• Watch Out for Scammers!

    We've now added a color code for all accounts. Orange accounts are new members, Blue are full members, and Green are Supporters. If you get a message about a sale from an orange account, make sure you pay attention before sending any money!

How fast to push a 175 grain bullet in a gas gun?

W

wyominglarry

Private
Full Member
Minuteman
Apr 16, 2005
8
0
73
casper, wyoming
I just built an AR 10 type rifle.

I have been loading and shooting 175 grain bullets in my M1A pushing them to 2550-2580 fps.

What is the recommended fps speed using the same bullet, but in an AR 10 type rifle?

I am assuming that all gas guns need to keep the pressure down and run the same bullets with identical speeds that are used in an M1A.
 
Re: How fast to push a 175 grain bullet in a gas gun?

it would depend on the length of barrel but probrably 2500-2550
 
Re: How fast to push a 175 grain bullet in a gas gun?

You realize that your M1A is a "gas gun" right?

And since you don't have to worry about bending an op-rod on an AR10 I all bet you can run them faster and harder. You will more than likely run into issues with tearing the cases up or failure to extract/feed before you actuall cause damage to the rifle.

Worry about pressure not speed. Speed is a good thing if everything functions.

If I were you I would just work up to the same load you use in your M1A so you can use the same ammo in both.
 
Re: How fast to push a 175 grain bullet in a gas gun?

The most I've gotten through my ArmaLite with a 21" Noveske barrel is 2600-2630 with 44.6-45gr of Varget.
 
Re: How fast to push a 175 grain bullet in a gas gun?

Using LC-90 cases and 210M primers with 45gr of Varget I get 2760fps with my 24" Kreiger. I run a Tubbs CWS also.
 
Re: How fast to push a 175 grain bullet in a gas gun?

I didn't mention it but I am also using the Tubbs CWS and the heaviest buffer possible.
 
Re: How fast to push a 175 grain bullet in a gas gun?

It is a POF in 308 with a 20" barrel.

I know my M1A is a gas gun.

I know that the M1A has to be loaded for the pressure curve of the powder and if the load is too fast using the 175 grain bullet. This will really hammer the bolt into the rear of the receiver.

I just wanted to know if an AR 10 type gas gun can take a faster load without damaging the rifle.

I plan on shooting the loads I have worked up for the M1A in the POF. I just did not know if I can push the fps over 2550 in an AR 10 type rifle.
 
Re: How fast to push a 175 grain bullet in a gas gun?

44 grains of Varget.... gets me around 2500 on a 20" barrel.
 
Re: How fast to push a 175 grain bullet in a gas gun?

Factory Armalite AR10T w/2060 rnds down the tube.

80 deg., 178 Amax, 44.5 gr. Varget, BR2's, FGMM brass, 2.810 COAL = 2639 fps avg from 25 rnds. Been shooting it a long time but planning on backing it off a bit because I get a little ejector swipe. This load shoots great though. As always, start way low and work up.

okie
 
Re: How fast to push a 175 grain bullet in a gas gun?

Hey Okie,

What's "ejector swipe"?

Thank you.
 
Re: How fast to push a 175 grain bullet in a gas gun?

Why not look at an adjustable gas block/plug for both rifles?

Couldn't you then pretty much run whatever for loads and not hurt the gun?
 
Re: How fast to push a 175 grain bullet in a gas gun?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: unrepentant</div><div class="ubbcode-body">Hey Okie,

What's "ejector swipe"?

Thank you. </div></div>

Marks made on brass by the ejector, sometimes caused by hot loads during ejection. Sometimes it actually shaves off tiny pieces (specs) of the brass that you'll see around the bolt face.

okie
 
Re: How fast to push a 175 grain bullet in a gas gun?

How far down the barrel is the gas port...




<span style="color: #FF0000"><span style="font-weight: bold">AND</span></span>




what are the pressure specs for the gas system?

It's usually stated as XX,XXX PSI (CUP or Piezo?), +/- X,XXX PSI.

Until you have answers to those questions, you're all just mentally proving nothing. Sammy Hagar had a much more rude term for it. I know it for the M1A, but no one on any gun board in the past 8 years has ever been able to give me the figures for the AR systems, the FN system, or any other semiauto.
 
Re: How fast to push a 175 grain bullet in a gas gun?

Grump, not sure if you were talking to me or not but...

I'm not gonna empty my safe to measure but as with any AR10T I'm sure the gas tube is rifle length...whatever that is.

Dont have any idea what kind of equipment you would need to measure PSI or CUP in a load but I definately dont have it or know anyone that does besides ammo manufacturers and have never read it for AR10's. It may be a mistake but I have always assumed that modern AR10's (along with all other modern 308 based AR's) were built to withstand pressures created by todays 308 ammunition. I have 5 manuals, 2 list PSI for the max loads for Varget which is what I'm using.

Lee manual: 45.0 gr, 57,946 PSI, 2690 FPS, 2.800 OAL.
Lyman manual: 45.2 gr, 59,300 PSI, 2708 FPS, 2.800 OAL.

Not sure what the CUP or PSI info does for me since I am pretty much basing my max load on what the manuals list as such in grains for the particular powder I'm useing. How do you use this info to determine your max velosity which is what the OP was asking about? TIA.

okie

PS. Sammy's hell on the git fiddle (nothin like King Edward though) but dont think I would count on him for proving anything mentally in presicion shooting.
wink.gif
 
Re: How fast to push a 175 grain bullet in a gas gun?

Barrels on all these modern rifles are more than adequate to handle the chamber pressures of all ammo and even a lot of the probably-overpressure loads I see described here with some frequency.

But the pressure curve drops off drastically after the bullet goes only six inches down the bore. Even the pressure curve of the new Hornady 1780gr HPBT ammo, with the most progressive burn ever attained to date, is still pretty much the same shape, just pushed a few inches further down the bore.

If a person combined a Pressure Trace readout with calibrated inputs to QuickLOAD, then maybe the port pressure could be estimated with reasonable accuracy. I *do* know that running QuickLOAD did match some 1980s NRA published data on WW-748 loads in .308, right down to the lighter bullet loads having port pressures almost beyond the max specs, and the heavy (173, 180 and 190s) bullet loads having lower port pressures the heavier the bullet.

What baffles me is that with all the stuff I've read on the M16 system over the years, I've NEVER seen any statement of the gas port pressure specs.

Same with the AR10/SR25 and whatever all the variants are. Would love to see it with the FN-FAL as well, 'cause I downloaded some stuff that wouldn't cycle an inch-pattern FN, not even fully extract with the gas system fully adjusted for "weak" ammo, but those same loads cycled and locked the bolt back on an M1A that same day. I think QuickLOAD estimated the port pressure at close to 2,000 PSI less than minimum spec, no less! Then there's the CUP does not exactly equal PSI problem.

Until I can get any data on port pressure specs, all I can say to the OP is that a 20-inch barrel should usually be able to get 2550 fps out of a max charge of 4895, 4064, maybe 3031, Varget, RL-15, or WW-748. About the only pressure sign I trust is the radius of the primer compared to those of factory loads using the same brand of primer, but then only if the case is not excessively resized (false high pressure signs then).
 
Re: How fast to push a 175 grain bullet in a gas gun?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">What baffles me is that with all the stuff I've read on the M16 system over the years, I've NEVER seen any statement of the gas port pressure specs.</div></div>

Here's a good article with gas port pressure graphs for 5.56 ARs:

http://www.armalite.com/images/Tech%20No...24%E2%80%A6.pdf
 
Re: How fast to push a 175 grain bullet in a gas gun?

Today I was getting 2630fps consistently with a charge of 43gr of RE15 pushing a 178gr AMAX.

Primers looked good, but I got some ejector marks on some case heads. I don't think it was due to pressure, I think it was more due to a sharp edge. It actually raised a little curl of brass, but it didn't look like the kind of flow you get on a Remington 700 when you push the limits.

Enviromental Variables were as follows:
63*F
29.53 Hg
33% Humidity
380' ASL

Rifle:
21" Noveske 7.62 MATCH chamber
Rifle length gas system
Rifle length buffer

Chrony was a little more than 10' away. I forgot my tape today.
 
Re: How fast to push a 175 grain bullet in a gas gun?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LoneWolfUSMC</div><div class="ubbcode-body">Today I was getting 2630fps consistently with a charge of 43gr of RE15 pushing a 178gr AMAX.

Primers looked good, but I got some ejector marks on some case heads. I don't think it was due to pressure, I think it was more due to a sharp edge. It actually raised a little curl of brass, but it didn't look like the kind of flow you get on a Remington 700 when you push the limits.

Enviromental Variables were as follows:
63*F
29.53 Hg
33% Humidity
380' ASL

Rifle:
21" Noveske 7.62 MATCH chamber
Rifle length gas system
Rifle length buffer

Chrony was a little more than 10' away. I forgot my tape today. </div></div>

Did the marks look like this:

8wl7ki.jpg
 
Re: How fast to push a 175 grain bullet in a gas gun?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sinister</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">What baffles me is that with all the stuff I've read on the M16 system over the years, I've NEVER seen any statement of the gas port pressure specs.</div></div>

Here's a good article with gas port pressure graphs for 5.56 ARs:

http://www.armalite.com/images/Tech%20No...24%E2%80%A6.pdf</div></div>

Ah, at last!!

So nominal for a full-length AR15 type is 13,000 PSI at the port. I *guess* that it should work well enough with +/- 2,000 PSI like the M14 system, but can anyone verify that?

I would also conclude that cycling gets sub-optimal somewhere LESS than 26,000 PSI (the carbine operating pressures), so maybe the + side of the pressure tolerances might be much higher...

Next question, for this thread, is whether those pressures and timelines in the operating cycle apply to the 7.62/AR10 types...
 
Re: How fast to push a 175 grain bullet in a gas gun?

I have heard 19,500 for AR10 type is what is needed to cycle, I don't have any documentation to back that up though.
 
Re: How fast to push a 175 grain bullet in a gas gun?

I dont know if this applies, but my FNAR which has a 20" barrel spits out a 175gr Fed GMM at 2610 ft/sec.
 
Re: How fast to push a 175 grain bullet in a gas gun?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: okiefired</div><div class="ubbcode-body">Grump, not sure if you were talking to me or not but...

I'm not gonna empty my safe to measure but as with any AR10T I'm sure the gas tube is rifle length...whatever that is.

Dont have any idea what kind of equipment you would need to measure PSI or CUP in a load but I definately dont have it or know anyone that does besides ammo manufacturers and have never read it for AR10's. It may be a mistake but I have always assumed that modern AR10's (along with all other modern 308 based AR's) were built to withstand pressures created by todays 308 ammunition. I have 5 manuals, 2 list PSI for the max loads for Varget which is what I'm using.

Lee manual: 45.0 gr, 57,946 PSI, 2690 FPS, 2.800 OAL.
Lyman manual: 45.2 gr, 59,300 PSI, 2708 FPS, 2.800 OAL.

Not sure what the CUP or PSI info does for me since I am pretty much basing my max load on what the manuals list as such in grains for the particular powder I'm useing. How do you use this info to determine your max velosity which is what the OP was asking about? TIA.

okie

PS. Sammy's hell on the git fiddle (nothin like King Edward though) but dont think I would count on him for proving anything mentally in presicion shooting.
wink.gif




</div></div>

I'm not sure how they "measure" internal pressure, but I know it can be figured out mathematically using the pressure volume relationship. P1V1=P2V2. It gets a little more complicated than that, of course, but if you knew the gas expansion of X amount of powder when it burns, you could theoretically figure out the pressure created. That information can be turned into a non-linear downward sloping curve as the volume increases (i.e. the bullet goes down the barrel).

The chemical engineers at the powder manufacturing plants know the expansion properties of burning gun powder. They feed that info over to the ammunition manufacturers who do the math relating those properties to the volume of the case vs. powder volume. That same info is probably fed to the writers of various reloading manuals. That's why it's important to have an up-to-date manual.

Just guessing here.
-Erik
 
Re: How fast to push a 175 grain bullet in a gas gun?

Quickload gives an output on pressure as bullet travels down the barrel no idea how accurate it actually is. It does seem in the ballpark though
 
Re: How fast to push a 175 grain bullet in a gas gun?

Dosn't matter,
accuracy - brass life - throat erosion - primer flow - neck splitting - timing - tight or loose chamber - seating depth - etc will dictate all

2550- 2750 ??
 
Re: How fast to push a 175 grain bullet in a gas gun?

<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: LoneWolfUSMC</div><div class="ubbcode-body">Today I was getting 2630fps consistently with a charge of 43gr of RE15 pushing a 178gr AMAX.

Primers looked good, but I got some ejector marks on some case heads. I don't think it was due to pressure, I think it was more due to a sharp edge. It actually raised a little curl of brass, but it didn't look like the kind of flow you get on a Remington 700 when you push the limits.

Enviromental Variables were as follows:
63*F
29.53 Hg
33% Humidity
380' ASL

Rifle:
21" Noveske 7.62 MATCH chamber
Rifle length gas system
Rifle length buffer

Chrony was a little more than 10' away. I forgot my tape today. </div></div>

Did the marks look like this:

8wl7ki.jpg


</div></div>



i have had factory loaded blackhills look exactly like that!
 
Re: How fast to push a 175 grain bullet in a gas gun?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Erik S.</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: okiefired</div><div class="ubbcode-body">Grump, not sure if you were talking to me or not but...

I'm not gonna empty my safe to measure but as with any AR10T I'm sure the gas tube is rifle length...whatever that is.

Dont have any idea what kind of equipment you would need to measure PSI or CUP in a load but I definately dont have it or know anyone that does besides ammo manufacturers and have never read it for AR10's. It may be a mistake but I have always assumed that modern AR10's (along with all other modern 308 based AR's) were built to withstand pressures created by todays 308 ammunition. I have 5 manuals, 2 list PSI for the max loads for Varget which is what I'm using.

Lee manual: 45.0 gr, 57,946 PSI, 2690 FPS, 2.800 OAL.
Lyman manual: 45.2 gr, 59,300 PSI, 2708 FPS, 2.800 OAL.

Not sure what the CUP or PSI info does for me since I am pretty much basing my max load on what the manuals list as such in grains for the particular powder I'm useing. How do you use this info to determine your max velosity which is what the OP was asking about? TIA.

okie

PS. Sammy's hell on the git fiddle (nothin like King Edward though) but dont think I would count on him for proving anything mentally in presicion shooting.
wink.gif




</div></div>

I'm not sure how they "measure" internal pressure, but I know it can be figured out mathematically using the pressure volume relationship. P1V1=P2V2. It gets a little more complicated than that, of course, but if you knew the gas expansion of X amount of powder when it burns, you could theoretically figure out the pressure created. That information can be turned into a non-linear downward sloping curve as the volume increases (i.e. the bullet goes down the barrel).

The chemical engineers at the powder manufacturing plants know the expansion properties of burning gun powder. They feed that info over to the ammunition manufacturers who do the math relating those properties to the volume of the case vs. powder volume. That same info is probably fed to the writers of various reloading manuals. That's why it's important to have an up-to-date manual.

Just guessing here.
-Erik </div></div>

Hell of a guess there Eric
wink.gif
. Was the word "measure" not the correct word to use? Isn't "figuring out mathmatically" the same as measuring? How bout calculate or.....sipher?
smile.gif
You're right though, it is a bit more complicated than that. Case expansion, wall thickness (strength), neck tension and bullet distance from lands and grooves come into play just to name a few. Gas operation or bolt? Hell, we can list variables for a while.

I was just pointing out the info in a couple of the manuals I have.

okie
 
Re: How fast to push a 175 grain bullet in a gas gun?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Falar</div><div class="ubbcode-body">
Did the marks look like this:

8wl7ki.jpg

</div></div>

Yep. Exactly like that.
 
Re: How fast to push a 175 grain bullet in a gas gun?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LoneWolfUSMC</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Falar</div><div class="ubbcode-body">
Did the marks look like this:

8wl7ki.jpg

</div></div>

Yep. Exactly like that. </div></div>

IMO those kind of marks mean you are getting within 1/2" grain or so of max but still have some room to go. Check out item #5 in this link, according to ArmaLite these marks are considered "normal" and I will agree, I've had them on some factory loads:

ArmaLite Tech Note 17

ETA: The pic I posted were my handloads. 46.5gr Varget under 155gr Scenars in new Winchester cases.
 
Re: How fast to push a 175 grain bullet in a gas gun?

My reply was never meant to nit-pick word usage, just offering a different take on determining internal case pressure. I simply assumed that you were inferring that some sort of machine or pressure transducer would be required to measure pressure by your use of the word "equipment".

There are many variables that come into play when determining internal case pressure. I suppose one would also have to know how long the powder continues to burn after the bullet has left the case. Way out of my league either way. I would guess the max pressure may not occur until the bullet is some ways down the barrel.

-Erik

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: okiefired</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Erik S.</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: okiefired</div><div class="ubbcode-body">Grump, not sure if you were talking to me or not but...

I'm not gonna empty my safe to measure but as with any AR10T I'm sure the gas tube is rifle length...whatever that is.

Dont have any idea what kind of equipment you would need to measure PSI or CUP in a load but I definately dont have it or know anyone that does besides ammo manufacturers and have never read it for AR10's. It may be a mistake but I have always assumed that modern AR10's (along with all other modern 308 based AR's) were built to withstand pressures created by todays 308 ammunition. I have 5 manuals, 2 list PSI for the max loads for Varget which is what I'm using.

Lee manual: 45.0 gr, 57,946 PSI, 2690 FPS, 2.800 OAL.
Lyman manual: 45.2 gr, 59,300 PSI, 2708 FPS, 2.800 OAL.

Not sure what the CUP or PSI info does for me since I am pretty much basing my max load on what the manuals list as such in grains for the particular powder I'm useing. How do you use this info to determine your max velosity which is what the OP was asking about? TIA.

okie

PS. Sammy's hell on the git fiddle (nothin like King Edward though) but dont think I would count on him for proving anything mentally in presicion shooting.
wink.gif




</div></div>

I'm not sure how they "measure" internal pressure, but I know it can be figured out mathematically using the pressure volume relationship. P1V1=P2V2. It gets a little more complicated than that, of course, but if you knew the gas expansion of X amount of powder when it burns, you could theoretically figure out the pressure created. That information can be turned into a non-linear downward sloping curve as the volume increases (i.e. the bullet goes down the barrel).

The chemical engineers at the powder manufacturing plants know the expansion properties of burning gun powder. They feed that info over to the ammunition manufacturers who do the math relating those properties to the volume of the case vs. powder volume. That same info is probably fed to the writers of various reloading manuals. That's why it's important to have an up-to-date manual.

Just guessing here.
-Erik </div></div>

Hell of a guess there Eric
wink.gif
. Was the word "measure" not the correct word to use? Isn't "figuring out mathmatically" the same as measuring? How bout calculate or.....sipher?
smile.gif
You're right though, it is a bit more complicated than that. Case expansion, wall thickness (strength), neck tension and bullet distance from lands and grooves come into play just to name a few. Gas operation or bolt? Hell, we can list variables for a while.

I was just pointing out the info in a couple of the manuals I have.

okie </div></div>
 
Re: How fast to push a 175 grain bullet in a gas gun?

What constitutes a max load for a gas gun is different than for a bolt action. The main issue with a semi is gas port pressure rather than chamber pressure. Gas volume is fixed and pre-set to work within a certain range.

Although there is a cause and effect relationship, it is a variable. Faster powders generate higher chamber pressures and lower gas port pressures and vice-versa.

Powders like 4895, 4064, Varget, RE-15 are within the burning range spectrum. That range is what the system is designed around, loaded to the equivalent of Federal GMM ammo. That will give around 2550fps from a 20" barrel and about 2650 from a 24". It should be adequate from an 18" as well. You don't want to run a slower powder in a gas gun.

Anyway, there is no need to run a 175 308 over 2550fps to get to 1000yds stable. A higher BC means more at extended range than a 100 fps, so if velocity becomes an issue, run a lighter, higher BC bullet like the Scenar, Berger or the new design Sierra Palma Match bullet. There is an accuracy node at that level, so I'd lean toward running the lightest, best accurate load that achieves that velocity goal.

Since 1000yds is beyond the range of effective 308 terminal performance, apart from target shooting, there is nothing to be gained from a hotter load, so why stress the reciprocating parts to achieve a few more fps?



TC
 
Re: How fast to push a 175 grain bullet in a gas gun?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Top Cat</div><div class="ubbcode-body">
Anyway, there is no need to run a 175 308 over 2550fps to get to 1000yds stable. A higher BC means more at extended range than a 100 fps, so if velocity becomes an issue, run a lighter, higher BC bullet like the Scenar, Berger or the new design Sierra Palma Match bullet. There is an accuracy node at that level, so I'd lean toward running the lightest, best accurate load that achieves that velocity goal.
</div></div>

The Sierra "Palma" is named such because it was designed for Palma competition rules. If those rules stated unlimited bullet weight, you would see the 155's disappear from the line. They would be replaced by 175's and up pushing as fast as they could.

Long range load selection is all about reducing wind drift.

Select a high BC bullet and drive it as hard as you accurately can.
 
Re: How fast to push a 175 grain bullet in a gas gun?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Falar</div><div class="ubbcode-body">
LoneWolfUSMC said:
IMO those kind of marks mean you are getting within 1/2" grain or so of max but still have some room to go. Check out item #5 in this link, according to ArmaLite these marks are considered "normal" and I will agree, I've had them on some factory loads:</div></div>

I was getting them intermittently with 43gr of RE15 under the 178 AMAX, but that was with Federal brass.

I am not real worried about it until I start seeing primers flatten out or FP cratering.

Next trip out I will probably work up another grain and a half and see where the scatter node sits. This was a half-ass workup where I just loaded a couple to look for pressure signs then loaded 20 at my OBT node. It seemed to work though. I just wish I loaded a couple past the OBT node to see what it looked like.
Click to expand...
 
Re: How fast to push a 175 grain bullet in a gas gun?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Erik S.</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: okiefired</div><div class="ubbcode-body">Grump, not sure if you were talking to me or not but...

I'm not gonna empty my safe to measure but as with any AR10T I'm sure the gas tube is rifle length...whatever that is.

Dont have any idea what kind of equipment you would need to measure PSI or CUP in a load but I definately dont have it or know anyone that does besides ammo manufacturers and have never read it for AR10's. It may be a mistake but I have always assumed that modern AR10's (along with all other modern 308 based AR's) were built to withstand pressures created by todays 308 ammunition. I have 5 manuals, 2 list PSI for the max loads for Varget which is what I'm using.

Lee manual: 45.0 gr, 57,946 PSI, 2690 FPS, 2.800 OAL.
Lyman manual: 45.2 gr, 59,300 PSI, 2708 FPS, 2.800 OAL.

Not sure what the CUP or PSI info does for me since I am pretty much basing my max load on what the manuals list as such in grains for the particular powder I'm useing. How do you use this info to determine your max velosity which is what the OP was asking about? TIA.

okie

PS. Sammy's hell on the git fiddle (nothin like King Edward though) but dont think I would count on him for proving anything mentally in presicion shooting.
wink.gif




</div></div>

I'm not sure how they "measure" internal pressure, but I know it can be figured out mathematically using the pressure volume relationship. P1V1=P2V2. It gets a little more complicated than that, of course, but if you knew the gas expansion of X amount of powder when it burns, you could theoretically figure out the pressure created. That information can be turned into a non-linear downward sloping curve as the volume increases (i.e. the bullet goes down the barrel).

The chemical engineers at the powder manufacturing plants know the expansion properties of burning gun powder. They feed that info over to the ammunition manufacturers who do the math relating those properties to the volume of the case vs. powder volume. That same info is probably fed to the writers of various reloading manuals. That's why it's important to have an up-to-date manual.

Just guessing here.
-Erik</div></div>

The new Hornady Manual (7th edition) has load data for service rifles in 308 and 5.56. It also has a section in 3006 for the Garand. I load for and shoot semi autos in all three calibers. I keep the brass marked as to which rifle it was used in and follow procedures I have developed for that individual rifle. The bolt guns get loaded hotter then the semi autos. The Garand seems to be the most susceptible to damage by over loading or choosing the wrong powder according to many sources. Just an FYI.
 
Re: How fast to push a 175 grain bullet in a gas gun?

I have the Hornady Manual, but it seems that the "Service Rifle" loads listed are rather anemic for the AR pattern rifles. The test rifle listed for them is an M1A type rifle (don't remember the specifics right now).

As always, start low and work up. ALWAYS wear safety glasses when working up loads. I hate shooting precision rifles with safety glasses on, but this is one case where I suck it up and deal with the loss in clarity.
 
Re: How fast to push a 175 grain bullet in a gas gun?

Erik S., sorry bout that. My reply sounded a little harsh after rereading and I didn't intend for it to be that way. I'm no engineer (obviously) so I'm pretty easily overwhelmed. I just ment that my feeble mind cant come close to comming up with a formula that would include all the variables needed to calculate the pressures involved. It may be nitpicking, but to be totally accurate, I think all would have to be included.

As for the ejector marks, I never REALLY worry about them either since all other signs are good. However, even though my ejector is very sharp cornered too, I can always reduce if not completely eliminate the marks simply by reducing the charge a tad. I'm with LoneWolf though in that I think for best accuracy most bullets should be pushed to or very near max SAFE limits. In my experience, these loads usually produce ejector marks too.

okie
 
Re: How fast to push a 175 grain bullet in a gas gun?

i get those marks with factory loaded black hills ALOT
 
Re: How fast to push a 175 grain bullet in a gas gun?

No need to appologize. After being on these forums for so long, I am not easily offended, just didn't want to make any enemies
smile.gif


I wish I had the time to delve into the specifics of these kinds of topics. I suppose my reloading doesn't go far beyond my reloading manual. haha

I try to load light anyway and if I can't find something that works in the lower 75% of the recommended powder charge after playing around with bullet seating, I find a different bullet. So far, I haven't had to look any further than the 178gr A-max and 175gr SMK in my .308.

-Erik

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: okiefired</div><div class="ubbcode-body">Erik S., sorry bout that. My reply sounded a little harsh after rereading and I didn't intend for it to be that way. I'm no engineer (obviously) so I'm pretty easily overwhelmed. I just ment that my feeble mind cant come close to comming up with a formula that would include all the variables needed to calculate the pressures involved. It may be nitpicking, but to be totally accurate, I think all would have to be included.

As for the ejector marks, I never REALLY worry about them either since all other signs are good. However, even though my ejector is very sharp cornered too, I can always reduce if not completely eliminate the marks simply by reducing the charge a tad. I'm with LoneWolf though in that I think for best accuracy most bullets should be pushed to or very near max SAFE limits. In my experience, these loads usually produce ejector marks too.

okie </div></div>
 
Re: How fast to push a 175 grain bullet in a gas gun?

Getting 2645 consistently out of BL-C2 max load in the manual. I can't remember what it is right at the moment and I don't have the manual with me. I think it is 46.0 gr. It takes about 11.2 mil to get to 1000 yds.
 
You must log in or register to reply here.

Similar threads

GreenJavelin
SCAR 20S RANGE REPORT: 175 SMK vs 168 ELDM
Replies
4
Views
285
BCP
BCP
4
AR 10 338 RCM ...sure lets build this at home.
Replies
3
Views
182
KYAggie
KYAggie
R
Bolt gun velocities vs gas gun velocities?
Replies
19
Views
803
Pappasniper
P
Dirtracer151
Tuning a gas gun/false pressure signs
Replies
22
Views
738
Cascade Hemi
C
Clint H
New Small-Frame Build Range Report
Replies
8
Views
502
bfoosh006
bfoosh006
Top Bottom
Back