Modern Sporter - Build Discussions

Depending on which brand of dies you are using, your FL dies may actually be small base. Dillon for example are a small base die, but are labeled as full length.

Neck sizing for a semi auto is a definetly not a recommended procedure, and will cause issues..
 
What's the deal with bolt failure and the 6.5grendel? Lots on conflicting info on the net, some say you gotta replace the bolt every 5000 rounds and to only use certain manufacturers. I definitely don't want to risk blowing up anything.
 
play.soccer said:
What's the deal with bolt failure and the 6.5grendel? Lots on conflicting info on the net, some say you gotta replace the bolt every 5000 rounds and to only use certain manufacturers. I definitely don't want to risk blowing up anything.
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The bolt face on the 7.62x39 or 6.5 Grendel bolt is opened up considerably from what a 223 has. Meaning material is removed to very close to the edge of the locking lugs. On "some" bolt brands AKA the cheap crap ones some of the 7.62x39 rifles employ the bolt heads crack and fail around the recoil lugs. This is one of the reasons we have not offered 7.62x39 in the past. The Grendel uses the same bolt head, but assuming one uses a high quality bolt head there does not seem to be a problem.
So far we have several thousand rounds out of the 6.5 Grendel we have been shooting PRS matches with as well as hunting with and no issues at all, but it is a JP bolt.

I have ordered a Brownell's bolt assembly for 1 of my own builds as it is cost effective, but don't have any rounds down range on it yet.
 
Well I’m in for the 2nd production run!! I just sent in my deposit. I’m new this this, so I stuck with the default options during the ordering process, but I couldn’t be more excited! Summer can’t come soon enough. Looking forward to browsing through everyone’s build ideas to help me navigate my own build. It’s defin going to be a learning process.

Hats off to ATRS for their outstanding customer service, and updates. It has a lot to do with my decision to purchase, not to discount the crazy hype these Modern Sporters are generating.

Cheers everyone!
 
alberta tactical rifle said:
The bolt face on the 7.62x39 or 6.5 Grendel bolt is opened up considerably from what a 223 has. Meaning material is removed to very close to the edge of the locking lugs. On "some" bolt brands AKA the cheap crap ones some of the 7.62x39 rifles employ the bolt heads crack and fail around the recoil lugs. This is one of the reasons we have not offered 7.62x39 in the past. The Grendel uses the same bolt head, but assuming one uses a high quality bolt head there does not seem to be a problem.
So far we have several thousand rounds out of the 6.5 Grendel we have been shooting PRS matches with as well as hunting with and no issues at all, but it is a JP bolt.

I have ordered a Brownell's bolt assembly for 1 of my own builds as it is cost effective, but don't have any rounds down range on it yet.
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Bolt face depths on the Grendel vs 7.62 are slightly different aren’t they? Which would cause head space issues if used interchangeably (potentially)... otherwise the bolts are identical?

Would be a perfect world to have a 223, 7.62 and 6.5 all rolled into one firearm.
3 uppers, with 2 interchanging bolts... but I’m thinking this is unlikely because of the above (if memory serves from prior reading on the 2 bolt differences)
 
koesdibyo said:
Bolt face depths on the Grendel vs 7.62 are slightly different aren’t they? Which would cause head space issues if used interchangeably (potentially)... otherwise the bolts are identical?

Would be a perfect world to have a 223, 7.62 and 6.5 all rolled into one firearm.
3 uppers, with 2 interchanging bolts... but I’m thinking this is unlikely because of the above (if memory serves from prior reading on the 2 bolt differences)
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I dont think there is any headspace difference on the grendel or 7.62 as the grendel is from the 6ppc or 220 russian and the 220 is a necked down 7.62. The 6.8 spc and 224 valk are from the 30 remington. That's why JP offers a grendel and a 6.8 spc/valk bolt
 
koesdibyo said:
Bolt face depths on the Grendel vs 7.62 are slightly different aren’t they? Which would cause head space issues if used interchangeably (potentially)... otherwise the bolts are identical?

Would be a perfect world to have a 223, 7.62 and 6.5 all rolled into one firearm.
3 uppers, with 2 interchanging bolts... but I’m thinking this is unlikely because of the above (if memory serves from prior reading on the 2 bolt differences)
Click to expand...

If I recall yes, the 7.62x39 has a different depth to the bolt face, and that if I'm not mistaken (which is entirely possible cause I haven't read up on this in a couple of years) but if I'm not mistaken that's the big difference from 6.5 Grendel type I and type II. Type I used a 7.62x39 bolt where as type II got it's own bolt face which required adjusting the headspacing on the chamber.

Personally, if you're going that far into it. I'd get a seperate bolt carrier group for each upper, seperate charging handle. Then it's just swap a complete upper on (literally takes under 3 seconds) and away you go.
 
play.soccer said:
Seems like one should buy a barrel/bolt combo that's been headspace from the factory.
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THAT certainly is the best way to go. We have seen several thou difference in headspace with generic barrel/bolt set ups. In theory any bolt should headspace correctly with any barrel, but in the real world there are tolerance differences. Even different gages will result in differing headspace factors.
Best plan is to cut the chamber and employ the bolt that is going to be used in that rifle, this reduces any possibility of too much or too little headspace.
 
ATRS Shaun said:
If I recall yes, the 7.62x39 has a different depth to the bolt face, and that if I'm not mistaken (which is entirely possible cause I haven't read up on this in a couple of years) but if I'm not mistaken that's the big difference from 6.5 Grendel type I and type II. Type I used a 7.62x39 bolt where as type II got it's own bolt face which required adjusting the headspacing on the chamber.

Personally, if you're going that far into it. I'd get a seperate bolt carrier group for each upper, seperate charging handle. Then it's just swap a complete upper on (literally takes under 3 seconds) and away you go.
Click to expand...


A proper Alexander Arms bolt has a 0.136" recess. A 7.62x39 bolt has a 0.125" recess. Bill Alexander did this specifically so that the cheap (and prone to failure) 7.62x39 bolts at the time could not be used in his rifles. I'm sure he also did it to sell more bolts when he released the 6.5 Grendel commercially.

Type 1 vs Type 2 Grendel bolts are because of Les Baer. Here is a better than I can do explanation, copied from elsewhere on the internet.

6.5 GRENDEL: TYPE I VS. TYPE II

I get a lot of questions by clients on difference between 6.5 Grendel Type I and Type II, so I've decided to jot down major points. The difference is in head spacing!

The original Grendel, and what we now call Type II 6.5 Grendel, was designed to be used with a Grendel bolt, or.136 head spacing.

The patent was never released and to avoid any legal litigations, Les Baer Custom had adjusted 6.5 Grendel design of the barrel to make it .125 head spacing. We are now call it Type I Grendel. LBC has .295 diameter neck while Grendel has .300 diameter neck.LBC has a straight taper in the throat while Grendel has a compound taper.

The beauty is, LBC designed the .264 LBC cartridge to be completely compatible with a 6.5 Grendel. It also take 7.62x39 standard bolt, which in the long run gives a client greater flexibility to interchange their barrels on AR-15 platform while keeping the costs down.

Hope it answers some questions on a basic level. You decide which type of Grendel is right for you!
 
I was hoping for some help. I’ve never built a rifle before. I have flipped through every page of this thread, but still have a lot of questions bouncing around my head. There are a lot of abbreviations used for parts ordered and manufacturers- I literally have no idea what you’re all talking about :).

I was hoping someone could provide a list of parts and tools needed to complete a build for the Modern Sporter. Just a general “barrel, trigger, hand guard, safety, springy thingy for the whatsamacallit, etc”. It would great to have a checklist I could reference when ordering parts to ensure I have everything needed for the final build. Also, if there are any particular tools needed as well.

Thanks in advance!
 
quikcolin said:
I was hoping for some help. I’ve never built a rifle before. I have flipped through every page of this thread, but still have a lot of questions bouncing around my head. There are a lot of abbreviations used for parts ordered and manufacturers- I literally have no idea what you’re all talking about :).

I was hoping someone could provide a list of parts and tools needed to complete a build for the Modern Sporter. Just a general “barrel, trigger, hand guard, safety, springy thingy for the whatsamacallit, etc”. It would great to have a checklist I could reference when ordering parts to ensure I have everything needed for the final build. Also, if there are any particular tools needed as well.

Thanks in advance!
Click to expand...

What I use;

Vise
1/2” Torque wrench
Wheeler torque wrench
Roll pin punches
Reaction rod
Brass hammer
Armorer’s wrench
Barrel nut wrench (sometimes they come with your handguard)
Grease for barrel nut
Oil
Pliers
Tape
Loctite 243

Parts;

Lower parts kit
Handguard
Gas block
Gas tube
Stock
Receiver extension
Receiver extension castle nut
Stock
Buffer and spring
Barrel
Dust cover (I don’t believe it’s included)
Bolt carrier group
Optic
Optic mount
Flash hider/muzzle brake
Shims/crush washer for FH/MB.
 
griffin86 said:
What I use;

Vise
1/2” Torque wrench
Wheeler torque wrench
Roll pin punches
Reaction rod
Brass hammer
Armorer’s wrench
Barrel nut wrench (sometimes they come with your handguard)
Grease for barrel nut
Oil
Pliers
Tape
Loctite 243

Parts;

Lower parts kit
Handguard
Gas block
Gas tube
Stock
Receiver extension
Receiver extension castle nut
Stock
Buffer and spring
Barrel
Dust cover (I don’t believe it’s included)
Bolt carrier group
Optic
Optic mount
Flash hider/muzzle brake
Shims/crush washer for FH/MB.
Click to expand...

A good list, I would also add to that that a few points

- Receiver extension is commonly referred to as a buffer tube. Of which there are 3 common varieties, rifle length (fits A2 stocks, magpul PRS, generally the longer stocks), ad then for collapsibles you have mil spec or commercial which is simply a difference of diameter. Neither is better than the other, however you need to match the stock you purchase to the buffer tube (receiver extension) you purchase. Both commercial, or both milspec.

-If using a rifle length buffer tube, you don't need the castle nut. If using a collapsible you need a castle nut AND a receiver end plate.

- dust cover (ejection port cover) is not included. I suggest the strike industries ones, as they are easier to install, and bigger then that, they don't damage the finish.



note: We have syringes of the molybdenum barrel nut grease (MIL-G-21164D) available for sale $20 each. Much cleaner method of application and little to no waste at all. A 1/4 oz (or 7 mL volume) of grease is enough to build I would venture 8-10 rifles.
 
ATRS Shaun said:
A good list, I would also add to that that a few points

- Receiver extension is commonly referred to as a buffer tube. Of which there are 3 common varieties, rifle length (fits A2 stocks, magpul PRS, generally the longer stocks), ad then for collapsibles you have mil spec or commercial which is simply a difference of diameter. Neither is better than the other, however you need to match the stock you purchase to the buffer tube (receiver extension) you purchase. Both commercial, or both milspec.

-If using a rifle length buffer tube, you don't need the castle nut. If using a collapsible you need a castle nut AND a receiver end plate.

- dust cover (ejection port cover) is not included. I suggest the strike industries ones, as they are easier to install, and bigger then that, they don't damage the finish.



note: We have syringes of the molybdenum barrel nut grease (MIL-G-21164D) available for sale $20 each. Much cleaner method of application and little to no waste at all. A 1/4 oz (or 7 mL volume) of grease is enough to build I would venture 8-10 rifles.
Click to expand...

Thanks Griffin and Shaun.

Shaun, I’ve noticed you guys carry many of the parts I would want on my Modern Sporter. Do you offer assembly? If I ordered a handful parts when my upper and lower are ready, could you install them? The remaining few parts I could do on my own...
 
ATRS Shaun said:
A good list, I would also add to that that a few points

- Receiver extension is commonly referred to as a buffer tube. Of which there are 3 common varieties, rifle length (fits A2 stocks, magpul PRS, generally the longer stocks), ad then for collapsibles you have mil spec or commercial which is simply a difference of diameter. Neither is better than the other, however you need to match the stock you purchase to the buffer tube (receiver extension) you purchase. Both commercial, or both milspec.

-If using a rifle length buffer tube, you don't need the castle nut. If using a collapsible you need a castle nut AND a receiver end plate.

- dust cover (ejection port cover) is not included. I suggest the strike industries ones, as they are easier to install, and bigger then that, they don't damage the finish.



note: We have syringes of the molybdenum barrel nut grease (MIL-G-21164D) available for sale $20 each. Much cleaner method of application and little to no waste at all. A 1/4 oz (or 7 mL volume) of grease is enough to build I would venture 8-10 rifles.
Click to expand...

Are you able to source the strike industries ejection port cover for us and have them ship with out receiver sets?
 
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