I haven't seen this topic addressed, but as the Model 8/81 operates on the long recoil principle, there must be some minimum recoil impulse required to achieve reliable action functioning. Not to give a Physics lecture, impulse is essentially recoil force X Time, which is the same as the bullet (and powder gas) mass X the bullet (and powder gas) muzzle velocity. Assuming that powder charges and the mass of the rifle's moving parts and the spring constants of the recoil springs are about the same for all Model 81's, then there should be a minimum value of the product of bullet weight X bullet muzzle velocity to ensure functioning, which I'll call N. Therefore, if N is known, and you want to develop a load giving the minimum muzzle velocity that will still result in reliable functioning for any given bullet weight, all you should have to do is to calculate V = N/Bullet weight. The question is, what is the constant, N, for the Model 8/81? As near as I can determine from data taken from various reloading manuals, a minimum N is probably in the range of 230,000 to 250,000 (i.e. a 100 grain bullet at MVs from 2300 to 2500 ft/sec would probably achieve proper functioning but any lower MV would probably not). Has anyone looked at this?
This question is sort of related to the allegedly lower velocity of the WWII-era .30 Remington loads used by the FBI in their Model 81s. Does anyone know for sure what the ballistics of the FBI loads actually were and if the cartridges themselves can be distinguished from normal .30 Remington cartridges, such as by differences in headstamps or box markings? Were the FBI's Model 81s mechanically any different from a normal Model 81, such as by having weaker barrel recoil springs, etc.? Also, why did the FBI even want lighter .30 Rem loads - Were the FBI agents at that time just all Wussies, or was there a concern about over-penetration?
Has anyone tried developing loads for the .30 Remington using very heavy bullets? I have quite a few .308 220 grain RN-FMJ bullets that I would like to load for use in the Model 81, and I think I know about what propellants and charges would be safe, but my concern is whether a 220 grain bullet would be adequately stabilized at the 1:12" twist rate of the Remington 81 barrel. Calculations indicate bullet stability is borderline OK, but experience is often better than calculation.
Model 8/81 Functioning
Model 8/81 Functioning
Last edited by DWalt on Thu Jan 20, 2011 8:15 pm, edited 1 time in total.
Re: Model 8/81 Functioning
The proposed ballistics for the FBI 81 in .30Rem were to replicate the ballistics of the 351 Winchester round. And yes, after failed testing with a standard 81, Remington replaced the 30Rem recoil spring with a 25Rem recoil spring and the rifle functioned properly.
Cam Woodall
Site Co-Administrator
Site Co-Administrator
Re: Model 8/81 Functioning
Yes, I have found all that information, but was unable to find any actual data as to what the bullet weight and muzzle velocity of the FBI load were. Plus what does "ballistics equivalent to the .351" mean? In velocity? In muzzle energy? In penetration? Something else? If they liked the performance of the 07 in .351 so much, why didn't they just stick with it instead of going with the Model 81?
Re: Model 8/81 Functioning
Interesting discussion, I have nothing to help out but I am interested to see where this goes. 
Though defensive violence will always be “a sad necessity” in the eyes of men of principle, it would be still more unfortunate if wrongdoers should dominate just men. - St. Augustine
Re: Model 8/81 Functioning
Some info from an internal Remington letter dated Aug. 31, 1938,
the Department of Justice was not satisfied with the service of their 351 Winchester rifles, so they wanted to see if Remington could supply them a rifle in .30Rem with a 160 grain metal cased bullet "loaded to give the same ballistics as the Winchester caliber .351".
Rereading the letter it was not the recoil spring that was changed but the buffer spring. I dont have any additional information about the cartridge other than it was called "special velocity" and the bolt would fail to lock back using .30Rem buffer springs.
the Department of Justice was not satisfied with the service of their 351 Winchester rifles, so they wanted to see if Remington could supply them a rifle in .30Rem with a 160 grain metal cased bullet "loaded to give the same ballistics as the Winchester caliber .351".
Rereading the letter it was not the recoil spring that was changed but the buffer spring. I dont have any additional information about the cartridge other than it was called "special velocity" and the bolt would fail to lock back using .30Rem buffer springs.
Cam Woodall
Site Co-Administrator
Site Co-Administrator
Re: Model 8/81 Functioning
I doubt if you will find any load data for a 220 gr. bullet for the .30 Remington. This cartridge as well as the 30-30 WCF were developed to shoot a 160 gr. The real issue I see with that heavy bullet is that it might create a cartridge too long to function in the Model 8 - 81. It might be feasible with the .300 Savage but here the case neck is probably too short.
As far as loading for the Model 8 and 81 these guns like to have a nice sharp load to function properly. I work up my loads and will not load any stronger than necessary, but there is a lot of gun to recoil to make the thing work right.
Another thought is that the 220 grain bullet might seat to deep into the 30 R or 300 S case and create a compressed powder charge, and it would certainly reduce case volume somewhat.
As far as loading for the Model 8 and 81 these guns like to have a nice sharp load to function properly. I work up my loads and will not load any stronger than necessary, but there is a lot of gun to recoil to make the thing work right.
Another thought is that the 220 grain bullet might seat to deep into the 30 R or 300 S case and create a compressed powder charge, and it would certainly reduce case volume somewhat.
KEN
Re: Model 8/81 Functioning
Regarding the 220 grain load, there is enough volume for the .30 Remington case to seat a 220 grain RN bullet to achieve a cartridge OAL of 2.52" without propellant compression. From my Quickload software, the most satisfactory load would use IMR 3031 in the range of 22-24 grains, and the velocity should be in the 1700 to 1800 ft/sec neighborhood. Chamber pressure should be within the 35,000 psi limit. The only questions would be functionality and bullet stability. The JBM Ballistics software estimates a .30 caliber 220 grain bullet stability factor of about 1.6, with 1.5 being marginally stable, in the M81 barrel's rifling twist of 1:12". I think functionality of this load in the Model 81 would also be good as MxV is over 300,000, which should produce more than enough recoil impulse. But theory is not always fact, and I was hoping that someone had tried such a load and could provide performance information. If not, maybe I'll be the first.
Regarding the .30 Rem's equivalency to the .351 WSL, the standard factory .351 load is given as having a MV of 1850 ft/sec with a 180 grain bullet. Assuming (possibly incorrectly) that "Ballistic Equivalence" to the FBI meant having the same muzzle velocity as the .351, then the FBI load would use a 160 grain bullet (as has been stated) at 1850 ft/sec. One wonders why they didn't want a loaded-down 180 grain version of the .35 Remington instead of the .30 Remington, as then they could have achieved exactly the same ballistic performance in the Model 81 as the 07 using .351 - except I believe that the magazine capacity of the Model 81 is only 4 rounds in .35 Remington rather than 5. I don't know if such a reduced .35 Rem load would have been hot enough to work the standard action reliably. So unless someone knows the full story, I guess the logic behind the FBI's decision that a downloaded version of the .30 Remington in a rifle having a 5 round fixed magazine was superior to the 10 (or more) round capacity of the Winchester 07 using a removable magazine (which also allows much faster reloading) chambered for a different cartridge of substantially the same power must remain a mystery. I do have some sources in cartridge collecting circles, so I will try to find out if more authoritative information about the FBI .30 Remington load exists. I will post it if I find anything.
Regarding the .30 Rem's equivalency to the .351 WSL, the standard factory .351 load is given as having a MV of 1850 ft/sec with a 180 grain bullet. Assuming (possibly incorrectly) that "Ballistic Equivalence" to the FBI meant having the same muzzle velocity as the .351, then the FBI load would use a 160 grain bullet (as has been stated) at 1850 ft/sec. One wonders why they didn't want a loaded-down 180 grain version of the .35 Remington instead of the .30 Remington, as then they could have achieved exactly the same ballistic performance in the Model 81 as the 07 using .351 - except I believe that the magazine capacity of the Model 81 is only 4 rounds in .35 Remington rather than 5. I don't know if such a reduced .35 Rem load would have been hot enough to work the standard action reliably. So unless someone knows the full story, I guess the logic behind the FBI's decision that a downloaded version of the .30 Remington in a rifle having a 5 round fixed magazine was superior to the 10 (or more) round capacity of the Winchester 07 using a removable magazine (which also allows much faster reloading) chambered for a different cartridge of substantially the same power must remain a mystery. I do have some sources in cartridge collecting circles, so I will try to find out if more authoritative information about the FBI .30 Remington load exists. I will post it if I find anything.