What velocities are possible in an M1A?

[Grump]

Been studying the posts here for a few weeks and have found an underlying opinion that .308 bolt guns can run loads at higher pressures than semi-autos.

I know that the 22-inch barrel won't give speeds like the 24, 26, and even 30-inch barrels do...but what speeds should be attainable with an M1A?

I have a 168-gr load with AA2520 and 168s at 2600 fps at 7 ft screens (about equal to M852's 2550 at 78 feet) that is showing pretty bright chamber scrub 1/2-inch above the rim. With this going on, I'm not sure I can safely get 2550 or 2600 with 175s, like a lot of people are reporting.

Thanks!

 

[learjet]

Re: What velocities are possible in an M1A?

i got 2550 w 175s in mine, w 42g of varget if i remember right. upped the charge a wee bit more and lost accuracy and velocity. gun just felt like it was batterin itself. gave up on that quick. my m1a likes scenars, and a max of 46g of varget in winnie cases. i usually load 45 in the m1a. been awhile, and im not near my data, dont remember the velocities

for comparison i got 2950 outta a 26" savage / mcgowen bbl w 47g of varget, but settled on 46.5

 

[308isgreat]

Re: What velocities are possible in an M1A?

My hunting load for my Springfield Scout is 44.5 gr W748 under a Sierra 165 BTHP Gameking that averages 2650 fps. I have reloaded these cases multiple times and see no signs of high pressure.

I do use an adjustable gas port, so I'm sure this helps out.

 

[learjet]

Re: What velocities are possible in an M1A?

yep my rifle really likes the 165gkhp as well. thats my secret bullet for the ole m1a.

 

[Grump]

Re: What velocities are possible in an M1A?

What can I reasonably expect with 155s?

Thanks!

 

[Falar]

Re: What velocities are possible in an M1A?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Grump</div><div class="ubbcode-body">What can I reasonably expect with 155s?

Thanks! </div></div>

I have been loading for an AR10, not an M1A but have also had trouble getting velocity anywhere near bolt gun territory. My fastest load with 155 Scenars is 2743fps w/46gr of Varget in Winchester cases, CCI BR2 primers and no crimp. 21" Stainless 1/10" Polygonal barrel.

 

[Shady_Jay]

Re: What velocities are possible in an M1A?

that sucks. I push 175SMKs at 2722fps out of a 10T. Ragged edge of pressure but it shoots great.

 

[Falar]

Re: What velocities are possible in an M1A?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Captain Kick-Ass</div><div class="ubbcode-body">that sucks. I push 175SMKs at 2722fps out of a 10T. Ragged edge of pressure but it shoots great. </div></div>

I have a load with 175gr SMKs that runs about 2631 with 45gr of Varget, but it is also on the ragged edge with deep ejector marks on the brass. Not too far off considering your barrel is 3" longer than mine. Are you using Varget? It is known to have some lot-to-lot variation.

 

[sinister]

Re: What velocities are possible in an M1A?

The limitation on the M1A/M14 is the pressure curve -- too slow a powder (to get that bullet moving fast out of a 22-inch barrel) and high pressure at the gas piston and you get one tremendous bang/hammer effect on the op rod before the case finishes obturation.

The Marines had the "G4" load for Camp Perry and the 1,000-yard service rifle iron sight matches. I don't recall the 4895 charge but you could only use the brass once. I watched a young Marine (I believe he was a Captain) fire those rounds out of his M14 and every case was split.

I've used as much as 44.5 - 45 grains of Varget behind a 175 in my old M1A and the charge was so hot the action wouldn't cycle. A second or two later (once the brass shrank and cooled back to original diameter) you could hand-cycle the action and it would extract and eject.

180s and 190s were popular, but the AMU also drilled a 1/64-inch vent hole in the end of the gas system nut (my nomenclature is off).

You'd know the M14/M1A action was getting the snot knocked out of it because you'd hear this ringing as the bolt hit the back of the receiver.

The AR-10T doesn't have the same op-rod limitation but I use the Tubb CWS to try to keep the bolt carrier group locked as long as possible.

Bolt-action Palma shooters try to get 2900-2950 out of 155s out of 28+ inch barrels with substantial Varget charges (46.3). You're not going to get those kind of velocities out of a 22-inch M14 or 20-inch M110 barrel, especially at Quantico or Camp Perry on hot/humid days. Maybe out west (New Mexico, Colorado, Utah, Wyoming, Montana, Idaho) at altitude and low humidity.

 

[Shady_Jay]

Re: What velocities are possible in an M1A?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Falar</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Captain Kick-Ass</div><div class="ubbcode-body">that sucks. I push 175SMKs at 2722fps out of a 10T. Ragged edge of pressure but it shoots great. </div></div>

I have a load with 175gr SMKs that runs about 2631 with 45gr of Varget, but it is also on the ragged edge with deep ejector marks on the brass. Not too far off considering your barrel is 3" longer than mine. Are you using Varget? It is known to have some lot-to-lot variation. </div></div>

Using RE15, same burn rate....... but I just like RE15

 

[learjet]

Re: What velocities are possible in an M1A?

im away from my data for a few weeks, but i think my velocity w 45g of varget, and scenars was just shy of 2800. was 32 moa to 1 k if i remember right, from the m1a.

the m1a is a hoot, and brings lots of smiles and funny looks when u shoot it lr and have it dialed in. it however, can be a cranky expensive sob to maintain. i was gonna take mine to the Badlands for a class, but 2 months prior she started acting up. still shot nice lil groups, just every few rounds those groups moved hehe. hung her on the wall and grabbed my bolt gun, class went great. never did get back to the m1a. the beddings tired, and the bbls gettin old, i dunno, just havent felt like rubbin money on it lately. someday i guess.

the guy who got me into m1as 15years ago shot competition w his back then, he told me then taht to simply maintian his rifle(he paid an armorer) cost him $1 per round, and he shot his alot.

they r fun! but they can haunt u, and parts are expensive, esp if u usem hard w hot loads

 

[Grump]

Re: What velocities are possible in an M1A?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Falar</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Captain Kick-Ass</div><div class="ubbcode-body">that sucks. I push 175SMKs at 2722fps out of a 10T. Ragged edge of pressure but it shoots great. </div></div>

I have a load with 175gr SMKs that runs about 2631 with 45gr of Varget, but it is also on the ragged edge with deep ejector marks on the brass. Not too far off considering your barrel is 3" longer than mine. Are you using Varget? It is known to have some lot-to-lot variation. </div></div>
I just don't want to go into the ejector mark territory.

With H4895 and Varget and I think also IMR4895, I was getting what looks like pressure signs at 2750 with 155s. Since M80 ball *should* get 2800 at the typical screen distance (2750 at 78 feet was the military standard), and our newer powders have some reputation of being able to exceed the traditional speeds, I'm wondering whether 2750 is the real safe limit for 155s in an M1A.

At my usual altitudes, this speed calculates to them still being supersonic at 1,000, but they are also up to halfway into the technical definition of transsonic (mach 1.2).

 

[Falar]

Re: What velocities are possible in an M1A?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Grump</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Falar</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Captain Kick-Ass</div><div class="ubbcode-body">that sucks. I push 175SMKs at 2722fps out of a 10T. Ragged edge of pressure but it shoots great. </div></div>

I have a load with 175gr SMKs that runs about 2631 with 45gr of Varget, but it is also on the ragged edge with deep ejector marks on the brass. Not too far off considering your barrel is 3" longer than mine. Are you using Varget? It is known to have some lot-to-lot variation. </div></div>
I just don't want to go into the ejector mark territory.

With H4895 and Varget and I think also IMR4895, I was getting what looks like pressure signs at 2750 with 155s. Since M80 ball *should* get 2800 at the typical screen distance (2750 at 78 feet was the military standard), and our newer powders have some reputation of being able to exceed the traditional speeds, I'm wondering whether 2750 is the real safe limit for 155s in an M1A.

At my usual altitudes, this speed calculates to them still being supersonic at 1,000, but they are also up to halfway into the technical definition of transsonic (mach 1.2). </div></div>

This is what my 2750 load with Varget and 155 Scenars looks like. It looks a little warm but AR10s are tough on brass and my factory winchester ammo's cases/primers look the same.

 

[Grump]

Re: What velocities are possible in an M1A?

Wow. I'd expect zero radius left on the primers by the time your brass starts flowing into the ejector hole like that.

One of the things that prompts my questions in this thread is that my primers with this new barrel are WAY flat in both old FC brass (weight around 167 gr or so) and in LC brass. The FC stuff shows less of an ejector mark than yours on some loads that are well below (2 grains or more) published maximums.

I have some new test loads to run, resized NOT to minimum case dimensions, to see how much the .010-.015 difference between sized and fired cases' headspacing has to do with it. It's definitely a short case life thing.

You're saying that factory loads in Winchester brass ALSO show ejector marks? I thought the Winnie stuff was harder than that.

 

[sinister]

Re: What velocities are possible in an M1A?

Spike (here in the forums) won the Farr Trophy at Perry shooting one of Hook Bouton's M1A/M14 re-builds. He might share his loads if you IM/PM him.

 

[Falar]

Re: What velocities are possible in an M1A?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Grump</div><div class="ubbcode-body">Wow. I'd expect zero radius left on the primers by the time your brass starts flowing into the ejector hole like that.

One of the things that prompts my questions in this thread is that my primers with this new barrel are WAY flat in both old FC brass (weight around 167 gr or so) and in LC brass. The FC stuff shows less of an ejector mark than yours on some loads that are well below (2 grains or more) published maximums.

I have some new test loads to run, resized NOT to minimum case dimensions, to see how much the .010-.015 difference between sized and fired cases' headspacing has to do with it. It's definitely a short case life thing.

You're saying that factory loads in Winchester brass ALSO show ejector marks? I thought the Winnie stuff was harder than that. </div></div>

Yes, here is one Winchester Supreme 168gr thrown in with my loads, ignore what appears to be a popped primer. I decapped it myself to examine it more carefully.

And just for the hell of it, here is a load that got me 2800fps with 155gr Scenars, but was too hot. Once again ignore the loose primer, I decapped it for a closer look at the primer and pocket. Look at those ejector marks! I never even got within 1/2gr of listed max.

 

[sinister]

Re: What velocities are possible in an M1A?

Just remember -- a cast Springfield Armory M1A receiver is technically not as strong as an M14 forging, and an M14 is a piston-driven action.

A steady diet of very high pressure loads can contribute to something like this (courtesy the Wisconsin Rifle Team):

 

[Michael]

Re: What velocities are possible in an M1A?

Win brass, WLR primer, 175 matchking, 41.1 grains H4895 = 2550fps at 60 degrees and 1000 asl. At 95 degrrees it's 2571fps.
Brass lands in a pile 30 inches from the ejection port at 3 O'clock. You won't even feel the recoil.