[Allen Humphrey]

I can't comment on getting a 175gr bullet up to 2600 in a 22" barrel with 4064 as I have not tried, but regarding the gas plug... is yours the adjustable or the vented version? I'm confident you could dial in an adjustable plug to protect the gas system with a heavy load. I'm not so confident it would cycle on lighter loads.

At risk of sounding like a fan-boy of the Sierra 168 TMK, I've had good luck in one rifle with them. They have a G1 BC of .535 and can get pushed faster. Might be worth a look depending on what you are wanting to accomplish.

Edit: I'm loading the TMK to longer than mag length. I could load them short enough, but they may not like the "jump" necessary... just a thought.

 

[Thedutchman]

2600 ish is the run of the mil velocity for 168’s. Maybe 2600 is ok for the 175’s? M118LR is currently loading 43.3 of RL15. Last I clocked M118 out of my Loaded was 2650 avg.
Your pressures sound OK to me. Glad you have a Schuster plug if you plan to feed your rifle a steady diet of the heavier stuff.
Remember, primers aren’t always the best way to tell if you are dealing with higher pressures. Softer vs harder cups on various manufacturers primers.
I look more toward extractor swipes for over pressure signs.

 

[Puritan]

I can't comment on getting a 175gr bullet up to 2600 in a 22" barrel with 4064 as I have not tried, but regarding the gas plug... is yours the adjustable or the vented version? I'm confident you could dial in an adjustable plug to protect the gas system with a heavy load. I'm not so confident it would cycle on lighter loads.

At risk of sounding like a fan-boy of the Sierra 168 TMK, I've had good luck in one rifle with them. They have a G1 BC of .535 and can get pushed faster. Might be worth a look depending on what you are wanting to accomplish.

Edit: I'm loading the TMK to longer than mag length. I could load them short enough, but they may not like the "jump" necessary... just a thought.

Thanks, it's the Non-Adjustable gas plug.

 

[Puritan]

I look more toward extractor swipes for over pressure signs.

Thanks. I've always gotten some degree of extractor swiping in this rifle even when using factory ammo so I'm not sure what to look for. I wish someone marketed an affordable device for checking chamber pressures.

 

[Thedutchman]

Light swipes are one thing. Huge swipes and a small ring where the brass floats into the hole where the ejector and spring are is another.
a photo of rings/swipes.

 

[KurtC]

Since the Berger 175 OTM is very similar to the 175 SMK, I find it hard to believe that you are not up around 2600 with 43.3 grains of 4064. I can only guess that you have a very tight barrel.

I'm hitting 2600 with the 175 SMK and 43 grains of 4064 in a Federal match case, but my barrel is a chrome lined USGI.

 

[TheShooter]

Since the Berger 175 OTM is very similar to the 175 SMK, I find it hard to believe that you are not up around 2600 with 43.3 grains of 4064. I can only guess that you have a very tight barrel.

I'm hitting 2600 with the 175 SMK and 43 grains of 4064 in a Federal match case, but my barrel is a chrome lined USGI.

What would you use in a nato case 42.5?

 

[Puritan]

Light swipes are one thing. Huge swipes and a small ring where the brass floats into the hole where the ejector and spring are is another.
a photo of rings/swipes.

Thanks for the photos. I haven't seen anything like this on my cases (yet).

 

[KurtC]

What would you use in a nato case 42.5?

That's exactly what I use in an LC case.

 

[Puritan]

Since the Berger 175 OTM is very similar to the 175 SMK, I find it hard to believe that you are not up around 2600 with 43.3 grains of 4064. I can only guess that you have a very tight barrel.

I'm hitting 2600 with the 175 SMK and 43 grains of 4064 in a Federal match case, but my barrel is a chrome lined USGI.

My barrel is just an SAI NM (although the rest of the rifle is SAI standard). Not sure why you are getting higher MV than I am. What is you're bullet seating depth? Do you know how Lapua and Federal Match case volumes compare? Do you think your load is causing excessive battering of the op rod? Would you say that SMK data is interchangeable for the Berger OTM? Sorry for all the questions - thanks.

 

[KurtC]

2.815-20, depending on the shape of the SMK tip.

Don't know about Lapua cases. Too expensive for a gas gun.

I use a non adjustable Schuster plug in all my rifles.

I think the SMK and Berger OTM are close enough for government work.

No problem. I was on the range earlier and haven't started drinking for the evening.

 

[Thedutchman]

As you move the bullet farther away from the lands, the pressure always goes down. Obviously we’re not crunching the heck out of the powder but y’all know what I mean. Use mag length as your jam measurement and go 10 thou-20 thou less than that.
Lapua cases are similar in internal case volume to that of Fed. Match cases. In fact, most commercial cases are very very close to one another regarding case volume. It’s when you move to NATO cases where the charge weights start to become more separated.
I would say those two bullets are almost identical when measuring out charge weights and finding accuracy nodes.
cheers
Dutch

 

[Puritan]

2.815-20, depending on the shape of the SMK tip.

Don't know about Lapua cases. Too expensive for a gas gun.

I use a non adjustable Schuster plug in all my rifles.

I think the SMK and Berger OTM are close enough for government work.

No problem. I was on the range earlier and haven't started drinking for the evening.

Maybe I need a new chronograph then because it sounds like all our components are similar - 2.815 OAL on all my reloads. My Shooting Chrony is old, but still works every time (except that one time I forgot to replace the battery). Maybe it's lost some sensitivity over the years. Thanks for the info. I'll hold off until at least tomorrow for further inquiries so imbibe at will!

 

[Puritan]

As you move the bullet farther away from the lands, the pressure always goes down. Obviously we’re not crunching the heck out of the powder but y’all know what I mean. Use mag length as your jam measurement and go 10 thou-20 thou less than that.
Lapua cases are similar in internal case volume to that of Fed. Match cases. In fact, most commercial cases are very very close to one another regarding case volume. It’s when you move to NATO cases where the charge weights start to become more separated.
I would say those two bullets are almost identical when measuring out charge weights and finding accuracy nodes.
cheers
Dutch

Thanks Dutch. I have gotten around 2600 fps depending on temperature with 42.2 grains IMR 4064 in 7.62x51 Nammo Military brass (Midway had a sale), but for some reason I'm not getting that in the Lapua 308 cases (also owned by Nammo group). It shot ok, but not quite as accurate as 41.1 grains, which produced significantly less MV. By ok I mean ok for me which was 2.75 inches at 200 yards vs 2.25 inches. Not quite moa accuracy, but I'm old and shaky.

 

[KurtC]

If you would have said in the first post that you were getting 2.75" groups at 200 yds, we could have saved a lot of space on the Forum server.

Unless you are planning on shooting 800-1k yds, I wouldn't worry about getting 2600 fps.

 

[RAMMAC]

How far from the muzzle are you placing the chronograph? Do you compensate for that distance?

An LC case has less volume than a typical Lapua case. In my records I show that the LC cases that I tested had an average volume equivalent of 53.3gr of water while the Lapua brass has an average of 55gr of water.

The volume difference can create a velocity difference of about 30 to 40 FPS and not compensating for the distance from the muzzle can create another 25 to 30 FPS difference so you could easily have a 70 FPS error without even considering the error from how the chronograph was setup and it's intrinsic accuracy error.

 

[Puritan]

If you would have said in the first post that you were getting 2.75" groups at 200 yds, we could have saved a lot of space on the Forum server.

Unless you are planning on shooting 800-1k yds, I wouldn't worry about getting 2600 fps.

1000 yards is the plan. I've mentioned this in other posts, but my 14 year old has taken an interest in long distance shooting so I've been making some upgrades and doing some maintenance to the M1A so he can take it over. A Rem 700 Milspec or 700P would be a better 1000 yard gun admittedly, but with Remington selling off much of its manufacturing business the M1A will suffice for now. With respect to the 2.75" groups, those were the best and not the 4" norms I was otherwise getting. It still felt inadequate considering all the hardware on the rifle like an 8-32x scope and Flatline-Ops Scope Level ring. I'm sure the rifle can do much better with more consistent ammo and someone with less astigmatic eyes behind the trigger. I hope you had a great day at the range.

 

[Puritan]

How far from the muzzle are you placing the chronograph? Do you compensate for that distance?

An LC case has less volume than a typical Lapua case. In my records I show that the LC cases that I tested had an average volume equivalent of 53.3gr of water while the Lapua brass has an average of 55gr of water.

The volume difference can create a velocity difference of about 30 to 40 FPS and not compensating for the distance from the muzzle can create another 25 to 30 FPS difference so you could easily have a 70 FPS error without even considering the error from how the chronograph was setup and it's intrinsic accuracy error.

Thanks RAMMAC. The shooting range I took these measurements at prohibits chronograph use closer than 10 feet from the bench. I usually just find the first level spot past this point and set up my tripod there so distance might be playing a role, but probably not that much. The case volume comparison between LC and Lapua is awesome, thanks so much for providing that info and the associated FPS changes.

 

[charlie98]

My Shooting Chrony is old,

I have a very old original Chrony... it does have it's senior moments. Some days it lays out readings lickety split, other days it fights me through half my ammo stash trying to get a good reading. Light at an angle, particularly, jacks it up, as does overhead cloud cover and other meteorological nonsense. Just so you are aware.