6.8 spc or .300 ham'r?

[Beck]

I’ve had a total of 4 7.62x39 barrels mounted in 2 different uppers and 3 different lowers and have never had a feed or ejection issue in any of them. I’m mean not a single malfunction ever. I have far more troubles getting 223 uppers to work cycle and eject. The only mags I use are 10 round C products mags. For the purpose I use them for 10 rounds is plenty for me. No desire for a bigger one.

Guess I'm late to the party. LOL
I've got 6 ARs chambered in 6.8 and 5 ARs chambered in x39(I'm retired and like to build stuff.) All of them run flawlessly. I mostly use 10 round ASC mags. I reload for all of them. I've thought about building a 300 HAM'R, but one of my x39 AR's has a .308 bore, so I get to use all the .308 bullets for it. I don't think the 300 HAM'R could touch that one. So I feel like it might be a step backward for me to get the HAM'R.

I never knew the x39 could be so accurate till I built an AR chambered in one.
The 6.8 isn't dead. Just about everybody who wanted one has at least one, or 6. LOL

There it is... you two are proof it can be right !!!

 

[Phaedrus/69]

Ten rounds mags though? That's not many Freedom Pills!

 

[MISportsman]

Well, I won't fault anyone for considering safety issues first, but I've never heard of an AR chambered in x39 blowing up. It's not so much about hot rodding, but rather bringing the cartridge up to it's full potential. The SAAMI standard for x39 is anemic... just plain wrong. Can't put it in any clearer terms. SAAMI is different than Europe's C.I.P. in that SAAMI is voluntary/advisory, while C.I.P. is mandatory.

The C.I.P. countries that import and allow citizens to posses AR type firearms in 7.62x39 could not do so unless that firearm passes the more rigorous C.I.P. pressure testing in one of the many proof houses in Europe.

After it passes it is then stamped with the mark of the proof house it was tested in. The pressure threshold is far... and I mean FAR above SAAMI for 7.62x39 and many other cartridges. If an AR chambered in x39 is going blow to pieces it would be during C.I.P. pressure tests, but the reality is they don't blow up over there either. Jamming and feeding problems are a real thing in x39 ARs. Success or failure depends on one's knowledge and skills.



Yeah true, I've heard the horror stories... mostly feeding and cycling issues with x39 in the AR. On the other hand I've seen the success stories.

I would be happy with about any of the calibers mentioned in this thread. If/when a person might want to experiment with x39 in an AR, the failures and successes combined present a wealth of knowledge and guidance when selecting components for a successful build. There's a certain satisfaction in being part of an elite that has success, when the naysayers are standing around scratching their heads wondering how you did it, because they insisted it couldn't be done.

The issues with an AR x39 are primarily gas port, feed ramp, and magazine quality related, and easily remedied. Of course the guys who give up before they start are never gonna know the thrill of it all.

Oh by the way, I like the SKS. I remember seeing nice Yugos advertised in Shotgun News back in the day after I'd bought my Mini-30. I still kick myself for not buying one back when they didn't cost much more than a tank of gas for my Chevy Blazer.

I wish I could find some load data for x39 loads at its full potential. Even if I don't end up with an ar in it, my daughter has a cz 527 in x39 that I'm sure can handle more than factory loads

 

[WestKentucky]

I love my 6.8 but it’s no mythical deer laser. It’s silly accurate and very effective, but it has limited range and cases aren’t the most plentiful. Easy to find, but not likely going to pick them up at the DNR range every week.

HAMR is awesome by most accounts but it has its downsides too. Your in a AR15 mag well and that limits your overall length. Since you want a bullet length to be roughly 2.5 to 3 times its diameter that further limits you when looking at ballistics beyond 200 yards. In the 30 caliber range you really start hitting snags because your bullet needs to be at least 3/4 inch long. At least with 6.8 your looking at .65 inches and saving a little bit of case volume potential. Not much but a little.

With all of the options out there on the market now I still think 6.8 is one of the best for hunting. It’s a good combo of case size, bullet size, and there are decent bullets to be had in the right weight class. Options on 30 cal are there, but they tend to be on the heavy side which again limits range. I lean to 6.8 but I’m partial to it because I own one. I wouldn’t be opposed to HAMR but I’m not going to replace the 6.8 with it.

 

[someguy2800]

Ten rounds mags though? That's not many Freedom Pills!

I hear the 20 round mags work well. Most of the trouble you hear about seams to be the 30’s. When I go hunting with mine I take 2 10 round mags. 1 is more than enough but I figure I better take 2 in case I drop the first one in the swamp.

 

[greyling22]

I think we can all agree that while there are some differences, pros and cons, and all that, the x39, ham'r, grendel, 6.8spc, 277 wolverine, 25-45, 7mm tcu, etc are all adequate rounds, and all perform in the same ballpark.

 

[sevt_chevelle]

Another guy with a flawless x39 AR. Built to do something different and run cheap steal ammo.
I run nothing but duramags, 1-10 and about 15-30 round mags, nothing no problems.

Using a Satern barrel with a BCM thermal fit upper and this rifle shoots MOA and less.

 

[MISportsman]

For the question of the thread, I'm leaning towards the 6.8 spc for my build. There is so much more available now for it and it will definitely fit the bill for what I'm going to use it for. The .300 ham'r sounds sweet and I'm not ruling it out for a possible future build. However if bca drops the prices of their x39 uppers any more I might have to pick up one of them just for fun lol.

 

[Double Naught Spy]

I built a 6.5 grendel last summer, that's why I'm looking into the 2 cartridges I am

I would not normally choose the .300 Ham'r over the 6.8, BUT sense you already have a 6.5 Grendel, getting a 6.8 spc would really be far too much duplication of terminal performance at normal hunting distances (inside 200 yards) and so I would choose the .300 Ham'r (given the 2 choices you listed) to have something more different.

 

[BreechFace]

I would not normally choose the .300 Ham'r over the 6.8, BUT sense you already have a 6.5 Grendel, getting a 6.8 spc would really be far too much duplication of terminal performance at normal hunting distances (inside 200 yards) and so I would choose the .300 Ham'r (given the 2 choices you listed) to have something more different.

I must have missed where he had a 6.5 Grendel. I would agree with @Double Naught Spy, building a 6.8 SPC II would be redundant for the most part.

 

[BreechFace]

So what AR calibers do you have?

 

[MISportsman]

So what AR calibers do you have?

I have 5.56 of course, 6.5 grendel, .450 bushmaster, and an ar-10 in .308. The 6.5 grendel was my 1st build and I got addicted lol.

 

[MISportsman]

I would not normally choose the .300 Ham'r over the 6.8, BUT sense you already have a 6.5 Grendel, getting a 6.8 spc would really be far too much duplication of terminal performance at normal hunting distances (inside 200 yards) and so I would choose the .300 Ham'r (given the 2 choices you listed) to have something more different.

My biggest fear with the ham'r is ammo availability. I am capable of doing limited reloading and factory is only available through wilson combat and sig. I would feel much better if another one of the mainstream ammo makers would pick it up.

 

[BreechFace]

So I mirror you quite a bit, but filled in a gap.

556, 7.62x39, 300blk, 6.8 SPC II, 450 Bushmaster.

Based on your list I would say you have a gap in the 30 cal, which is what you were initially leaning towards.

My 7.62x39 gets used a lot more than my 300 blk pistol which is dedicated for a HD role with a suppressor. I like the 7.62x39 quite a bit better than the 300 blk for supers, but the 300blk is hard to beat for subs, especially with LeHigh Defense and Maker Rex bullets.

 

[BreechFace]

I've been threatening my wallet with a .358 Yeti build, but its overlap with the 450 Bushmaster keeps me with a slightly fuller wallet. But I can see myself doing a Yeti build eventually, it just looks like a great round for hunting in similar capacities of the 450 BM.

 

[BreechFace]

So it seems if you want a 30 cal option you have a few choices: 300 BLK, 7.62x39 or 300Ham'r.

Looking at Wilson Combat's velocity numbers it seems that I can best their 125gr loadings with the 7.62x39 and 123gr SST's and CFE BLK out of a 16" barrel. So not sure what the appeal is there.

https://www.wilsoncombat.com/wp-content/uploads/2020/05/300-HAMR-LOAD-DATA-5-20F1.pdf

And despite the 0.003" difference in bullet diameter 0.308" bullets work with a 0.311" bore.

 

[BreechFace]

Anyone know what the case capacity of 300 HAMR cases? It’s oddly or conveniently hard to find on the web.

I suspect is eerily similar if not less than the 7.62x39.

 

[BreechFace]

Anyone know what the case capacity of 300 HAMR cases? It’s oddly or conveniently hard to find on the web.

I suspect is eerily similar if not less than the 7.62x39.

Found one thread that states both the 300HAMR and the 7.62x40wt have similar case capacities and are 5-6gr more than 300 BLK. With 300 BLK case capacity around 25.1gr give or take that puts 300HAMR at 30.1 - 31.1 gr of H2O.

Now the 7.62x39 is around 35.5 gr of H2O, so now I know why I’m able to see better velocities out of the 7.62x39. Which puts the 300HAMR in no mans land.

Providing I have the HAMR’s case capacity correct, as I’m relying on a post on this thread (post #20).

 

[someguy2800]

The selling points I personally see to the 300 hamr is that it uses standard magazines and if you intend to handload you can use abundant 223 brass to make it. Outside of those two points I don't see the appeal over a 7.62x39.

 

[BreechFace]

The selling points I personally see to the 300 hamr is that it uses standard magazines and if you intend to handload you can use abundant 223 brass to make it. Outside of those two points I don't see the appeal over a 7.62x39.

I’ve read that it needs 300blk magazines. Which makes sense for the same reasons as 300 blk they are much more front heavy than 556.

 

[MISportsman]

I was pretty sure I was going to build one of the two calibers I mentioned, but the more you guys talk about the x39 and its true potential with hand loads the better it sounds

 

[Double Naught Spy]

My biggest fear with the ham'r is ammo availability. I am capable of doing limited reloading and factory is only available through wilson combat and sig. I would feel much better if another one of the mainstream ammo makers would pick it up.

Well then I would pick a caliber other than the .300 Ham'r.

 

[BreechFace]

I was pretty sure I was going to build one of the two calibers I mentioned, but the more you guys talk about the x39 and its true potential with hand loads the better it sounds

Keep in mind that a lot of US manufactured ammo is a bit watered down to SAAMI pressures where 7.62x39 gets a lot of performance gains running between SAAMI and CIP pressures, a lot of European/Combloc ammo can be found running higher pressures. So understand that when reloading a lot of US data will be neutered to what the 7.62x39 can actually achieve when loading under the guidelines of CIP pressures.

Max SAAMI pressure = 45,010psi
Max CIP pressure = 51,490psi

So the CIP chambers and testing of the 7.62x39 yield 12.5% greater pressure allowance than the SAAMI chamber pressures.

For reloading if you want to hunt with it, CFE BLK and 123gr Hornady SST's are a great pairing. CFE BLK really opened up the potential of the 7.62x39, everyone who reloads for the round says the same.

You maybe surprised the accuracy you can find with some steel cased ammo as well with a good platform to shoot from.

 

[BreechFace]

It really looks to me like the 300 HAMR was trying to do what the 7.62x39 already does when I look at the velocity numbers on Bill Wilson's site.

 

[BreechFace]

If you do end up doing a 7.62x39 just a few pointers, if you want to consider in the build.

1. I would stick with carbine gas, if you desire to run steel case, to help with the dirtier nature.
2. Run a heavier buffer H2 (H3 if it will run will be better) this will increase dwell time allowing for pressure to subside a few more milliseconds to ease wear on locking lugs.
3. C-Products magazines work great, I really only use the 5 rounders for hunting and 20 rounders for range. I've heard to stay away from the 30 rounders but that the 28 rounders will work.
4. A big part of getting the 7.62x39 running right is having a good wide feed ramp in the barrel extension, early on in the life (we are talking 15 years ago) of 7.62x39 barrel manufacturers were using standard 556 feed ramps and were having major issues. Barrel manufacturers today probably have all realized this and don't do that anymore, but it's always good to double check with the barrel maker to make sure they accounted for a 7.62x39 feedramp in the extension.

It is one of my favorite AR chamberings, it really is one of the perfect cartridges for starting young kids out with hunting, mild mannered and great performance with handloads.