Pros & Cons of Upgrading the TM Thompson M1A1

FNG · October 21st, 2005, 01:31

I'm looking to do a simple spring, shim and bushing upgrade. SP120 or something similar. I need input from people who have done this before or have read something I might have missed (I have read A LOT!). High "rate of fire' doesn't mean much to me. Consistency means a lot. What else should I change? Gears, Piston, etc? From what I've read, an upgrade of this calibre should not require 'High Torque' gears or upgraded piston or piston head. I don't want to use more than an 8.4V battery. I have read about the problem of losing 'semi auto' or it firing in 'bursts' of 3-4 rounds per trigger pull in semi auto. Although I've read that this happens, no-one has ever wrote about a fix for it that I could find. Any help or advise would very appreciated.

Mantelope · October 21st, 2005, 01:45

I've never used an M1A1, but I do know about the P90, the other V6 gun. An SP120 will probably give you close to 450FPS. I'd recommend an SP100 or comparable instead. For better consistency, consider getting this Systema headset: http://www.wgcshop.com/pcart/shopper...m=SYS-ZS-03-44, and a tightbore barrel. These parts are really the only things that interact directly with the BB or the air pushing it. Replacing parts like the gears or the piston will not help consistency.

An 8.4V large should be enough for an SP100 or even 110 upgrade.

I shouldn't need to mention that the experience of the airsmith installing the parts is as important as the parts themselves.

FNG · October 21st, 2005, 02:13

The spring charts I've looked at say the 'SP120' should get you about 425 fps. SP100 around 385 fps. I've installed several SP100 springs in various guns with everything from stock to Systema Helical gears. They all fire around 340 to 365 fps. How could the SP120 make that far of a jump? If someone has a better spring to recommend I'm all ears....or eyes...whatever.

Mantelope · October 21st, 2005, 02:34

I'm looking at Illusion's spring chart, and the SP120 gave him around 430FPS. The longer barrel in the M1A1 I'm guessing would make up for the rest. Why not use an SP110?

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October 21st, 2005, 01:31	#1
FNG Trader rating Join Date: May 2005 Location: Toronto	Pros & Cons of Upgrading the TM Thompson M1A1 I'm looking to do a simple spring, shim and bushing upgrade. SP120 or something similar. I need input from people who have done this before or have read something I might have missed (I have read A LOT!). High "rate of fire' doesn't mean much to me. Consistency means a lot. What else should I change? Gears, Piston, etc? From what I've read, an upgrade of this calibre should not require 'High Torque' gears or upgraded piston or piston head. I don't want to use more than an 8.4V battery. I have read about the problem of losing 'semi auto' or it firing in 'bursts' of 3-4 rounds per trigger pull in semi auto. Although I've read that this happens, no-one has ever wrote about a fix for it that I could find. Any help or advise would very appreciated.

October 21st, 2005, 01:45	#2
Mantelope Scotty aka harleyb Trader rating Join Date: Mar 2004 Location: Toronto, Ontario	I've never used an M1A1, but I do know about the P90, the other V6 gun. An SP120 will probably give you close to 450FPS. I'd recommend an SP100 or comparable instead. For better consistency, consider getting this Systema headset: http://www.wgcshop.com/pcart/shopper...m=SYS-ZS-03-44, and a tightbore barrel. These parts are really the only things that interact directly with the BB or the air pushing it. Replacing parts like the gears or the piston will not help consistency. An 8.4V large should be enough for an SP100 or even 110 upgrade. I shouldn't need to mention that the experience of the airsmith installing the parts is as important as the parts themselves. __________________

October 21st, 2005, 02:34	#4
Mantelope Scotty aka harleyb Trader rating Join Date: Mar 2004 Location: Toronto, Ontario	I'm looking at Illusion's spring chart, and the SP120 gave him around 430FPS. The longer barrel in the M1A1 I'm guessing would make up for the rest. Why not use an SP110? __________________

October 21st, 2005, 02:13	#3
FNG Trader rating Join Date: May 2005 Location: Toronto	The spring charts I've looked at say the 'SP120' should get you about 425 fps. SP100 around 385 fps. I've installed several SP100 springs in various guns with everything from stock to Systema Helical gears. They all fire around 340 to 365 fps. How could the SP120 make that far of a jump? If someone has a better spring to recommend I'm all ears....or eyes...whatever.

Pros & Cons of Upgrading the TM Thompson M1A1

Upgrades & Modifications