I was just curious what everyone else has been getting shooting the FGMM 168 HP with a 18" barrel. I have been trying to figure what velocity gain I would get with a 22 or 24" barrel or if its worth keeping it at 18"? Thanks for any help.
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Range Report 308 18" barrel Velocity
- Thread starter Strangedays
- Start date
Re: 308 18" barrel Velocity
i was getting a very consistent 2645 fps with fgmm 168's out of my .299 bore, 18.5" barrel.
i was getting a very consistent 2645 fps with fgmm 168's out of my .299 bore, 18.5" barrel.
Re: 308 18" barrel Velocity
I recently chrono'd some FGMM 168 out of my SPS-T 20" (yes, I know not 18") and a 10 string average gave me an avg of 2540 at 40F and 3400 MSL.
I recently chrono'd some FGMM 168 out of my SPS-T 20" (yes, I know not 18") and a 10 string average gave me an avg of 2540 at 40F and 3400 MSL.
Re: 308 18" barrel Velocity
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: strangedays</div><div class="ubbcode-body">I have been trying to figure what velocity gain I would get with a 22 or 24" barrel or if its worth keeping it at 18"? Thanks for any help. </div></div>
The gain would be equivalent to another 125 yards of accurate fire. That is, if you current load can be accurate at 800 yards, the longer barrel using the same cartrige would be accurate out to 925 yard. If you are currently accurte to 1100 yards, the longer tube would be accurate to 1225.
It is UNLIKELY that FGMM 168 is accurate beyond 875 yards as the BC is simply not up to par with the 175s and modern 155s.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: strangedays</div><div class="ubbcode-body">I have been trying to figure what velocity gain I would get with a 22 or 24" barrel or if its worth keeping it at 18"? Thanks for any help. </div></div>
The gain would be equivalent to another 125 yards of accurate fire. That is, if you current load can be accurate at 800 yards, the longer barrel using the same cartrige would be accurate out to 925 yard. If you are currently accurte to 1100 yards, the longer tube would be accurate to 1225.
It is UNLIKELY that FGMM 168 is accurate beyond 875 yards as the BC is simply not up to par with the 175s and modern 155s.
Re: 308 18" barrel Velocity
I know its not 168...but out of my 16.5 inch barrel, I am running the Fed Match 175's at 2460, 70F @ sea level. Hope it helps.
I know its not 168...but out of my 16.5 inch barrel, I am running the Fed Match 175's at 2460, 70F @ sea level. Hope it helps.
Re: 308 18" barrel Velocity
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Winny</div><div class="ubbcode-body">I know its not 168...but out of my 16.5 inch barrel, I am running the Fed Match 175's at 2460, 70F @ sea level. Hope it helps.</div></div>
Don't know about the OP, but it sure as crap helped me out ALOT!!
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Winny</div><div class="ubbcode-body">I know its not 168...but out of my 16.5 inch barrel, I am running the Fed Match 175's at 2460, 70F @ sea level. Hope it helps.</div></div>
Don't know about the OP, but it sure as crap helped me out ALOT!!
Re: 308 18" barrel Velocity
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tweek5896</div><div class="ubbcode-body">Who's barrel are you using? my 20 inch is at 2590. </div></div>
I have a match fluted bull which has been cryod. Why would the barrel brand matter on FPS? I get great groups I was looking for some numbers for exbal to round off and save a little ammo on getting the shooting book filled out. I shoot right around 2700-3200 feet above sea level.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tweek5896</div><div class="ubbcode-body">Who's barrel are you using? my 20 inch is at 2590. </div></div>
I have a match fluted bull which has been cryod. Why would the barrel brand matter on FPS? I get great groups I was looking for some numbers for exbal to round off and save a little ammo on getting the shooting book filled out. I shoot right around 2700-3200 feet above sea level.
Re: 308 18" barrel Velocity
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: strangedays</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tweek5896</div><div class="ubbcode-body">Who's barrel are you using? my 20 inch is at 2590. </div></div>
I have a match fluted bull which has been cryod. Why would the barrel brand matter on FPS? I get great groups I was looking for some numbers for exbal to round off and save a little ammo on getting the shooting book filled out. I shoot right around 2700-3200 feet. </div></div>
I think the barrel and particularily the chamber make a huge difference in fps. I think factors such as type of rifling, twist rate, how the rifling was made (cut vs button), how tight or loose is the chamber, etc all make a huge difference in fps, even from the exact same barrel length.
For example, just on Sat - I was chrono'ing some loads and another SH member was testing identical loads in his rifle. Since he had chrono'd those loads previously on an Ohler 35P, I was curious how close his same rifle and same load would chrono on my CED M2. Before he shot it across my chrono, he said he had previously gotten just over 2700 fps with his 175SMK and varget load in his new Bartlein 22" tightbore barrel. Anyway, long story short: His loads on my chrono match almost exactly what he had gotten on another chrono so I know they are accurate. I then shoot the identical load in my 20" factory SPS-Tac with the loose chamber. Expecting only about 50 fps difference for my 2" shorter tube (~25 fps per inch loss of velocity ), instead I was a whopping 150 fps slower. Which I attribute that extra 100fps to his tighter chamber, slightly faster twist (his 1:11 vs my 1:12) and probably a tighter tolerance in the cut rifling of his custom barrel vs my factory tube. All those add up to big differences in velocity not strictly caused by longer or shorter barrel length.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: strangedays</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Tweek5896</div><div class="ubbcode-body">Who's barrel are you using? my 20 inch is at 2590. </div></div>
I have a match fluted bull which has been cryod. Why would the barrel brand matter on FPS? I get great groups I was looking for some numbers for exbal to round off and save a little ammo on getting the shooting book filled out. I shoot right around 2700-3200 feet. </div></div>
I think the barrel and particularily the chamber make a huge difference in fps. I think factors such as type of rifling, twist rate, how the rifling was made (cut vs button), how tight or loose is the chamber, etc all make a huge difference in fps, even from the exact same barrel length.
For example, just on Sat - I was chrono'ing some loads and another SH member was testing identical loads in his rifle. Since he had chrono'd those loads previously on an Ohler 35P, I was curious how close his same rifle and same load would chrono on my CED M2. Before he shot it across my chrono, he said he had previously gotten just over 2700 fps with his 175SMK and varget load in his new Bartlein 22" tightbore barrel. Anyway, long story short: His loads on my chrono match almost exactly what he had gotten on another chrono so I know they are accurate. I then shoot the identical load in my 20" factory SPS-Tac with the loose chamber. Expecting only about 50 fps difference for my 2" shorter tube (~25 fps per inch loss of velocity ), instead I was a whopping 150 fps slower. Which I attribute that extra 100fps to his tighter chamber, slightly faster twist (his 1:11 vs my 1:12) and probably a tighter tolerance in the cut rifling of his custom barrel vs my factory tube. All those add up to big differences in velocity not strictly caused by longer or shorter barrel length.
Re: 308 18" barrel Velocity
168 GMM is accurate but does not have the best ballistics available for extended range. It's fine to 600-800 yards and is fine at that range out of an 18" barrel.
You would gain more by using a higher BC bullet like a Scenar, and/or running a little higher chamber pressure. That requires handloading, but 175gr GMM Match ammo would be a step up.
Both those options would extend range a lot farther than an extra 10" of barrel would if you stick with 168 GMM.
TC
168 GMM is accurate but does not have the best ballistics available for extended range. It's fine to 600-800 yards and is fine at that range out of an 18" barrel.
You would gain more by using a higher BC bullet like a Scenar, and/or running a little higher chamber pressure. That requires handloading, but 175gr GMM Match ammo would be a step up.
Both those options would extend range a lot farther than an extra 10" of barrel would if you stick with 168 GMM.
TC
Re: 308 18" barrel Velocity
The Barrel is button rifled and 1-10 twist rate. I think I better just have buy a chrono then I can get the right info for my custom loads which shoot much better than the federals anyways.
The Barrel is button rifled and 1-10 twist rate. I think I better just have buy a chrono then I can get the right info for my custom loads which shoot much better than the federals anyways.
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