TRW M-14 National Match Barrel
What is the difference between the TRW standard M-14 barrel and the National Match barrel?
To err is human, to moo is bovine.
To err is human, to moo is bovine.
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Hey BB - I know nothing about your issue, I guess I am doing a SGT. Schults on this one. Just wanted to say hey.
Boomer
"Success is to be measured not so much by the position that one has reached in life as it is by the obstacles which one has overcome while trying to succeed"
NRA Life Member0 -
Well I have a TRW NM barrel on my M1A. It's TE is <1.0 and the groups I've shot with it have been more impressive than any other groups I've achieved with a service rifle. It truly does achieve 1/2 minute of angle even if I can't anymore. I can only believe that the TRW barrels that made the NM cut were truly exceptional. I used to shoot a TRW M-14 in competition that had been matched out with a standard TRW barrel and it didn't come close to the NM barrel.Beach 0 -
In each case Boeboe (and "hey" to you as well) TRW produced it barrels in house at what was then known as the Ordnance Works, organized inside the elctro-mechanical group of its jet parts division in Cleveland (I was lucky enough to have met a fellow who was an jr. engineer at TRW at that time and involved in the M14 project). Basically the two barrels were identical except that NM barrels were made to much tighter specs. Standard M14 service rifle barrels were produced using drawing number F7790190 specs which called for a bore with a land diameter of 0.2995 + .002 inch maximum deviation and a groove diameter of 0.3075 + .002 inch deviation as a maximum. NM specifications called for tolerences roughly half of the amount allowed for service grade barrels and NM barrles had to be a true .30 caliber with only a scant .001 inch deviation. Although the groove deminsions were .3075 inch on NM barrels as well as service barrels, there was just a .001 inch deviation allowed on NM as opposed to the .002 on serive barrels. The NM barrels were also checked for straightness by means of a gage for their full length as well as carefully checked for correct crown as well as barrel taper. My own M1A has nearly all TRW parts as well as a NM TRW barrel...exceptional is all I can say!
Mark T. Christian0 -
Hey Boomer and Mark, and Beech as well. Thanks for the response. I have an unusual story to tell. Sort of funny, sort of sad, but with a real moral and yet another question. See my post titled "M-14 Variation Value" and let me know what you think.
To err is human, to moo is bovine.0 -
simply put...trw = chevy. NM was the GMC.
former air operations officer SEAL Delivery Vehicle Team 2. former navy skeet team, navy rifle/pistol team member. co-owner skeetmaster tubes inc.. owner/operator professional shooting instruction.0 -
opps, forgot. guys correct me if im wrong, but the standard bbl was for 147gr (ball) bullets. the NM was designed for the 173gr match bullet. later redesignated (special ball.) there may be a twist difference issue. i/e: standard trw - 1/12 and the NM - 1/10? im away from my books. i cant remember. might want to check it out.
former air operations officer SEAL Delivery Vehicle Team 2. former navy skeet team, navy rifle/pistol team member. co-owner skeetmaster tubes inc.. owner/operator professional shooting instruction.0 -
Most NM barrels were produced at the Springfield Arsenal - although some other manufacturers have been called on to 'select' them. Note, I said 'select', not produce. Bottom line, all M-14 barrels, whereever manufactured (and M1) are air-guaged to measure the internal dimensions. As noted above, there are dimensional specifications the barrels must meet for acceptance. And the barrels are either accepted or rejected. When NM barrels were needed - a 'demand' or 'order' for X number of NM barrels would be issued.
As also noted above - the Specifications for NM barrels had much tighter tolerances for absolute internal dimensions as well as for the degree of variation in dimensions throughout the length of the entire bore.
Actually, they are all barrels from a general production run. When an 'order' called for X number of NM barrels, all that happened was that as each of the general production barrels was air-guaged, those that happen to fall within the tighter NM specs were pulled, marked NM, and set aside until the number necessary to fill the order had been accumulated.
When that number was met, they stopped pulling these barrels from the general production and marking them NM. So, in fact, (while I don't know the actual percentages) a lot of 'rack' barrels actually meet NM spec's. But with no specific 'order' for NM grade barrels, even if the barrels happen to fall within the NM Spec, there was no call for pulling them aside and identifying them as NM.
The 7.62 ball bullet is somewhat different from the M2 ball bullet. But either bullet will shoot equally well in the 10" twist Garand or the 12" twist M-14. However, in fact the - the National Match Bullet is remarkably different in weight and shape from either of the ball bullets noted above. Nevertheles, it was the bullet loaded in NM ammunition for either gun. The NM bullet shot very well in the M1's 10" twist barrel at virtually all ranges. However, the M-14's 12" twist, coupled with the lower velocity generated by the 7.62 cartridge, compounded by further velocity loss due to the M-14s shorter barrel, results in a significant loss of projectile stability at around 1,000 yards. It shoots very well at the short and mid ranges - perhaps better than from a 10" twist. But, a fair number of M-14s with the match bullet - will actually lose stability a little before 1,000 yards. Witness the Major Service Competitions. For years the M-14 rifle was mandated and everybody shot U.S.Match issued on the firing line - so it was all from the same lot in any given event. While the majority of the guns shot 'round' holes in the 1,000 yard targets, as noted above a fair number of these NM M-14s shot oblong to flat-out crosswise bullet holes in those targets. Same guns, same ammo, same range, same weather, same match, same relay - the velocity is so close to the 'edge' at 1,000 yards that any of a number of things that can lower velocity by even a few fps at the muzzle (bore dimensions, bore wear, throat wear, etc.) can make the difference as you approach at 1,000 yards.
Best.........!
MAD DAWG0
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