I was reading in my Sierra reloading book they recommend a reduced load for semi-auto actions compared to bolt action. They claimed this helps to reduce the potential for damaging the action of the automatic. Comparing some of the reductions they were as little at 0.2-0.3 grains up to about 1 grain.

Do you reduce your loads?

Thanks

I work up the load for each individual rifle, whether SA or bolt, starting on the low suggested load side and work up while watching for any signs of excessive pressure.

I have a couple of 30-06 target rifles (bolt guns) that show pressure signs with lighter loads than those used in my M1 Garands.

Regards,
hm

Yes, always "mild" loads for my 300WM BAR.

Matching the ammo to the gun to get the cases to fly 5 feet and land on the ground can be done.
calculating how far cases fly

The springs can also be changed to match the ammo.


In wildboar's BAR, the gas regulator can be changed or modified to match the ammo. The jet in his 300WM regulator is probably .077". A 7mmMag regulator from Browning is .066". A larger one could be used for hotter ammo and a smaller jet could be used for hotter ammo. I have built them from scratch, but it is easier to modify the Browning parts.

In a FAL, there is a dial, for adjusting the gas by-pass to match the ammo.

A gun with the proper taper in the hydraulic cylinder, and springs for returning to battery, is ammo independent, and will have constant force throughout the travel and stop just in time. A high constant for hot ammo and a low constant for wimpy ammo. My father designed one for the M55, and it is still fighting in Israel. I had to call him to calculate how far cases fly.


What does it all mean?
You don't want hot ammo that hammers the slide or bolt against the frame or receiver.
You don't want wimpy ammo that make the gun jam.
So you can adjust the ammo, or adjust the gun.

Tnekkcc's post raises something that happened to me. I had gotten several M1 Garands and cleaned them up. I cleaned them up and took them shooting. One began to misfire during the session, so I cased it and dealt with it when I got home.

On disassembly, I found the recoil spring had pretty well disintegrated. It was a mess.

Point: If you are going to be loading for a autoloader, take it apart and check the recoil spring!

Also, my very old Sierra Manual suggest using bullet weights in the middle of the range for the caliber/bore and powders in the middle of the recommended range. In sum, stay in the middle with bullets, powders and charges. And check those springs! Kudude

I am loading for an older gentleman who recently started competing in military firearm matches..

he picked up a real cream puff of an M1 Garand from the CMP..

after trying a batch of different loads I recommended for his rifle... we found the most accurate was with IMR 4064 and AA 4064...

charge weight was 52.5 grains according to the book...however he did have some jamming problems and ejection problems...

I dropped the charge back to 50 grains instead and the problem instantly disappeared and the groups tightened up even more..

in a bolt action, it is immaterial when you down load...

folks also need to know there is two definitions of downloading..

one involves lower pressure and velocity, and one involves lower velocity only but still maintain close to SAAMI specs on pressure....

they aren't interchangable and don't produce the same results.....on firearm function even tho the MV may be the same...

You have to know what gas guns, and the characteristics of the gun gun in question.

Most gas guns on the market are military surplus, or commercial versions of a military rifle. These rifles were designed in tandem with a specific type of ammunition. The country that issued these rifles also issued to their troops the appropriate ammunition for the rifle. Their troops were not expected, if not forbidden, to reload for their issue weapons.

Then these rifles are declared surplus and the civilian who gets one is usually oblivious to the operating characteristics, and wants to fire any brand, make, weight, type of ammunition in his rifle.

A military service rifle should be fed ammunition close in bullet weight, gas port pressure, and velocity, to the issue ammunition. A semi automatic mechanism is very limited in the operating envelope of its ammunition. A bolt gun can digest anything.

You will also find that commercial ammunition is usually loaded to higher pressures and velocities than military ammunition. More horsepower sells cars and ammunition. So ammunition makers sell what the market buys.

The M1 Garand for example, was type 1 classified in 1936. The ammunition of the time was a 150 grain bullet at 2700 fps. Much of that ammunition gave breech pressures in the middle 40,000 pound range. I have chronographed LC ammunition from the 50’s to the 60’s, and the typical velocity is 2650 fps. Federal commercial ammunition is closer to 2900 fps. This higher pressure ammunition slams and bangs the Garand mechanism too much. It will also cause funny malfunctions as the action is moving faster than designed. Malfunctions as bolt overrides and clip jams. The mechanical damage is less apparent, but it will show up in cracked receivers and bent operating rods.

My favorite load in my match 30-06 Garands is a 168 SMK, 47.0 IMR 4895. I have shot a 150 SMK and 47.5 grs IMR 4895 and the velocity was an LC equivalent. In terms of IMR 4064, 48.0 grains provides the same velocity as 47.0 IMR 4895. I would never stuff 50.0 grs of IMR 4064 behind a 150, 168 or 175 grain bullet and use it in a Garand. Too hot.

Some gas guns, like the FN/FAL have gas systems that can be adjusted. However it is still not appropriate to fire ammunition that produces a higher than service ammo breech pressure.