needs.

If you had said that you are interested in trying to shoot it 800 yards then the AI option with a couple more inches of barrel would be worth it but I don't think there is any gains to be seen based on your intended use. A shorter barrel standard 7-08 will easily do what you need and will be more reliable and less finicky than trying to AI a semi auto.

7-08 is noticeably softer shooting than a 308, I would stick to rounds in the 140-155 grain range and if hunting is part of the intended use I wouldn't even bother with a brake. Maybe get the muzzle threaded just in case you change your mind later but it's probably not needed unless you're sensitive to recoil.
I just sold a Rem 700 in 7-08 and even with it's pencil barrel and tupperware stock that helped the rifle weigh in very light it was still very gentle on the shoulder.
 
I don't have extensive trigger time with mine yet. But I would not hesitate to shoot it at any game at 300M. I have shot it to 600M once so far and quite easily went 5/5 on a 30% IPSC. I look forward to shooting it at 1000M. I should be supersonic to 1100M or so. Might fling some at a mile just for the hell of it.

I have a second upper and a 6.5 blank of unknown origin I have debated chambering in 260AI. Then without putting a gas system on it see if it will feed and chamber rounds manually. If it doesn't I can still cut the chamber off and run a 260 or creed reamer in and then put a gas system on it.
 
Let me preface the following by saying I'm talking about a bolt gun, but I haven't had any feeding issues with my 7mm-08 AI, even when running it fast. That being said, 7mm-08 is a cartridge that doesn't benefit a ton from the AI process if velocity is what you're after. Of course my bolt rifle will shoot factory 7mm-08 well under an inch so personally I don't see a downside to the chambering as long as you go in understanding that reamers and dies are tough to find and by virtue of that expensive.
 
Getting the feel this whole Stag 10 thing is going to end up with more than one upper. First set-up is going to be a standard 7mm-08 at 18.6”. Not recoil sensitive, but threaded none the less. DONE.

Now to start researching barrels. VISA is probably safe for a few more days.

Griffin86, thanks for the offer to run some dummie rounds. Going to pass at this time. Figure I’ll start with something simple. Exotic can come later.

Appreciate everyone’s input.
 
Personally, I wouldn't. The gains from ai on 7-08 are pretty minimal. Typically less than 100fps. The whole attraction to ai is that you would only have to neck size your brass and you'd have minimal stretching and longer case life but if I was running a semi I would be full length sizing every time anyway.
 
savagelh said:
Personally, I wouldn't. The gains from ai on 7-08 are pretty minimal. Typically less than 100fps. The whole attraction to ai is that you would only have to neck size your brass and you'd have minimal stretching and longer case life but if I was running a semi I would be full length sizing every time anyway.
Click to expand...

That's just what you tell people.
 
Hitzy said:
Just go 6.5 Creed...better suited for max velocity with a 2.800 OAL.
Click to expand...

My modern hunter in 6.5CM is pushing a 130gr ELD-M at 2700fps. I wouldn't have bought it in 6.5 if I wasn't hoping to get it out to 800+ yards though.

If the OP wasn't set on a 7-08 I'd just say to go with a 308 since he's not planning to go past 300 yards anyway. None of the other cartridges have anything on a 308 at that distance. Simple, cheap components, and it's what the action is designed to be running.
 
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