Good info regarding cartridge pressures and twist rates. For those of us that enjoy TC Contenders, looks like we should either shy away from the Hammer, or try to reload it to 300 blackout velocity / pressures.
dellet
Gold $$ Contributor
No, if you have a contender and want velocity use the Ham’r. They both have the same max pressure.
This is my own opinion, but it’s true of many “improved cartridges”. The dumbest part of the 300 Ham’r is marketing it to AR15 users. Sadly if a cartridge can’t be shot in an AR, it won’t generate any sales these days.
The problem with the Ham’r is that it shares the max length of 300 BLK. So any bullet loaded to magazine length in the Ham’r that extends below the base of the neck starts losing any precious case capacity it was designed to increase. Kind of like cutting off a tree limb while sitting on the limb side, not trunk side. It has diminishing returns.
You have added case capacity of a longer body, with say an inside diameter of around .340” being filled with a .308” bullet. Body length is about .250” longer on the Ham’r, but much of that actual volume is lost with bullet mass. So limits bullet selection.
Loading the Ham’r in a single shot you can maximize case volume well what the blackout can achieve with most bullets. But again due to the longer throat of the blackout, you can gain some back with the blackout. When you start playing hand loader games, comparing cartridge potential gets cloudy.
Then comparing powder selection between Blackout and Ham’r if you use the powders that ecxel in the blackout with 100% density, you hit a pressure max limit in the Ham’r before max density. So you have to use a slower powder.
Comparing many of these cartridges really comes down to the question of, if you run a race with a broken leg, with which one broken will you run faster. Right or left?
dellet
Gold $$ Contributor
That doesn’t make any sense, there is no context. Case head size, diameter, has no bearing on how much pressure a given case can support. Case design, material and thickness determines that. Example a 45 colt case can not tolerate the pressures a 223 case is designed to operate at.
Wilson Combat introduced the 300HAM’R in 2018. WC and Sig Sauer were planning to release rifles chambered in the cartridge, and as part of this Sig submitted the cartridge to SAAMI. It was certified in Jan 2020 just a few months before COVID derailed everything everywhere. Since then, WC has offered a 300HAM’R barrel conversion kit for the Ruger American, and in Fall 2025 they did a limited run of barrel kits for Savage rifles.
It is official, Savage is now offering Model 110 rifles (16.5”, 1:12) chambered in 300HAM’R.
Savage - Rifles chambered in 300HAM’R
For those who might be interested and don’t want to break the bank trying something different. At present Wilson Combat is the primary manufacturer of 300HAM’R ammo, which also owns Lehigh Defense. I wonder if a major ammo manufacturer will start offering 300HAM’R ammo so that I can find it at my LGS.
Update: Remington is slated to produce ammunition for the 300HAM’R.
It is official, Savage is now offering Model 110 rifles (16.5”, 1:12) chambered in 300HAM’R.
Savage - Rifles chambered in 300HAM’R
For those who might be interested and don’t want to break the bank trying something different. At present Wilson Combat is the primary manufacturer of 300HAM’R ammo, which also owns Lehigh Defense. I wonder if a major ammo manufacturer will start offering 300HAM’R ammo so that I can find it at my LGS.
Update: Remington is slated to produce ammunition for the 300HAM’R.
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dellet
Gold $$ Contributor
Bolt thrust is calculated by the surface area of the inside of the case head, multiplied by the peak pressure.
These numbers will differ by manufacturer or even lot numbers and reflect full chamber pressure, which is not typical
223 = .300”
7.62 X 39 =.370”
With 55,000 psi applied the
.223 case will generate 3888 pounds on the bolt face
7.62x39 case will generate 5920 pounds on the bolt face
Failure due to high thrust pressure seems to rarely be a single event failure. More due to excessive pounding over time.
If you have other information, I’d be really interested
A Look at Bolt Lug Strength - Lilja
All action designers are concerned primarily with producing a safe and functional product. All other considerations such as weight, finish, eye appeal and other cosmetics are secondary. From a safety standpoint, the strength of the bolt lugs is of prime concern. Bolt lug shear strength depends...
dellet
Gold $$ Contributor
You’re grabbing at straws. First I stated clearly that full chamber pressure is rarely applied. That’s your sticky brass. But more importantly that’s a pointless argument.
If both cartridges have the same peak pressure, and both have equal reduction in force do to the brass grabbing the chamber wall, pick your percentage, the larger case head will have more driving force than the smaller case head. The 7.62x39 will require a 94% reduction to drop to the same pressure a 223 will have with a 90% reduction. The 223 At 50% reduction, the 7.62x39 will need a 60%.
If you apply total surface area contact and differing coefficients of friction im sure you can find examples that do not fit the basic formulas, but as in your photo example shows, barrels and hoop strength blow apart in single event high pressure failures. Bolt thrust failures are cumulative. That’s why AR15 bolts are considered consumable parts that fail due to fatigue, constant pounding. Increase the force of the pounding and they will fail sooner.
2 AR10, 3 AR 300BO, no bolt failures. Shot an AK once, not impressed. Shot the above 223, Gkid evidently had some BO in the mag and filled it with 223. I get a couple slight hand/face cuts. Only time I shot the 223. 300 Hamr was designed for med weight bullets, kinda like the M1 carbine & x39. BO is more versatile.
dellet
Gold $$ Contributor
You’ve lost me completely. I’m not sure if you’re trying to make a point or ask a question. Or what either might be
The 7.62x40 WT was Wilson Combat’s initial cartridge. It was geared toward light bullets (90-125gr). The cartridge performed well and garnered a small loyal following. With the goal of achieving/surpassing 30-30 Win performance, Bill Wilson refocused his efforts and put a lot of time into testing barrel twist and bullet selection.
After proving up the cartridge it was introduced as the 300 HAM’R. The main difference is the case is 1mm longer (7.62x41mm) and reamer provides for a little longer throat to handle the longer/heavier projectiles ranging from 90gr to 150gr that fit within the AR15 mag length restriction (2.26”)
The magic has been matching the bullet/barrel twist as well as inviting the shooting community to help test and improve the final product. The open interaction / community engagement seems to be key difference in grass roots success of 300HAM’R.
After proving up the cartridge it was introduced as the 300 HAM’R. The main difference is the case is 1mm longer (7.62x41mm) and reamer provides for a little longer throat to handle the longer/heavier projectiles ranging from 90gr to 150gr that fit within the AR15 mag length restriction (2.26”)
The magic has been matching the bullet/barrel twist as well as inviting the shooting community to help test and improve the final product. The open interaction / community engagement seems to be key difference in grass roots success of 300HAM’R.
I may be weird but I look at the difficulty of making loadable cases and actual loading. 7.62-39 boxer primed brass is hard to find around here, never seen it for sale locally. Making 300blk cases is a long slow process, that may have been necessary for subsonic very heavy bullets but does nothing for the hunting bullets we are discussing here. The Hamr is one pass through a sizing die and ready to load. Comparisons of factory loaded ammo seem to be valid with a semi auto due to pressure but not a bolt action.
Just a minor correction on 300BO vs 300HAM’R case conversion. Both of these cartridges can be formed from .223/5.56 cases. To form / convert cases for either of these cartridges it is basically same steps and amount of work by either:
1) Trim excess material off .223 donor case and then run it through FL Sizing Die to form the new neck and shoulders; or
2) Run the .223 donor case through the FL Sizing Die and then trim off excess material
- For 300BO the .223 donor case is cut at the case body / shoulder junction. The new neck is formed from the case body material from donor case.
- For 300HAM’R the .223 donor case is cut at the junction of case neck and top of the shoulder. The new neck is formed out of shoulder material from donor case. This results in 300HAM’R case being approx. 1/4” longer than 300BO.
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