Ar10 300wsm

[FCS]

Point being that you can add a lot of gas tube length, the delay in unlocking is going to have minimal effect.

Correctly designed gas system length, properly sized port, proper buffer spring K value, proper buffer weight and understanding that you'll only get to run a very narrow range of bullet weights.

How long are you planning on barrel being?
Planning to run suppressed or unsuppressed?

 

[Jakediesel06]

Atleast 26” and unfortunately I can’t get a suppressor where I live

 

[FCS]

My reasons were
1. sounds like you cant reap the full benefits of the wsm before you run into over pressure. Not so much from over pressure but timing of the system with that much gas volume. a custom barrel with +2 gas system might be much more beneficial.
2. the WSM is .075" longer case than the SAUM and its hard to fit in and AR10 mag or is severely bullet limited.

I dont believe the 300 SAUM is even really around anymore so its not much of an option any longer.
The KAK uppers come with the ejection port enlarged already.

Plenty easy to get 300 SAUM brass, you'll have to reload for AR gas gun in short magnum to make it work so factory ammo is bit of a moot point IMHO.

 

[FCS]

Atleast 26” and unfortunately I can’t get a suppressor where I live

I probably wouldn't go over 22", would run +2" gas if not +3" gas. Dwell time works against you pretty heavily given the burn rate and powder charge. You won't be losing much velocity.
Don't look at bolt gun velocities, you will be slower in an AR when rifle actually reliably cycles, shoots accurately and brass lasts past a single use.

 

[FCS]

What bullet are you looking to use?

 

[Jakediesel06]

What bullet are you looking to use?

Haven’t got that far yet

 

[Jakediesel06]

I probably wouldn't go over 22", would run +2" gas if not +3" gas. Dwell time works against you pretty heavily given the burn rate and powder charge. You won't be losing much velocity.
Don't look at bolt gun velocities, you will be slower in an AR when rifle actually reliably cycles, shoots accurately and brass lasts past a single use.

Wanted to go longer to help gas system. Dwell time as in the time the bullet is on barrel?

 

[FCS]

Dwell time as in time bullet is still in bore of barrel past gas port, this dictates the gas impulse into gas key that unlocks bolt and cycles BCG.

Bullet is the first thing you need to be looking at, IMHO.

 

[Jakediesel06]

Plenty easy to get 300 SAUM brass, you'll have to reload for AR gas gun in short magnum to make it work so factory ammo is bit of a moot point IMHO.

I am leaning toward the 300saum because it seems to most feasible. Why is that? Would like to have the ability to go to the store and buy ammo and not have to relie on reloads alone

 

[Jakediesel06]

Dwell time as in time bullet is still in bore of barrel past gas port, this dictates the gas impulse into gas key that unlocks bolt and cycles BCG.

Bullet is the first thing you need to be looking at, IMHO.

Guessing because I’ll be limited on what I can use. Not saying it the right way just in past building I built rifle and found what it shot best. I realize this would be the most complicated build by far if I go forward with it

 

[FCS]

I am leaning toward the 300saum because it seems to most feasible. Why is that? Would like to have the ability to go to the store and buy ammo and not have to relie on reloads alone

Burn rate of powder used in factory ammo is not going to be well matched to an AR in a short magnum configuration. Typically, most factory ammo is a case full of the slowest burning ball powder that will work. "Match" ammo is an exception but there isn't much match ammo in 300 WSM / SAUM / RCM.

AR in short magnum is going to be a fairly special, needs very specific ammo to work much less work well / give sub MOA accuracy.

 

[RyanScott]

There are factory guns in 300WM, 30-06 or 300NM. You’d be better off buying something with a warranty.

 

[FCS]

Guessing because I’ll be limited on what I can use. Not saying it the right way just in past building I built rifle and found what it shot best. I realize this would be the most complicated build by far if I go forward with it

Pick bullet you want to use.
Determine cartridge that will give you desired velocity.
Determine magazine system that will allow needed OAL (you are mag limited on this project)
Determine receiver needed that will utilize magazine system (you are receiver limited on this project)
Determine port location and size (start small, you can always open up port)
Have reamer ground
Build rifle and project really gets started, especially with a short magnum AR.

You'll want a heavier than normal buffer, definitely going to want a full rifle buffer not a CAR buffer.
You'll want a heavier spring K.
Magazines are going to be a PITA.

IF you love tinkering, putzing then you'll really enjoy building up a WSM / SAUM AR.
Do you have access to machine tools? Buddy with a machine shop? If not, start making friends!

Not saying project should be abandoned but you'll want to go into this with your eyes open. There is a reason that you don't see WSM / SAUM ARs. Many have trouble shooting a 308 AR well, that is compounded appreciably going to a WSM / SAUM.

 

[Jakediesel06]

There are factory guns in 300WM, 30-06 or 300NM. You’d be better off buying something with a warranty.

Something I’m considering for sure. I like the Nemo watchman. Wish is was available in 300prc

 

[Jakediesel06]

Pick bullet you want to use.
Determine cartridge that will give you desired velocity.
Determine magazine system that will allow needed OAL (you are mag limited on this project)
Determine receiver needed that will utilize magazine system (you are receiver limited on this project)
Determine port location and size (start small, you can always open up port)
Have reamer ground
Build rifle and project really gets started, especially with a short magnum AR.

You'll want a heavier than normal buffer, definitely going to want a full rifle buffer not a CAR buffer.
You'll want a heavier spring K.
Magazines are going to be a PITA.

IF you love tinkering, putzing then you'll really enjoy building up a WSM / SAUM AR.
Do you have access to machine tools? Buddy with a machine shop? If not, start making friends!

Not saying project should be abandoned but you'll want to go into this with your eyes open. There is a reason that you don't see WSM / SAUM ARs. Many have trouble shooting a 308 AR well, that is compounded appreciably going to a WSM / SAUM.

Exactly what I’m trying to do. Finding out I’ll probably be in over my head but that’s how you learn. Also seeing if it would be worth it in the end finding more and more variables in every step.

 

[RyanScott]

Call them and see if they can/will do PRC. I suspect the mags aren’t long enough but maybe.

 

[FCS]

Exactly what I’m trying to do. Finding out I’ll probably be in over my head but that’s how you learn. Also seeing if it would be worth it in the end finding more and more variables in every step.

End goal being?

What is a 300 WSM AR giving you that a 6.5 Creed or 260 AR isn't?
More energy on target with 300WSM but ballistics will be similar using 6.5mm bullet.
Do you really need more energy on target?

 

[Earnhardt]

The easiest way to determine what the end result for your 300 wsm Ar will be/can be, is to use Quick Load.

The determining factor for your build is a ~2.8” COAL. Due to mag length
And with a 300 wsm you are fairly limited to the types/weights of bullets you can use.

Get 10 pieces of brass. New/once fired, and set up dummy rounds with the bullets you want to use.
You can use a Hornady Comparator and set up Those dummy rounds

$153 for QuickLoads can save you a lot of money in the long run

 

[FCS]

The easiest way to determine what the end result for your 300 wsm Ar will be/can be, is to use Quick Load.

The determining factor for your build is a ~2.8” COAL. Due to mag length
And with a 300 wsm you are fairly limited to the types/weights of bullets you can use.

Get 10 pieces of brass. New/once fired, and set up dummy rounds with the bullets you want to use.
You can use a Hornady Comparator and set up Those dummy rounds

$153 for QuickLoads can save you a lot of money in the long run

Few more variables than QL accounts for in an AR setup. QL is nice tool, will give you a decent idea of possible velocity but not where rifle will run smoothly. AR must run smoothly, reliably to be accurate.

 

[kl7883]

kak has the bolt issue taken care of. i have one of their complete uppers in 300wsm. i just got the lower in a few days to finish the build. my kac magazines holds them nicely. i will at some point order a bartlein or kreiger barrel. for the money, you cannot beat the kak

 

[FCS]

kak has the bolt issue taken care of. i have one of their complete uppers in 300wsm. i just got the lower in a few days to finish the build. my kac magazines holds them nicely. i will at some point order a bartlein or kreiger barrel. for the money, you cannot beat the kak

What bullet are you planning on using?
How long is bbl?
Curious to learn powder / velocity that works best for accuracy, reliable cycling and brass life once you have this running.

 

[kl7883]

i am planning on running shelf ammo. i have a hundred or so norma cases if i want to roll my own with a 190gr matchking. the barrel is 19" yes i think that will definintly be a learning curve........a big one. i will use only a few different types of ammo to lessen muddying of the waters

 

[kl7883]

What bullet are you planning on using?
How long is bbl?
Curious to learn powder / velocity that works best for accuracy, reliable cycling and brass life once you have this running.

after reading all of your posts, i now see even further what you were saying. i may just jump right into reloading and go with 200-220 gr range to see if i can get it to run smoothly...

 

[Greg Langelius *]

Oddly enough; I'm encountering difficulties not unlike the 300WSM in an AR10, with such a lesser round as the 6.5 Grendel in the AR 15.

The commonalities suggest that the power of the cartridge is less a significant factor than the cartridge base diameter.

IMHO, something with a rebated rim, not too unlike the 6.5-284, could permit a beefier bolt face rim, allowing a stronger extractor shaft. I'm not so sure the straight .284 wouldn't be a successful approcach.

I broke an extractor in my 24" 6.5G, by exceeding published max by only a minuscule additional charge.

I surmise that the extra 4" of barrel over my 20" 6.5G prolonged dwell to a point that exceeded the extractor's stress limits. Both rifles use the same rifle length gas system.

I have replaced my extractor with the JP Enterprises 6.5 Grendel Improved extractor, and am now constraining further load development with the 24"barrel to bullets of under 100gr weight. Published max loads are, IMHO, a particularly critical issue with the 6.5G. In the event that this fails, I have a new 20" Barrel, Identical to the one on the 20" Upper that I alredy have; and that will be my final solution.

So, a rebated rim (as I just discovered exists with the 300WSM), an improved extractor ala the JP Enterprises 6.5G Improved version, a longer gas system, some constraint on overall barrel length, bullet weight constraint, maybe some propellant manipulation to reduce pressure spikes, and some advancement could possibly be achieved.

Greg

FCS, I finally got to read your posts, and they are very insightful. Anyone licks this, I'm betting on you.

 

[FCS]

Oddly enough; I'm encountering difficulties not unlike the 300WSM in an AR10, with such a lesser round as the 6.5 Grendel in the AR 15.

The commonalities suggest that the power of the cartridge is less a significant factor than the cartridge base diameter.

IMHO, something with a rebated rim, not too unlike the 6.5-284, could permit a beefier bolt face rim, allowing a stronger extractor shaft.

I broke an extractor in my 24" 6.5G, by exceeding published max by only a minuscule additional charge.

I surmise that the extra 4" of barrel over my 20" 6.5G prolonged dwell to a point that exceeded the extractor's stress limits. Both rifles use the same rifle length gas system.

So, a rebated rim (as I just discovered exists with the 30WSM), an improved extractor ala the JP Enterprises 6.5G Improved version, a longer gas system, some constraint on overall barrel length, bullet weight constraint, maybe some propellant manipulation to reduce pressure spikes, and some advancement could possibly be achieved.

Greg

I running a 0.480 rebated rim 300 WSM case, benefit of friend having a machine shop and Barnard in 6BR but wanted a 300 WSM bbl. Since he made form tool, programmed CNC I just had to supply him some brass so I could get 0.480 diameter head, 300 WSM brass.

Problems I’ve run into w/WSM are mainly related to burn rate / time - pressure history curve.
Running longer gas system,
IIRC, 3” longer than rifle.
300 WSM upper has been sitting in corner for a few years, might need to pull it out and see what it’ll do. I’ve learned a few things since I last tinkered with it.

6.5 Grendel is significantly easier.
I prefer 120 Nosler BT, 120 Amax / ELD-M, SMK, Scenar or Berger MATCH BT. 100 gr versions of above work really well also.
Greg - What powder in your 6.5 Grendel?
How heavy is buffer?
Springco spring or STAG factory spring?

 

[Khavic]

I know it is fun to tinker around and build your own stuff. I do it all the time, but for what you're looking to do why not just contact Noreen Firearms, and ask for a 300WSM? They already offer 30-06, 25-06, and 270 Win. I'd bet dollars to donuts they could probably turn one out for you.

 

[Jakediesel06]

I’ve thouht about that/thinking about that. Why I would lean toward 300wsm in ar10 is because of a more compact plateform.

 

[kl7883]

that is excellent feedback sir!!! much appreciated

 

[Vidar]

Bumping this thread for new info. I have a KAK 19" Upper inbound(I'm going to run it 100% suppressed) and I would like to see if there is any new info.

Anyone try shooting 215 bergers? I know I will have to stuff the bullet into the brass to get it to fit in a Larue mag. Or should I stick to 185gr?

Thanks All!

 

[Matthew488]

I know it's been awhile since last post on this thread. But I'll post here as I jumping down the rabbit hole and doing an Aero Precision M5 build in 7mm Sherman Short Tactical. I have most of my parts and barrel is probably 1-2 months out.
I'll post more as I get info.

 

[Cwballistics]

I know it's been awhile since last post on this thread. But I'll post here as I jumping down the rabbit hole and doing an Aero Precision M5 build in 7mm Sherman Short Tactical. I have most of my parts and barrel is probably 1-2 months out.
I'll post more as I get info.

Any chance yours came to fruition? I just built a 6.5sst on an aero and wondering how much to back off the initial charge. The only data out there is for bolt guns. I’m about to do a 6arc and seeing that they have 2 sets of published data, one for bolt and one for gas, got me wondering about starting charge weight for the sst. It seems to be a similar situation with this KAK magnum bolt.

Thanks

 

[wvfarrier]

Any chance yours came to fruition? I just built a 6.5sst on an aero and wondering how much to back off the initial charge. The only data out there is for bolt guns. I’m about to do a 6arc and seeing that they have 2 sets of published data, one for bolt and one for gas, got me wondering about starting charge weight for the sst. It seems to be a similar situation with this KAK magnum bolt.

Thanks

I ran factory ammo for my KAK 300wsm and chrono'd them. Then started building loads off that velocity and went from there. I settled on the Barnes 150 ttsx as it allowed me to seat a little further out and still maintain mag compatibility. I also had a load for the 130's but i felt it was too light for the wsm. The 165s shot really well but I couldnt seat them out as far as I wanted.

 

[tobylazur]

My reasons were
1. sounds like you cant reap the full benefits of the wsm before you run into over pressure. Not so much from over pressure but timing of the system with that much gas volume. a custom barrel with +2 gas system might be much more beneficial.
2. the WSM is .075" longer case than the SAUM and its hard to fit in and AR10 mag or is severely bullet limited.

I dont believe the 300 SAUM is even really around anymore so its not much of an option any longer.
The KAK uppers come with the ejection port enlarged already.

#1 is the reason I shyed away from it while I was researching it (I’ve just finished a wsm bolt gun, and was building an AR10 at the time)

 

[Top O' Texas]

My reasons were
1. sounds like you cant reap the full benefits of the wsm before you run into over pressure. Not so much from over pressure but timing of the system with that much gas volume. a custom barrel with +2 gas system might be much more beneficial.
2. the WSM is .075" longer case than the SAUM and its hard to fit in and AR10 mag or is severely bullet limited.

I dont believe the 300 SAUM is even really around anymore so its not much of an option any longer.
The KAK uppers come with the ejection port enlarged already.

I know this thread is from the way back machine, but this might shed some lite about short mags in an AR10 platform?

I've built a 6.5prc 22" +2 gas (haven't shot it yet) 8 twist. I went 8 twist due to bullet weight limits due to needing more oal. Most are 135gr and under, but Lapua 144fmj is just right! Mags in most cases are limiting to 2.800", but m118 mags gets you 2.830-2.845". The worst thing is the feed ramps are double feed and the cartridge sits in the middle due to diameter and would best be served as a single feed. Accuracy Systems sells many short mag uppers and should be of help on mags for them? I also have a 7saum in an AR10 platform (28" +2gas 9 twist). +2 puts port @ 14.7". If you want a specific tube length go to White Oak Armory. Virginia Arsenal (might be closed for business) produced 6.5wsm which would have higher pressure and higher gas volume being in a smaller bore (with same powder and weight used). With bolt push back due to (supposedly higher pressure and maybe gas volume) could benefit from a higher spring pressure and a heavier buffer if the gas port size and location isn't ideal. Going off H&S recommendations about feed lips per cartridge is where I'm going to start on feeding possible issues. KAK is the only place I've been able to find bolts for short mag cartridges and enlarged ejection ports (enlarged the height from bottom of port down as to be able to used the ejection door for closure (length remains the same). As mention before on 30cal cartridges I think the 300rcm (6.5prc based) and 300saum would be more ideal even though velocity is less than the wsm cartridges. The 7saum can be used (not ideally though) up to 185's with Nosler's rdf @ 2.825" using m118 mags. I'll test the cartridges when I get the go/no-go's in to make sure headspace is correct.

 

[Top O' Texas]

Gas expands at 5000fps, you could coil the gas tube around the 25 yard line and barely slow it down.

Don't let bullet velocity be confused with gas expansion inside the case as it will expand faster when it explodes (controlled explosion) in milliseconds.

 

[Top O' Texas]

I probably wouldn't go over 22", would run +2" gas if not +3" gas. Dwell time works against you pretty heavily given the burn rate and powder charge. You won't be losing much velocity.
Don't look at bolt gun velocities, you will be slower in an AR when rifle actually reliably cycles, shoots accurately and brass lasts past a single use.

So true! That's part of the reason 6.5creeds in gas guns went to the + gas......................well not entirely! Aero Precision makes a standard rifle length gas system that works extremely well (I have 2 barrels from them). I also have barrels from 3 other mfg's with standard gas length that over pressures and pops primers badly along with 2 other mfg's that use +2 (proof being 1) that has the same issue of being over gassed. AP has the gas port a best sized for non-adjustable gas blocks using standard weight springs and buffers.

 

[Grendelman]

Hello, I'm new here and was looking for some insight on building a .300WSM on a AR-10 platform including a 22" Deadshot barrel, magnum length gas system (14in), 1:10 twist, an adjustable gas block and between 160-180gr weight projectile also including a PRS Gen 3 butt stock. I would like to ask if anyone could give me a good buffer weight to start with? Thank you.

 

[Top O' Texas]

Hello, I'm new here and was looking for some insight on building a .300WSM on a AR-10 platform including a 22" Deadshot barrel, magnum length gas system (14in), 1:10 twist, an adjustable gas block and between 160-180gr weight projectile also including a PRS Gen 3 butt stock. I would like to ask if anyone could give me a good buffer weight to start with? Thank you.

What I can tell you is limited? What is "magnum length" is there's a possibility it's a +2", but not any verification yet? Get LaRue mags for best oal of ~2.865" +/- .005". I have s 7saum snd 6.5prc in an AR10, but no developments yet or fired it to check recoil function. Check port size? I'm checking on a few recoil setups (standard rifle, A5 and carbine) as not knowing how mubuffer will be needed? I'm on a few forums gathering info from others that do have short mags and wssm's.

 

[Top O' Texas]

The 1 thing you might want to do is figure out what bullet you want to use, make 3 dummy rounds and send them in along with the bolt for headspacing. Tell them what/how much "lead/throat" you want. The upper will need an enlarged ejection port. KAK uppers aren't that great. If you're good with a drimmel do the work yourself. If you don't plan on using the port cover you can enlarge part of the top and if so on using the cover only enlarge the bottom portion so the cover will catch.

 

[knuckleballz]

Hello, I'm new here and was looking for some insight on building a .300WSM on a AR-10 platform including a 22" Deadshot barrel, magnum length gas system (14in), 1:10 twist, an adjustable gas block and between 160-180gr weight projectile also including a PRS Gen 3 butt stock. I would like to ask if anyone could give me a good buffer weight to start with? Thank you.

Get a JP heavy buffer with the different springs. Buy an extra tungsten weight and run all 3 tungsten weights and the strongest spring. Also consider running an adjustable gas key on your bolt carrier for better gas adjustment. The adjustment is too course on SLR gas blocks between clicks for magnum cartridges.

 

[sinister]

I would like to ask if anyone could give me a good buffer weight to start with? Thank you.

An XH Heavy Buffer plus a Tubb Carrier Weight System.

 

[Grendelman]

I wasn't going to use the KAK upper do to it's bad reviews and I would rather use and mod my own upper so I can get the port door oppening just right but I was going to use a KAK Bolt that will match the barrel I'm going to use. As for the Magnum gas length is where the barrel gas port is 14 inches up on the barrle. I have no idea what +2 or +3 means in that regard. I'm in the midle of building a .308 now with a 1:10 twist and I'm hoping that will help me figure out what bullet weghts work best with that twist. I'm not a reloader but I have been wanting to get into it. I have read a lot of threads on that as well and I do thank you for the info you have given me.

 

[Grendelman]

Get a JP heavy buffer with the different springs. Buy an extra tungsten weight and run all 3 tungsten weights and the strongest spring. Also consider running an adjustable gas key on your bolt carrier for better gas adjustment. The adjustment is too course on SLR gas blocks between clicks for magnum cartridges.

Thank you. I will look into all of that.

 

[Grendelman]

An XH Heavy Buffer plus a Tubb Carrier Weight System.

What is a Tubb Carrier Weight System?

 

[Top O' Texas]

I wasn't going to use the KAK upper do to it's bad reviews and I would rather use and mod my own upper so I can get the port door oppening just right but I was going to use a KAK Bolt that will match the barrel I'm going to use. As for the Magnum gas length is where the barrel gas port is 14 inches up on the barrle. I have no idea what +2 or +3 means in that regard. I'm in the midle of building a .308 now with a 1:10 twist and I'm hoping that will help me figure out what bullet weghts work best with that twist. I'm not a reloader but I have been wanting to get into it. I have read a lot of threads on that as well and I do thank you for the info you have given me.

The +2 is 2" longer than standard rifle length gas system (12.7" + 2) for 14 7". The 22" 6.5prc I have is with the +2 so it gets the gas port closer to the muzzle in hopes/helping reduce gas pressure to the bcg without increasing buffer weight?

 

[Top O' Texas]

What is a Tubb Carrier Weight System?

The "CWS" is a 3 weight system you install at the rear of the bcg. Consist of a sleeve/bushing and 2 internal weights (fit inside the sleeve/bushing). Combo willbe, sleeve/bushing only ir with 1 of the 2 weights.

 

[Grendelman]

The +2 is 2" longer than standard rifle length gas system (12.7" + 2) for 14 7". The 22" 6.5prc I have is with the +2 so it gets the gas port closer to the muzzle in hopes/helping reduce gas pressure to the bcg without increasing buffer weight?

 

[Grendelman]

Thank you, that helps a lot. I asume that means mine will be a +2. This will be my second AR-10. First one is a .308 and I'm still waiting for the last few peices to come in today. I'm sure I'll learn a lot as I go and thank you again for all the helpful info.

 

[Top O' Texas]

Thank you, that helps a lot. I asume that means mine will be a +2. This will be my second AR-10. First one is a .308 and I'm still waiting for the last few peices to come in today. I'm sure I'll learn a lot as I go and thank you again for all the helpful info.

KAK states "magnum length" on their 300wsm complete uppers, but unsure if their's are a +2? 19" barrel with a possibility of 14-14.7" gas system?

 

[Top O' Texas]

Thank you, that helps a lot. I asume that means mine will be a +2. This will be my second AR-10. First one is a .308 and I'm still waiting for the last few peices to come in today. I'm sure I'll learn a lot as I go and thank you again for all the helpful info.

From reading (from other forums) about people having cycling issues with rifle length gas on 308's it all came down to gas port size. Check port size as with some variances it should still work fine.