Higher velocity loads: pick cases with heavier weight and smaller water capacity, or lighter weight cases with larger water capacity?

[tonyben]

Looking to make some higher velocity loads for my M14's. Should I pick a case that's heavier with smaller internal volume or lighter with a larger internal volume?

Heavier cases should mean thicker case heads which will resist case head separation over multiple reloadings. Might get 3 loads before scrapping.

Lighter cases will fail quicker. Might have to use these cases once or twice, then scrap.

Tony.

 

[marazzi59]

I find this to be a real interesting question but would be concerned about hurting the m14 action possibly if you get to far out of normal specs. My guess is more powder is faster.

 

[243winxb]

The most important thing to remember about military brass is that the internal capacity will probably be less than commercial .308 Win brass, because military brass often has thicker webs or casewalls.. https://www.accurateshooter.com/cartridge-guides/308win/

Sierra- loading for the service rifle.

 

[Doom]

First and foremost the M14 must meet certain criteria that other rifles do not. The M14 gas system using a long operating rod that is designed for a certain range of gas pressure at the gas port. Exceeding that pressure can damage the OP Rod and render the firearm unusable. Hence the guidance for certrain powders within a burn rate range. Chamber Peak pressure is usually not the limiting factor in the M14.

Obviously lighter cases usually result in larger chamber volume on firing and require more powder to reach the same chamber pressure and ultimately nearly the same velocity and port pressure for a given chamber pressure. The converse will also be true.

I would be very leery of trying to chase a velocity higher than this recommend for the M14 for various bullet weights.

 

[Webster]

Looking to make some higher velocity loads for my M14's. Should I pick a case that's heavier with smaller internal volume or lighter with a larger internal volume?

Heavier cases should mean thicker case heads which will resist case head separation over multiple reloadings. Might get 3 loads before scrapping.

Lighter cases will fail quicker. Might have to use these cases once or twice, then scrap.

Tony.

There are safety issues. A little faster doesn't make it better. Go for accuracy not speed.

 

[tonyben]

I'll be using a modified gas system which vents pressure and doesn't overwork the operating rod. We have adjustable gas plugs. I'll be loading primarily 168's and 175's. I do have some 185 juggernauts though.

I can also shut off the gas valve and look for pressure signs before proceeding.

Tony.

 

[Doom]

I'll be using a modified gas system which vents pressure and doesn't overwork the operating rod. We have adjustable gas plugs. I'll be loading primarily 168's and 175's. I do have some 185 juggernauts though.

I can also shut off the gas valve and look for pressure signs before proceeding.

Tony.

You've got it covered. Lighter brass means more powder, more mass of gas and more velocity. how much depends...

 

[Zero333]

I have an M1A and you don't want spicy loads. It beats the hell out of the brass and the rifle wears out much faster.

I recommend something like...

150 gr bullets @ 2,750 fps
165/168 gr bullets @ 2,600 fps
175/180 gr bullets @ 2,550 fps

Any faster I don't recommend.

I use F.C. brass and it gets a bit beat up. Mainly you get a ding on the brass from extraction deflection and the rims can get worn out after several reloads.

My M1A has a 18.5" barrel so my velocities suffer a little compared to the 22" barrel of the M14/M1A.
But the 308 is a very efficient cartridge so velocities don't suffer much down to 20" barrels.

I would avoid once fired military brass because it's a bitch to work with. Have to get rid of the primer crimp,.. reduce powder charges compared to commercial brass. Only brand new L.C. brass is the only milspec brass I recommend.

 

[Zero333]

Forgot to add.. The longest lasting 308win brass I've every used is Winchester.
It's one of the lightest and it's surprisingly excellent in the most common cartridges like the 223rem, 308win, 243win (any cartridge based from the 308win like 7mm08 etc..) and 30'06 to name a few..

In my M1A, I use F.C. brass because I have at least few thousand of them doing nothing and 90% of them are from FGMM factory ammo which the brass is extremely consistent weight wise. FGMM 308win factory ammo brass is as consistent in weight as the best of the best.. I've weighed 100 random pieces from different lots of 308 FGMM ammo, and the difference between lightest and heaviest was about 2.0 gr or less. And I'm talking about boxes of FGMM that were manufactured at least 10 years apart from each other.

 

[Laurie]

On the principles of the original question, higher capacity = higher MVs, whilst low capacity sees a higher peak pressure for any given charge weight.

That sounds contradictory, but it's not. Reduce the combustion chamber volume and pressure rises, but the weight of the charge that achieves maximum safe, or useable, pressure is less, as is the energy input. Use a high capacity case and loading to the same pressure requires more powder. More powder = more energy has been input = higher MV, even though the thermodynamic efficiency of a typical smallarms cartridge is only in the low 30s %, so > 70% of the additional powder's energy is wasted in noise, heat, recoil etc.

In any one cartridge design, the resulting differences in MVs are usually very small between makes of case. The differences in capacities between case makes though are such that switching a maximum, worse already over-maximum, pressure charge from a higher capacity model to a lower one can be enough to create the straw that breaks the camel's back leading Bad Things happening.

On a different scale, designing a bigger case using more powder is the usual way of gaining additional performance, so the 30-06 is more powerful than 308 Win for instance. It also reduces efficiency as measured by ME units generated per grain weight of powder burned. The rule of thumb is to take the case capacity change % and divide it by four to get the resulting MV change providing all else remains unchanged (barrel length, bullet weight, peak pressure). So, increasing the case capacity by 20% gives c. 5% MV increase. Likewise reducing it, so the changes are small. I've no experience of the capacities of ex-GI 7.62 brass, but the water capacities of fireformed commercial 308 Win cases I've measured fired in a single rifle chamber range from 56.0 to 57.4gn, the latter an unusually thin/light batch of 1990s Norma that weighed 160gn, over 20gn less than Lapua or RWS. That's a 2.5% capacity change, so loading this Norma brass with a bit more powder would be expected to produce another 0.62% MV, c. 17 fps in a set-up running at 2,800 fps.

As to case-strength, a heavier case isn't guaranteed to be stronger. It is the case thickness / strength at the join between the solid case-head and the case-walls that often determines that. A case can have a very thick head adding substantially to the overall weight, but a weak join and/or thin/weak lower walls and be weaker overall than a lighter but better constructed example. In the UK and parts of the GB Commonwealth we have a unique prone discipline called Match Rifle that sees 308 Win rifles used only at 1,000/1,100, and 1,200 yard distances (at 1,500 yards on one Australian range). As you can imagine, bullet choice and obtaining maximum MVs are key. 30 odd years ago, these characters discovered the thin-wall 160gn Norma brass I mentioned and thought 'Hey Presto, the answer to our prayers!' As it turned out, these cases might have had more room and could accept higher charges, but they failed or wore out quickly at lower pressures than equivalent quality heavy makes, so there was no net performance gain, only an increase in risk of over-loading.

 

[William Vogel]

I'll be using a modified gas system which vents pressure and doesn't overwork the operating rod. We have adjustable gas plugs. I'll be loading primarily 168's and 175's. I do have some 185 juggernauts though.

I can also shut off the gas valve and look for pressure signs before proceeding.

Tony.

How fast are you looking for? I’d use the lighter cases and shut off the gas system. That’s what I’ve been doing but not for any reason other than being able to easily recover my brass with minimal damage. Ejected cases get beat up in the center of the body with the signature M1A dent and then the necks can get damaged when they hit the ground. I built a brass catcher that’s large enough to catch it most of the time but I’m putting more energy into making sure my brass is recovered than focusing. The heavy brass will thin with firing in a normal chamber and I’d experiment with the thinner brass to find what works.

 

[Ggmac]

Looking to make some higher velocity loads for my M14's. Should I pick a case that's heavier with smaller internal volume or lighter with a larger internal volume?

Heavier cases should mean thicker case heads which will resist case head separation over multiple reloadings. Might get 3 loads before scrapping.

Lighter cases will fail quicker. Might have to use these cases once or twice, then scrap.

Tony.

Why ! The m1a is a great rifle as is . Accuracy is the goal , if you want fasterget a bolt rifle in another caliber.
Stay with in the military specs on loads . Your receiver is a cast receiver, nothing wrong with it but it’s not a military forged unit . UNLESS its a class 3

 

[tonyben]

This is for research purposes. See the post below regarding new barrels from Lothar-Walther and a new unannounced rifling.

New US Made M14 Lothar Walther barrels with ICR rifling for More FPS

LW sent me a test barrel. It's the first US made LW M14 barrel to come out of their US facility. The CEO of LW gave me authorization to mention their new rifling that, as far as I know, is the first time the public will have heard of ICR rifling, boasting faster velocities compared to other...

forum.accurateshooter.com

New Lothar Walther US Made M14 Barrels & New ICR Rifling. First Look!

Lothar Walther is now producing M14 barrels in the US. This video showcases their first M14 barrel which also features their new, never announced, ICR rifling which boasts higher velocity gains over c

rumble.com

They claim better accuracy at higher velocities and I'm already seeing 2700+ FPS out of their 22" barrel they sent me with 175 grain M118LR from 2006.

My rifle is a LRB M25 using a hammer forged receiver and a TRW bolt in a JAE chassis. Of the ammo I tested, my handloads were the most inaccurate and slowest with higher SD's. The factory ammo I was using wasn't the best, but it was better than my loads.

I've got SMK's, Berger LRT's and OTM's as well as 168 hybirds and 185 Juggernauts to try.

I typically sort cases by weight and use a Chargemaster 1500 for powder dispensing. I need to do some things different and tighten my routine.

I'm using a Redding FL S-die with a bushing and a competition seater die.

Tony.

 

[William Vogel]

This is for research purposes. See the post below regarding new barrels from Lothar-Walther and a new unannounced rifling.

New US Made M14 Lothar Walther barrels with ICR rifling for More FPS

LW sent me a test barrel. It's the first US made LW M14 barrel to come out of their US facility. The CEO of LW gave me authorization to mention their new rifling that, as far as I know, is the first time the public will have heard of ICR rifling, boasting faster velocities compared to other...

forum.accurateshooter.com

New Lothar Walther US Made M14 Barrels & New ICR Rifling. First Look!

Lothar Walther is now producing M14 barrels in the US. This video showcases their first M14 barrel which also features their new, never announced, ICR rifling which boasts higher velocity gains over c

rumble.com

They claim better accuracy at higher velocities and I'm already seeing 2700+ FPS out of their 22" barrel they sent me with 175 grain M118LR from 2006.

My rifle is a LRB M25 using a hammer forged receiver and a TRW bolt in a JAE chassis. Of the ammo I tested, my handloads were the most inaccurate and slowest with higher SD's. The factory ammo I was using wasn't the best, but it was better than my loads.

I've got SMK's, Berger LRT's and OTM's as well as 168 hybirds and 185 Juggernauts to try.

I typically sort cases by weight and use a Chargemaster 1500 for powder dispensing. I need to do some things different and tighten my routine.

I'm using a Redding FL S-die with a bushing and a competition seater die.

Tony.

You have to be careful with the secant ogive bullets because they like to be close to the lands. The tangent ogive like the smk are way more tolerant of jump and with the mag length of 2.820 you’re probably going to have to find something with a lot of trial. I’m using Starline brass, CCI #34 primers, 43.5 grains of A2495 and smk 155 palma at 2.820. It’s great at 100 yards and I’m still practicing at distance. My rifle is just like yours except the Broughton heavy barrel. I watched your video. My barrel contour is like yours.

 

[Zero333]

I found practically all CCI Large and Small Rifle primers to have stronger cups and safer for semi-auto duty. I never used CCI # 34 or # 41 for semi auto duty, but always try to stick with CCI primers. There are exceptions with primers.

But back to the question of brass capacity and velocity, @Laurie has it all covered for you.

I've seen 20" AR-10 barrels deliver superb velocities with 150 gr SP bullets and still cycle normally and be within limits. I'm talking about 150 gr Hornady Interlock bullets @ 2,950 fps without a hickup.

So there is plenty of truth about some barrels delivering more velocity than expected,.. but it's the M14 system that doesn't like that kind of pressures/velocities. AR-10 Large frame type AR's are nothing like M14's.

You can always give it a shot, but don't over due it for the sake of the rifle.

 

[searcher]

Looking to make some higher velocity loads for my M14's. Should I pick a case that's heavier with smaller internal volume or lighter with a larger internal volume?

Heavier cases should mean thicker case heads which will resist case head separation over multiple reloadings. Might get 3 loads before scrapping.

Lighter cases will fail quicker. Might have to use these cases once or twice, then scrap.

Tony.

If only looking for three loadings, go with the thinner brass.

 

[Doom]

Winchester 308 cases are going to be the lightest and have the most volume. Sometimes it shows up as BHA cases. The case head is shaped differently. This brass was designed for Palma Match ammunition some time ago and Winchester changed their standard brass to the design. You can look up ballon head cases for more info.