284win mag Feeding issue for AR10 magazine

[KANEDA SHON]

ok guys, I'm thinking about creating a new AR10 (not AR15) recently, paying attention to the excellent ballistic graph of a 7mm bullet. and I am thinking of making an ar10 using 284win which has a case capacity a little more than 7-08win, but there is some problem with the base size of the bullet as shown in the picture below.
Since 284win is basically using rebated rim, I think 308win and 284win are compatible with the same 0.473inch rim. However, because the base size is slightly larger than 284win by 0.03inch, it is possible that the standard ar10 magazine will not be slightly stiff or the ammunition will not be inserted. Also, I think this will greatly reduce the capacity of the magazine.

If there is a problem, I am thinking of making a customized wild cat cartrige with the base size reduced to 0.501>0.475. I wonder if anyone here has ever put 284win in an ar10 magazine?

 

[FeMan]

I have not but COAL will be a serious issue. The bullet will have to be seated so deep that it will eat up valuable case capacity. I have a couple friends who use a 284 Sheehane with success in short (bolt) action setups. They use a 0.030" freebore and feed from AI mags very reliably. The Sheehane shoulder gives them back much of the case capacity lost to the bullet base. They get 2800 or so fps with 180 grain bullets. I think that might work well in an AR10 platform.

 

[KANEDA SHON]

I have not but COAL will be a serious issue. The bullet will have to be seated so deep that it will eat up valuable case capacity. I have a couple friends who use a 284 Sheehane with success in short (bolt) action setups. They use a 0.030" freebore and feed from AI mags very reliably. The Sheehane shoulder gives them back much of the case capacity lost to the bullet base. They get 2800 or so fps with 180 grain bullets. I think that might work well in an AR10 platform.

That's right. I confirmed that there could be a problem when loading bullets over 168grain. So there are two options that we're thinking about right now. The first is to use 284 win of a conventional less than 168 grain bullet, and the second is to make a wild cat cartridge with a shoulder position modified downward like the picture, using a shell company like Paterson. However, I am worried whether it will work without any problems when 284win (or modified) is put into the existing 308win magazine because the base diameter of the brass is more than 0.03inch (0.69mm) larger than the existing 308.

 

[simo hayha]

Just neck up 6.5 Creed

 

[Fuj]

Take the 284 Winchester and shorten it to the same length
as the .308 and 7/08 class of cases. My SA284 has 3.5 grains
of powder over the 7/08. You would run a much shorter throat
then my single shots but I just achieved 2804 fps with the Hornady
190 gr A-tip. This case works in a conventional AR10 mag, but you
lose 2 rounds to capacity.

284 Win / My SA284 / My even shorter 284 ELF

 

[Fuj]

Just neck up 6.5 Creed

Going to a 7 Creed over the 7/08 is going backwards.
If not a lot of monkeying around, I'd do the 7/08 Ackley,
which I was going to do but the 284 cat made more
sense, for my heavier match bullets. The problem with the
Ackley is feeding issues in an auto. Maybe also with the
35 degree shoulder on the 284, but could change that to
30 degrees. The other aspect to look at is the reliability
of the rebated rim in an auto application. I have no input
on that.

 

[KANEDA SHON]

Take the 284 Winchester and shorten it to the same length
as the .308 and 7/08 class of cases. My SA284 has 3.5 grains
of powder over the 7/08. You would run a much shorter throat
then my single shots but I just achieved 2804 fps with the Hornady
190 gr A-tip. This case works in a conventional AR10 mag, but you
lose 2 rounds to capacity.

284 Win / My SA284 / My even shorter 284 ELF

Thank you. That was the answer I wanted!!!
The important thing is to set the "length of the base" and the "position of the shoulder" to be equal to 7-08rem.
Can you recommend the AR10 magazine you used? Some people reported that the increased diameter of the brass base makes the bullet a little stiff when feeding the bullet to the magazine, making it difficult to fit.

 

[KANEDA SHON]

Take the 284 Winchester and shorten it to the same length
as the .308 and 7/08 class of cases. My SA284 has 3.5 grains
of powder over the 7/08. You would run a much shorter throat
then my single shots but I just achieved 2804 fps with the Hornady
190 gr A-tip. This case works in a conventional AR10 mag, but you
lose 2 rounds to capacity.

284 Win / My SA284 / My even shorter 284 ELF

"I just achieved 2804 fps with the Hornady 190 gr A-tip"
Could you tell me the length of the barrel used at this time? Is it 24 inches?

 

[Fuj]

Thank you. That was the answer I wanted!!!
The important thing is to set the "length of the base" and the "position of the shoulder" to be equal to 7-08rem.
Can you recommend the AR10 magazine you used? Some people reported that the increased diameter of the brass base makes the bullet a little stiff when feeding the bullet to the magazine, making it difficult to fit.

Magazine was an early steel Armalite. Initial test were when I was
catting the Schmidt and Reuben case the dropped it in favor of a
284 Winchester case. Empty cases stacked just fine.

 

[Fuj]

"I just achieved 2804 fps with the Hornady 190 gr A-tip"
Could you tell me the length of the barrel used at this time? Is it 24 inches?

It's my Savage actioned target rifle with a 30" Brux, I shoot
matches with.

 

[6bra1k]

or just do some more research. there use to be a company in colorado(?) that did large format ar's. 300 wsm 30'06 300wm.
you may not have to reinvent the wheel..just buy a rifle.

 

[dk17hmr]

Several companies have made WSM AR10s maybe one of their mags will work?

I have a win 88 and the magazine over all length is a problem with fancy new bullets. Barnes TSX fit decently at 2.800

 

[Coyotefurharvester]

AR 10 7Saum was marketed for while,thought about building one to go with my bolt gun. Have a case of factory 160 partition ammo I could start with.

 

[Louisiana Shooter]

^ this. There's a mag bolt head for AR-10 for this purpose.

 

[Fuj]

Alright, and my thoughts.....A quick search with no digging shows
a company called KAK. Looks like you can get complete magnum
bolt groups. From that point, and I like playing with 7mm's, I'd do
a hard look at the 7-PRC.

 

[KANEDA SHON]

좋아, 그리고 내 생각은 ..... 파기 쇼없이 빠른 검색
KAK라는 회사입니다. 완전한 매그넘을 얻을 수 있을 것 같습니다
볼트 그룹. 그 시점부터 저는 7mm로 노는 것을 좋아합니다.
7-PRC를 열심히 살펴보세요.

yea, I also recently heard about the reputation of 7-300prc.
Thanks to lower recoil and higher ballistics, if you set 500 yards to zero, you can fire up to 650 yards with only 15 inches of adjustment without adjusting the turret. Since 300prc can be used only by replacing the total heat, I think the next rifle I will make will be 300prc rifle with a 26 inch barrel length with a high probability.

 

[mac86951]

COL would be the issue for sure. 7 Saum would be a better choice, you can choose almost any 7mm and load under the 2.825 (2.800 realistic) mag length.

Yup, if feeds from a 308 mag; but a little adjustment to the follower and feed lips and it feeds even better.

-Mac

 

[KANEDA SHON]

COL would be the issue for sure. 7 Saum would be a better choice, you can choose almost any 7mm and load under the 2.825 (2.800 realistic) mag length.

Yup, if feeds from a 308 mag; but a little adjustment to the follower and feed lips and it feeds even better.

-Mac

I see. After hearing the advice of the people here, I think I've decided to make AR10 based on 7-300wsm or 7mm SAUM. Could you tell me the 7mm SAUM conversion kit that you recommend? I would choose this if I could use 7mm SAUM (or 7-300WSM) on AR10 by exchanging only bolt head, bolt, barrel and magazine.

 

[mac86951]

I see. After hearing the advice of the people here, I think I've decided to make AR10 based on 7-300wsm or 7mm SAUM. Could you tell me the 7mm SAUM conversion kit that you recommend? I would choose this if I could use 7mm SAUM (or 7-300WSM) on AR10 by exchanging only bolt head, bolt, barrel and magazine.

I've got a lot of recommendations, some of those may actually be good ideas too!

In my experience the KAK bolts are garbage; but the dual ejector idea is of interest. So let me start with an assumption of your knowledge and a disclaimer. AR-10 means Armalite, not DPMS LR-308/Knights SR-25; parts interchangeable nature and determination is up to you!

I've built a LR-7Saum, and these are my experiences from my rifle. I've seen an Armalite done similarly and experiences match.


Person to talk with! Carl at Accuracy Systems Inc in Byers CO. Tell him Mac sent you. I don't get a discount, but he'll know how to correct what I've stated wrong.


AR differences from 308:
Bolt change, KAK offers one, I've heard bad things; but if they're headspaced right maybe they're ok. I have an old surplus mil-spec one from the 300SAUM experiment days. Maybe KAK is good, i like the dual ejector idea. A bushed bolt and matching firing pin would be a great idea. As would extra extractors.


Barrel, and barrel extension. Naturally modified to fit the fat case and chamber. I'd recommend minimum rifle length +2" on gas tube. Twist rate:. Get something reasonable. Seriously 190s going 3000+fps from an AR? I can do 162s at 2950fps from a 24" without issue. Berger 180vld from a 24 at 2700s is really pushing it from the AR.

By all means get an adjustable gas block. JP rifles or equivalent.

Upper receiver ejection port; kiss the dust cover good bye; port gets opened to clear brass

Other than that, the AR functions with 308 components. I picked up a hydraulic buffer and when combined with muzzle break, it's a light recoiling rifle with a massive BANG.

308 mags are picky, some will feed, some.need feed lips modified, some need the mag insert modified as well.

I found the CRC metal mags to work well, using a 20rd 308 for 5 rounds of 7mm (it would hold more, but why? I don't make that much $).

Factory ammo will almost always pierce primers, and when that happens the primer piece that is missing will find it's way under the extractor and break it, or jam up the FCG making a click no bang failure.

If you know your 10's well; then tuning it is a separate process and one worthy of a good shooter.

 

[mac86951]

I've got a lot of recommendations, some of those may actually be good ideas too!

In my experience the KAK bolts are garbage; but the dual ejector idea is of interest. So let me start with an assumption of your knowledge and a disclaimer. AR-10 means Armalite, not DPMS LR-308/Knights SR-25; parts interchangeable nature and determination is up to you!

I've built a LR-7Saum, and these are my experiences from my rifle. I've seen an Armalite done similarly and experiences match.


Person to talk with! Carl at Accuracy Systems Inc in Byers CO. Tell him Mac sent you. I don't get a discount, but he'll know how to correct what I've stated wrong.


AR differences from 308:
Bolt change, KAK offers one, I've heard bad things; but if they're headspaced right maybe they're ok. I have an old surplus mil-spec one from the 300SAUM experiment days. Maybe KAK is good, i like the dual ejector idea. A bushed bolt and matching firing pin would be a great idea. As would extra extractors.


Barrel, and barrel extension. Naturally modified to fit the fat case and chamber. I'd recommend minimum rifle length +2" on gas tube. Twist rate:. Get something reasonable. Seriously 190s going 3000+fps from an AR? I can do 162s at 2950fps from a 24" without issue. Berger 180vld from a 24 at 2700s is really pushing it from the AR.

By all means get an adjustable gas block. JP rifles or equivalent.

Upper receiver ejection port; kiss the dust cover good bye; port gets opened to clear brass

Other than that, the AR functions with 308 components. I picked up a hydraulic buffer and when combined with muzzle break, it's a light recoiling rifle with a massive BANG.

308 mags are picky, some will feed, some.need feed lips modified, some need the mag insert modified as well.

I found the CRC metal mags to work well, using a 20rd 308 for 5 rounds of 7mm (it would hold more, but why? I don't make that much $).

Factory ammo will almost always pierce primers, and when that happens the primer piece that is missing will find it's way under the extractor and break it, or jam up the FCG making a click no bang failure.

If you know your 10's well; then tuning it is a separate process and one worthy of a good shooter.

Let's see if this posts. 100y 5-shot group in 90+ weather.

Edit:. Just lased the distance, 100m if it matters.