Heavier Powder Loads Meant for Bolt Actions Used In Gas Guns
- Thread starter Edsel
- Start date
M14s had a gas shut-off for grenade launching.
As for using a shut-off to use slow-powder bolt gun loads...what's the point?
As for using a shut-off to use slow-powder bolt gun loads...what's the point?
I have some .308 Winchester rounds loaded all the way to 44.5 grains with IMR 4064, but stopped at 43.5 grains after noticing some cratering on the primers.
I also read that the higher end of the range (IMR listing) would probably be safer if only used on Bolt Guns.
I wanted to fire them off instead of pulling the bullets and reusing the powder - but was wondering if that was safe.
I also read that the higher end of the range (IMR listing) would probably be safer if only used on Bolt Guns.
I wanted to fire them off instead of pulling the bullets and reusing the powder - but was wondering if that was safe.
Edsel,
This is a misunderstood topic. A gas gun can handle the same "heavy load" a bolt gun can.
The issue is running some (not all) gas guns w powders in a certain burn range that is incompatible with the original design of the action/system.
That is to say that as long as you select a powder in the correct burn range, you can hot rod the gas gun similar to a bolt gun without issue.
If however, you choose to "hot rod" your gas gun with a powder outside the recommended powder burn range, the range of cons range from "a cyclic rate so fast that it causes double feeds" to potentially damaging the operating rod of certain guns. The point at which damage to the rifle occurs is generally unknown and takes many rounds (probably thousands) of rounds to manifest itself since its a form of fatigue failure.
This is a misunderstood topic. A gas gun can handle the same "heavy load" a bolt gun can.
The issue is running some (not all) gas guns w powders in a certain burn range that is incompatible with the original design of the action/system.
That is to say that as long as you select a powder in the correct burn range, you can hot rod the gas gun similar to a bolt gun without issue.
If however, you choose to "hot rod" your gas gun with a powder outside the recommended powder burn range, the range of cons range from "a cyclic rate so fast that it causes double feeds" to potentially damaging the operating rod of certain guns. The point at which damage to the rifle occurs is generally unknown and takes many rounds (probably thousands) of rounds to manifest itself since its a form of fatigue failure.
Yea I had the same issue. Had some of my bolt gun loads with 43.5 gr of Varget behind a 168 gr pill. This was my go to load for my R700 but after I sold that I decided to seat the bullet a little deeper (wouldn't fit in the mag as it say) and shoot it out of my M1A. When I looked at the service load with varget, it maxed out at about 41.5 gr I believe.
The weird part is, even at 43.5 gr Varget my muzzle velocities were still slower than factory Hornady and BH ammo, I shot the remaining 50 of the 43.5 varget loads with no issues (granted the accuracy wasn't as good as my 4895 load). Still haven't decided whether to shoot my Hornady and BH ammo or just sell it as the velocities are well above the max load listed in Lyman and Hornady's service rifle loads.
The weird part is, even at 43.5 gr Varget my muzzle velocities were still slower than factory Hornady and BH ammo, I shot the remaining 50 of the 43.5 varget loads with no issues (granted the accuracy wasn't as good as my 4895 load). Still haven't decided whether to shoot my Hornady and BH ammo or just sell it as the velocities are well above the max load listed in Lyman and Hornady's service rifle loads.
Edsel
Look at the gas port location on the M1 Garand and then the gas port location on the M14/M1A, one problem with rifles that have the gas port located at the mid point of the barrel is pressure in the barrel as the action cycles. What this means is the bolt is moving to the rear while pressure is still in the barrel. This is hard on the rifle and your brass, on top of this your fired case can end up longer than the chamber because the residual pressure pushes the unsupported shoulder of the case forward as the action opens.
A cars engine has a red line on the tachometer to remind you from over stressing the engine and your M1A has a safe operating pressure range that doesn't over stress and wear out moving parts early in their life.
If there is still pressure in the barrel and the bolt is moving to the rear this will cause increased bolt lug wear and also on the bolt lugs recesses. And this is governed by your port pressure and the pressure range it was designed to operate at.
And when you exceed this port pressure you have gone past the red line on the tach and are over stressing the moving parts.
Look at the gas port location on the M1 Garand and then the gas port location on the M14/M1A, one problem with rifles that have the gas port located at the mid point of the barrel is pressure in the barrel as the action cycles. What this means is the bolt is moving to the rear while pressure is still in the barrel. This is hard on the rifle and your brass, on top of this your fired case can end up longer than the chamber because the residual pressure pushes the unsupported shoulder of the case forward as the action opens.
A cars engine has a red line on the tachometer to remind you from over stressing the engine and your M1A has a safe operating pressure range that doesn't over stress and wear out moving parts early in their life.
If there is still pressure in the barrel and the bolt is moving to the rear this will cause increased bolt lug wear and also on the bolt lugs recesses. And this is governed by your port pressure and the pressure range it was designed to operate at.
And when you exceed this port pressure you have gone past the red line on the tach and are over stressing the moving parts.
The FALs are adjustable.
I adjust the BARs by making my own gas regulator.
But with AR15s without adjustment, I am just screwed.
No amount, from 35kpsi to 80 kpsi will cycle the action with Blue Dot and 35 gr. Not enough gas pressure times time product.
And yet 80 kpsi with a heavy bullet and slow powder will cause the bolt and carrier to hammer the rifle. Too much pressure times time product.
I adjust the BARs by making my own gas regulator.
But with AR15s without adjustment, I am just screwed.
No amount, from 35kpsi to 80 kpsi will cycle the action with Blue Dot and 35 gr. Not enough gas pressure times time product.
And yet 80 kpsi with a heavy bullet and slow powder will cause the bolt and carrier to hammer the rifle. Too much pressure times time product.
Firing off a few and checking for pressure signs/hard ejection should be fine.
When I had my AR10s my go-to load was 43 grains of varget in LC brass with a 175 grain bullet or 178. Shots lots of that without issue no matter the length of the gas system. In my M1A with a non-slotted gas piston I dropped it to 42, with a slotted piston I got to 43.5. If you are using winchester then figure another grain or two added on as winchester is much roomier than LC.
You don't say what bullet weight you are shooting but my Hornady manual for service rifle loads lists the 155 grain bullet and 43.2 grains of IMR-4064 as a max load. You also need to remember your reloads do not have crimped primers and high port pressure can cause the primer to back out of the primer pocket further and deform more when fired.
It doesn't matter what bullet weight he is shooting. The powder listed is in the correct burn range...he could shoot a 240gr bullet and NOTHING will happen to his rifle because the port pressure will be within design tolerance.
You can "upset" the rifle's timing with light bullets, again, the key here is using correct burn range powder. If he were shooting RL-17, then I would recommend getting the bored and ported gas plug or an adjustable gas plug to keep the pressure within tolerance.
You gain nothing by shooting reduced loads (of correct burn range powder) out of a gas-gun except less recoil and crappy ballistics.
I thought I typed the bullet in - must have overlooked that.
It's a Nosler Custom Competition 168 grain BTHP. Did some load development between 41 and 43.5 grains of IMR 4064 in 0.1 grain increments, started noticing livelier recoil and primer craters around 43.5 grains.
Strangely, FGMM 175 grain always produces these craters.
The rifle's a SIG 716 with a 16" barrel and 1 in 10" rifling.
I fired off all the "nuisance" rounds this afternoon with the gas port on suppressed up to 44.1 grains, and off between 44.2 and 44.5 grains.
Thanks, guys.
It's a Nosler Custom Competition 168 grain BTHP. Did some load development between 41 and 43.5 grains of IMR 4064 in 0.1 grain increments, started noticing livelier recoil and primer craters around 43.5 grains.
Strangely, FGMM 175 grain always produces these craters.
The rifle's a SIG 716 with a 16" barrel and 1 in 10" rifling.
I fired off all the "nuisance" rounds this afternoon with the gas port on suppressed up to 44.1 grains, and off between 44.2 and 44.5 grains.
Thanks, guys.
