Fairly new to reloading but have never reloaded for a single shot Thompson Pro Hunter. A friend wants to stuff 210gr Berger VLD's (probably watched it on tv) into his 300 Mag. Any advice concerning the loading of a T/C Pro Hunter would be great. Doesn't seem as simple as figuring out Case Length, Seating Depth, and OAL as a Bolt gun. Probably be best to just stick to SAAMI Case Length and OAL then just play with seating depth? Thoughts and Tricks to the Trade on these style guns welcomed.
Help Loading Thompson Pro Hunter 300 Magnum
- Thread starter 1J04
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Re: Help Loading Thompson Pro Hunter 300 Magnum
The trick is in the case sizing. Headspace is created at the barrel/frame gap. Production tolerences vary from gun to gun, but you will want to just bump the shoulder .0015-.002" when sizing. A general "full-length sizing" will probably give you too much HS and you will get a case separation eventually. Bullet seating depth is limited to the throat length rather than magazine length in a bolt gun. Use a once-fired case and determine max COAL with your preferred bullet.
The trick is in the case sizing. Headspace is created at the barrel/frame gap. Production tolerences vary from gun to gun, but you will want to just bump the shoulder .0015-.002" when sizing. A general "full-length sizing" will probably give you too much HS and you will get a case separation eventually. Bullet seating depth is limited to the throat length rather than magazine length in a bolt gun. Use a once-fired case and determine max COAL with your preferred bullet.
Re: Help Loading Thompson Pro Hunter 300 Magnum
The Berger 210 gr. in .30 cal. is a <span style="font-weight: bold">long</span> bullet. If the barrel has the typical twist rate it may allow instability in the flight of the bullet and lead to poor accuracy. This is beyond the abilities of the handloader to correct. Thompson make a good gun but if a person want to shoot "special VLD bullets" he may need a "special" barrel.
The Berger 210 gr. in .30 cal. is a <span style="font-weight: bold">long</span> bullet. If the barrel has the typical twist rate it may allow instability in the flight of the bullet and lead to poor accuracy. This is beyond the abilities of the handloader to correct. Thompson make a good gun but if a person want to shoot "special VLD bullets" he may need a "special" barrel.
Re: Help Loading Thompson Pro Hunter 300 Magnum
Billyboy and mrjimsfc thanks for the advice and info, it's greatly appreciated. Can you tell me the best way to set up ordinary RCBS Dies for this gun so as to just bump the shoulder minimally. Regarding the case head seperation, it just happened after 3 reloads!! Did the COAL with once fired case, marked bullet and found the lands. Any suggestions as to what Dies to have him get for this gun? Typical 28" barrel (1/10?). Any info/ideas from the board is appreciated.
Billyboy and mrjimsfc thanks for the advice and info, it's greatly appreciated. Can you tell me the best way to set up ordinary RCBS Dies for this gun so as to just bump the shoulder minimally. Regarding the case head seperation, it just happened after 3 reloads!! Did the COAL with once fired case, marked bullet and found the lands. Any suggestions as to what Dies to have him get for this gun? Typical 28" barrel (1/10?). Any info/ideas from the board is appreciated.
Re: Help Loading Thompson Pro Hunter 300 Magnum
You need to get a headspace guage (comparator) of some kind. Hornady, RCBS, etc. You measure a few once-fired cases and then you adjust your full-length sizing die so that a resized case mesures .0015-.002" shorter than the once-fired case. This way you are doing a "partial full length sizing" on your cases and introducing minimal headspace so that your cases do not stretch as much when fired. Any regular die set will work, it is all in how you adjust the sizing die.
You need to get a headspace guage (comparator) of some kind. Hornady, RCBS, etc. You measure a few once-fired cases and then you adjust your full-length sizing die so that a resized case mesures .0015-.002" shorter than the once-fired case. This way you are doing a "partial full length sizing" on your cases and introducing minimal headspace so that your cases do not stretch as much when fired. Any regular die set will work, it is all in how you adjust the sizing die.
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