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In general, is SAAMI approval of this cartridge positive/negative/neutral? What are the long-term prospects for this cartridge (please no 6.5G commentary, I'm not asking about 6.5G)?  I've waited till all the marketing died down; now may consider...

It's generally a positive and can be hugely positive. The only real negative comes when the round has problems and is accepted before the problems are addressed. Kind of what happened with the 6.8 and what lead to multiple chambers. If the round is properly thought out then SAAMI opens it up to the whole market and everyone is using the same specs which is good.

I'm probably going to build one based on the Wilson 20" barrel. SAAMI doesn't affect me one way or the other; I generally reload, build my own, etc.  The round fits my needs; at least on paper it looks like it will; tbd.

It will be a major plus.  The cartridge has gone through development without any problems surfacing, and is now open for other companies to get on board.  I know of two major ammunition companies that are interested and some rifles companies looking closely at it.

Shooters will like the additional sources for ammo and reloaders will love having 30-plus bullets to choose from. (as well as being able to use surplus 5.56 brass to form the 300 HAM'R)

It's 300 Blackout with better supersonic performance but they sacrificed subsonic performance to achieve it.  So depending on what you need it may or maybe be useful.  Personally I rarely use supersonic ammo in my 300BO so 300 Ham'r has little draw for me.

I have a 30 RAR for the supersonic stuff.  

The 300 HAM'R was posted on the SAAMI web site yesterday in the new caliber section

SAAMI approval is positive. It helps standardize the cartridge. Won't be a wildcat anymore. So liability for ammo makers goes down. So more factory ammo becomes available. Big plus.

I am sure it was tested but what happens if you try to chamber 300 BO in a 300 HAMR?  Is there any chance of getting it to ignite and what happens if it does?  Anything like what happen when a 308 Win is fired in a 30-06?

That was asked before and I did my own testing.  A Blackout round will seat too deeply to fire in a 300 HAM'R chamber, and HAM'R cartridge will not chamber in a Blackout rifle.  I do believe that is an aspect SAAMI takes into account during their testing.
After a few thousand rounds I could not find any fault with the 300 HAM'R and had exactly one failure to fire.  That single time was a result of a primer being inserted upside down during the reloading.  I have tested Wilson's ammunition, reloads with factory brass, and reloads with brass I formed from LC 5.56 surplus.  All performed well.
As part of my testing I have used Wilson Combat AR rifles (they are nice) and those I built myself and all made me happy.  After 48 years of hunting and reloading, and about 20 years of reviewing firearms I have always tried my best not to mislead anyone.  There are other cartridges I have tested and have liked, but I see a bright future for the 300 HAM'R.

Thanks for the reply.  I figured it would simply go too deep to head space.  It might "work" in a control fed bolt gun similar to a similar mix up of 308 in 30-06.  But this is really an AR cartridge so it's fairly irrelevant.

It will be interesting to see where HAMR goes.  I still like my 300BO for suppressed shooting.

You're right, for suppressed and sub-sonic shooting, the 300 Blackout is your best option in a rifle cartridge.  I would be curious myself about a control feed bolt gun.

But then again, "DON'T DO THAT! should suffice.  

Does the 300 HAMR sacrifice it's short barrel friendliness for that increased super sonic ability?

.300blk is mainly appealing to me for being efficient with supers in a small package, not for subs.

I would think with the same bullet and same barrel length, 300 HamR would out perform 300 BO in the velocity department independent of barrel length.  That said I would guess the differences would shrink as the barrel gets shorter.

I wasn't thinking velocity wise, more about flash & noise like a short 5.56 barrel. I was thinking more case capacity = longer barrel for complete burn.

I agree I think it will be worst for flash and noise.  Even if you were just trying to match the 300 BO velocity it would take slightly more powder due to the extra case volume.  Its probably not significantly worst but should be a little worst.

BARREL LENGTH EFFECT ON VELOCITY
300 HAM’R

125 SIERRA SBT PH 20" bbl 2534 FPS
125 SIERRA SBT PH 18" bbl 2498 FPS (-36)
125 SIERRA SBT PH 16.25" bbl 2486 FPS (-12)
125 SIERRA SBT PH 14.5" bbl 2441 FPS (-45)
125 SIERRA SBT PH 12.5" bbl 2367 FPS (-74)
TOTAL VELOCITY LOSS FROM 20” TO 12.5” 167 FPS

130 SPEER FNHC 20" bbl 2485 FPS
130 SPEER FNHC 18" bbl 2460 FPS (-25)
130 SPEER FNHC 16.25" bbl 2438 FPS (-22)
130 SPEER FNHC 14.5" bbl 2412 FPS (-26)
130 SPEER FNHC 12.5" bbl 2346 FPS (-66)
TOTAL VELOCITY LOSS FROM 20” TO 12.5” 139 FPS

150 SPEER FNHC 20" bbl 2202 FPS
150 SPEER FNHC 18" bbl 2194 FPS (-8)
150 SPEER FNHC 16.25" bbl 2171 FPS (-23)
150 SPEER FNHC 14.5" bbl 2146 FPS (-24)
150 SPEER FNHC 12.5" bbl 2105 FPS (-41)
TOTAL VELOCITY LOSS FROM 20” TO 12.5” 97 FPS

ALL TESTING WAS DONE WITH THE SAME BARREL PROGRESSIVELY SHORTENED FOR NO BARREL TO BARREL VARIATION AND ALL AMMO FOR EACH LOAD FROM THE SAME LOT. ALSO ALL SHOOTING WAS DONE DURING A 5 HOUR PERIOD ON THE SAME DAY USING A LABRADAR TO MINIMIZE THE EFFECT OF ATMOSPHERIC CONDITIONS. ALL CHRONOGRAPH STRINGS WERE 10 SHOTS WITH THE HIGH AND LOW SHOT REMOVED FOR AN AVERAGE OF THE REMAINING 8 SHOTS.

AS YOU CAN SEE AS THE BULLET WEIGHT WENT UP BARREL LENGTH HAD LESS EFFECT ON VELOCITY. AVERAGING THE 16.25” TO 20” NUMBERS IT WORKS OUT TO 10.5 FPS PER INCH.

Thanks for the chart.

I'm a little bummed it stopped at 12.5" because when I said short I was thinking more along the lines of the 7-9" .300blk barrels.

Short barrel 300 Ham'r numbers

If you notice, it will push the 125gr bullet nearly as fast as the 110, 300BLK will not.

As Bill said there however, they've tested different powders, I'd expect the numbers climbed a bit. Depending on purpose, those 125gr numbers could be enough to sway someone that way vs. The 300BLK.

That test was done early on in the cartridge development before we had good PSI pressure test data, muzzle velocity #s we get now out of a 18" barrel with pressures +/- 55k are:

110gr Hornady SP 2650fps
125gr Sierra SPT PH 2550fps
130gr Speer HAM'R HOT-CORE 2510fps
135gr Speer HAM'R BONDED 2470fps
150gr Speer BTSP 2340fps

All with Hodgdon CFEBLK

Bill, have you re-run the numbers on the short (~8") barrels?

Maverick was interested in the short barrel supersonic performance. The Ham'r already seemed to be slightly faster than 300BLK in that realm, but if you've tested powders that have bumped velocity up, for those that need more velocity in the short barrels the Ham'r would be a no-brainer over the 300BLK IMO.

Just to answer the "why" in my case (can't speak for Maverick), in WA we can't have a loaded weapon in the vehicle while hunting. EXCEPT a pistol, if you have a carry permit. The short pistols are exceptionally handy to get in and out of a vehicle with compared to any longer barrel, and where I hunt, it's relatively common to come around a bend in the road and have a game animal standing in the road 25yds ahead of you, or just off it. It would be one hell of a gun for defense in the car as well.

That was my exact thought as well.

I like the "numbers" that I see, but would need to know flash, blast, gas, recoil, and function out of a really short barrels.

I do find it interesting that it is often compared to 300blk, but 300blk was designed to replace the 9mm MP5SD and with a mag swap, have more energy than a 5.56 MK18.

Seems like a better comparison would be: 7.62x40WT, 7.62x39, 6.5G, and Six8.  I say this because I'm guessing that +90% of 300blk barrels sold now are 10.5" inches or shorter, and it is just the opposite for the other calibers listed.   Different playing fields.

It starts to come down to a matter of powder type, case shape, and capacity.   If 300 Ham'r has good manners out of sub 10 inch barrels, it can really cut into 300blk a bit (on the super side).  If it is a teeth rattling, flaming dragon and needs +12 inches settle down, then it is a different story.

You guys are hitting the nail on the head.

I'm currently building an AR pistol to carry whitetail hunting in WI. I intended to go .300BLK due to the acceptable terminal performance of the 110gr TAC-TX inside 100 yards and the efficiency of .300BLK out of 7-9" barrels.

I already own plenty of hunting rifles, including 5.56 and 6.5G AR's, but a really short AR pistol would be VERY handy in the thick woods. There is also the same deal about loaded pistols & vehicles in WI.

I've looked into 6.8 SPC II, 6.5 Grendel, 350 Legend, 450 Bushmaster, and 458 Socom instead of the .300BLK but I always found myself coming up with the .300BLK just suiting this niche use better or easier.

6.8, 6.5G, and .300BLK appear to be pretty damn comparable for the inside 100 yards use. Only 6.8 and .300BLK have barrels available in the 7-9" range. The 6.8 and .300BLK seem to be very tolerable in barrels of that length as well. 6.5G might be as well, but there isn't a ton of info out there from those barrel lengths. I lean towards the .300BLK here as 6.8 introduces parts and components that won't fit in with the rest of my stuff.

350 legend seems decent on paper but I have no requirement for a straightwall cartridge and it seems like there might be kinks to iron out with it still. Also I haven't seen any short barrels but I suppose a 9mm barrel could be easily converted.

450 & 458 are basically just more than necessary. I figure they'd be extra fun out of a pistol as well. They also have the same problem with unique parts and components.

If .300 HAM'R can be an improvement over .300BLK in the supersonic department without making 7-9" barrels uncomfortable to shoot (especially as I don't wear hearing protection while hunting) then I see no reason NOT to get one. It would just be a question of finding the right length barrel, converting a .300blk one, or having one made.

You might be interested then in the .30 HRT.  6.8 case based, unaltered 6.8 mags, 110 gr. TTSX out of a 24” barrel up to 3000 fps and 2800 fps out of a 16” barrel.  Those are hot loads and case life is short but drop velocity by 100 fps and case life is very much improved.  It’s a very interesting round but reloader only.  Faster than all the 5.56 based .308 calibers and an excellent 300 yard deer round.

I only have 11.3", 16.2", 18" and 20" uppers so I asked the company to send me down a 8". I'll do some experimenting with the 8" and 11.3" which is the shortest I'd want a "hunting pistol" and advise.

Can you use the 22 Nosler case for the 30HRT?

Tony

You know Tony, I don't see why you couldn't?  The Nosler is pretty much just a 6.8 with a rebated rim isn't it, maybe a bit longer, but you have to shorten the 6.8 case for the .30 HRT anyway.  That might be the best use of the .22 Nosler yet.  If you can take the 5.56 up to 30 I don't see why you couldn't with the Nosler unless they use a very thin neck on the Nosler to begin with, which I doubt.  If you anneal before expanding and take expansion up in several steps, you shouldn't loose too many cases if any at all.  I certainly take the 6.8 down to .22 without excessive neck thickening so I really don't see a problem going the other way.
I'm not really sure why one would want to do the rebated rim though.  It's not like 6.8 bolts are super expensive and you'd still have to use 6.8 magazines.  I've tried to make various 5.56 mags work with all of my 6.8 cats and after 4 or 5 rounds it's a no-go.  Plus, the longer COAL allowed by PRI 6.8 mags is always very much welcomed.

That's amazing, thank you!

Glanced at a ballistics chart with a 125gr TNT load.... meh.

Interesting.