Jap. Headspace Problem
I've fired thousands of rounds through Jap 7.7 mm service rifles that were arsenal converted to 30-06 for use by the Korean Service Corps. They were very accurate even with the 30 caliber bullet in a 7.7mm bore. However, after 500 rounds, the bolts set back and the chambers accepted the 1.951 No-Go gage.
Headspace was restored in every case by installing another bolt.
These 7.7mm rifles were designed to shoot a 42,000psi load. The 30-06 is a 50,000psi load. Although they will not come apart with very heavy loads, headspace progressively increases.
For limited use as a deer hunting rifle, that fires a box of ammo a year, the problem is academic. But to use such conversions for a lot of target work or varminting, it's a mistake.
The 6.5 Jap may very well also respond to a new bolt but using higher pressure than the issue 6.5 Jap will put you in the same boat after a while. Phil Sharp estimated Jap military ammo pressure at 35,000psi.
It fired a 138 grain bullet at 2400fps. Some .257 Roberts loadings are at 50,000psi.
At least a few technical gun writers like Julian Hatcher and Phil Sharp recommended these rifles not be used for conversions because of poor quality.
Headspace was restored in every case by installing another bolt.
These 7.7mm rifles were designed to shoot a 42,000psi load. The 30-06 is a 50,000psi load. Although they will not come apart with very heavy loads, headspace progressively increases.
For limited use as a deer hunting rifle, that fires a box of ammo a year, the problem is academic. But to use such conversions for a lot of target work or varminting, it's a mistake.
The 6.5 Jap may very well also respond to a new bolt but using higher pressure than the issue 6.5 Jap will put you in the same boat after a while. Phil Sharp estimated Jap military ammo pressure at 35,000psi.
It fired a 138 grain bullet at 2400fps. Some .257 Roberts loadings are at 50,000psi.
At least a few technical gun writers like Julian Hatcher and Phil Sharp recommended these rifles not be used for conversions because of poor quality.
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If a new bolt fixed the problem, it sounds to me like the setback was in the lugs, not the recesses in the reciever, or?
"...hit your enemy in the belly, and kick him when he is down, and boil his prisoners in oil- if you take any- and torture his women and children. Then people will keep clear of you..." -Admiral of the Fleet Lord Fisher, speaking at the Hague Peace Conf0 -
most 6.5 mm japs. were very good quality, and THE strongest military action (possible tie with the '17 enfield?). action or bolt lug setback are almost unheard of with these, I remember reading of some blow-up testes p.o. ackley did on military actions and the jap. came out on top. that said, I still don't like working on them (lousey safty, hard to bed, hard to barrel compaired to most othe actions). 0 -
Japan ran out of good quality steel at the end of WWII and made some guns with cast steel which were of poor quality and less strength the the original Jap. actions. -- The tests done by Ackley were done with the original good quality actions which were indeed very strong................[8D] 0 -
The Japs are awfully strong! See May '56 Amer Rif of report of firing 30/06 US GI mil ammo in a 6.5 that had been rechambered but not rebored! I have had a late war (last ditch) proofed to 92,000 PSI with no damage to gun. One of the consultants for AA has reported excess pressure stripping the threads of a commercial rebbl so that bbl was ejected, with no damage to receiver.
Morty
Have fun, be careful!0 -
YEAGER from JENKINTOWN in PHILADELPHIA (one of the best gunsmiths of the last 50 years in north america) built large quantities of sporter rifles on these actions (TYPE 38, TYPE 99). my father owned one, in .308, and it was superb. this action (allowing that you get a PRE-1944 production gun) is the strongest military bolt action ever produced (HATCHERS NOTEBOOK, ELEMENTS OF ORDANANCE, etc...) and were superior to the MAUSER, ENFIELD, and SPRINGFIELD, etc...
i have never encountered an ARISAKA that had bad or improper headspace, and do not know how to fix the problem. best regards, mike.
What other dungeon is so dark as ones own heart, what jailer so inexorable as ones own mind.0 -
Some of you guys don't want to understand that Japanese guns wont bear up to a lot of shooting with full power 30-06 or equivalent.
Sure they'll take a few heavy proof loads ,they're safety breeched so you're not likely to burst a case head and blow up an action that way, but that doesn't mean you can do a lot of shooting with them.
As an example,you can fire a small number of proof loads with the Springfield but headspace will grow. That's how guns fail. The elastic limit of overstressed parts is exceeded and parts begin to give or yield and change dimension. We're not talking of gross overloads that break parts or blow up actions.
The US Arsenal converted Jap 99s were of the earlier type with smoother finish, checkered safeties and ladder sights. It was clear the bolt lugs were yielding although by visual examination they looked ok.
The recent questioner, puzzled why his 6.5x.257 Jap "suddenly" had excess headspace probably didn't notice it growing. I doubt that it was all that sudden.
When you consider the Jap action gave up headspace under the 19% overload of the '06 M1 Ball, you have to wonder how the headspace would look after 500 rounds of 7.7mm service ammunition.
I suspect the rifles were designed for a limited service life.
Some of their service pistols have a similar reputation.0 -
my type 99 (23RD SERIES MU) prints sub-1" groups at 100 yds off of a bagged benchrest. i have fired in excess of 500 rds through it in the last 3 months. 4 full boxes of NORMA 180 GR SP, and the balance in handloads (formed from GI `06 BRASS with a 150 gr FMJ/BALL head). the handloads are "hot loads" within 5% of the published recomended maximum load.
the gun exhibits no headspace problems, and accuraccy has impoved (marginaly) over the course of fire. the ammo i am using is certainly hotter than the original MIL SPEC JAPANESE issue ammo. both my TYPE 99 ARISAKA`s are early production (late 1939) and they function perfectly.
i have not heard of or experianced the problems you describe / allude to. we load a large quantity of 7.7 JAP for local shooters, and we have handled, sold, cleaned, inspected, and restored over 20 of these guns in the last year. we currently have 9 ARISAKA`s in stock, includine early production guns and so called "LAST DITCH" guns.
perhaps we have simply been very lucky, but we have had no problems with these guns. perhaps other members could chime in.
best regards, mike.
What other dungeon is so dark as ones own heart, what jailer so inexorable as ones own mind.0 -
Have a close friend who swears by them and handloads to near 7Mag loading. He gets them to shoot abut as good as anything else out there and like I said, he loads them hot. Been doing that for well over 25 years. He claims they are the strongest of all bolt actions and I have never heard him mention heaspace problems and he's the kind who would say somehting abut it if he experienced it. I personally am a Mauser fan. That folks is my nickle's worth. 0 -
Mike, 80 rds of 180gr Norma 7.7 (39,000psi) + 420 rds of 150 gr loads near commercial loading table "maximum" neither equals the military load of 42,000psi or 500 rds of the US 30-06 M1 ball load at 50,000psi.
AJ Christ, as to loading to 7mm Mag pressures of 55,000psi, I believe your friend must like to live on the edge.
I have reported my experiences accurately.
As I didn't trust these conversions, I carried the 1.950 and 1.951 in my pocket during firing sessions and watched the headspace repeatedly go out of specification after 500 rds of M1 ball.0
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